Patent Publication Number: US-11649817-B2

Title: Operating multiple fracturing pumps to deliver a smooth total flow rate transition

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application No. 62/620,663, titled “Operating Multiple Fracturing Pumps to Deliver a Smooth Total Flow Rate Transition,” filed Jan. 23, 2018, the entire disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     High-volume, high-pressure pumps are utilized at wellsites for a variety of pumping operations. Such operations may include drilling, cementing, acidizing, water jet cutting, hydraulic fracturing, and other wellsite operations. In some pumping operations, several pumps may be fluidly connected to a well via various fluid conduits and/or a manifold. During such operations, the fluid conduits and/or the manifold distributes low-pressure fluid from a mixer, a blender, and/or other sources among the pumps and combines pressurized fluid from the pumps for injection into the well. Success of the pumping operations at a wellsite may be affected by many factors, such as efficiency, failure rates, and safety related to operation of the pumps. Systematic high pressure and flow rate spikes and vibrations generated by the pumps may cause mechanical fatigue, wear, and/or other damage to the pumps, which may decrease pumping flow rates, quality of downhole operations, and/or efficiency. 
     To ensure that the pumps produce the intended flow rates or otherwise operate as intended, human operators at the wellsite may manually control or adjust operation of each pump and the associated transmission during downhole pumping operations. For example, during a fracturing job, the flow rate of slurry that is being pumped directly affects pressure at the wellhead, and pressure spikes and dips formed by the fracturing pumps decrease quality of the fracturing job. The pump operator thus attempts to manage the operation of the pumps such that the pumps deliver a smooth total flow rate during slurry flow rate transition (i.e., increase and decrease) phases of the fracturing job. 
     However, operating fracturing pumps manually by controlling transmissions (e.g., gear selection) and prime movers (e.g., throttles of motors/engines) does not lend itself to such pump control due. For example, the pump operator is able to control just one pump at a time. Furthermore, the pumps may be constructed using different components and may have different levels of wear and tear, such that the pumps cannot be accurately controlled via the same transmission and prime mover settings. That is, different fracturing pump components (e.g., the engine, the transmission, the power end, the fluid end, etc.) may have different parameters and capabilities, and different wear levels of different pump components increase the variability in operating the pumps to achieve a target flow rate. 
     SUMMARY OF THE DISCLOSURE 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify indispensable features of the claimed subject matter, nor is it intended for use as an aid in limiting the scope of the claimed subject matter. 
     The present disclosure introduces an apparatus that includes a controller having a processor and a memory storing coded instructions that, when executed by the processor, are for operation of the controller to change a cumulative pumping rate of multiple pump units of a pumping system by adjusting individual pumping rates of the pump units, including such that each temporary dip or spike of an individual pumping rate of one of the pump units is automatically offset by a predetermined temporary adjustment of an individual pumping rate of another one or more of the pump units to thereby reduce effects of the temporary dip or spike on the cumulative pumping rate of the pump units. 
     The present disclosure also introduces a method that includes causing operation of a controller to change a cumulative pumping rate of multiple pump units by adjusting individual pumping rates of the pump units, including such that each temporary dip or spike of an individual pumping rate of one of the pump units is automatically offset by a predetermined temporary adjustment of an individual pumping rate of another one or more of the pump units to thereby reduce effects of the temporary dip or spike on the cumulative pumping rate of the pump units. 
     The present disclosure also introduces a method including receiving a rate distribution plan describing each adjustment to individual pumping rates of multiple pump units of a pumping system that will accomplish a cumulative pumping rate change of the pumping system. The pump units are grouped into a first group of the pump units for which the individual pumping rates adjustments are increases and a second group of other ones of the pump units for which the individual pumping rates adjustments are decreases. The method also includes generating a first list of the pump units in the first group sorted by magnitude of the increases, generating a second list of the pump units in the second group sorted by magnitude of the decreases, and generating a transition schedule of ordered transition steps to be executed to accomplish the cumulative pumping rate change. Each transition step includes the individual pumping rate adjustment to be accomplished for one of the pump units, and the transition steps are ordered by decreasing magnitude of alternating increasing and decreasing individual pumping rate adjustments. 
     The present disclosure also introduces an apparatus including a controller capable of communicatively connecting to each pump unit controller of multiple pump units. Each pump unit controller is in communication with at least one of a variable frequency drive, an engine throttle, a gear shifter, a prime mover, or a transmission of the corresponding pump unit. The controller includes a programmable processor having a memory device and an interface circuit connected to an input device. The programmable processor is operable to process coded instructions from the input device and communicate the coded instructions to the pump unit controllers. The at least one of the variable frequency drive, the engine throttle, the gear shifter, the prime mover, and/or the transmission of each pump unit is responsive to the coded instructions to change a cumulative pumping rate of the pump units. Each temporary dip or spike of an individual pumping rate of one of the pump units is automatically offset by a predetermined temporary adjustment of an individual pumping rate of another one or more of the pump units to thereby reduce effects of the temporary dip or spike on the cumulative pumping rate of the pump units. 
     These and additional aspects of the present disclosure are set forth in the description that follows, and/or may be learned by a person having ordinary skill in the art by reading the material herein and/or practicing the principles described herein. At least some aspects of the present disclosure may be achieved via means recited in the attached claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG.  1    is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure. 
         FIG.  2    is a schematic perspective view of a portion of an example implementation of the apparatus shown in  FIG.  1    according to one or more aspects of the present disclosure. 
         FIG.  3    is a schematic sectional view of a portion of an example implementation of the apparatus shown in  FIG.  2    according to one or more aspects of the present disclosure. 
         FIG.  4    is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure. 
         FIG.  5    is a graph related to one or more aspects of the present disclosure. 
         FIG.  6    is a flow-chart diagram of at least a portion of an example implementation of a method according to one or more aspects of the present disclosure. 
         FIGS.  7 - 10    are graphic depictions related to one or more aspects of the present disclosure. 
         FIG.  11    is a schematic associated with the example method depicted in  FIG.  6   . 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features or combinations of features. Specific examples of components and arrangements are described below to simplify the present disclosure. These are merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
