Patent Publication Number: US-11662747-B2

Title: Articulated fluid delivery system with swivel joints rated for high pressure and flow

Description:
RELATED APPLICATIONS AND PRIORITY CLAIMS 
     This application is a continuation of co-pending, commonly-invented and commonly-owned U.S. Nonprovisional patent application Ser. No. 16/826,648 filed Mar. 23, 2020, which is a divisional application of co-pending, commonly-invented and commonly-owned U.S. Nonprovisional patent application Ser. No. 16/673,460 filed Nov. 4, 2019, which is a continuation of commonly-invented and commonly-owned U.S. Nonprovisional patent application Ser. No. 16/406,927 filed May 8, 2019, now U.S. Pat. No. 10,466,719 issued Nov. 5, 2019. Ser. No. 16/406,927 claims the benefit of and priority to the following two (2) commonly-owned U.S. Provisional Patent Applications: (1) Ser. No. 62/734,749, filed Sep. 21, 2018; and (2) Ser. No. 62/811,595, filed Feb. 28, 2019. Ser. No. 16/406,927 is also a continuation-in-part of each of the following two (2) commonly-owned U.S. Nonprovisional Patent Applications: (1) Ser. No. 16/037,687 filed Jul. 17, 2018, now abandoned, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/649,008, filed Mar. 28, 2018; and (2) Ser. No. 16/221,279 filed Dec. 14, 2018, now U.S. Pat. No. 10,550,659 issued Feb. 4, 2020, which also claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/649,008, filed Mar. 28, 2018. The disclosures of the following eight (8) commonly-owned U.S. Provisional and Nonprovisional Patent Applications are further incorporated herein by reference in their entirety: (1) Ser. No. 16/826,648 filed Mar. 23, 2020; (2) Ser. No. 16/673,460, filed Nov. 4, 2019; (3) Ser. No. 16/406,927, filed May 8, 2019; (4) Ser. No. 62/649,008, filed Mar. 28, 2018; (5) Ser. No. 62/734,749, filed Sep. 21, 2018. (6) Ser. No. 62/811,595, filed Feb. 28, 2019; (7) Ser. No. 16/037,687, filed Jul. 17, 2018; and (8) Ser. No. 16/221,279, filed Dec. 14, 2018. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates to the field of fluid delivery, advantageously at high volumes and pressures, from surface-deployed equipment to wells drilled through subsurface formations. More particularly, in some embodiments, this disclosure relates to such fluid delivery to each of a plurality of wells having surface locations proximate each other via a remote controlled delivery system. 
     BACKGROUND 
     Wells drilled through subsurface formations are used for, among other purposes, extracting useful fluids such as oil and gas. Some subsurface formations are treated (“stimulated”) by pumping fluid under pressure into such formations for the purpose of creating, propagating and propping open networks of fractures to enhance extraction of oil and gas. This technique is commonly known as “fracking”. It is known in the art to drill wells for fracking substantially along the geologic trajectory of certain subsurface formations, while drilling a plurality of such “directional” or “lateral” wells from proximate surface locations. U.S. Patent Application Publication No. 2011/0030963 filed by Demong et al. (“Demong”) discloses an exemplary arrangement of wells having proximate surface locations. Demong also describes controlled fluid pumping and valve equipment enabling selective opening of one or more wells to (1) fracking fluid delivery into selected wells or (2) flow from the subsurface formation to the surface. 
     Demong&#39;s background disclosure provides a useful general discussion of at least some aspects of the state of the current art. Demong&#39;s background is also applicable background to the technology described in this disclosure. The following background discussion includes adaptations of Demong&#39;s background disclosure where applicable to this disclosure. 
     During typical fracking operations, fluid is pumped into the formation at pressures that exceed the fracture pressure of the formations. The fractures in the formation thus opened up may be held open by pumping of material (proppant) that supports the fracture structurally after the fluid pressure on the formation is relieved. Other fluid treatments may include, for example, pumping acid into the wellbore to dissolve certain minerals present in the pore spaces of the formations that reduce the formation permeability. 
     Wellbores may be drilled into hydrocarbon-bearing formations along directed trajectories that may deviate from vertical. In land-based fracking deployments, such deviated wellbores may be drilled, for example, so that the surface locations of the wellbores are closely spaced on a relatively small land area called a “pad”, while the lowermost portions of the wellbore extend laterally from the respective surface locations in a selected drainage pattern. Such arrangement reduces or minimizes the amount of land surface affected by the fracking operations. 
     Conventionally, fracking operations on multiple wells drilled from a common surface pad typically require multiple connections and disconnections in order to (1) connect the pumping equipment hydraulically to one well, (2) pump the fluid, then (3) disconnect the pumping equipment from the well before another well can be fluid treated. Such conventional piping configurations often involve laying pipe from each fracking fluid delivery truck to a central collection manifold and then in single or multiple lines to the well being treated. The result is that a costly separate rig-up and rig down is required for every fracture treatment. Such operations can create, among other exposures, safety risks to personnel working on or near the pad or platform, and interference with the operation of wellbores that are producing oil and/or gas while the fluid treatment equipment is connected and disconnected from various wellbores on the pad or platform. Such connection and disconnection operations may also take considerable amounts of time to perform. 
       FIG.  1    illustrates “zipper fracking”, a conventional (prior art) approach to optimizing the multiple pipe connections described immediately above. On  FIG.  1   , pumping units  10  deliver fluid at pressure into manifold M 1 . Pumping units  10  may be conventional fracking pump and delivery trucks such as illustrated on  FIG.  1   . Manifold M 1  may be known colloquially as a “missile” in some embodiments. Fluid transfer lines  20  on  FIG.  1    deliver fluid from manifold M 1  to manifold M 2 . Manifold M 2  may be known colloquially as a “zipper frack” in some embodiments. Manifold M 2  provides a plurality of control outputs  30 . Control outputs  30  are each connected by one or more fluid delivery pipes to a “goat head” style manifold  40  atop a wellhead W. In oilfield fracking and well completion parlance, “goat head” refers to a style of manifold with a hollow body providing multiple fluid line connection points (e.g. flange faces). 
     Fluid delivery to wellheads W on  FIG.  1    is controlled by actuation of control valves on control outputs  30 . Advantageously, flow through each fluid delivery pipe connecting a control output  30  to a corresponding goat head  40  is independently controlled by a separate control valve. In this way, an operator may actuate different control valves at different times to deliver fluid from manifold M 2  to selected wellheads W as desired. 
     The drawbacks of“zipper fracking” according to  FIG.  1    include that the setup is very inefficient in use of hardware such as control outputs  30  and corresponding control valves. The setup of  FIG.  1    calls for considerable hardware spending its time idle. Likewise, the labor required for setup and teardown is high, since each control output  30  requires multiple fluid delivery pipes to be physically connected and then disconnected from a goat head  40 . 
       FIG.  2    illustrates another conventional (prior art) approach to delivering fracking fluid to a wellhead. Crane truck CT is positioned nearby a wellhead W into which fluid is desired to be delivered. Crane C on crane truck CT advantageously provides telescoping boom TB. As shown on  FIG.  2   , crane C and telescoping boom TB bring wellhead connector WC nearby wellhead W. A first operator, also nearby wellhead W, then manhandles wellhead connector WC onto wellhead W as wellhead connector WC hangs suspended from telescoping boom TB. Meanwhile, a second operator (not illustrated on  FIG.  2   ) assists by making adjustments to the suspended position of wellhead connector WC via operation of crane C and telescoping boom TB. 
     Once the first operator has secured wellhead connector WC to wellhead W, piping P on crane truck CT may be connected to fracking fluid at operating pressures and delivery volumes. Fluid delivery to wellhead W may commence. 
     At the completion of fluid delivery, fluid flow through piping P is terminated, and the first operator may disconnect wellhead connector WC from wellhead W. The second operator then actuates crane C and telescoping boom TB to move wellhead connector WC towards a second wellhead W in range to be connected in the same manner as the first. Alternatively, the second operator moves wellhead connector WC onto crane truck CT with crane C. Crane truck CT may then be physically relocated to a position nearby a new wellhead W to be serviced. 
     There are several drawbacks to prior art fluid delivery according to  FIG.  2   . There are operator safety issues, particularly with the first operator required to manhandle wellhead connector WC onto wellhead W. The operation also optimally requires two operators. The operators must be skilled. Depending on local conditions and the skill level of the operators, manual connection of wellhead connector WC onto wellhead may be slow and imprecise. It is also likely that only a small number of wellheads W will be in range of crane truck CT without need for physically relocating crane truck CT. 
     There is therefore a need in the art for an improved fluid connection and delivery system for multiple wellheads that can reduce the amount of and complexity of conduit between fluid apparatus and selected wellheads in a multiple well system. Such an improved fluid delivery system will advantageously reduce risks to operating personnel safety. Embodiments of such an improved fluid delivery system will further optimize fluid delivery in high-pressure, high-volume fracking operations. Such optimizations will advantageously include automated and robotic control over spatial positioning of the fluid delivery system with respect to wellheads to be serviced. 
     SUMMARY AND TECHNICAL ADVANTAGES 
     These and other needs in the prior art are addressed by a fluid delivery system including an articulated fluid delivery unit (FDU) comprising, in preferred embodiments, a first boom section concatenated in articulated fashion to a turret, and a second boom section concatenated in articulated fashion to the first boom section. The turret rotates about a generally vertical axis. A stinger assembly is provided at a distal end of the second boom section. The stinger assembly includes a fluid connection adapter for connection to a mating fluid connection housing assembly provided on a wellhead. The stinger assembly includes rotating connections allowing independent rotation (or tilting) of the fluid connection adapter. In preferred embodiments, the stinger assembly provides two (2) such rotating connections configured to rotate in orthogonal planes. 
     Control over spatial positioning of the FDU is enabled by rotational control at multiple axes of rotation at corresponding articulating or rotating connections on board the FDU. In preferred embodiments, there are five (5) independently-controlled axes of rotation: turret, first boom section to turret, second boom section to first boom section, stinger assembly to second boom section and second orthogonal rotation at stinger assembly. Independent control of rotation at each of these axes allows an operator to establish a measured directional bearing at each axis, such that a set of values for all directional bearings at a given time defines the FDU&#39;s current spatial position. In preferred embodiments, the FDU may “learn” a desired spatial position (e.g., with the fluid connection adapter positioned immediately above a desired wellhead) by storing the set of directional bearings values corresponding to that spatial position. The FDU may then return to that spatial position robotically in the future when instructed to recall and take up again the corresponding set of directional bearings values. [The term “robotic” or “robotically” as used in this disclosure is intended to mean, consistent with plain English usage, that the FDU takes action as a machine capable of carrying out a series of actions by itself, responsive to instructions from a source such as a software routine]. 
     In preferred embodiments, control over FDU&#39;s spatial position is by remote control. In such embodiments, a user directs movement of the FDU via a wirelessly-connected hand-held controller. In some embodiments, the controller may also store and recall sets of directional bearings values corresponding to spatial positions that the user directs the FDU to “learn”. 
     In preferred embodiments, the FDU delivers fluid to its destination via fluid-bearing piping and fittings connected to articulating or rotating components such as the turret, the first and second boom sections and the stinger assembly. The fluid-bearing piping and fittings include a fluid inlet, a plurality of swivel joints and a fluid connection adapter all in fluid flow communication. The swivel joints facilitate FDU articulation and rotation. Currently preferred embodiments of the FDU are designed for fracking fluid delivery service, in which the FDU is asked to deliver fracking fluid at operating pressures of not less than about 7,500 psi (“ksi”), and more preferably not less than about 10,000 psi (“10 ksi”), and yet more preferably not less than about 15,000 psi (“15 ksi”), all at delivery volumes requiring a 7″ or 8″ internal diameter (“ID”) pipe. As described in more detail in this disclosure, designing a serviceable 7″-8″ ID swivel joint rated for 15 ksi working pressure has proved challenging. Commercially-available swivel joints rated for 15 ksi service are typically available in sizes up to 4″ ID only and will not deliver the volume of fluid required for fracking operations. Larger ID commercially-available swivel joints have proven unable to withstand the tensile stresses imparted by 15 ksi working pressure. Thus, in preferred embodiments, each swivel joint has an internal diameter of not less than about 7 inches. Further, each swivel joint is preferably capable of retaining an internal pressure of not less than about 7,500 psi (“7.5 ksi”), and more preferably capable of rotation while retaining an internal pressure of not less than about 7.5 ksi. More preferably, each swivel joint is preferably capable of retaining an internal pressure of not less than about 10,000 psi (“10 ksi”), and more preferably capable of rotation while retaining an internal pressure of not less than about 10 ksi. Yet more preferably, each swivel joint is capable of retaining an internal pressure of not less than about 15 ksi, and more preferably capable of rotation while retaining an internal pressure of not less than about 15 ksi. 
     FDU embodiments according to this disclosure include two swivel joint embodiments whose designs have been specifically engineered and tested to withstand internal working pressures of 15 ksi with ID at least 7″. Significant effort and investment has been made to solve a problem and meet a need in this regard that the prior art appeared neither to recognize or address. As described in more detail further below, the disclosure of commonly-assigned U.S. Provisional Patent Application Ser. No. 62/811,595, filed Feb. 28, 2019, incorporated herein by reference, describes at least one previous swivel joint design that was engineered, tested and then rejected as unable to withstand an internal working pressure of 15 ksi with an ID of at least 7″. Rejection of this previous design was a precursor to designing the swivel joint embodiments disclosed herein. 
     It is therefore a technical advantage of the disclosed fluid delivery system to deliver fluid to a desired delivery destination (such as a wellhead) quickly, efficiently, safely and precisely. Once the FDU has been physically positioned in a desired jobsite location, FDU embodiments including stored and recalled spatial positioning allow repeated deliveries to wellheads whose spatial position the FDU has “learned”. The FDU can further make quick, safe and precise and safe returns to wellheads that have previously received fluid. 
     A further technical advantage of the disclosed fluid delivery system is that in some embodiments, a first inclinometer is provided on the FDU superstructure or chassis. This first inclinometer may measure, quantitatively, the degree to which the FDU stands “out of level” in its current jobsite position. In FDU embodiments including stored and recalled spatial positioning, “out of level” information from the first inclinometer may correct sets of directional bearings data measured at axes of rotation. 
     A further technical advantage of the disclosed fluid delivery system is that in some embodiments, a second inclinometer is provided on the stinger assembly to maintain the fluid connection adapter in a constant plumb vertical attitude during motion of the FDU. This second inclinometer may measure, quantitatively, the degree to which the fluid connection adapter is currently “out of plumb vertical” during other motion of the FDU. In some FDU embodiments, “out of plumb vertical” information from the second inclinometer may direct the FDU to make automated adjustments to maintain the fluid connection adapter in a constant plumb vertical attitude regardless of the current motion of other FDU components. This feature facilitates, for example, entry of the fluid connection adapter into the fluid connection housing assembly at the wellhead. 
     A further technical advantage of the disclosed fluid delivery system is that it may be remotely operable in preferred embodiments. 
     A further technical advantage of the disclosed fluid delivery system is that it embodiments include swivel joints specifically designed for the high operating pressures and fluid flow volumes demanded by fracturing fluid delivery service. 
     A further technical advantage of the disclosed fluid delivery system is that, in currently preferred embodiments, fluid-bearing piping and fittings include swivel joint embodiments rated for fracking fluid delivery working pressures and delivery volumes. Swivel joint embodiments disclosed herein also allow rotation under operating pressure. Rotation under pressure allows small positional adjustments to be made to the FDU  100  “on the fly” during fluid delivery to a wellhead. The ability to make small positional adjustments “on the fly” maintains continuous fluid flow during such adjustments, thereby allowing, for example, “on the fly” compensation for fluid surges or vibration. In contrast, comparative swivel joints in the prior art are known to require positional (rotational) locking while under operating pressure, and especially while fluid is being delivered to a wellhead. Thus, if the operator does not position the fluid delivery system precisely prior to beginning fluid delivery to a well, fluid delivery may have to be interrupted later on if small positional adjustments need to be made. 
     A further technical advantage of the disclosed fluid delivery system is that in some embodiments, wall thickness monitoring is provided to monitor wall thickness of delivery piping and fittings in locations at risk of loss of wall thickness during service. 
     A further technical advantage of the disclosed fluid delivery system is that some embodiments may provide an integrated nightcap capability. In such embodiments, a nightcap is stored on the stinger assembly. More preferably, the nightcap is positioned longitudinally opposed to the fluid connection adapter on the stinger assembly. In such embodiments, the nightcap assumes a rest position pointing generally upwards while the fluid connection adapter is pointing generally downwards ready for fluid delivery to a wellhead. When the nightcap is desired to be deployed, a user may rotate the stinger assembly so that the nightcap and the fluid connection adapter are inverted. The nightcap is now in position to be inserted into a wellhead. 
     A further technical advantage of the disclosed fluid delivery system is that its design favors robustness and dependability. Embodiments of the disclosed fluid delivery system minimize moving parts and hydraulics in order to enhance robustness at high pressures in larger diameters. 
     In accordance with a first aspect, therefore, this disclosure describes embodiments of a fluid delivery system including a fluid delivery unit (FDU), the FDU comprising: a turret and a stinger assembly separated by first and second boom sections in which the boom sections are concatenated via a rotatable connection; a fluid inlet; a fluid connection adapter deployed on the stinger assembly; and a plurality of swivel joints, such that the fluid inlet, the swivel joints and the fluid connection adapter are in fluid flow communication; wherein: (1) each boom section has a turret end and a stinger end; (2) the turret end of the first boom section is rotatably connected to the turret; and (3) the stinger end of the second boom section is rotatably connected to the stinger assembly; wherein rotation of the turret defines rotation about an axis A 1  on a directional bearing B 1 ; wherein rotation of the turret end of the first boom section about the turret defines rotation about an axis A 2  on a directional bearing B 2 ; wherein rotation of the turret end of the second boom section about the stinger end of the first boom section defines rotation about an axis A 3  on a corresponding directional bearing B 3 ; wherein rotation of the stinger assembly about the stinger end of the second boom section defines rotation about an axis A 4  on a corresponding directional bearing B 4 ; wherein the stinger assembly is further configured to rotate about an axis A 5  on a corresponding directional bearing B 5 ; wherein the FDU further includes a plurality of rotary encoders R[1 . . . 5], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . 5] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . 5] to establish sets of measured bearings values B VAL [1 . . . 5], wherein sets of B VAL [1 . . . 5] define corresponding spatial positions for the FDU; wherein the FDU is configured to store and recall sets of B VAL [1 . . . 5]; wherein the FDU is further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . 5]. 
     In embodiments according to the first aspect, rotation about axis A 5  is in an orthogonal plane to rotation about axis A 4 . 
     In embodiments according to the first aspect, a controller is configured, via wireless communication, to allow a user to perform at least one activity selected from the group consisting of: (a) actuating rotation about selected ones of axes A[1 . . . 5]; (b) deploying a nightcap positioned on the stinger assembly; and (c) storing and recalling sets of B VAL [1 . . . 5]. 
     In embodiments according to the first aspect, a first inclinometer is configured to correct sets of B VAL [1 . . . 5] for the FDU being out of out of level. 
     In embodiments according to the first aspect, a second inclinometer is configured to maintain the fluid connection adapter in a constant plumb vertical attitude during motion of the FDU. 
     In embodiments according to the first aspect, at least one swivel joint includes: a first elbow, an annular lip formed on the first elbow, a first housing piece received over the first elbow and retained by the annular lip; a second elbow, an exterior threaded pin surface formed on the second elbow, a second housing piece received over the second elbow; a swivel collet, wherein swivel collet threads on the swivel collet threadably engage with the threaded pin surface such that the second housing piece is retained by the swivel collet; first and second rotary bearings separated by the swivel collet such that the first housing piece is received over the second rotary bearing and the second housing piece is received over the first rotary bearing, wherein rigid connection of the first and second housing pieces allows independent differential rotation between the first and second elbows about the first and second rotary bearings. 
     In embodiments according to the first aspect, at least one swivel joint includes: a first elbow, an annular lip formed on the first elbow, a first housing piece received over the first elbow and retained by the annular lip; an integral pin, an annular rib formed on a proximal end of the integral pin, a second housing piece received over the integral pin and retained by the annular rib; first and second rotary bearings separated by the annular rib such that the first housing piece is received over the second rotary bearing and the second housing piece is received over the first rotary bearing, wherein rigid connection of the first and second housing pieces allows independent differential rotation between the first elbow and the integral pin about the first and second rotary bearings. In some embodiments, a second elbow is rigidly connected to a distal end of the integral pin. 
     In some embodiments according to the first aspect, a slew drive is configured to actuate rotation about at least one of axes A[1 . . . 5]. In other embodiments according to the first aspect, a piston is configured actuate at least one of axes A[1 . . . 5]. 
     In accordance with a second aspect, this disclosure describes embodiments of a fluid delivery system including a fluid delivery unit (FDU), the FDU comprising: a turret and a stinger assembly separated by first and second boom sections in which the boom sections are concatenated via a rotatable connection; a fluid inlet; a fluid connection adapter deployed on the stinger assembly; and a plurality of swivel joints, each swivel joint having an internal diameter of not less than about 7 inches, each swivel joint further capable of rotation while retaining an internal pressure of not less than about 10,000 psi; wherein the fluid inlet, the swivel joints and the fluid connection adapter are in fluid flow communication; wherein: (1) each boom section has a turret end and a stinger end; (2) the turret end of the first boom section is rotatably connected to the turret; and (3) the stinger end of the second boom section is rotatably connected to the stinger assembly; wherein rotation of the turret defines rotation about an axis A 1  on a directional bearing B 1 ; wherein rotation of the turret end of the first boom section about the turret defines rotation about an axis A 2  on a directional bearing B 2 ; wherein rotation of the turret end of the second boom section about the stinger end of the first boom section defines rotation about an axis A 3  on a corresponding directional bearing B 3 ; wherein rotation of the stinger assembly about the stinger end of the second boom section defines rotation about an axis A 4  on a corresponding directional bearing B 4 ; wherein the stinger assembly is further configured to rotate about an axis A 5  on a corresponding directional bearing B 5 ; wherein the FDU further includes a plurality of rotary encoders R[1 . . . 5], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . 5] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . 5] to establish sets of measured bearings values B VAL [1 . . . 5], wherein sets of B VAL [1 . . . 5] define corresponding spatial positions for the FDU; wherein the FDU is configured to store and recall sets of B VAL [1 . . . 5]; wherein the FDU is further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . 5]. 
     In embodiments according to the second aspect, rotation about axis A 5  is in an orthogonal plane to rotation about axis A 4 . 
     In embodiments according to the second aspect, a controller is configured, via wireless communication, to allow a user to perform at least one activity selected from the group consisting of: (a) actuating rotation about selected ones of axes A[1 . . . 5]; (b) deploying a nightcap positioned on the stinger assembly; and (c) storing and recalling sets of B VAL [1 . . . 5]. 
     In embodiments according to the second aspect, a first inclinometer is configured to correct sets of B VAL [1 . . . 5] for the FDU being out of out of level. 
     In embodiments according to the second aspect, a second inclinometer is configured to maintain the fluid connection adapter in a constant plumb vertical attitude during motion of the FDU. 
     In embodiments according to the second aspect, at least one swivel joint includes: a first elbow, an annular lip formed on the first elbow, a first housing piece received over the first elbow and retained by the annular lip; a second elbow, an exterior threaded pin surface formed on the second elbow, a second housing piece received over the second elbow; a swivel collet, wherein swivel collet threads on the swivel collet threadably engage with the threaded pin surface such that the second housing piece is retained by the swivel collet; first and second rotary bearings separated by the swivel collet such that the first housing piece is received over the second rotary bearing and the second housing piece is received over the first rotary bearing, wherein rigid connection of the first and second housing pieces allows independent differential rotation between the first and second elbows about the first and second rotary bearings. 
     In embodiments according to the second aspect, at least one swivel joint includes: a first elbow, an annular lip formed on the first elbow, a first housing piece received over the first elbow and retained by the annular lip, an integral pin, an annular rib formed on a proximal end of the integral pin, a second housing piece received over the integral pin and retained by the annular rib; first and second rotary bearings separated by the annular rib such that the first housing piece is received over the second rotary bearing and the second housing piece is received over the first rotary bearing, wherein rigid connection of the first and second housing pieces allows independent differential rotation between the first elbow and the integral pin about the first and second rotary bearings. In such embodiments, a second elbow is rigidly connected to a distal end of the integral pin. 
     In accordance with a third aspect, this disclosure describes embodiments of a fluid delivery system including a fluid delivery unit (FDU), the FDU comprising: a turret and a stinger assembly separated by a plurality of concatenated boom sections S[1 . . . N] in which adjacent boom sections are connected via rotatable connections; a fluid inlet; a fluid connection adapter deployed on the stinger assembly; a plurality of swivel joints, such that the fluid inlet, the swivel joints and the fluid connection adapter are in fluid flow communication; wherein: (1) each boom section has a turret end and a stinger end; (2) the turret end of boom section S[1] is rotatably connected to the turret; (3) the stinger end of one boom section S[1 . . . N−1] is rotatably connected to the turret end of an adjacent boom section S[2 . . . N]; and (4) the stinger end of boom section S[N] is rotatably connected to the stinger assembly; wherein rotation of the turret defines rotation about an axis A[1] on a directional bearing B[1]; wherein rotation of the turret end of boom section S[1] about the turret defines rotation about an axis A[2] on a directional bearing B[2]; wherein rotation of the turret end of one boom section S[2 . . . N] about the stinger end of an adjacent boom section S[1 . . . N−1] defines rotation about a corresponding axis A[3 . . . N+1] on a corresponding directional bearing B[3 . . . N+1]; wherein rotation of the stinger assembly about the stinger end of boom section S[N] defines rotation about an axis A[N+2] on a corresponding directional bearing B[N+2]; wherein the stinger assembly is further configured to rotate about Q additional rotational axes A[N+3 . . . N+2+Q] each on a corresponding directional bearing B[N+3 . . . N+2+Q]; wherein the FDU further includes a plurality of rotary encoders R[1 . . . N+2+Q], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . N+2+Q] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . N+2+Q] to establish sets of measured directional bearings values B VAL [1 . . . N+2+Q], wherein sets of B VAL [1 . . . N+2+Q] define corresponding spatial positions for the FDU; wherein the FDU is configured to store and recall sets of B VAL [1 . . . N+2+Q]; wherein the FDU is further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . N+2+Q]. 
     In embodiments according to the third aspect, rotation about one of axes A[N+3 . . . N+2+Q] is in an orthogonal plane to rotation about axis A[N+2]. 
     In embodiments according to the third aspect, a controller is configured, via wireless communication, to allow a user to perform at least one activity selected from the group consisting of: (a) actuating rotation about selected ones of axes A[1 . . . N+2+Q]; (b) deploying a nightcap positioned on the stinger assembly; and (c) storing and recalling sets of B VAL [1 . . . N+2+Q]. 
     In embodiments according to the third aspect, a first inclinometer corrects sets of B VAL [1 . . . N+2+Q] for the FDU being out of out of level. 
     In embodiments according to the third aspect, a second inclinometer maintains the fluid connection adapter in a constant plumb vertical attitude during motion of the FDU. 