       FIG.  1    is a schematic view of at least a portion of an example environment in which a control system according to one or more aspects of the present disclosure may be utilized. The figure shows a wellsite  102 , a wellbore  104  extending from the terrain surface of the wellsite  102 , a partial sectional view of a subterranean formation  106  penetrated by the wellbore  104 , a wellhead  108 , and a wellsite system  100  comprising various pieces of equipment or components located at the wellsite  102 . The wellsite system  100  may be operable to transfer various materials and additives between corresponding sources and destinations, such as for blending or mixing and subsequent injection into the wellbore  104  during fracturing operations. 
     The wellsite system  100  may comprise a mixing unit  108  (referred to hereinafter as a “mixer”) fluidly connected with one or more tanks  110  and a container  112 . The container  112  may contain a first material and the tanks  110  may contain a liquid. The first material may be or comprise a hydratable material or gelling agent, such as cellulose, clay, galactomannan, guar, polymers, synthetic polymers, and/or polysaccharides, among other examples. The liquid may be or comprise an aqueous fluid, such as water or an aqueous solution comprising water, among other examples. The mixer  108  may be operable to receive the first material and the liquid, via two or more conduits or other material transfer means (hereafter simply “conduits”)  114 ,  116 , and mix or otherwise combine the first material and the liquid to form a base fluid, which may be or comprise that which is known in the art as a gel. The mixer  108  may then discharge the base fluid via one or more fluid conduits  118 . 
     The wellsite system  100  may further comprise a mixer  124  fluidly connected with the mixer  108  and a container  126 . The container  126  may contain a second material that may be substantially different than the first material. For example, the second material may be or comprise a proppant material, such as quartz, sand, sand-like particles, silica, and/or propping agents, among other examples. The mixer  124  may be operable to receive the base fluid from the mixer  108  (via the one or more conduits  118 ) and the second material from the container  126  (via one or more conduits  128 ) and mix or otherwise combine the base fluid and the second material to form a mixture. The mixture may be or comprise that which is known in the art as a fracturing fluid. 
     One or more conduits  130  may communicate the mixture from the mixer  124  to a manifold  136 , which may be known in the art as a missile or a missile trailer. The manifold  136  may comprise a low-pressure manifold  138  and a high-pressure manifold  140  (as well as various valves and diverters not labeled in  FIG.  1   ). The manifold  136  may distribute the mixture to a fleet of pump units  150  via the low-pressure distribution manifold  138 . Although the pump fleet is shown comprising six pump units  150 , the pump fleet may comprise another number of pump units  150  within the scope of the present disclosure. The manifold  136  and the pump units  150  (and perhaps other components) collectively form a pumping system  135 . 
     Each pump unit  150  may comprise a pump  152 , a prime mover  154 , and perhaps a heat exchanger  156 . Each pump unit  150  may receive the mixture from a corresponding outlet of the low-pressure manifold  138 , such via one or more conduits  142 , and then pressurize the mixture and discharge the high-pressure mixture into a corresponding inlet of the high-pressure manifold  140 , such as via one or more conduits  144 . The pressurized mixture may then be discharged from the high-pressure manifold  140  into the wellbore  104 , such as via one or more conduits  146 , the wellhead  105 , and perhaps various additional valves, conduits, and/or other hydraulic circuitry (not shown) fluidly connected between the manifold  136  and the wellbore  104 . 
     The wellsite system  100  may also have a control center  160  comprising a controller  161  (e.g., a processing device, a computer, a PLC, etc.), which may be operable to provide control to one or more portions of the wellsite system  100  and/or to monitor health and functionality of one or more portions of the wellsite system  100 . The controller  161  (also referred to herein as the coordinating controller  161 ) may be communicatively connected with the various wellsite equipment described herein, and may be operable to receive signals from and transmit signals to such equipment to perform various operations described herein. For example, the controller  161  may be operable to monitor and control one or more portions of the mixers  108 ,  124 , the pump units  150 , the manifold  136 , and various other pumps, conveyers, and/or other wellsite equipment (not shown) disposed along the conduits  114 ,  116 ,  118 ,  128 ,  130 , such as may be collectively operable to move, mix, separate, and/or measure the fluids, materials, and/or mixtures described above and inject such fluids, materials, and/or mixtures into the wellbore  104 . The controller  161  may store control commands, operational parameters and set-points, coded instructions, executable programs, and other data or information, including for implementing one or more aspects of the operations described herein. Communication between the controller  161  and the various portions of the wellsite system  100  may be via wired and/or wireless communication means. However, for clarity and ease of understanding, such communication means are not depicted in  FIG.  1   , and a person having ordinary skill in the art will appreciate that such communication means are within the scope of the present disclosure. 
     A field engineer, equipment operator, or field operator (collectively referred to hereinafter as a “wellsite operator”)  164  may operate one or more components, portions, or systems of the wellsite equipment and/or perform maintenance or repair on the wellsite equipment. For example, the wellsite operator  164  may assemble the wellsite system  100 , operate the wellsite equipment (e.g., via the controller  161 ) to perform the fracturing operations, check equipment operating parameters, and/or repair or replace malfunctioning or inoperable wellsite equipment, among other operational, maintenance, and repair tasks, collectively referred to hereinafter as wellsite operations. The wellsite operator  164  may perform wellsite operations individually or with other wellsite operators. 
     The controller  161  may be communicatively connected with one or more human-machine interface (HMI) devices, such as may be utilized by the wellsite operator  164  for entering or otherwise communicating the control commands to the controller  161 , and for displaying or otherwise communicating information from the controller  161  to the wellsite operator  164 . The HMI devices may include one or more input devices  167  (e.g., a keyboard, a mouse, a joystick, a touchscreen, etc.) and one or more output devices  166  (e.g., a video monitor, a printer, audio speakers, etc.). The HMI devices may also include a mobile communication device  168  (e.g., a smartphone, a tablet computer, a laptop computer, etc.). Communication between the controller and the HMI devices may be via wired and/or wireless communication means. 
     One or more of the containers  112 ,  126 , the mixers  108 ,  124 , the pump units  150 , and the control center  160  may each be disposed on corresponding trucks, trailers, and/or other mobile carriers  122 ,  134 ,  120 ,  132 ,  148 ,  162 , respectively, such as may permit their transportation to the wellsite surface  102 . However, one or more of the containers  112 ,  126 , the mixers  108 ,  124 , the pump units  150 , and the control center  160  may each be skidded or otherwise stationary, and/or may be temporarily or permanently installed at the wellsite surface  102 . 
       FIG.  1    depicts the wellsite system  100  as being operable to transfer additives and produce mixtures that may be pressurized and injected into the wellbore  104  during hydraulic fracturing operations. However, it is to be understood that the wellsite system  100  may be operable to transfer other additives and produce other mixtures that may be pressurized and injected into the wellbore  104  during other oilfield operations, such as cementing, drilling, acidizing, chemical injecting, and/or water jet cutting operations, among other examples. Accordingly, unless described otherwise, the one or more fluids being pumped by a pump unit  150  may be referred to hereinafter as simply “a fluid.” 