     In embodiments according to the third aspect, at least one swivel joint includes: a first elbow, an annular lip formed on the first elbow, a first housing piece received over the first elbow and retained by the annular lip; a second elbow, an exterior threaded pin surface formed on the second elbow, a second housing piece received over the second elbow; a swivel collet, wherein swivel collet threads on the swivel collet threadably engage with the threaded pin surface such that the second housing piece is retained by the swivel collet; first and second rotary bearings separated by the swivel collet such that the first housing piece is received over the second rotary bearing and the second housing piece is received over the first rotary bearing, wherein rigid connection of the first and second housing pieces allows independent differential rotation between the first and second elbows about the first and second rotary bearings. 
     In embodiments according to the third aspect, at least one swivel joint includes: a first elbow, an annular lip formed on the first elbow, a first housing piece received over the first elbow and retained by the annular lip, an integral pin, an annular rib formed on a proximal end of the integral pin, a second housing piece received over the integral pin and retained by the annular rib; first and second rotary bearings separated by the annular rib such that the first housing piece is received over the second rotary bearing and the second housing piece is received over the first rotary bearing, wherein rigid connection of the first and second housing pieces allows independent differential rotation between the first elbow and the integral pin about the first and second rotary bearings. In such embodiments, a second elbow is rigidly connected to a distal end of the integral pin. 
     In some embodiments according to the third aspect, a slew drive is configured to actuate rotation about at least one of axes A[1 . . . N+2+Q]. In other embodiments according to the third aspect, a piston is configured actuate at least one of axes A[1 . . . N+2+Q]. 
     In accordance with a fourth aspect, this disclosure describes embodiments of a fluid delivery system including a fluid delivery unit (FDU), the FDU comprising: a turret and a stinger assembly separated by a plurality of concatenated boom sections S[1 . . . N] in which adjacent boom sections are connected via rotatable connections; a fluid inlet; a fluid connection adapter deployed on the stinger assembly; a plurality of swivel joints, such that the fluid inlet, the swivel joints and the fluid connection adapter are in fluid flow communication; wherein: (1) each boom section has a turret end and a stinger end; (2) the turret end of boom section S[1] is rotatably connected to the turret; (3) the stinger end of one boom section S[1 . . . N−1] is rotatably connected to the turret end of an adjacent boom section S[2 . . . N]; and (4) the stinger end of boom section S[N] is rotatably connected to the stinger assembly; wherein rotation of the turret defines rotation about an axis A[1] on a directional bearing B[1]; wherein rotation of the turret end of boom section S[1] about the turret defines rotation about an axis A[2] on a directional bearing B[2]; wherein rotation of the turret end of one boom section S[2 . . . N] about the stinger end of an adjacent boom section S[1 . . . N−1] defines rotation about a corresponding axis A[3 . . . N+1] on a corresponding directional bearing B[3 . . . N+1]; wherein rotation of the stinger assembly about the stinger end of boom section S[N] defines rotation about an axis A[N+2] on a corresponding directional bearing B[N+2]; wherein the FDU further includes a plurality of rotary encoders R[1 . . . N+2], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . N+2] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . N+2] to establish sets of measured directional bearings values B VAL [1 . . . N+2], wherein sets of B VAL [1 . . . N+2] define corresponding spatial positions for the FDU; wherein the FDU is configured to store and recall sets of B VAL [1 . . . N+2]; wherein the FDU is further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . N+2]. 
     In embodiments according to the fourth aspect, a controller is configured, via wireless communication, to allow a user to perform at least one activity selected from the group consisting of: (a) actuating rotation about selected ones of axes A[1 . . . N+2]; (b) deploying a nightcap positioned on the stinger assembly; and (c) storing and recalling sets of B VAL [1 . . . N+2]. 
     The foregoing has outlined rather broadly some of the features and technical advantages of the technology embodied in the disclosed fluid delivery system technology, in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosed technology may be described. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same inventive purposes of the disclosed technology, and that these equivalent constructions do not depart from the spirit and scope of the technology as described and as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of embodiments described in detail below, and the advantages thereof, reference is now made to the following drawings, in which: 
         FIG.  1    illustrates one prior art arrangement for delivery of fluid to selected wellheads; 
         FIG.  2    illustrates another prior art arrangement for delivery of fluid to a selected wellhead; 
         FIG.  3    illustrates an embodiment of Fluid Delivery Unit (FDU)  100  delivering fluid to selected wellheads in accordance with this disclosure; 
         FIG.  4    further illustrates an embodiment of Fluid Delivery Unit (FDU)  100  delivering fluid to selected wellheads in accordance with this disclosure; 
         FIG.  5    is an elevation view of an embodiment of FDU  100  according to this disclosure; 
         FIG.  6    is a perspective view of spatial positioning of FDU  100  embodiments according this disclosure, illustrating rotation axes A 1  through A 5  on which corresponding directional bearings B 1  through B 5  may be selected; 
         FIG.  7    is a further perspective view of an embodiment of FDU  100  according to this disclosure, in which spatial positioning and other aspects of FDU  100  are under control of controller  200 ; 
         FIG.  8    illustrates a currently preferred embodiment of controller  200 ; 
         FIG.  9    illustrates, in isolation, a currently preferred layout of connected fluid-bearing piping and fittings on board an embodiment of FDU  100  according to this disclosure; 
         FIG.  10    is an enlarged view as shown on  FIG.  9   ; 
         FIGS.  1 A,  11 B and  11 C  illustrate assembled, section and exploded views respectively of swivel joint embodiment  500 A; 
         FIGS.  12 A,  12 B and  12 C  illustrate assembled, section and exploded views respectively of swivel joint embodiment  500 B; 
         FIG.  13 A  illustrates currently preferred embodiments of stinger assembly  600  in detail, and of nightcap  1000  generally; 
         FIG.  13 B  is a section as shown on  FIG.  13 A ; 
         FIG.  13 C  is an exploded view of  FIG.  13 A ; 
         FIGS.  14 A,  14 B and  14 C  illustrate a currently preferred embodiment of nightcap  1000  and its associated features; and 
         FIG.  15    is a schematic generally illustrating wall thickness monitoring according to this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of embodiments provides non-limiting representative examples using Figures and schematics with part numbers and other notation to describe features and teachings of different aspects of the disclosed technology in more detail. The embodiments described should be recognized as capable of implementation separately, or in combination, with other embodiments from the description of the embodiments. A person of ordinary skill in the art reviewing the description of embodiments will be capable of learning and understanding the different described aspects of the technology. The description of embodiments should facilitate understanding of the technology to such an extent that other implementations and embodiments, although not specifically covered but within the understanding of a person of skill in the art having read the description of embodiments, would be understood to be consistent with an application of the disclosed technology. 
       FIGS.  1  and  2    of this disclosure illustrate examples of the prior art on which the disclosed technology seeks to improve.  FIGS.  1  and  2    are discussed in detail above in the “Background” section. 
       FIGS.  3  through  15    of this disclosure illustrate currently preferred embodiments of the disclosed fluid delivery system technology. For the purposes of the following disclosure,  FIGS.  3  through  15    should be viewed together. Any part, item, or feature that is identified by part number on one of  FIGS.  3  through  15    will have the same part number when illustrated on another of  FIGS.  3  through  15   . It will be understood that the embodiments as illustrated and described with respect to  FIGS.  3  through  15    are exemplary only and serve to illustrate the larger concept of the technology. The inventive material set forth in this disclosure is not limited to such illustrated and described embodiments. 
     Fluid Delivery Unit (FDU)  100   
       FIGS.  3  and  4    illustrate an embodiment of Fluid Delivery Unit (FDU)  100  delivering fluid to selected wellheads W 1  through W 4  in accordance with this disclosure.  FIG.  3    is a general plan drawing, and  FIG.  4    is a general perspective drawing, each illustrating a currently preferred embodiment of FDU  100  in an exemplary jobsite deployment.  FIG.  5    is an elevation view of an embodiment of FDU  100  by itself.  FIGS.  6  and  7    are perspective views illustrating currently preferred embodiments of spatial positioning of the FDU  100  embodiment of  FIG.  5   . Spatial positioning is described in detail in a separate section of this disclosure further below.  FIG.  9    illustrates, in isolation, a currently preferred layout of connected fluid-bearing piping and fittings on board the FDU  100  embodiment of  FIG.  5   . Generally,  FIG.  9    depicts such fluid-bearing piping and fittings including a fluid inlet  106 , a plurality of swivel joints  500 A,  500 B and a fluid connection adapter  900  all in fluid flow communication.  FIG.  10    is an enlarged view as shown on  FIG.  9   . 
       FIGS.  3  and  4    illustrate FDU  100  deployed on site via truck trailer T. Deployment on truck trailer T is currently preferred for convenience in bringing FDU  100  to a desired location. However, the scope of this disclosure is not limited to the manner by which FDU  100  is deployed on site.  FIGS.  3  and  4    (and especially  FIG.  4   ) further illustrate FDU  100  deployed to deliver fluid (such as fracking fluid) to selected wellheads W 1  through W 4  within reach of FDU  100 . Again, the scope of this disclosure is not limited to fracking fluid delivery service. FDU  100  may also be deployed in other applications for which it is suited. 
     It will be appreciated from  FIGS.  3  and  4    that FDU  100  is disposed to deliver fluid anywhere within its range. Depiction on  FIGS.  3  and  4    of delivery to a selected one of wellheads W 1  through W 4  is for illustrative convenience only. Currently preferred embodiments of FDU  100  include rotating base turret  102  which, as may be seen on  FIG.  4   , enables FDU  100  to deliver fluid anywhere within range on a 360-degree rotation of turret  102 . For more examples of possible fluid delivery ranges for some embodiments, see  FIG.  4 B  and associated disclosure of commonly-assigned U.S. Provisional Patent Application Ser. No. 62/811,595, filed Feb. 28, 2019 (the disclosure of which provisional application is incorporated herein by reference). It will nonetheless be understood that fluid delivery ranges illustrated on  FIGS.  3  and  4    hereof, and on FIG. 4B of Ser. No. 62/811,595 are exemplary only and that the scope of this disclosure is not limited to such illustrated fluid delivery ranges. Further, both smaller scale and larger scale embodiments of FDU  100  are within the scope hereof. 
       FIG.  3    shows FDU  100  receiving fluid ultimately from pumping units  10 . As with the prior art depiction of  FIG.  1   , pumping units  10  may be conventional fracking pump and delivery trucks (as illustrated), although the scope of this disclosure is indifferent to the manner by which fluid is ultimately made available to FDU  100 . On  FIG.  3   , pumping units  10  deliver fluid at pressure into manifold M 1 . Again as with the prior art depiction of  FIG.  1   , manifold M 1  may be known colloquially as a “missile” in some embodiments. Fluid transfer lines  20  on  FIG.  3    deliver fluid from manifold M 1  to FDU fluid inlet  106 . Seen more clearly on  FIGS.  5 ,  6  and  7   , the illustrated embodiment of FDU fluid inlet  106  may be of the manifold style commonly referred to as a “goat head” in oilfield fracking and well completion operations, with a hollow body providing multiple connection points (e.g. flange faces) to connect to individual fluid transfer lines  20 . In the embodiment illustrated on  FIG.  3    through  FIG.  7   , up to seven (7) fluid transfer lines  20  may be connected to FDU fluid inlet  106  for delivery of fluid by FDU  100  to selected wells within reach of FDU  100 . It will nonetheless be appreciated that FDU fluid inlet  106  as illustrated on  FIG.  3    through  FIG.  7    is exemplary only, and other non-illustrated embodiments may provide more or fewer supply lines. The scope of this disclosure is not limited to any particular design of FDU fluid inlet  106 . Moreover, although not illustrated, additional fluid pressure (e.g. via additional pumping) may be provided in some embodiments between manifold M 1  and FDU inlet manifold  106 . Such additional fluid pressure, if required, helps ensure FDU  100  is receiving fluid for delivering to wellheads at desired service pressures and flow rates/volumes. 
       FIG.  4    illustrates FDU  100  providing stinger assembly  600  at a distal delivery end thereof. Stinger assembly  600  is described in greater detail below in a separate section of this disclosure. However,  FIG.  4    depicts stinger assembly  600  including fluid connection adapter  900 .  FIG.  4    also shows each wellhead W 1  through W 4  disposed to receive fluid via a fluid connection housing assembly  950  connected to the top thereof. Fluid connection housing assemblies  950  are advantageously alike in that fluid connection adapter  900  on stinger assembly  600  is configured to be received and locked into any one of a desired fluid connection housing assembly  950  prior to delivery of fluid to a corresponding wellhead W 1  through W 4 . 
     Currently preferred embodiments of fluid connection adapter  900  and fluid connection housing assembly  950  are consistent with embodiments described in the following commonly-assigned disclosures, all of which are incorporated herein by reference: U.S. Provisional Patent Application Ser. No. 62/649,008 filed Mar. 28, 2018; U.S. Nonprovisional patent application Ser. No. 16/037,687 filed Jul. 17, 2018; and U.S. Nonprovisional patent application Ser. No. 16/221,279 filed Dec. 14, 2018 (collectively the “Preferred Fluid Connection Designs”). It will be nonetheless understood that although currently preferred embodiments deploy fluid connection adapter  900  and fluid connection housing assembly  950  consistent with the Preferred Fluid Connection Designs, the scope of this disclosure is not limited to any particular design of connection between stinger assembly  600  and wellheads W 1  through W 4 . 
       FIG.  5    is an elevation view of an embodiment of FDU  100  according to this disclosure. As described above with respect to  FIGS.  3  and  4   ,  FIG.  5    shows FDU  100  preferably deployed on site via truck trailer T, although the scope if this disclosure is not limited in this regard. The embodiment of FDU  100  on  FIG.  5    provides FDU superstructure  101  rigidly attached to truck trailer T. As shown on  FIGS.  4  and  5   , FDU superstructure  101  provides conventional outriggers OR for stabilizing and leveling FDU  100 . In other embodiments, outriggers OR may be connected to truck trailer T. The scope of this disclosure is not limited to the manner in which FDU  100  may be stabilized and leveled. Conventional hydraulic controls may actuate and manipulate outriggers OR to set FDU  100  in stable and level fashion on the local terrain. 