       FIG.  2    is a perspective schematic view an example implementation of a portion of an instance of the pump units  150  shown in  FIG.  1    according to one or more aspects of the present disclosure.  FIG.  3    is a side sectional view of a portion of the pump unit  150  shown in  FIG.  2   . Portions of the pump unit  150  shown in  FIGS.  2  and  3    are shown in phantom lines, such as to prevent obstruction from view of other portions of the pump unit  150 . The following description refers to  FIGS.  1 - 3   , collectively. 
     The pump unit  150  comprises a pump  202  operatively coupled with and actuated by a prime mover  204 . The pump  202  includes a power section  208  and a fluid section  210 . The fluid section  210  may comprise a pump housing  216  having a plurality of fluid chambers  218 . One end of each fluid chamber  218  may be plugged by a cover plate  220 , such as may be threadedly engaged with the pump housing  216 , while an opposite end of each fluid chamber  218  may contain a reciprocating member  222  slidably disposed therein and operable to displace the fluid within the corresponding fluid chamber  218 . Although the reciprocating member  222  is depicted as a plunger, the reciprocating member  222  may also be implemented as a piston, diaphragm, or another reciprocating, fluid-displacing member. 
     Each fluid chamber  218  is fluidly connected with a corresponding one of a plurality of fluid inlet cavities  224  each adapted for communicating fluid from a fluid inlet  226  into the corresponding fluid chamber  218 . The fluid inlet  226  may be in fluid communication with the corresponding conduit  142  for receiving fluid from the low-pressure manifold  138 . Each fluid inlet cavity  224  may contain an inlet valve  228  operable to control fluid flow from the fluid inlet  226  into the corresponding fluid chamber  218 . Each inlet valve  228  may be biased toward a closed flow position by a spring or another biasing member  230 , which may be held in place by an inlet valve stop  232 . Each inlet valve  228  may be actuated to an open flow position by a predetermined differential pressure between the corresponding fluid inlet cavity  224  and the fluid inlet  226 . 
     Each fluid chamber  218  is also fluidly connected with a fluid outlet cavity  234  extending through the pump housing  216  transverse to the reciprocating members  222 . The fluid outlet cavity  234  is adapted for communicating pressurized fluid from each fluid chamber  218  into one or more fluid outlets  235  fluidly connected at one or both ends of the fluid outlet cavity  234 . The fluid outlets  235  may be in fluid communication with the corresponding conduit  144  for communicating pressurized fluid to the high-pressure manifold  140 . The fluid section  210  also contains a plurality of outlet valves  236  each operable to control fluid flow from a corresponding fluid chamber  218  into the fluid outlet cavity  234 . Each outlet valve  236  may be biased toward a closed flow position by a spring or other biasing member  238 , which may be held in place by an outlet valve stop  240 . Each outlet valve  236  may be actuated to an open flow position by a predetermined differential pressure between the corresponding fluid chamber  218  and the fluid outlet cavity  234 . The fluid outlet cavity  234  may be plugged by cover plates  242 , such as may be threadedly engaged with the pump housing  216 . 
     During pumping operations, portions of the power section  208  rotate in a manner that generates a reciprocating linear motion to move the reciprocating members  222  longitudinally within the corresponding fluid chambers  218 , thereby alternatingly drawing and displacing the fluid within the fluid chambers  218 . With regard to each reciprocating member  222 , as the reciprocating member  222  moves out of the fluid chamber  218 , as indicated by arrow  221 , the pressure of the fluid inside the corresponding fluid chamber  218  decreases, thus creating a differential pressure across the corresponding fluid inlet valve  228 . The pressure differential operates to compress the biasing member  230 , thus actuating the fluid inlet valve  228  to an open flow position to permit the fluid from the fluid inlet  226  to enter the corresponding fluid inlet cavity  224 . The fluid then enters the fluid chamber  218  as the reciprocating member  222  continues to move longitudinally out of the fluid chamber  218  until the pressure difference between the fluid inside the fluid chamber  218  and the fluid at the fluid inlets  226  is low enough to permit the biasing member  230  to actuate the fluid inlet valve  228  to the closed flow position. As the reciprocating member  222  begins to move longitudinally back into the fluid chamber  218 , as indicated by arrow  223 , the pressure of the fluid inside the fluid chamber  218  begins to increase. The fluid pressure inside the fluid chamber  218  continues to increase as the reciprocating member  222  continues to move into the fluid chamber  218  until the pressure of the fluid inside the fluid chamber  218  is high enough to overcome the pressure of the fluid inside the fluid outlet cavity  234  and compress the biasing member  238 , thus actuating the fluid outlet valve  236  to the open flow position and permitting the pressurized fluid to move into the fluid outlet cavity  234 , the fluid outlets  235 , and the corresponding fluid conduit  144 . 
     The pump unit  150  may comprise one or more flow rate sensors  203  fluidly coupled with or along the fluid outlets  235  in a manner permitting monitoring of a fluid flow rate of the fluid flowing through the fluid outlets  235 . Each flow sensor  203  may be or comprise a flow meter operable to measure the volumetric and/or mass flow rate of the fluid discharged from the pump unit  150 , and to generate signals or information indicative of the flow rate of the fluid discharged from the pump unit  150 . The pump unit  150  may further comprise a pressure sensor  205  disposed in association with the fluid section  210  in a manner permitting the sensing of fluid pressure at the fluid outlets  235 . For example, the pressure sensor  205  may extend through one or more of the cover plates  242  or other portions of the corresponding pump housing  216  to monitor pressure within the fluid outlet cavity  234  and, thus, the fluid outlets  235  and the corresponding outlet conduits  144 . 
     The fluid flow rate generated by the pump unit  150  may depend on the physical size of the reciprocating members  222  and fluid chambers  218 , as well as the pump unit operating speed, which may be defined by the speed or rate at which the reciprocating members  222  cycle or move within the fluid chambers  218 . The pumping speed, such as the speed or the rate at which the reciprocating members  222  move, may be related to the rotational speed of the power section  208  and/or the prime mover  204 . Accordingly, the fluid flow rate generated by the pump unit  150  may be controlled by controlling the rotational speed of the power section  208  and/or the prime mover  204 . 
     The prime mover  204  may be or comprise a gasoline, diesel, or other engine, a synchronous, asynchronous, or other electric motor (e.g., a synchronous permanent magnet motor), a hydraulic motor, or another prime mover operable to drive or otherwise rotate a drive shaft  252  of the power section  208 . The drive shaft  252  may be enclosed and maintained in position by a power section housing  254 . To prevent relative rotation between the power section housing  254  and the prime mover  204 , the power section housing  254  and prime mover  204  may be fixedly coupled together or to a common base, such as a trailer of the mobile carrier  148 . 
     The prime mover  204  may comprise a rotatable output shaft  256  operatively connected with the drive shaft  252  via a gear train or transmission  262 , which may comprise at a spur gear  258  coupled with the drive shaft  252  and a corresponding pinion gear  260  coupled with a support shaft  261 . The output shaft  256  and the support shaft  261  may be coupled, such as may facilitate transfer of torque from the prime mover  204  to the support shaft  261 , the pinion gear  260 , the spur gear  258 , and the drive shaft  252 . For clarity,  FIGS.  2  and  3    show the transmission  262  comprising a single spur gear  258  engaging a single pinion gear  260 , however, it is to be understood that the transmission  262  may comprise a plurality of corresponding sets of gears, such as may permit the transmission  262  to be shifted between different gear sets (i.e., combinations) to control the operating speed of the drive shaft  252  and the torque transferred to the drive shaft  252 . Accordingly, the transmission  262  may be shifted between different gear sets (“gears”) to vary the pumping speed and torque of the power section  208  and, thereby, vary the fluid flow rate and maximum fluid pressure generated by the fluid section  210 . 
     The transmission  262  may also comprise a torque converter (not shown) operable to selectively connect (“lock-up”) the prime mover  204  with the transmission  262  and permit slippage (“unlock”) between the prime mover  204  and the transmission  262 . The torque converter and the gears of the transmission  262  may be shifted manually by the wellsite operator  164  or remotely via a gear shifter, which may be incorporated as part of a pump unit controller  213 . The gear shifter may receive control signals from the controller  161  and output a corresponding electrical or mechanical control signal to shift the gear of the transmission  262  and lock-up the transmission, such as to control the fluid flow rate and the operating pressure of the pump unit  150 . 
     The drive shaft  252  may be implemented as a crankshaft comprising a plurality of axial journals  264  and offset journals  266 . The axial journals  264  may extend along a central axis of rotation of the drive shaft  252 , while the offset journals  266  may be offset from the central axis of rotation by a distance and spaced 120 degrees apart with respect to the axial journals  264 . The drive shaft  252  may be supported in position within the power section  208  by the power section housing  254 , wherein two of the axial journals  264  may extend through opposing openings in the power section housing  254 . 
     The power section  208  and the fluid section  210  may be coupled or otherwise connected together. For example, the pump housing  216  may be fastened with the power section housing  254  by a plurality of threaded fasteners  282 . The pump  202  may further comprise an access door  298 , which may facilitate access to portions of the pump  202  located between the power section  208  and the fluid section  210 , such as during assembly and/or maintenance of the pump  202 . 
     To transform and transmit the rotational motion of the drive shaft  252  to a reciprocating linear motion of the reciprocating members  222 , a plurality of crosshead mechanisms  285  may be utilized. For example, each crosshead mechanism  285  may comprise a connecting rod  286  pivotally coupled with a corresponding offset journal  266  at one end and with a pin  288  of a crosshead  290  at an opposing end. During pumping operations, walls and/or interior portions of the power section housing  254  may guide each crosshead  290 , such as may reduce or eliminate lateral motion of each crosshead  290 . Each crosshead mechanism  285  may further comprise a piston rod  292  coupling the crosshead  290  with the reciprocating member  222 . The piston rod  292  may be coupled with the crosshead  290  via a threaded connection  294  and with the reciprocating member  222  via a flexible connection  296 . 
     The pump unit  150  may further comprise one or more rotational position and speed (“rotary”) sensors  211  operable to generate a signal or information indicative of rotational position, rotational speed, and/or operating frequency of the pump  202 . For example, one or more of the rotary sensors  211  may be operable to convert angular position or motion of the drive shaft  252  or another rotating portion of the power section  208  to an electrical signal indicative of pumping speed of the pump unit  150 . One or more of the rotary sensors  211  may be mounted in association with an external portion of the drive shaft  252  or other rotating member of the power section  208 . One or more of the rotary sensors  211  may also or instead be mounted in association of the prime mover  204  to monitor the rotational position and/or rotational speed of the prime mover  204 , which may be utilized to determine the pumping speed of the pump unit  150 . Each rotary sensor  211  may be or comprise an encoder, a rotary potentiometer, a synchro, a resolver, and/or an RVDT (rotary variable differential transformer), among other examples. 
     The pump unit controller  213  may further include prime mover power and/or control components, such as a variable frequency drive (VFD) and/or an engine throttle control, which may be utilized to facilitate control of the prime mover  204 . The VFD and/or throttle control may be connected with or otherwise in communication with the prime mover  204  via mechanical and/or electrical communication means (not shown). The pump unit controller  213  may include the VFD in implementations in which the prime mover  204  is or comprises an electric motor, and the pump unit controller  213  may include the engine throttle control in implementations in which the prime mover  204  is or comprises an engine. For example, the VFD may receive control signals from the controller  161  and output corresponding electrical power to control the speed and the torque output of the prime mover  204  and, thus, control the pumping speed and fluid flow rate of the pump unit  150 , as well as the maximum pressure generated by the pump unit  150 . The throttle control may receive control signals from the controller  161  and output a corresponding electrical or mechanical throttle control signal to control the speed of the prime mover  204  to control the pumping speed and, thus, the fluid flow rate generated by the pump unit  150 . Although the pump unit controller  213  is shown located near or in association with the prime mover  204 , the pump unit controller  213  may be located or disposed at a distance from the prime mover  204 . For example, the pump unit controller  213  may be located within or form a portion of the control center  160 . 
     A resistance temperature detector (RTD) or other temperature sensor  207  may be disposed in association with the prime mover  204 , such as to generate a signal or information indicative of a temperature of the prime mover  204 . For example, the temperature sensor  207  may monitor the temperature within a motor winding, an engine housing, or within another portion of the prime mover  204 . The temperature sensor  207  may be in communication with the controller  161 , which may shut down the prime mover  204  if the detected temperature level exceeds a predetermined temperature level. 
     A moisture sensor  209  may also be disposed in association with the prime mover  204 , such as to generate a signal or information indicative of moisture present at or near the prime mover  204 . The moisture sensor  209  may be in communication with the controller  161 , which may shut down the prime mover  204  if excessive moisture is detected by the moisture sensor  209 . 
     As described above, the controller  161  may be further operable to monitor and control various operational parameters of the pump units  150 . The controller  161  may be in communication with the various sensors of the pump units  150 , including the flow rate sensors  203 , the pressure sensors  205 , the temperature sensor  207 , the moisture sensor  209 , and the rotary sensor  211 , to facilitate monitoring of the pump units  150 . The controller  161  may be in communication with the transmission  262  via the gear shifter of the controller  213 , such as to control the flow rate and pressure generated by the pump unit  150  to facilitate control of the pump unit  150 . The controller  161  may also be in communication with the prime mover  204  via the VFD of the controller  213  if the prime mover  204  is an electric motor or via the throttle control of the controller  213  if the prime mover  204  is an engine, such as may permit the controller  161  to activate, deactivate, and control the flow rate generated by the pump unit  150 . 