     FDU  100  on  FIG.  5    further includes rotating base turret  102 . Turret  102  is disposed to rotate about FDU superstructure  101 . As previously described with reference to  FIG.  4   , preferred embodiments of turret  102  enable FDU  100  to deliver fluid anywhere within range on a 360-degree rotation of turret  102 .  FIG.  5    further depicts first boom section  103  and second boom section  104 . First and second boom sections  103 ,  104  are concatenated via a rotatable connection to be further described below. First boom section  103  has a turret end  103 T and a stinger end  103 S (referring to stinger assembly  600 , also shown on  FIG.  5   ). Second boom section  104  also has a turret end  104 T and a stinger end  104 S. Turret end  103 T of first boom section  103  is rotatably connected to turret  102  as described further below with reference to  FIG.  6   . As shown on  FIG.  5   , rotation of first boom section  103  about turret  102  is actuated by extension and retraction of first boom piston  105 A. Stinger end  103 S of first boom section  103  connects to turret end  104 T of second boom section  104  also via a rotating connection described further below with reference to  FIG.  6   . As shown on  FIG.  5   , rotation of second boom section  104  about first boom section  103  is actuated by extension and retraction of second boom piston  105 B. Stinger end  104 S of second boom section  104  is rotatably connected to stinger assembly  600  also as described further below with reference to  FIG.  6    and  FIGS.  13 A,  13 B and  13 C . Actuation of rotation of stinger assembly  600  about second boom section  104  is described in detail further below in a separate section of this disclosure. 
     It will therefore be appreciated from  FIG.  5    that first and second boom sections  103 ,  104  on FDU  100  are articulated boom sections connected via rotating connections whose independent rotation allows FDU  100  to deploy stinger assembly  600  (and fluid connection adapter  900 ) to reach and connect to selected wellheads within range. Preferred embodiments, as illustrated, provide two (2) concatenated boom sections  103 ,  104 . The scope of this disclosure is not limited, however, to two (2) concatenated boom sections  103 ,  104 , and other embodiments (not illustrated) may deploy more or fewer concatenated articulated boom sections. 
     In preferred embodiments illustrated and described with reference to  FIGS.  7  and  8   , operators may use remote-controlled spatial positioning to rotate turret  102  and extend/retract boom sections  103 ,  104  in order to deploy stinger assembly  600  (and fluid connection adapter  900 ) to reach and connect to selected wellheads within range. Such spatial positioning is described in detail further below in a separate section of this disclosure. In other embodiments (not illustrated), conventional hydraulic controls may enable user-operated rotation of turret  102  and user-operated extension/retraction of boom section  103 ,  104  as required to deploy stinger assembly  600  (and fluid connection adapter  900 ) to reach and connect to selected wellheads within range. The scope of this disclosure is not limited to a particular mode of user control. 
       FIG.  9    illustrates, in isolation, a currently preferred layout of connected fluid-bearing piping and fittings on board the FDU  100  embodiment of  FIG.  5   .  FIG.  10    is an enlarged view as shown on  FIG.  9   .  FIGS.  9  and  10    depict FDU fluid inlet  106  connected by fluid-bearing piping and fittings all the way to fluid connection adapter  900  on stinger assembly  600 . Fluid-bearing piping and fittings include swivel joint embodiments  500 A,  500 B as further described below with reference to  FIGS.  11 A through  11 C  and  FIGS.  12 A through  12 C . Currently preferred embodiments of swivel joints  500 A,  500 B are described in detail below in a separate section of this disclosure. Fluid-bearing piping and fittings on  FIGS.  9  and  10    further include union assemblies  300  and clamp assemblies  400 . Currently preferred embodiments of union assemblies  300  are further described below with reference to  FIGS.  11 A through  11 C . Currently preferred embodiments of clamp assemblies  400  are further described below with reference to  FIGS.  12 A through  12 C . Fluid-bearing piping and fittings on  FIGS.  9  and  10    further include delivery piping  120  and conventional fittings  130  such as standard elbows. 
     It will be appreciated that the scope of this disclosure is not limited to the currently preferred layout of fluid-bearing piping and fittings illustrated on  FIGS.  9  and  10   . The layout illustrated on  FIGS.  9  and  10    is configured for the embodiment of FDU  100  on  FIG.  5   , which itself is an exemplary embodiment of FDU  100 . The layout of fluid-bearing piping and fittings on a particular FDU  100  embodiment will depend on the design of the FDU  100  embodiment. 
     It will be further appreciated that the scope of this disclosure includes embodiments in which FDU does not just deliver fluid from a source to a wellhead W. The scope of this disclosure also includes non-illustrated embodiments in which FDU delivers fluid from a wellhead W to a desired destination. 
     In other, non-illustrated embodiments, fluid-bearing piping could be routed inside boom sections rather than on the side of the boom section. 
     Swivel Joint Embodiments  500 A and  500 B 
     As has been previously noted, currently preferred embodiments of FDU  100  according to this disclosure are designed for delivery of fracking fluid to wellheads. In some FDU  100  embodiments designed for fracking service, fluid-bearing piping and fittings are designed for 7,500 psi (“7.5 ksi”) internal fluid pressures (plus an appropriate factor of safety), and more preferably for 10 ksi internal fluid pressures (plus an appropriate factor of safety), and yet more preferably for 15 ksi internal fluid pressures (plus an appropriate factor of safety). Such FDU  100  embodiments designed for fracking service further deliver fluid volumes suitable for fracking operations downhole. Such fluid delivery volumes typically necessitate a 7″-8″ internal diameter (“ID”). 
     Designing a 7″-8″ ID swivel joint rated for 15 ksi working pressure has proved challenging. Commercially-available swivel joints rated for 15 ksi service are typically available in sizes up to 4″ ID only. Swivel joints with 4″ ID will not deliver the volume of fluid required for fracking operations. Larger ID commercially-available swivel joints have proven unable to withstand the tensile stresses imparted by 15 ksi working pressure. It will be understood that increasing the diameter of the swivel joint while maintaining the operating pressure increases geometrically the tension static load force exerted by the pressure at the ID circumference. Such static load forces act to “break apart” the swivel joint at its outer circumference. 
     As a result, several custom designs have been proposed, designed and tested with Finite Element Analysis (FEA) to arrive at a suitable design for swivel joint embodiments  500 A,  500 B as described herein for fracking fluid delivery service. The disclosure of U.S. Provisional Patent Application Ser. No. 62/811,595, filed Feb. 28, 2019, incorporated herein by reference, describes a previous design PD 1  that had to be rejected for use with fracking fluid delivery service because the FEA indicated that PD 1  would likely fail under load if asked to deliver the volume of fracking fluid required at 15 ksi operating pressure. 
       FIGS.  1 A through  12 C  of this disclosure illustrate two swivel joint embodiments  500 A and  500 B engineered to be suitable for the currently preferred fracking fluid delivery embodiments of FDU  100  described in this disclosure. Differences generally between swivel joint embodiments  500 A and  500 B include that swivel joint embodiment  500 A is a pin and collet design, whereas swivel joint embodiment  500 B is an integral pin design. 
     Swivel joint embodiments  500 A and  500 B, as described and illustrated herein, are the result of a subsequent, refined design of swivel joint that FEA indicated would perform under load if asked to deliver the volume of fracking fluid required at 15 ksi operating pressure. Embodiments of swivel joints  500 A,  500 B were originally selected at 8″ ID in order to be sure to enable FDU  100  to deliver fluid at required volumes. FEA demonstrated that although a performing design in accordance with swivel joints  500 A and  500 B above was available, this 8″ ID design created an undesirably heavy fluid-bearing piping and fittings layout for FDU  100 . 
     Design then moved to a 7″ ID for swivel joint embodiments  500 A,  500 B, with an associated design change to 7″ ID fluid-bearing piping and fittings layout on FDU  100 . It was determined that a 7″ ID assembly would also deliver an acceptable volume of fracking fluid at an operating pressure of 15 ksi. Migrating to a 7″ design brought several technical advantages over the 8″ design: (a) lower overall weight of fluid-bearing piping and fittings layout; (b) wider commercial availability of standard parts such as delivery pipe, flanges and elbows; and (c) higher margin of safety at 15 ksi operating pressure. With regard to the higher margin of safety, FEA showed that the 7″ embodiment would hold up to 1.9 million lbs force static load at the circumference, well exceeding the goal of 1.3 million lbs force static load for 15 ksi rated operating pressure. 
     Referring now to U.S. Provisional Patent Application Ser. No. 62/811,595 (“&#39;595”), filed Feb. 28, 2019, incorporated herein by reference, FIGS. 8A and 8B of &#39;595 depict FEA results for 7″ ID embodiments of swivel joints  500 A and  500 B respectively from  FIGS.  11 A through  12 C  in this disclosure. FIG. 8C of &#39;595 depicts a further FEA chart for a 7″ ID embodiment of swivel joint  500 B from  FIGS.  12 A through  12 C  of this disclosure. As can be seen on FIGS. 8A through 8C of &#39;595, FEA determined that 7″ ID embodiments of swivel joints  500 A and  500 B would perform under load if asked to deliver the volume of fracking fluid required at 15 ksi operating pressure. 
     Swivel joint embodiments  500 A,  500 B on  FIGS.  11 A through  12 C  also allow rotation under operating pressure. This feature is yet a further technical advantage over known prior art swivels in fracking service. Swivel joint embodiments  500 A,  500 B allow such rotation under pressure even while fluid is being delivered to a wellhead. Rotation under pressure in turn allows small positional adjustments to be made to FDU  100  “on the fly” during fracking fluid delivery to a wellhead. The ability to make small positional adjustments “on the fly” maintains continuous fluid flow during such adjustments, and further reduces stresses on FDU  100  and its components. 
     In contrast, comparative swivel joints in the prior art are known to require positional (rotational) locking while under operating pressure, and especially while fluid is being delivered to a wellhead. If, as in the prior art, the swivel joints are locked during fluid delivery, the delivery system is prevented from making small positional adjustments to suit environmental conditions during delivery, such as, for example, to compensate for small displacements due to fluid surges or vibration. Thus, in the prior art, if the operator does not position the fluid delivery system precisely prior to beginning fluid delivery to a well, fluid delivery may have to be interrupted later on if small positional adjustments need to be made. Fluid delivery will have to be stopped to unlock the swivels so that positional adjustment can be made. Further, even if positional adjustments are not needed, the boom components may be unnecessarily stressed with locked swivels if initial positioning is imprecise. 
       FIG.  1 A  depicts an exterior view of swivel joint embodiment  500 A as fully assembled.  FIG.  11 B  is a section as shown on  FIG.  11 A .  FIG.  11 C  is an exploded view of  FIG.  11 A . Looking at  FIGS.  11 A,  11 B and  11 C  together, swivel joint embodiment  500 A includes first elbow  501  with an annular lip  502  formed on a proximal end thereof. When swivel joint  500 A is assembled (refer  FIGS.  11 A and  11 B ), first housing piece  503  is received over first elbow  501  and is retained by annular lip  502 . 
     With further reference to  FIGS.  11 A,  11 B and  11 C  together, first and second housing pieces  503 ,  506  receive rotary bearings  504 A and  504 B separated by swivel collet  505 . Rotary bearings  504 A,  504 B will be described in more detail below. Second elbow  508  has exterior threaded pin surface  509  and exterior seal groove  512  formed on a proximal end thereof. Second housing piece  506  is received over second elbow  508 . Swivel collet  505  has internal swivel collet threads  511  such that, when swivel collet threads are threadably engaged with exterior threaded pin surface  509  on second elbow  508 , second housing piece  506  and rotary bearing  504 A are retained by swivel collet  505 , and second housing piece  506  is received over rotary bearing  504 A. Rotary bearing  504 B is received on the other side of swivel collet  505  from rotary bearing  504 A, and first housing piece  503  is received over rotary bearing  504 B. First and second housing pieces  503 ,  506  are rigidly connected together with fasteners  507 . As fasteners  507  connect first and second housing pieces  503  and  506 , exterior seal groove  512  on second elbow  508  is received into annular lip  502  on first elbow  501 . Seal ring  513 , as received into exterior seal groove  512 , forms a rotating seal between first and second elbows  501 ,  508  while still allowing independent differential rotation between first and second elbows  501 ,  508  within swivel joint embodiment  500 A. 
     Looking further now at  FIGS.  11 A,  11 B and  11 C  together, union assemblies  300  are depicted at the distal ends of each of first and second elbows  501 ,  508 . Union assemblies  300  are preferably alike throughout this disclosure, and are formed by union collet  302  received into union nut  301 . Union nut  301  is then threadably received onto a first fitting (e.g. first or second elbows  501 ,  508  per  FIGS.  11 A,  11 B and  11 C ) via threaded engagement between union nut threads  304  and fitting threads  303  on the first fitting. At the same time, union collet  302  is threadably received onto a second fitting (e.g. one end of fluid connection adapter  900  or one end of a piece of delivery piping  120  per  FIGS.  13 A,  13 B and  13 C )) via threaded engagement between union collet threads  305  and mating threads provided on the end of the second fitting. Preferably the threaded engagement between union collet  302  and the second fitting is via a left hand thread, while the threaded engagement between union nut  301  and the first fitting is via a conventional right hand thread. In this way, when union nut  301  is tightened down on the first fitting, tightening rotation of the threaded engagement between union nut  301  and the first fitting will also cause tightening of the threaded engagement between union collet  302  and the second fitting. 
       FIG.  12 A  depicts an exterior view of swivel joint embodiment  500 B as fully assembled.  FIG.  12 B  is a section as shown on  FIG.  12 A .  FIG.  12 C  is an exploded view of  FIG.  12 A . Looking at  FIGS.  12 A,  12 B and  12 C  together, swivel joint embodiment  500 B includes first elbow  521  with an annular lip  522  provided on a proximal end thereof. When swivel joint  500 B is assembled (refer  FIGS.  12 A and  12 B ), first housing piece  523  is received over first elbow  521  and is retained by annular lip  522 . 