     Although  FIGS.  2  and  3    show the pump unit  150  comprising a triplex reciprocating pump  202 , which has three fluid chambers  218  and three reciprocating members  222 , implementations within the scope of the present disclosure may include the pump  202  as or comprising a quintuplex reciprocating pump having five fluid chambers  218  and five reciprocating members  222 , or a pump having other quantities of fluid chambers  218  and reciprocating members  222 . It is further noted that the pump  202  described above and shown in  FIGS.  2  and  3    is merely an example, and that other pumps, such as diaphragm pumps, gear pumps, external circumferential pumps, internal circumferential pumps, lobe pumps, and other positive displacement pumps, are also within the scope of the present disclosure. 
     The present disclosure further provides various implementations of systems and/or methods for controlling various portions of the wellsite system  100 , including the pump units  150  described above. An implementation of such system may comprise a control system  300 , such as may be operable to monitor and/or control operations of the pump units  150 , including fluid flow rate generated by the pump units  150 .  FIG.  4    is a schematic view of a portion of an example implementation of the control system  300  according to one or more aspects of the present disclosure. The following description refers to  FIGS.  1 - 4   , collectively. 
     The control system  300  may include a controller  310  communicatively connected with each pump unit  150 . For example, the controller  310  may be communicatively connected with each flow sensor  203 , pressure sensor  205 , temperature sensor  207 , moisture sensor  209 , rotary sensor  211 , and prime mover  204  and transmission  262  via each pump unit controller  213 . For clarity, these and other components in communication with the controller  310  will be collectively referred to hereinafter as “sensors and controlled components.” The controller  310  may be operable to receive signals or information from the various sensors of the control system  300 , the received signals or information being indicative of the various operational parameters of the pump units  150 . The controller  310  may be further operable to process such operational parameters and communicate control signals to the prime movers  204  and the transmissions  262  to execute example machine-readable instructions to implement at least a portion of one or more of the example methods and/or processes described herein, and/or to implement at least a portion of one or more of the example systems described herein. The controller  310  may be or form a portion of the controller  161  described above. 
     The controller  310  may be or comprise, for example, one or more general-purpose or special-purpose processors, such as of personal computers, laptop computers, tablet computers, personal digital assistant (PDA) devices, smartphones, servers, internet appliances, and/or other types of computing devices. For clarity and ease of understanding, the example implementation of the controller  310  depicted in  FIG.  4    includes just one processor  312 , it being understood that multiple processors  312  may exist. 
     The processor  312  may be a general-purpose programmable processor, such as may comprise a local memory  314  and that may execute coded instructions  332  present in the local memory  314  and/or another memory device. The processor  312  may execute, among other things, machine-readable instructions or programs to implement the example methods and/or processes described herein. The programs stored in the local memory  314  may include program instructions or computer program code that, when executed by an associated processor, control the pump units  150  in performing the example methods and/or processes described herein. The processor  312  may be, comprise, or be implemented by one or a plurality of processors of various types suitable to the local application environment, and may include one or more general-purpose or special-purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as non-limiting examples. Other processors from other families are also appropriate. 
     The processor  312  may be in communication with a main memory  317 , such as may include a volatile memory  318  and a non-volatile memory  320 , perhaps via a bus  322  and/or other communication means. The volatile memory  318  may be, comprise, or be implemented by random access memory (RAM), static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), dynamic random access memory (DRAM), RAMBUS dynamic random access memory (RDRAM), and/or other types of random access memory devices. The non-volatile memory  320  may be, comprise, or be implemented by read-only memory, flash memory, and/or other types of memory devices. One or more memory controllers (not shown) may control access to the volatile memory  318  and/or non-volatile memory  320 . The controller  310  may be operable to store or record information entered by the wellsite operator  164  and/or information generated by the sensors and controlled components on the main memory  317 . 
     The controller  310  may also comprise an interface circuit  324 . The interface circuit  324  may be, comprise, or be implemented by various types of standard interfaces, such as an Ethernet interface, a universal serial bus (USB), a third-generation input/output (3GIO) interface, a wireless interface, and/or a cellular interface, among other examples. The interface circuit  324  may also comprise a graphics driver card. The interface circuit  324  may also comprise a communication device, such as a modem or network interface card to facilitate exchange of data with external computing devices via a network (e.g., Ethernet connection, digital subscriber line (DSL), telephone line, coaxial cable, cellular telephone system, satellite, etc.). One or more of the sensors and controlled components may be connected with the controller  310  via the interface circuit  324 , such as may facilitate communication between the sensors and controlled components and the controller  310 . 
     One or more input devices  326  may also be connected to the interface circuit  324 . The input devices  326  may permit the wellsite operator  164  to enter the coded instructions  332 , operational target set-points, and/or other data into the processor  312 . The operational target set-points may include, but are not limited to, a pressure target set-point, a flow rate target set-point, a combined flow rate transition curve set-point, a pump operating or pumping speed target set-point, and a time or duration target set-point, among other examples. The coded instructions may also include a flow rate transition schedule for each pump unit  150  and a combined flow rate transition schedule for the pump units  150  allocated for a job. The coded instructions  332  and operational target set-points are described in more detail below. The input devices  326  may be, comprise, or be implemented by a keyboard, a mouse, a touchscreen, a track-pad, a trackball, an isopoint, and/or a voice recognition system, among other examples. One or more output devices  328  may also be connected to the interface circuit  324 . The output devices  328  may be, comprise, or be implemented by display devices (e.g., a liquid crystal display (LCD) or cathode ray tube display (CRT)), printers, and/or speakers, among other examples. The controller  310  may also communicate with one or more mass storage devices  330  of the controller  310  and/or a removable storage medium  334 , such as may be or include floppy disk drives, hard drive disks, compact disk (CD) drives, digital versatile disk (DVD) drives, and/or USB and/or other flash drives, among other examples. 
     The coded instructions  332 , the operational target set-points, and/or other data may be stored in the mass storage device  330 , the main memory  317 , the local memory  314 , and/or the removable storage medium  334 . Thus, the controller  310  may be implemented in accordance with hardware (perhaps implemented in one or more chips including an integrated circuit, such as an ASIC), or may be implemented as software or firmware for execution by the processor  312 . In the case of firmware or software, the implementation may be provided as a computer program product including a computer-readable medium or storage structure embodying computer program code (i.e., software or firmware) thereon for execution by the processor  312 . 