     With further reference to  FIGS.  12 A,  12 B and  12 C  together, first and second housing pieces  523 ,  526  receive rotary bearings  524 A and  524 B such that rotary bearings  524 A,  524 B are separated by annular rib  531  formed on a proximal end of integral pin  525 . Rotary bearings  524 A,  524 B will be described in more detail below. Integral pin  525  provides first and second bearing contact surfaces  528 ,  529  either side of annular rib  531 . Rotary bearing  524 A is received onto second bearing contact surface  529 , and rotary bearing  524 B is received onto first bearing contact surface  528 . Second housing piece  526  is received over rotary bearing  524 A and integral pin  525 . First and second housing pieces  523 ,  526  are rigidly connected together with fasteners  527 . Integral pin  525  also has exterior seal groove  532  provided on the proximal end thereof. As fasteners  527  connect first and second housing pieces  523  and  526 , exterior seal groove  532  on integral pin  525  is received into annular lip  522  on first elbow  521 . Seal ring  533  as received into exterior seal groove  532  forms a rotatable seal between integral pin  525  and first elbow  521  while still allowing independent differential rotation between integral pin  525  and first elbow  521  within swivel joint embodiment  500 B. 
       FIGS.  12 A,  12 B and  12 C  each further depict clamp assembly  400  rigidly connecting a distal end of integral pin  525  to a proximal end of second elbow  536 . Clamp assemblies  400  are preferably alike throughout this disclosure. Clamp assembly  400  includes an annular fitting lip  404  and an annular fitting groove  405  each provided on a proximal end of a fitting to be clamped to integral pin  525  (e.g. on a proximal end of second elbow  536  per  FIGS.  12 A,  12 B and  12 C ). First clamp housing piece  401  is received into fitting groove  405 . Second clamp housing piece  403  is received over the distal end of integral pin  525 . Clamp collet  402  provides internal clamp collet threads  407 . Clamp collet  402  rigidly affixes to the distal end of integral pin  525  via threaded engagement of clamp collet threads  407  with integral pin threads  406  provided on the distal end of integral pin  525 . The distal end of integral pin  525  is then received into fitting lip  404  such that when first and second clamp housing pieces  401 ,  403  are rigidly connected with fasteners  408 , fitting lip  404  bears down tightly on clamp collet  402 . Sealing between integral pin  525  and fitting lip  404  may be provided by conventional o-ring seals or the like. 
     With further reference to  FIGS.  12 A,  12 B and  12 C , it will be understood that clamp assembly  400  is provided to ensure that torque is transmitted into swivel joint embodiment  500 B through integral pin  525 , so that swivel joint  500 B may allow independent differential rotation between first and second elbows  521 ,  536 . By contrast with swivel joint embodiment  500 A on  FIGS.  11 A,  11 B and  11 C , clamp assembly  400  is not needed on swivel joint embodiment  500 A since second elbow  508  transmits torque directly into swivel joint  500 A via threaded engagement with swivel collet  505 , thereby allowing independent differential rotation between first and second elbows  501 ,  508 . 
     Looking further now at  FIGS.  12 A,  12 B and  12 C  together, union assemblies  300  are depicted at the distal ends of each of first and second elbows  521 ,  536 . Union assemblies  300  are preferably alike throughout this disclosure, and are described above in detail with reference to  FIGS.  11 A,  11 B and  11 C . 
     Rotary Bearings Embodiments in Swivel Joint Embodiments  500 A and  500 B 
     Currently preferred embodiments of rotary bearings  504 A,  504 B,  524 A,  524 B are illustrated in exploded form on  FIGS.  11 C and  12 C . It will be understood that such illustrated embodiments are exemplary only, and that the scope of this disclosure is not limited to the currently preferred rotary bearings embodiments illustrated on  FIGS.  11 C and  12 C . Currently preferred embodiments of rotary bearings  504 A,  504 B,  524 A,  524 B are annular thrust bearings, in which a rotary bearing assembly is formed by providing cylindrical roller bearings spaced radially in pockets around an annular plate (cage). The “caged” assembly is then itself interposed between two annular thrust plates (raceways), one above and one below, so that the cylindrical roller bearings in the bearing assembly bear against and roll against the annular thrust plates above and below. Suitable embodiments of rotary bearings  504 A,  504 B,  524 A,  524 B as illustrated on  FIGS.  11 C and  12 C  may include products available from The Timken Company of North Canton, Ohio, U.S.A., with current preference for model 100TP143. Timken advertises this design to be particularly suited to manage high radial loads even when misalignment, poor lubrication, contamination, extreme speeds or critical application stresses are present. As currently advertised by Timken: “Type TP thrust cylindrical roller bearings have two hardened and ground raceways and a window-type steel cage which retains one or more profiled rollers per pocket. When multiple rollers are used in each pocket, they are different lengths and are placed in staggered position relative to rollers in adjacent pockets to create overlapping roller paths. This minimizes wear of the raceways and therefore increases bearing life. Because of the simplicity of their design, type TP bearings are economical.” As noted, however, the scope of this disclosure is not limited to the above-described style of rotary bearings or to Timken® models. 
     Spatial Positioning of Fluid Delivery Unit (FDU)  100   
       FIGS.  6  and  7    depict spatial positioning aspects as deployed on currently preferred embodiments of FDU  100 . As depicted on  FIGS.  6  and  7   , spatial positioning is a mode of user-operated remote control of FDU  100 , in which, for example, fluid connection adapter  900  at a distal end of FDU  100  may be directed to be received into fluid connection housing assembly  950  on a desired target wellhead W T . It will be understood that spatial positioning of FDU  100  under guidance of remote control is an optional feature in accordance with this disclosure. Other embodiments may provide FDU  100  without the remote-controlled spatial positioning feature, in which case FDU  100  may be operated and positioned via conventional manual hydraulic controls. The scope of this disclosure is not limited to FDU  100  embodiments that deploy remote-controlled spatial positioning. 
     Focusing momentarily on currently preferred FDU  100  embodiments that deploy remote-controlled spatial positioning,  FIG.  7    shows that currently preferred FDU  100  embodiments deploy remote user operation via a remotely-operated controller  200  communicating wirelessly with FDU  100 .  FIG.  7    illustrates how the user of such a remotely-operated controller  200  may stand in a safe area that allows good visibility of target wellhead W T , facilitating precise connection between fluid connection adapter  900  and fluid connection housing assembly  950  via remote control operation of FDU  100 . 
     Such wireless communication may preferably be via radio frequency communication RF as shown on  FIG.  7   , although the scope of this disclosure is not limited in this regard.  FIG.  8    depicts one exemplary embodiment of controller  200 , as shown generally on  FIG.  7   .  FIG.  8   &#39;s embodiment of controller  200  is described below in detail in a separate section of this disclosure. It will be nonetheless understood that the scope of this disclosure includes many different embodiments of controller  200  on  FIG.  7    (including different layouts, features, modes and functionalities). 
     It will be further understood that FDU  100  embodiments that deploy spatial positioning are not limited to user operation via remote control. In other embodiments (not illustrated), may provide spatial positioning controls (including different layouts, features, modes and functionalities) deployed directly on truck trailer T or FDU superstructure  101 , for example. 
     Referring now to  FIG.  6   , currently preferred embodiments of FDU  100  provide axes of rotation A 1  through A 5 . As described elsewhere in greater detail in this disclosure, a slew drive is configured to actuate rotation about at least one of axes A[1 . . . 5], and a piston is configured to actuate rotation about at least one of axes A[1 . . . 5]. Rotation about axes A 1  through A 5  are defined as follows in such preferred embodiments: 
     A 1 —Rotation of turret  102  about FDU superstructure  101  (vertical axis); 
     A 2 —Rotation of turret end  103 T of first boom section  103  about turret  102  (horizontal axis); 
     A 3 —Rotation of turret end  104 T of second boom section  104  about stinger end  103 S of first boom section  103  (horizontal axis); 
     A 4 —Rotation of stinger assembly  600  about stinger end  104 S of second boom section  104  (horizontal axis); and 
     A 5 —Further rotation of stinger assembly  600  (horizontal axis). 
     It will be appreciated that axes of rotation A 4  and A 5  are in orthogonal planes to one another. In this way, according to the embodiment illustrated on  FIG.  6   , rotation of FDU  100  components about axes A 1  though A 5  bring about the following motions of fluid connection adapter  900  with respect to fluid connection housing assembly  950  on target wellhead W T : 
     A 1 —Set target azimuth for fluid connection adapter  900  towards target wellhead W T    
     A 2 —Elevate/lower and extend/retract fluid connection adapter  900  along target azimuth 
     A 3 —Further elevate/lower and extend/retract fluid connection adapter  900  along target azimuth 
     A 4 —Rotate (tilt) fluid connection adapter  900  in parallel plane to target azimuth 
     A 5 —Rotate (tilt) fluid connection adapter  900  in orthogonal plane to target azimuth 
     It will be thus seen with reference to  FIG.  6    that establishment of a directional bearing B 1  through B 5  on each of a corresponding one of axes A 1  through A 5  will collectively define a point in space for fluid connection adapter  900  within FDU  100 &#39;s reach. It therefore follows that a set of values B VAL [1 . . . 5] ascribed to each of directional bearings B 1  through B 5  will define the current spatial position for FDU  100 , and in particular for fluid connection adapter  900 . It further follows that a different set of values B VAL [1 . . . 5] ascribed to each of directional bearings B 1  through B 5  will define a corresponding spatial positon for a target for fluid connection adapter  900  on  FIG.  6   , such as fluid connection housing assembly  950  on target wellhead W T . 
     Illustrated embodiments of FDU  100  further include a plurality of rotary encoders R 1  through R 5 , one rotary encoder deployed at each of a corresponding one of axes A 1  through A 5 , such that each rotary encoder is configured to measure a corresponding one of directional bearings B 1  through B 5  to establish sets of measured bearings values B VAL [1 . . . 5]. As described immediately above, sets of B VAL [1 . . . 5] define corresponding spatial positions for FDU  100 . Looking now at  FIG.  7    alongside  FIG.  6   ,  FIG.  7    illustrates rotary encoders R 1  through R 3  provided at each of a corresponding one of axes A 1  through A 3 . Rotary encoders R 1  through R 3  measure current values B VAL [1 . . . 3] of directional bearings B 1  through B 3  at each of a corresponding one of axes A 1  through A 3 . It will be understood that stinger assembly  600  on  FIG.  7    provides rotary encoders R 4  and R 5  at axes A 4  and A 5 , respectively, for measurement of current values B VAL [4, 5] of directional bearings B 4  and B 5 , respectively. Rotary encoders R 4 , R 5  are omitted for clarity on  FIG.  7   , but are illustrated on  FIGS.  13 A,  13 B and  13 C , for example.  FIGS.  13 A,  13 B and  13 C  illustrate stinger assembly  600  in more detail. This disclosure describes stinger assembly  600  (including rotary encoders R 4 , R 5  as shown on  FIGS.  13 A,  13 B and  13 C ) in detail further below in a separate section. Suitable embodiments of rotary encoders R 1  through R 5  may include products available from Turck, Inc. of Minneapolis, Minn., U.S.A., although the scope of this disclosure is not limited in this regard. 
       FIG.  7    also illustrates currently preferred FDU  100  embodiments in which turret slew drive  110  is deployed on FDU superstructure  101 . Turret slew drive  110  rotates turret  102 . Turret slew drive  110  is conventional in preferred embodiments, in which at least one spur gear is provided to engage and drive annular gears on turret  102  so as rotate turret  102  about axis A 1 .  FIG.  7    depicts rotary encoder R 1  deployed in association with turret slew drive  110  as is also known in the art. Rotary encoder R 1  measures a current rotational position for turret  102  about axis A 1  so as to establish a current directional bearing B 1  about axis A 1 . Rotary encoder R 1  then transmits the current directional bearing B 1  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
     Rotary encoder R 2  on  FIG.  7    measures rotation at axis A 2  so as to establish a current directional bearing B 2  at axis A 2 . It will be recalled from earlier disclosure with respect to  FIG.  5    that turret  102  connects rotatably to turret end  103 T of first boom section  103  to establish axis A 2 .  FIG.  7    shows that extension and retraction of first boom piston  105 A actuates rotation about axis A 2 . Rotary encoder R 2  measures a current rotational position for first boom section  103  about axis A 2  so as to establish a current directional bearing B 2  about axis A 2 . Rotary encoder R 2  then transmits the current directional bearing B 2  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
     Rotary encoder R 3  on  FIG.  7    measures rotation at axis A 3  so as to establish a current directional bearing B 3  at axis A 3 . It will be recalled from earlier disclosure with respect to  FIG.  5    that stinger end  103 S of first boom section  103  connects to turret end  104 T of second boom section  104  to establish axis A 3 .  FIG.  7    shows that extension and retraction of second boom piston  105 B actuates rotation about axis A 3 . Rotary encoder R 3  measures a current rotational position for second boom section  104  about axis A 3  so as to establish a current directional bearing B 3  about axis A 3 . Rotary encoder R 3  then transmits the current directional bearing B 3  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
     Rotary encoder R 4  within slew drive  800 (R 4 ) on  FIGS.  13 B and  13 C  measures rotation at axis A 4  so as to establish a current directional bearing B 4  at axis A 4 .  FIG.  6    depicts a connection between stinger end  104 S of second boom section  104  and stinger assembly  600  to establish axis A 4 . As shown in more detail on  FIGS.  13 B and  13 C , stinger assembly  600  includes slew drive  800 (R 4 ) at axis A 4 . Actuation of slew drive  800 (R 4 ) at axis A 4  is described in detail further below with reference to  FIGS.  13 A,  13 B and  13 C  in a separate section of this disclosure. Rotary encoder R 4  within slew drive  800 (R 4 ) measures a current rotational position for stinger assembly  600  about axis A 4  so as to establish a current directional bearing B 4  about axis A 4 . Rotary encoder R 4  then transmits the current directional bearing B 4  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
     Rotary encoder R 5  within slew drive  800 (R 5 ) on  FIGS.  13 B and  13 C  measures rotation at axis A 5  so as to establish a current directional bearing B 5  at axis A 5 .  FIG.  6    depicts axis A 5  on stinger assembly  600 , where axis A 5  is in an orthogonal plane to axis A 4 . As shown in more detail on  FIGS.  13 B and  13 C , stinger assembly  600  includes slew drive  800 (R 5 ) at axis A 5 . Actuation of slew drive  800 (R 5 ) at axis A 5  is described in detail further below with reference to  FIGS.  13 A,  13 B and  13 C  in a separate section of this disclosure. Rotary encoder R 5  within slew drive  800 (R 5 ) measures a current rotational position for stinger assembly  600  about axis A 5  so as to establish a current directional bearing B 5  about axis A 5 . Rotary encoder R 5  then transmits the current directional bearing B 5  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
     In some embodiments, such as those illustrated on  FIG.  7   , FDU  100  provides first inclinometer I 1  deployed, for example, on FDU superstructure  101 . Suitable embodiments of first inclinometer I 1  may include products available from Axiomatic Technologies Corporation of Mississauga, Ontario, Canada, although the scope of this disclosure is not limited in this regard. First inclinometer I 1  is configured to correct sets of B VAL [1 . . . 5] for FDU  100  being “out of level”. More specifically, first inclinometer I 1  is configured to measure, quantitatively, the degree to which FDU  100  stands “out of level” in its current jobsite position. First inclinometer I 1  may send this “out of level” information to storage, memory and/or a data processing unit. The “out of level” information from first inclinometer I 1  may be used to correct current measured bearings values B VAL [1 . . . 5], as measured by rotary encoders R 1  through R 5 , for corresponding “out of level” variances at axes A 1  through A 5 . In some embodiments, first inclinometer I 1  may also be configured to send alarm information when first inclinometer I 1  detects that FDU may be becoming unstable, (i.e. “tipping”). 
     Exemplary operation and control sequences will now be described to give an understanding of spatial positioning on FDU  100  according to preferred embodiments hereof. In such preferred embodiments, the following operation and control sequences may be initiated and executed using controller  200  as illustrated on  FIGS.  7  and  8   . As previously noted, however, the scope of this disclosure is not limited to operation and control of FDU  100  using controller  200  embodiments illustrated on  FIGS.  7  and  8   . 
     With reference to  FIGS.  6  and  7   , a user may desire to operate FDU  100  with the goal of inserting fluid connection adapter  900  into fluid connection housing assembly  950  on target wellhead W T . The user may accomplish this goal, for example, by a combination of: (1) actuating turret slew drive  110  to rotate turret  102  to set a target azimuth for fluid connection adapter  900  towards fluid connection housing assembly  950  on target wellhead W T ; and (2) actuating first and second boom pistons  105 A,  105 B to elevate/lower and extend/retract fluid connection adapter  900  along the target azimuth until fluid connection adapter  900  is positioned generally above fluid connection housing assembly  950 . 
     Referring now to  FIGS.  13 A and  13 B , for example, the user may now actuate slew drive  800 (R 4 ) at axis A 4  and slew drive  800 (R 5 ) at axis A 5  to set fluid connection adapter  900  in a plumb vertical attitude directly above fluid connection housing assembly  950 . Further small adjustments to turret slew drive  110  and first and second boom pistons  105 A,  105 B may also assist with setting fluid connection adapter  900  in the desired plumb vertical attitude. 
     In some embodiments, such as illustrated on  FIG.  7   , stinger assembly provides second inclinometer  12  on stinger assembly  600 . Suitable embodiments of second inclinometer  12  may include products available from Axiomatic Technologies Corporation of Mississauga, Ontario, Canada, although the scope of this disclosure is not limited in this regard.  FIG.  14 A  shows second inclinometer  12  advantageously deployed on nightcap bracket face  1006 , for example, although the scope of this disclosure is not limited in this regard. In currently preferred embodiments on which second inclinometer  12  is deployed, second inclinometer  12  is configured to maintain fluid connection adapter  900  in a constant plumb vertical attitude during motion of FDU  100 . More specifically, second inclinometer  12  is configured to measure, quantitatively, the degree to which fluid connection adapter  900  is currently “out of plumb vertical” as the user actuates turret slew drive  110  and first and second boom pistons  105 A,  105 B to move fluid connection adapter  900  towards a desired target. Second inclinometer  12  may send this “out of plumb vertical” information to storage, memory and/or a data processing unit. The “out of plumb vertical” information from second inclinometer  12  may be used to make corresponding automated adjustments to slew drives  800 (R 4 ) and  800 (R 5 ) to maintain fluid connection adapter  900  in a constant plumb vertical attitude regardless of the current motion of other FDU  100  components. In embodiments deploying second inclinometer  12 , therefore, the user may, for example, move fluid connection adapter  900  directly above a fluid connection housing assembly  950  with fluid connection adapter  900  already set in the desired plumb vertical attitude. 
     In other embodiments, second inclinometer  2  may be configured to maintain fluid connection adapter  900  in a constant attitude other than plumb vertical. The scope of this disclosure is not limited in this regard. For example, it may be known that a target wellhead W T  is a specific rotational amount out of plumb vertical along a particular azimuth. In such cases, second inclinometer  2  may be configured to maintain fluid connection adapter  900  in a corresponding rotational amount out of plumb vertical along a corresponding azimuth. As a result, insertion of fluid connection adapter  900  into fluid connection housing assembly  950  on target wellhead W T  is facilitated. 
     It will now be appreciated that the current set of directional bearing values B VAL [1 . . . 5], as measured by rotary encoders R 1  through R 5  on corresponding axes A 1  through A 5 , represents the current spatial position of fluid connection adapter  900 . In some embodiments, the user may now instruct FDU  100  to “learn” the current spatial position of fluid connection adapter  900  by storing the current set of values B VAL [1 . . . 5] for directional bearings B 1  through B 5  for fluid connection adapter  900  as currently spatially positioned in a plumb vertical attitude directly above fluid connection housing assembly  950 . 
     The user may then insert fluid connection adapter  900  into fluid connection housing assembly  950  by making further small adjustments to first and second boom pistons  105 A,  105 B to lower fluid connection adapter  900  until received in fluid connection housing assembly  950 . Fluid connection adapter  900  may then be locked into fluid connection housing assembly  950 , forming a pressure seal therebetween, and FDU  100  may commence fluid delivery to target wellhead W T . 
     When fluid delivery is complete, fluid connection adapter  900  may be released from fluid connection housing assembly  950 . The user may now operate FDU  100  to withdraw fluid connection adapter  900  from current target wellhead W T . The user may then, consistent with immediately prior disclosure, move fluid connection adapter  900  towards a new target wellhead W T  within range for fluid delivery thereto. Further, also consistent with immediately prior disclosure, the user may instruct FDU  100  to “learn” the current spatial position of fluid connection adapter  900  at the new target wellhead W T  when fluid connection adapter  900  is spatially positioned in a plumb vertical attitude directly above fluid connection housing assembly  950  on the new target wellhead W T . 
     It will thus be appreciated that in preferred embodiments, the user may direct FDU  100  to “return” to previously-visited target wellheads W T , where FDU  100  has previously stored a set of values B VAL [1 . . . 5] for directional bearings B 1  through B 5  corresponding to fluid connection adapter  900 &#39;s spatial position above each of such previously-visited target wellheads W T . It will be recalled that FDU  100  is configured to store and recall sets of B VAL [1 . . . 5], and that FDU  100  is further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . 5]. Thus, the user may direct FDU  100  to “recall” a previously-stored set of directional bearings values B VAL [1 . . . 5] corresponding to a desired previously-visited target wellhead W T . Conventional data processing capability then robotically actuates turret slew drive  110 , first and second boom pistons  105 A,  105 B, and slew drives  800 (R 4 ) and  800 (R 5 ) so that FDU  100  robotically takes up the spatial position corresponding to the recalled set of directional bearings values B VAL [1 . . . 5]. This robotic actuation causes FDU  100  to move fluid connection adapter  900  to the previously-stored spatial position above the currently desired (and previously-visited) target wellhead W T . 
     It will be further appreciated that, consistent with the broader scope of this disclosure, a user may direct FDU  100  to “learn” and then “return” robotically to any desired spatial position within reach. The scope of this disclosure is not limited in this regard. For example, in another embodiment discussed further below, the user may instruct FDU  100  to take up, robotically, a previously-stored “fold” spatial position in which FDU  100  is folded for transport. 
     It will also be understood that the foregoing automated and robotic FDU  100  functionality may be embodied on software or firmware executable by conventional data processing architecture including memory, storage and processors. Referring momentarily to  FIG.  7   , such conventional data processing architecture may be deployed/distributed on FDU  100 , or on controller  200 , or elsewhere, and the scope of this disclosure is not limited to any particular enabling data processing architecture or the manner in which it is deployed on or distributed about FDU  100  generally. 
     This disclosure&#39;s description of spatial positioning has been, up to this point, with reference to currently preferred embodiments as illustrated on  FIGS.  6  and  7   . As noted above, such currently preferred embodiments include FDU configured with turret  102 , first and second boom sections  103 ,  104  and stinger assembly  600 . Independent rotation of these components with respect to one another on illustrated axes of rotation A 1  through A 5  allows measured or ordained spatial positioning of hardware located at a distal end of FDU  100 . The scope of this disclosure is not limited, however, to spatial positioning according to the currently preferred embodiments illustrated on  FIGS.  6  and  7    and described immediately above. The preferred illustrated and described embodiments herein are exemplary only. It will be appreciated that consistent with the more general scope of this disclosure, FDU  100  may include a turret and a stinger assembly separated by a plurality of concatenated boom sections S[1 . . . N], in which adjacent boom sections are connected via rotatable connections, and where N is a preselected number of boom sections according to the desired level of controllability of FDU  100 . In such embodiments, (1) each boom section has a turret end and a stinger end; (2) the turret end of boom section S[1] is rotatably connected to the turret; (3) the stinger end of one boom section S[1 . . . N−1] is rotatably connected to the turret end of an adjacent boom section S[2 . . . N]; and (4) the stinger end of boom section S[N] is rotatably connected to the stinger assembly. 
     In such broader embodiments, rotation of the turret defines rotation about an axis A[1] on a directional bearing B[1]; rotation of the turret end of boom section S[1] about the turret defines rotation about an axis A[2] on a directional bearing B[2]; rotation of the turret end of one boom section S[2 . . . N] about the stinger end of an adjacent boom section S[1 . . . N−1] defines rotation about a corresponding axis A[3 . . . N+1] on a corresponding directional bearing B[3 . . . N+1]; and rotation of the stinger assembly about the stinger end of boom section S[N] defines rotation about an axis A[N+2] on a corresponding directional bearing B[N+2]. 
     In further embodiments, again consistent with the more general scope of this disclosure, the stinger assembly may be further configured to rotate about Q additional rotational axes A[N+3 . . . N+2+Q] each on a corresponding directional bearing B[N+3 . . . N+2+Q]. FDU  100  further includes a plurality of rotary encoders R[1 . . . N+2+Q], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . N+2+Q] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . N+2+Q] to establish sets of measured directional bearings values B VAL [1 . . . N+2+Q], wherein sets of B VAL [1 . . . N+2+Q] define corresponding spatial positions for FDU  100 . FDU  100  may be configured to store and recall sets of B VAL [1 . . . N+2+Q], and further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . N+2+Q]. As described elsewhere in greater detail in this disclosure, a slew drive is configured to actuate rotation about at least one of axes A[1 . . . N+2+Q], and a piston is configured to actuate rotation about at least one of axes A[1 . . . N+2+Q]. 
     The general scope of this disclosure further includes embodiments in which stinger assembly  600  is not configured to rotate about additional axes beyond axis A 4  as illustrated on  FIGS.  6  and  7   . In such embodiments, FDU  100  may include a turret and a stinger assembly separated by first and second boom sections in which the boom sections are concatenated via a rotatable connection. Each boom section has a turret end and a stinger end, the turret end of the first boom section is rotatably connected to the turret; and the stinger end of the second boom section is rotatably connected to the stinger assembly. Rotation of the turret defines rotation about an axis A 1  on a directional bearing B 1 , rotation of the turret end of the first boom section about the turret defines rotation about an axis A 2  on a directional bearing B 2 , rotation of the turret end of the second boom section about the stinger end of the first boom section defines rotation about an axis A 3  on a corresponding directional bearing B 3 , and rotation of the stinger assembly about the stinger end of the second boom section defines rotation about an axis A 4  on a corresponding directional bearing B 4 . In such embodiments, FDU  100  further includes a plurality of rotary encoders R[1 . . . 4], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . 4] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . 4] to establish sets of measured bearings values B VAL [1 . . . 4]. Sets of B VAL [1 . . . 4] define corresponding spatial positions for FDU  100 . Similar to embodiments illustrated on  FIGS.  6  and  7   , FDU  100  may be configured to store and recall sets of B VAL [1 . . . 4], and FDU  10  may be further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . 4]. 
     Referring to the immediately preceding paragraph, it will be further appreciated that consistent with the more general scope of this disclosure, embodiments of FDU  100  may further include a turret and a stinger assembly separated by a plurality of concatenated boom sections S[1 . . . N], in which adjacent boom sections are connected via rotatable connections, and where N is a preselected number of boom sections according to the desired level of controllability of FDU  100 . In such embodiments, (1) each boom section has a turret end and a stinger end; (2) the turret end of boom section S[1] is rotatably connected to the turret; and (3) the stinger end of one boom section S[1 . . . N−1] is rotatably connected to the turret end of an adjacent boom section S[2 . . . N]. 