     The coded instructions  332  may include program instructions or computer program code that, when executed by the processor  312 , may cause the pump units  150  to perform methods, processes, and/or routines described herein. For example, the controller  310  may receive and process the operational target set-points entered by the operator  164  and the signals or information generated by the various sensors described herein indicative of the operational parameters of the pump units  150 . Based on the coded instructions  332  and the received operational target set-points and operational parameters, the controller  310  may send signals or information to the prime movers  204  and the transmissions  262  to cause the pump units  150  and/or other portions of the wellsite system  100  to automatically perform and/or undergo one or more operations or routines within the scope of the present disclosure. 
     However, as described above, gear shifts and other factors can result in sudden pressure and/or flow rate changes of the pumping system  135 , such as the sudden changes  400  in pressure  402  and flow rate  404  depicted in the graph of  FIG.  5   . The present disclosure introduces one or more aspects pertaining to reducing the sudden changes via automated, smooth (or smoother) rate transition methods utilizing the ability to closely monitor the automation state and operation parameters of the individual pump units  150  of the pumping system  135 .  FIG.  6    is a flow-chart diagram of at least a portion of an example implementation  500  of such method according to one or more aspects of the present disclosure. The method  500  may be performed in conjunction with at least a portion of the apparatus depicted in one or more of  FIGS.  1 - 4   . 
     The method  500  may comprise receiving  505  a New-Plan-Available flag from a rate distribution planner. Such receipt  505  may also or instead comprise receiving a new rate distribution plan. The rate distribution planner may be implemented as an algorithm, program, method, etc., within a master rate controller operable to plan the rates of the pump units  150 . The master rate controller may be, comprise, or be implemented via at least a portion of the processing systems described above. 
     For example, in the example implementation depicted in  FIG.  1   , when the pumping system  135  is operating to provide a cumulative pumping rate (i.e., the collective pumping rate of the currently operating ones of the pump units  150 ), the new plan describes how the pump units  150  are to be adjusted so that the pumping system will achieve a new “target” cumulative pumping rate. The new cumulative pumping rate of the pumping system  135  may be greater than or less than the current cumulative pumping rate. The New-Plan-Available flag indicates that a plan has been generated (e.g., by the master rate controller and/or other means) for distributing the new rates to the pump units  150  that will achieve the new cumulative pumping rate of the pumping system  135 . The new plan describes which (if any) pump units  150  will experience an increase in pumping rate, referred to herein as going-up or ramp-up pump units, and which (if any) pump units  150  will experience a decrease in pumping rate, referred to herein as going-down or ramp-down pump units. That is, the new plan describes how the throttles and/or gears of the currently operating ones of the pump units  150  are to be adjusted, and perhaps how one or more additional ones of the pump units  150  will also be engaged, so that the pumping system  135  will achieve the new cumulative pumping rate. 
     The method  500  comprises generating  510  a list of the going-up pump units and a list of the going-down pump units. A transition schedule is then generated  520  based on whether a total rate change request is an increase or a decrease and by selecting transitions from the generated up/down pump lists in the order that is most conducive for avoiding spikes and dips. Special transition steps may also be generated  530  for shifting pump gears, such as by estimating the dip that would be caused due to the gear shift, and by stacking pumps that can compensate for such dip by throttling up temporarily and then throttling back down when the dip is over. The transitions in the transition schedule are then executed  540  one by one, separated by a configurable delay. The special transitions are also performed  550  with, for example, a time-based strategy to closely align the dip of the gear shifting pump(s) with the rise and fall in rate from the compensating pump(s). 
     The method  500  may be implemented via one or more algorithms and/or computer programs to be executed by a controller (such as the controller  161 ,  310 ) to simultaneously and automatically operate a plurality of gear-shifting pump units (such as the pump units  150 ). The algorithms and/or computer programs may be entered into the controller (e.g., as part of the coded instructions  332 ) and executed by the controller to cause pumping operations at intended flow rates substantially without manual control by the wellsite operator  164 . The method  500  may be utilized/performed by the controller to operate the pump units to compensate for each other&#39;s flow rate and pressure dips and spikes during throttle and/or gear changing processes to achieve smooth transitions of the cumulative pumping rate of the pumping system  135 . For example, a flow rate dip resulting from shifting up gears of a first one of the pump units  150  may be negated, cancelled, or otherwise compensated for by a second one of the pump units  150  simultaneously throttling up, such that the increased flow rate of the second pump unit  150  compensates for the flow rate dip of the first pump unit  150  during the gear shift, thus maintaining a substantially smooth combined flow rate of the first and second pump units  150 . 
     Such compensation for flow rate dips due to gear shifts may be achieved by analyzing historical data to empirically estimate how flow rates change in response to throttle changes across different gears, throttle changes across different types of pumps, motors, transmissions, and their combinations (i.e., pump units), and/or throttle changes across different pressures. This knowledge can be used to operate multiple pump units simultaneously, while offsetting rate dips due to gear shifts. 
     For example, an archive of historical pump unit operation data may be mined to extract information related to throttle and rate change behavior across a wide variety of pump units operating over a wide variety of jobs and operating conditions. Changes in flow rate and throttle may be analyzed during gear shift transitions. Change rates can be determined via the slope of the flow rate and throttle during the gear shifts. For example, T/ t and R/ t (where is delta, T is throttle, t is time, and R is flow rate), may be determined for each gear shift within the data set, as schematically depicted in  FIG.  7   . The T/ t and R/ t values may be collected based on engine/transmission types, and these T/ t and R/ t values may be plotted against discharge pressure, as depicted in  FIG.  8   . Normal distributions of the results may then be used to generate approximate estimates for T/ t and R/ t, as also depicted in  FIG.  8    and in  FIG.  9   . As depicted in  FIG.  10   , the estimated T/ t and R/ t  602  can then be used to generate smoothing profiles  604  to be executed by other pump units, thereby achieving a smoother flow rate and/or pressure  606 . 
       FIG.  11    is a schematic of at least a portion of an example implementation of a method  700  in which the method  500  and other aspects above may be utilized. During a waiting stage  702 , the controller waits for the next target rate. When a new target rate is received  704  (from a wellsite operator  164 , another user, a controller/processing device, etc.), the controller enters a planning stage and generates  706  a new plan assigning flow rate changes to the available pumps. When the new plan becomes available  708 , the controller enters an execution stage during which the new plan is executed  710 , such as may include execution of an implementation of the method  500 . When the new plan has been executed  712 , the controller again awaits  702  the next pumping system transition. 
     The new plan may be generated  706  utilizing a transition planner, such as set forth below in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Example Transition Planner 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Pump 
                 Current 
                   