     In such broader embodiments, rotation of the turret defines rotation about an axis A[1] on a directional bearing B[1]; rotation of the turret end of boom section S[1] about the turret defines rotation about an axis A[2] on a directional bearing B[2]; rotation of the turret end of one boom section S[2 . . . N] about the stinger end of an adjacent boom section S[1 . . . N−1] defines rotation about a corresponding axis A[3 . . . N+1] on a corresponding directional bearing B[3 . . . N+1]; and rotation of the stinger assembly about the stinger end of boom section S[N] defines rotation about an axis A[N+2] on a corresponding directional bearing B[N+2]. 
     FDU  100  further includes a plurality of rotary encoders R[1 . . . N+2], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . N+2] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . N+2] to establish sets of measured directional bearings values B VAL [1 . . . N+2], wherein sets of B VAL [1 . . . N+2] define corresponding spatial positions for FDU  100 . FDU  100  may be configured to store and recall sets of B VAL [1 . . . N+2], and further configured to robotically take up a corresponding spatial position when directed to recall a previously-stored set of B VAL [1 . . . N+2]. 
     Controller  200   
     As described above with reference to  FIG.  7   , preferred embodiments of the disclosed fluid delivery system include remote control of the operation of FDU  100 . In such embodiments, control is preferably via a remote manual controller  200 , in which controller  200  preferably communicates with FDU  100  wirelessly via radio frequency communication RF (although the scope of this disclosure is not limited to such embodiments and preferences). In illustrated embodiments, controller  200  is configured, via wireless communication, to allow a user to perform several activities, including at least one activity selected from the group consisting of: (a) actuating rotation about selected ones of axes A[1 . . . 5]; (b) deploying a nightcap  1000  positioned on the stinger assembly  600 ; and (c) storing and recalling sets of B VAL [1 . . . 5]. 
       FIG.  8    illustrates a currently preferred embodiment of controller  200 . It will be understood that the embodiment of controller  200  depicted on  FIG.  8    is exemplary only, and numerous other alternative layouts of features and functions are within the scope of this disclosure. It will be further understood with reference to  FIG.  8    that alphanumeric references on controller  200  such as “A 1 ”, “H 2 ”, “L 3 ”, “D 4 ” are on-board short hand notations, marked on controller  200  solely to refer to corresponding controller operations used in actual operation of FDU  100 . Such alphanumerics have no relation, however, to similar part numbers used in this disclosure to indicate items on this disclosure&#39;s Figures. Thus, by way of example, “A 1 ” on controller  200  on  FIG.  8    refers solely to an internal controller operation only, and has no relation to this disclosure&#39;s description above of axis A 1  above with reference to  FIG.  6   . 
     Referring to  FIG.  8   , the illustrated embodiment of controller  200  includes boom joysticks  201 ,  202  and  203 . Controller  200  further includes joystick mode selector  204 . Boom joysticks  201 ,  202 ,  203  are all active when joystick mode selector  204  is set to MANUAL. Manual joystick mode allows independent control of rotary motion about each of axes A 1  through A 5  illustrated on  FIG.  6   . Manual joystick mode thus allows higher skill operators to control movement of FDU  100  entirely by manual joystick operation. 
     By contrast, only boom joysticks  201  and  202  are active when joystick mode selector  204  is set to AUTO. In auto joystick mode, operation of joysticks  201 ,  202  switches from rotary motion about axes A 1  through A 5  (per manual joystick mode described immediately above) to an X/Y/Z coordinate system, or to a left/right, in/out, and up/down command system based on joystick movement. This allows lower skill operators to operate FDU  100  with more simplicity. 
     Controller  200  on  FIG.  8    further includes nightcap joystick  205  and nightcap enable switch  205 A. Nightcap  1000  is described in more detail in this disclosure below with reference to  FIGS.  14 A,  14 B and  14 C . Moving nightcap joystick  205  on  FIG.  8    to the NIGHTCAP LOCK position activates nightcap engage/release mechanism  1008  on  FIG.  14 C  to engage on nightcap engagement pin  1009  when desiring, for example, to pull nightcap  1000  from wellhead W. Engaging on nightcap  1000  does not require use of nightcap enable switch  205 A on  FIG.  8   . Moving nightcap joystick  205  on  FIG.  8    to the UNLOCK NIGHTCAP position, however, also requires simultaneous pushing of nightcap enable switch  205 A (on left side of controller  200 ) in order to activate nightcap engage/release mechanism  1008  on  FIG.  14 C  to release nightcap engagement pin  1009 . This feature enhances safe removal of nightcap  1000  from nightcap engage/release mechanism  1008  on  FIG.  14 C  by reducing chances of an accidental nightcap release, for example. 
     As described above with reference to  FIGS.  6  and  7   , currently preferred embodiments of FDU  100  include a feature that allows FDU  100  to “learn” a desired spatial position by storing a set of measured values B VAL [1 . . . 5] for directional bearings B 1  through B 5  on corresponding axes A 1  through A 5  (refer  FIG.  6   ) where the set of measured directional bearing values B VAL [1 . . . 5] represents the “learned” spatial position. Such “learned” spatial positions may include, for example, FDU  100 &#39;s spatial position when delivering fluid to a selected wellhead. Memory within controller  200  may store sets of measured values B VAL [1 . . . 5] for directional bearings B 1  through B 5  corresponding to such “learned” spatial positions. FDU  100  may then, for example, return to the selected wellhead by retrieving the set of directional bearings values B VAL [1 . . . 5] from controller  200 &#39;s memory corresponding to the previously-stored spatial position for the wellhead. 
       FIG.  8    illustrates controller  200  including stored position selector  206  for selecting a desired FDU  100  spatial position to be addressed. Up to 12 (twelve) previously-stored positions may be stored in memory in the embodiment of controller  200  depicted on  FIG.  8   . The scope of this disclosure is not limited in this regard, however. 
     To store a current FDU  100  spatial position, stored position selector  206  is turned to select the memory location in which the current FDU  100  spatial position is desired to be stored. Pushing memory activate switch  206 A (on left side of controller  200 ) simultaneously with pushing store activate switch  206 B (on right side of controller  200 ) will cause controller  200  to store the current FDU  100  spatial position in the selected memory location. 
     To recall a previously-stored FDU  100  spatial position, stored position selector  206  is turned to select the memory location in which the desired previously-stored FDU  100  spatial position stored. Pushing memory activate switch  206 A (on left side of controller  200 ) simultaneously with pushing recall activate switch  206 C (on right side of controller  200 ) causes FDU  100  to move robotically to return to the spatial position previously stored in the selected memory location. As a safety precaution, FDU  100  advantageously moves only so long as both the memory activate switch  206 A and the recall activate switch  206 C are being actively pushed concurrently. Robotic FDU  100  motion stops if either switch is released. Controller  200  advantageously also performs additional safety checks prior to moving FDU  100  automatically, such as checking boom height and clearance. 
       FIG.  8    illustrates controller  200  further including fold mode selectors  207 A and  207 B. Controller  200 &#39;s memory also stores a preset “fold” spatial position in which FDU  100  is folded for transport. Activating fold mode selectors  207 A and  207 B simultaneously moves FDU  100  robotically the preset “fold” spatial position. Again, as a safety precaution, FDU  100  advantageously moves only so long as both fold mode selectors  207 A and  207 B are activated. Robotic FDU  100  motion stops if either of fold mode selectors  207 A or  207 B is deactivated. 
       FIG.  8    illustrates controller  200  further including emergency stop activator  208 . Activating emergency stop activator  208  causes all current motion of FDU  100  to stop immediately, and disables all further FDU  100  motion until emergency stop activator is affirmatively deactivated or reset. 
     Stinger Assembly  600  (and Actuation of Rotation Thereof about Second Boom Section  104 ) 
     As described above,  FIG.  6    depicts stinger assembly  600  connected to stinger end  104 S of second boom section  104  via a rotating connection.  FIG.  6    further depicts fluid connection adapter  900  deployed on stinger assembly  600 . As shown on  FIG.  6   , the rotating connection between stinger end  104 S of second boom section  104  and stinger assembly  600  is at axis A 4 . As further shown on  FIG.  6   , stinger assembly  600  also provides rotation about axis A 5 , where rotation about axis A 5  is in an orthogonal plane to rotation about axis A 4 .  FIGS.  13 A,  13 B and  13 C  illustrate currently preferred embodiments of stinger assembly  600  in detail.  FIG.  13 A  is general arrangement view of assembled stinger assembly  600 .  FIG.  13 B  is a section as shown on  FIG.  13 A , and  FIG.  13 C  is an exploded view of  FIG.  13 A .  FIGS.  13 A,  13 B and  13 C  also illustrate nightcap  1000  generally. Nightcap  1000  is described in detail below with reference to  FIGS.  14 A,  14 B and  14 C  in a separate section of this disclosure. 
     Looking at  FIGS.  13 A,  13 B and  13 C  together, swivel joint embodiment  500 B is rigidly connected to stinger end  104 S of second boom section  104  via boom flange  150 . In preferred embodiments, boom flange may be welded to second boom section  104 , although the scope of this disclosure is not limited to any particular rigid connection of boom flange  150  to second boom section  104 . Boom flange  150  is further preferably attached to swivel joint  500 B via fastener attachment to first housing piece  523 . In some embodiments, boom flange  150  may share fasteners  527  with first housing piece  523 . 
       FIGS.  13 A,  13 B and  13 C  further show first elbow of swivel joint embodiment  500 B rigidly connected to delivery piping  120  via union assembly  300 , all as described above more generally with reference to  FIGS.  12 A through  12 C . Swivel joint  500 B on  FIGS.  13 A through  13 C  also includes clamp assembly  400  for rigid connection with second elbow  536 , all again as described above more generally with reference to  FIGS.  12 A through  12 C . 
       FIGS.  13 A,  13 B and  13 C  further show first elbow  501  of swivel joint embodiment  500 A rigidly connected to swivel embodiment  500 B. It will be appreciated that in the preferred embodiments illustrated on  FIGS.  13 A through  13 C , second elbow  536  on swivel joint  500 B and first elbow  501  on swivel joint  500 A are the same fitting, obviating the need for connection pipe between swivel joints  500 A,  500 B. The scope of this disclosure is not limited in this regard, however. Second elbow  508  on swivel joint  500 A is rigidly connected to fluid connection adapter  900 , preferably via union assembly  300  as described above more generally with reference to  FIGS.  11 A through  11 C . 
       FIGS.  13 B and  13 C  show slew drive  800 (R 4 ) deployed on swivel joint embodiment  500 B and slew drive  800 (R 5 ) deployed on swivel joint embodiment  500 A. Slew drives  800 (R 4 ) and  800 (R 5 ) are conventional in preferred embodiments.  FIG.  13 C  shows slew drives  800 (R 4 ) and  800 (R 5 ) each including a fixed portion  801 , and a rotating portion  802  driven by worm drive  803 . Worm drives  803  each include a rotary encoder (R 4  and R 5 ) respectively. In more detail, worm drives  803  each include a hydraulically-driven worm gear motor plus a rotary encoder on board. The rotary encoder may measure current rotary displacement or set a desired rotary displacement corresponding to directional bearings B 4  or B 5 , as applicable. Suitable embodiments of slew drives  800 (R 4 ) and  800 (R 5 ) may include products available from Cone Drive Operations, Inc. of Traverse City, Mich., U.S.A., although the scope of this disclosure is not limited in this regard. It will also be appreciated that the scope of this disclosure is not limited to use of slew drives. The scope of this disclosure also includes non-illustrated embodiments in which rotation at axes A 1 , A 4  and A 5  is driven by hydraulic motors, hydraulic pistons assemblies, and the like. 
       FIGS.  13 A,  13 B and  13 C  thus illustrate, with additional reference to  FIG.  6   , that in currently preferred embodiments, rotation of swivel joint embodiment  500 B by slew drive  800 (R 4 ) enables rotation of stinger assembly  600  about axis A 4 . In illustrated embodiments, fixed portion  801  on slew drive  800 (R 4 ) connects rigidly to second housing piece  526  of swivel joint  500 B via conventional fasteners, for example. Rotating portion  802  on slew drive  800 (R 4 ) connects rigidly to clamp assembly  400  via bracket  810 . Conventional fasteners may connect rotating portion  802  to bracket  810 , and connect bracket  810  to clamp assembly  400 . In some embodiments, bracket  810  may share fasteners  408  with clamp assembly  400 . Worm drive  803  on slew drive  800 (R 4 ) thus rotates integral pin  525  and second elbow  536  on swivel joint  500 B via connection of rotating portion  802  to clamp assembly  400 . Rotary encoder R 4 , deployed in association with worm drive  803 , measures a current rotational position for swivel joint  500 B about axis A 4  so as to establish a current directional bearing B 4  about axis A 4 . Rotary encoder R 4  then transmits the current directional bearing B 4  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
       FIGS.  13 A,  13 B and  13 C  further illustrate, with additional reference to  FIG.  6   , that in currently preferred embodiments, rotation of swivel joint embodiment  500 A by slew drive  800 (R 5 ) enables rotation of stinger assembly  600  about axis A 5 . In illustrated embodiments, fixed portion  801  on slew drive  800 (R 5 ) connects rigidly to second housing piece  506  of swivel joint  500 A via conventional fasteners, for example. Rotating portion  802  on slew drive  800 (R 5 ) connects rigidly to nightcap bracket flange  1007  on nightcap bracket  1005 . In preferred embodiments, nightcap bracket  1005  attaches to second elbow  508  on swivel joint  500 A. Such attachment may be via conventional fasteners threaded into bosses provided in the exterior wall of second elbow  508 , as illustrated on  FIG.  13 A , for example. The scope of this disclosure is not limited in this regard. Worm drive  803  on slew drive  800 (R 5 ) thus rotates swivel collet  505  and second elbow  508  on swivel joint  500 A via connection of rotating portion  802  ultimately to second elbow  508 . Rotary encoder R 5 , deployed in association with worm drive  803 , measures a current rotational position for swivel joint  500 A about axis A 5  so as to establish a current directional bearing B 5  about axis A 5 . Rotary encoder R 5  then transmits the current directional bearing B 5  in real time to storage, memory and/or a data processing unit as a data element used in overall control of FDU  100 . 
     Nightcap  1000   
       FIGS.  14 A,  14 B and  14 C  illustrate a currently preferred embodiment of nightcap  1000  and its associated features, plus the deployment and operation thereof. Embodiments of nightcap  1000  described in this disclosure should be considered optional in conjunction with embodiments of FDU  100  herein. The scope of this disclosure is not limited as to whether or not FDU  100  embodiments include embodiments of nightcap  1000 . 
       FIG.  14 A  illustrates nightcap  1000  positioned longitudinally opposed to fluid connection adapter  900  on stinger assembly  600 . While preferred embodiments position nightcap  1000  longitudinally opposed to fluid connection adapter  900 , the scope of this disclosure is not limited in this regard. Nightcap engage/release mechanism  1008  includes an engagement receptacle for holding nightcap  1000  by nightcap engagement pin  1009  (engagement receptacle not specifically illustrated, refer  FIG.  14 C  for nightcap engagement pin  1009 ).  FIG.  14 A  shows nightcap engage/release mechanism  1008  deployed within nightcap bracket  1005 . In preferred embodiments, nightcap bracket  1005  attaches to second elbow  508  on swivel joint embodiment  500 A at axis A 5  (refer momentarily to  FIG.  6   ). Such attachment may be as illustrated on  FIG.  14 B , by conventional fasteners threaded into bosses provided in the exterior wall of second elbow  508 . The scope of this disclosure is not limited in this regard.  FIG.  13 C  illustrates preferred embodiments of nightcap bracket  1005  also including nightcap bracket flange  1007  for fastener attachment to rotating portion  802  of slew drive  800 (R 5 ) at axis A 5 . Such flange attachment is also shown on  FIGS.  14 A,  14 B and  14 C  but not called out by part number. Such flange attachment strengthens nightcap bracket  1005 &#39;s overall attachment. 
     It will be further appreciated from  FIGS.  14 A,  14 B and  14 C  that nightcap  1000  and fluid connection adapter  900  are similar in that both are configured to be received and remotely locked into fluid connection housing assembly  950 . Refer above to  FIG.  4    and associated disclosure for discussion of preferred embodiments of fluid connection adapter  900  and fluid connection housing assembly  950 . Refer also, for example, to commonly-assigned U.S. Nonprovisional Patent Application “Remotely Operated Fluid Connection And Seal”, Ser. No. 16/221,279 (referred to herein as the “&#39;279 Disclosure”). The &#39;279 Disclosure is incorporated herein by reference. The following description of nightcap  1000  and fluid connection adapter  900  generally follows and is consistent with the disclosure of FIGS. 3 and 4 of the &#39;279 Disclosure, and paragraphs 0048 and 0049 of the &#39;279 Disclosure. Nightcap  1000  and fluid connection adapter  900  are alternative adapter embodiments. Fluid connection adapter  900  provides an open connection to enable flow into (or out of) the wellhead W when fluid connection adapter  900  is received into fluid connection housing assembly  950 . By contrast, nightcap  1000  provides a blank or closed-off end to enable temporary closure of the wellhead W while nightcap  1000  is received into fluid connection housing assembly  950 . It will thus be appreciated from  FIGS.  14 A,  14 B and  14 C  that nightcap  1000  and fluid connection adapter  900  each share a common configuration at the distal ends thereof (the distal ends to be received into fluid connection housing assembly  950 ). In this way, such common configuration allows nightcap  1000  and fluid connection adapter  900  to be interchangeable when received into fluid connection housing assembly  950 . It will be further appreciated from reference to  FIG.  4    and associated disclosure that nightcap  1000  and fluid connection adapter  900  preferably each share a common configuration from among embodiments disclosed in the Preferred Fluid Connection Designs (as that term is defined above with reference to  FIG.  4   ), although the scope of this disclosure is not limited to the common configuration that nightcap  1000  and fluid connection adapter  900  might share. 
       FIGS.  14 A,  14 B and  14 C  also illustrate deployment and operation of nightcap  1000 . As described above,  FIG.  14 A  depicts, in preferred embodiments, nightcap  1000  positioned longitudinally opposed to fluid connection adapter  900 . In such embodiments, nightcap  1000  assumes a rest position pointing generally upwards while fluid connection adapter  900  points generally downwards during fluid delivery mode. When nightcap  1000  is desired to be deployed at a selected wellhead, the arrow on  FIG.  14 B  shows that slew drive  800 (R 5 ) at axis A 5  may be operated to rotate nightcap bracket  1005  so that nightcap  1000  and fluid connection adapter  900  are inverted. Thus, consistent with  FIG.  14 B , rotation of nightcap bracket  1005  brings nightcap  1000  into position to be inserted into fluid connection housing assembly  950  on a selected wellhead. 
       FIG.  14 C  depicts nightcap  1000  previously brought to a selected wellhead W and inserted and locked into fluid connection housing assembly  950  on the selected wellhead W. In preferred embodiments, such insertion and locking may be according to corresponding disclosure in the &#39;279 Disclosure, incorporated herein by reference. Nightcap engage/release mechanism  1008  may then be actuated to release nightcap bracket  1005  from nightcap  1000  by releasing nightcap engagement pin  1009  from the engagement receptacle within nightcap engage/release mechanism  1008 . As shown by the arrow on  FIG.  14 C , once nightcap bracket  1005  is released from nightcap  1000 , nightcap bracket  1005  may be raised from nightcap  1000 . As described elsewhere in this disclosure, nightcap engage/release mechanism  1008  is preferably actuated remotely from controller  200  (refer  FIGS.  7  and  8    herein and associated disclosure, for example), although the scope of this disclosure is not limited to remote actuation of nightcap engage/release mechanism  1008 . 
     Although not specifically illustrated herein, engagement and pickup of nightcap  1000  from fluid connection housing assembly  950  at a selected wellhead is generally the reverse operation to its deployment as described immediately above. Nightcap bracket  1005  may be brought down onto nightcap  1000  so that nightcap engagement pin  1009  is received into the engagement receptacle within nightcap engage/release mechanism  1008 . Nightcap engage/release mechanism  1008  may then be actuated to engage nightcap engagement pin  1009 . Nightcap  1000  may then be unlocked and released from fluid connection housing assembly  950 . In preferred embodiments, such unlocking and release from fluid connection housing assembly  950  may be according to corresponding disclosure in the &#39;279 Disclosure, incorporated herein by reference. Once nightcap  1000  is unlocked and released from fluid connection housing assembly  950 , nightcap bracket  1005  may be raised from fluid connection housing assembly  950  with nightcap  1000  attached. Nightcap engage/release mechanism  1008  is again preferably actuated remotely from controller  200  (refer  FIGS.  7  and  8    herein and associated disclosure, for example), although the scope of this disclosure is not limited to remote actuation of nightcap engage/release mechanism  1008 . 
     Wall Thickness Monitoring of Fluid-Bearing Pipe and Fittings 
     It will be appreciated that services and applications for which FDU  100  is designed include delivery of fluids that may be abrasive or corrosive to delivery pipe and fittings. Just by way of example, fracking fluids known in the art may contain solids that cause internal abrasion to delivery pipe and fittings when delivered at operational delivery pressures and volumes (speeds). Further, fracking fluids known in the art may contain ingredients that while beneficial to fracking operations, may also be internally corrosive to delivery pipe and fittings. 
     In such services and applications, therefore, it is advantageous to monitor wall thickness of delivery piping and fittings in selected regions and locations, where such selected regions and locations are at risk of loss of wall thickness during service. Preferably, such wall thickness monitoring is in real time, although the scope of this disclosure is not limited in this regard. 
       FIG.  15    is a schematic generally illustrating wall thickness monitoring according to this disclosure.  FIG.  15    depicts a section through fluid-bearing pipe or fitting  700 . The schematic of  FIG.  15    illustrates fluid-bearing pipe or fitting  700  generically with exemplary depiction of a conventional elbow fitting. However, the use of an elbow fitting on  FIG.  15    is exemplary only, and fluid-bearing pipe or fitting  700  may be any fluid-bearing fitting or length of fluid-bearing pipe, and the scope of this disclosure is not limited in this regard. 
       FIG.  15    further illustrates fluid flow vectors V within fluid bearing pipe or fitting  700 . The schematic of  FIG.  15    uses a convention in which fluid flow vectors V depict expected directions of flow, and in which larger fluid flow vectors V represent expected areas of faster flow. The overall fluid flow pattern depicted by fluid flow vectors V on  FIG.  15    would be expected by those of ordinary skill in the art, in that, at least with respect to the depicted elbow fitting, faster flow is expected near the inside turn and then towards the outside inner wall. 
     As noted above, faster flow of abrasive or corrosive fluids (such as commonly seen in fracking operations, for example) suggests that, at least with respect to the elbow fitting depicted on  FIG.  15   , wall thickness of the fitting may be expected to be at risk of loss near the inside turn and on the outside inner wall after the turn.  FIG.  15    depicts wall thickness sensors  750  deployed on the outside of fluid-bearing pipe or fitting  700  at these locations. Wall thickness sensors  750  are conventional, and may send wall thickness information periodically to conventional data processing equipment such as computers or digital monitors. Such data processing equipment may alert users that the wall thickness at the sensed locations has been lost to a point where fluid-bearing pipe or fitting  700  no longer has sufficient wall thickness to carry fluid safely at desired operating pressures and flows. Suitable embodiments of wall thickness sensors  750  may include products available from Dakota Ultrasonics Corporation of Scotts Valley, Calif., U.S.A., although the scope of this disclosure is not limited in this regard. 
     In other embodiments, this disclosure further describes a method for delivering fluid, the method comprising the steps of: 
     (a) providing a fluid delivery unit (FDU), comprising: a turret and a stinger assembly separated by first and second boom sections in which the boom sections are concatenated via a rotatable connection; a fluid inlet; a fluid connection adapter deployed on the stinger assembly; and a plurality of swivel joints, wherein the fluid inlet, the swivel joints and the fluid connection adapter are in fluid flow communication along a FDU fluid pathway; wherein: (1) each boom section has a turret end and a stinger end; (2) the turret end of the first boom section is rotatably connected to the turret; and (3) the stinger end of the second boom section is rotatably connected to the stinger assembly; wherein rotation of the turret defines rotation about an axis A 1  on a directional bearing B 1 ; wherein rotation of the turret end of the first boom section about the turret defines rotation about an axis A 2  on a directional bearing B 2 ; wherein rotation of the turret end of the second boom section about the stinger end of the first boom section defines rotation about an axis A 3  on a corresponding directional bearing B 3 ; wherein rotation of the stinger assembly about the stinger end of the second boom section defines rotation about an axis A 4  on a corresponding directional bearing B 4 ; wherein the stinger assembly is further configured to rotate about an axis A 5  on a corresponding directional bearing B 5 ; wherein the FDU further includes a plurality of rotary encoders R[1 . . . 5], one rotary encoder deployed at each of a corresponding one of axes A[1 . . . 5] such that each rotary encoder is configured to measure a corresponding one of directional bearings B[1 . . . 5] to establish sets of measured bearings values B VAL [1 . . . 5]; 
     (b) selectively moving ones of the turret, the boom sections and the stinger assembly to position the FDU in a first selected spatial position relative to a first fluid connection housing assembly; 
     (c) storing a first set of B VAL [1 . . . 5] corresponding to the first spatial position; 
     (d) connecting the fluid connection adapter to the first fluid connection housing assembly; 
     (e) commencing fluid flow to the fluid inlet such that fluid flows into the first fluid connection assembly via the FDU fluid pathway; 
     (f) terminating fluid flow to the fluid inlet; 
     (g) disconnecting the fluid connection adapter from the first fluid connection housing assembly; 
     (h) selectively moving ones of the turret, the boom sections and the stinger assembly to position the FDU in a second selected spatial position; and 
     (i) recalling the first set of B VAL [1 . . . 5]; wherein responsive to step (i), the FDU moves robotically to return the first spatial position. 
     In some method embodiments, each swivel joint may have an internal diameter of not less than about 7 inches, and each swivel joint may be further capable of retaining an internal pressure of not less than about 7,500 psi. In such method embodiments, each swivel joint may be further capable of rotation while retaining an internal pressure of not less than about 7,500 psi. In such method embodiments, step (e) preferably includes commencing fluid flow to the fluid inlet at a fluid pressure not less than about 7,500 psi. 
     In other method embodiments, each swivel joint may have an internal diameter of not less than about 7 inches, and each swivel joint may be further capable of retaining an internal pressure of not less than about 10,000 psi. In such method embodiments, each swivel joint may be further capable of rotation while retaining an internal pressure of not less than about 10,000 psi. In such method embodiments, step (e) preferably includes commencing fluid flow to the fluid inlet at a fluid pressure not less than about 10,000 psi. 
     In other method embodiments, each swivel joint may have an internal diameter of not less than about 7 inches, and each swivel joint may be further capable of retaining an internal pressure of not less than about 15,000 psi. In such embodiments, each swivel joint may be further capable of rotation while retaining an internal pressure of not less than about 15,000 psi. In such method embodiments, step (e) preferably includes commencing fluid flow to the fluid inlet at a fluid pressure not less than about 15,000 psi. 
     Although the material in this disclosure has been described in detail along with some of its technical advantages, it will be understood that various changes, substitutions and alternations may be made to the detailed embodiments without departing from the broader spirit and scope of such material as set forth in the following claims.