                 Target 
                 Rate 
                 Gear 
                 Fast 
               
               
                 Unit 
                 Rate 
                 Give 
                 Rate 
                 Increase 
                 Change? 
                 Lockup? 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 4.3 
                 0.2 
                 4.5 
                 +0.2 
                 No 
                 n/a 
               
               
                 2 
                 4.3 
                 0.2 
                 6.8 
                 +2.5 
                 Yes 
                 No 
               
               
                 3 
                 5.3 
                 0.8 
                 7.3 
                 +2.0 
                 Yes 
                 No 
               
               
                 4 
                 4.1 
                 0.4 
                 4.5 
                 +0.4 
                 No 
                 n/a 
               
               
                 5 
                 4.2 
                 0.3 
                 4.2 
                 0 
                 n/a 
                 n/a 
               
               
                 6 
                 6.2 
                 0.3 
                 6.2 
                 0 
                 n/a 
                 n/a 
               
               
                   
               
            
           
         
       
     
     In the table above, “give” is the amount of additional rate that a pump unit can provide without changing gears. Thus, in the example set forth in the table above, pump unit  1  is currently at 4.3 barrels per minute (bpm), and has a target rate of 4.5 bpm. This results in a rate increase of 0.2 bpm, which doesn&#39;t exceed the 0.2 give, so the rate increase can be accomplished by throttling up the pump motor without changing gears. However, pump unit  2  is currently at 4.3 bpm and has a target rate of 6.8 bpm. This results in a rate increase of 2.5 bpm, which exceeds the 0.2 give, so the rate increase will be accomplished by (at least) changing gears. Thus, the transition planner provides a snapshot of the planned transitions, can be used as a base for planning different combinations of transitions, and can also be used to determine each pump unit&#39;s give (e.g., based on an Automatic Rate Control (ARC) and/or other algorithm, process, or controller utilized in conjunction with each pump unit). 
     The transition schedule includes the transition steps and their execution order. Each step can include one or more pump units transitioning together to produce a smooth combined rate curve. As described above, the pump units are sorted into those going up in rate and those going down in rate. Transition steps are formed from the two groups, ordering pump units from largest to smallest rate change but alternating between the two groups, such as the “going up” pump unit having the largest change, then the “going down” pump unit having the largest change, then the “going up” pump unit having the second largest change, then the “going down” pump unit having the second largest change, and so on, with each step producing a smooth up or down transition. 
     As an example, each transition step may comprise a list of the one or more pump units involved in that transition step (e.g., Pump  1 , Pump  2 , Pump  5 ), the rate setpoints for those pump units (e.g., 5.2 bpm, 4.1 bpm, 4.4 bpm), a net effect of the new rates (e.g., +2.0 bpm), a flag or marker indicating that the transition step is a special transition step, and a combination index. A special transition step is one in which a pump unit that is changing gears is accompanied by a pump unit having give that will return back to its original rate after compensating for the dip. The combination index is an index representing a group of combinable transition steps. The transition steps are created in such an order as to reduce or prevent undershoot and overshoot, based on the net effect of the step and whether the total rate is aimed to increase or decrease, and the assigned rate so far. An example algorithm may be at least similar to the following: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 if (totalRateChange &gt; 0) 
               
            
           
           
               
               
            
               
                   
                 while (all pump unit transitions have not been added to transition schedule) 
               
            
           
           
               
               
            
               
                   
                 if (a “going down” pump unit can be added without the assigned rate so far going 
               
            
           
           
               
               
            
               
                   
                 negative) 
               
               
                   
                 AddToSchedule (“going down” pump unit with largest rate decrease) 
               
            
           
           
               
               
            
               
                   
                 else 
               
            
           
           
               
               
            
               
                   
                 AddToSchedule (“going up” pump unit with largest rate increase) 
               
            
           
           
               
            
               
                 else 
               
            
           
           
               
               
            
               
                   
                 while (all pump unit transitions have not been added to transition schedule) 
               
            
           
           
               
               
            
               
                   
                 if (a “going up” pump unit can be added without the assigned rate so far going 
               
            
           
           
               
               
            
               
                   
                 positive) 
               
               
                   
                 AddToSchedule(“going up” pump unit with largest rate increase) 
               
            
           
           
               
               
            
               
                   
                 else 
               
            
           
           
               
               
            
               
                   
                 AddToSchedule(“going down” pump unit with largest rate decrease) 
               
               
                   
                   
               
            
           
         
       
     
     The AddToSchedule action estimates whether a gear change is required. For example, if a gear change is not required, then the pump unit is added to the transition schedule. However, if a gear change is required, then the dip due to gear shift is estimated (based on, for example, data collected from historical analysis, as described above), the give of each available pump unit is determined, compensating pump units are assigned with an amount of rate increase sufficient to buffer the dip caused by the gear shift, and the shifting pump unit and buffering pump units are added to the transition schedule. 
     The transition steps are then combined, when possible. For example, two transition steps may be combinable if (1) they have no overlapping pump units in their pump unit lists, and (2) if their net effects are of different signs, and (3) if combining them would not change the order of net effects signage of the transition steps, and (4) if none of the pump units in the second transition step are part of the lists of any of the steps in between. 
     Each combined transition step may then be executed. For example, a millisecond-based timer may be utilized to align compensating pump units and to schedule in such a way as to maintain the configured ramp up and ramp down slope. While executing a special transition step, the duration of the corresponding dip may be estimated based on historical data and used to closely control when the compensating pump units increase their rates, when the compensating pump units subsequently decrease their rates, and when the compensation is over, and perhaps also for managing the slopes of the dipping pump unit and the sum of the compensating pump units so that they align to form as near-ideal of a compensation as possible. 
     Table 2 set forth below provides an example of a rate distribution plan that may be generated  706  as described above. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Example Rate Distribution Plan 
               
            
           
           
               
               
               
            
               
                 Pump 
                 Current Rate 
                 New Rate 
               
               
                 Unit 
                 (bpm) 
                 (bpm) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 0 
                 3.8 
               
               
                 2 
                 3.8 
                 5.2 
               
               
                 3 
                 4.1 
                 4.5 
               
               
                 4 
                 3.8 
                 4.1 
               
               
                 5 
                 3.8 
                 4.5 
               
               
                   
               
            
           
         
       
     
     In the example shown in Table 2, the cumulative pumping rate of the pumping system is being transitioned from 15.5 bpm to 22.1 bpm, including the addition of pump unit  1  and the ramp up of pump units  2 - 5 . Table 3 set forth below provides an example of a corresponding transition schedule that may be generated and executed  710  utilizing the method  500 . 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Example Transition Schedule 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Post Step 
                 Post Step 
               
               
                   
                 Pump 
                 New Rate 
                 Wait 
                 Cum. 
               
               
                 Step 
                 Unit 
                 (bpm) 
                 (second) 
                 Rate (bpm) 
               
               
                   
               
               
                 1 
                 1 
                 3.8 
                 x 1   
                 19.3 
               
               
                 2 
                 2 
                 5.2 
                 x 2   
                 21.0 
               
               
                   
                 4 
                 4.1 
               
               
                 3 
                 3 
                 4.5 
                 x 3   
                 21.4 
               
               
                   
                 4 
                 4.3 
               
               
                   
                 4 
                 4.1 
               
               
                 4 
                 5 
                 4.5 
                 x 4   
                 22.1 
               
               
                   
                 4 
                 4.3 
               
               
                   
                 4 
                 4.1 
               
               
                   
               
            
           
         
       
     
     Step 1 includes increasing pump unit  1  to 3.8 bpm, and then waiting for a period of x 1  seconds and/or until the cumulative pumping rate of the pumping system increases to (and perhaps substantially stabilizes at) 19.3 bpm. Step 2 includes increasing pump unit  2  to 5.2 bpm and increasing pump unit to 4.1 bpm, and then waiting for a period of x 2  seconds and/or until the cumulative pumping rate of the pumping system increases to (and perhaps substantially stabilizes at) 21.0 bpm. Step 3 includes increasing pump unit  3  to 4.5 bpm and temporarily increasing pump unit  4  to 4.3 bpm to compensate for the dip caused by the increase of pump unit  3  (e.g., due to a gear shift), then decreasing pump unit  4  back to 4.1 bpm, and then waiting for a period of x 3  seconds and/or until the cumulative pumping rate of the pumping system increases to (and perhaps substantially stabilizes at) 21.4 bpm. Step 4 includes increasing pump unit  5  to 4.5 bpm and temporarily increasing pump unit  4  to 4.3 bpm to compensate for the dip caused by the increase of pump unit  3  (e.g., due to a gear shift), then decreasing pump unit  4  back to 4.1 bpm, and then waiting for a period of x 4  seconds and/or until the cumulative pumping rate of the pumping system increases to (and perhaps substantially stabilizes at) 22.1 bpm. The time periods x 1 , x 2 , x 3 , and x 4  may be different or the same. 
     In view of the entirety of the present disclosure, including the figures and the claims, a person having ordinary skill in the art will readily recognize that the present disclosure introduces an apparatus that includes a controller comprising a processor and a memory storing coded instructions that, when executed by the processor, are for operation of the controller to change a cumulative pumping rate of a plurality of pump units of a pumping system by adjusting individual pumping rates of the pump units, including such that each temporary dip or spike of an individual pumping rate of one of the pump units is automatically offset by a predetermined temporary adjustment of an individual pumping rate of another one or more of the pump units to thereby reduce effects of the temporary dip or spike on the cumulative pumping rate of the pump units. 
     The controller may be a first controller, the apparatus may comprise a second controller comprising a processor and a memory storing coded instructions, and the first or second controller may be operable to: receive a rate distribution plan describing each adjustment to the individual pumping rate of each pump unit that will accomplish the cumulative pumping rate change; and generate a transition schedule of ordered transition steps to be executed to accomplish the cumulative pumping rate change, wherein each transition step includes the total adjustment of the individual pumping rate to be accomplished for at least one of the pump units, and wherein the transition steps are ordered by decreasing magnitude of alternating increasing and decreasing individual pumping rate adjustments. The at least one of the pump units for which the total individual pumping rate adjustment is to be accomplished in each transition step may be a first pump unit, and at least one of the transition steps may further include a temporary adjustment to the individual pumping rate of a second one of the pump units to compensate for a temporary dip or spike in the cumulative pumping rate that would otherwise be caused by the total adjustment of the individual pumping rate being accomplished for the first pump unit in that transition step. The ordered transition steps may include a first transition step and subsequent transition steps, wherein: if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is less than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest decreasing individual pumping rate adjustment; and if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is greater than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest increasing individual pumping rate adjustment. 
     The present disclosure also introduces a method comprising causing operation of a controller to change a cumulative pumping rate of a plurality of pump units by adjusting individual pumping rates of the pump units, wherein each temporary dip or spike of an individual pumping rate of one of the pump units is automatically offset by a predetermined temporary adjustment of an individual pumping rate of another one or more of the pump units to thereby reduce effects of the temporary dip or spike on the cumulative pumping rate of the pump units. 
     The controller may be a first controller, and the method may further comprise causing operation of the first controller or a second controller to: receive a rate distribution plan describing each adjustment to the individual pumping rate of each pump unit that will accomplish the cumulative pumping rate change; and generate a transition schedule of ordered transition steps to be executed to accomplish the cumulative pumping rate change, wherein each transition step includes the total adjustment to the individual pumping rate to be accomplished for at least one of the pump units, and wherein the transition steps are ordered by decreasing magnitude of alternating increasing and decreasing individual pumping rate adjustments. The at least one of the pump units for which the total individual pumping rate adjustment is to be accomplished in each transition step may be a first pump unit, and at least one of the transition steps may further include a temporary adjustment to the individual pumping rate of a second one of the pump units to compensate for a temporary dip or spike in the cumulative pumping rate that would otherwise be caused by the total adjustment of the individual pumping rate being accomplished for the first pump unit in that transition step. The ordered transition steps may include a first transition step and subsequent transition steps, wherein: if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is less than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest decreasing individual pumping rate adjustment; and if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is greater than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest increasing individual pumping rate adjustment. 
     The present disclosure also introduces a method comprising: (A) receiving a rate distribution plan describing each adjustment to individual pumping rates of a plurality of pump units that will accomplish a cumulative pumping rate change of a pumping system comprising the pump units; (B) grouping the pump units into: (i) a first group comprising the ones of the pump units for which the individual pumping rates adjustments are increases; and (ii) a second group comprising the other ones of the pump units for which the individual pumping rates adjustments are decreases; (C) generating a first list of the pump units in the first group sorted by magnitude of the increases; (D) generating a second list of the pump units in the second group sorted by magnitude of the decreases; and (E) generating a transition schedule of ordered transition steps to be executed to accomplish the cumulative pumping rate change, wherein each transition step includes the individual pumping rate adjustment to be accomplished for one of the pump units, and wherein the transition steps are ordered by decreasing magnitude of alternating increasing and decreasing individual pumping rate adjustments. 
     The method may further comprise: (A) determining that first ones of the transition steps will cause a temporary dip in the cumulative pumping rate of the pumping system; (B) adding to each of the first transition steps: (i) an increase to the individual pumping rate of another, dip-compensating one of the pump units to coincide with the temporary dip in the cumulative pumping rate of the pumping system; and (ii) a subsequent decrease of the individual pumping rate of the dip-compensating pump unit to restore the dip-compensating pump unit to its individual pumping rate at the beginning of that first transition step; (C) determining that second ones of the transition steps will cause a temporary spike in the cumulative pumping rate of the pumping system; and (D) adding to each of the second transition steps: (i) a decrease in the individual pumping rate of another, spike-compensating one of the pump units to coincide with the temporary spike in the cumulative pumping rate of the pumping system; and (ii) a subsequent increase of the individual pumping rate of the spike-compensating pump unit to restore the spike-compensating pump unit to its individual pumping rate at the beginning of that second transition step. 
     The ordered transition steps may include a first transition step and subsequent transition steps, and: if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is less than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest decreasing individual pumping rate adjustment; and if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is greater than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest increasing individual pumping rate adjustment. 
     The method may further comprise combining a first one of the transition steps and a second, later-ordered one of the transition steps into a single transition step if: the first and second transition steps do not include any of the same ones of the pump units; the first and second transition steps have opposite net effects on the cumulative pumping rate; combining the first and second transition steps does not change the order of net effects signage of all of the transition steps; and none of the pump units in the second transition step form part of any of the other transition steps occurring between the first and second transition steps. 
     The present disclosure also introduces an apparatus comprising a coordinating controller capable of communicatively connecting to each pump unit controller of a plurality of pump units, wherein: each pump unit controller is in communication with at least one of a variable frequency drive, an engine throttle, a gear shifter, a prime mover, or a transmission of the corresponding pump unit; the coordinating controller comprises a programmable processor having a memory device and an interface circuit connected to an input device; the programmable processor is operable to process coded instructions from the input device and communicate the coded instructions to the pump unit controllers; the at least one of the variable frequency drive, the engine throttle, the gear shifter, the prime mover, and/or the transmission of each pump unit is responsive to the coded instructions to change a cumulative pumping rate of the pump units; and each temporary dip or spike of an individual pumping rate of one of the pump units is automatically offset by a predetermined temporary adjustment of an individual pumping rate of another one or more of the pump units to thereby reduce effects of the temporary dip or spike on the cumulative pumping rate of the pump units. 
     The coordinating controller or another controller of the apparatus may be operable to: receive a rate distribution plan describing each adjustment to the individual pumping rate of each pump unit that will accomplish the cumulative pumping rate change; and generate a transition schedule of ordered transition steps to be executed to accomplish the cumulative pumping rate change, wherein each transition step includes the total adjustment of the individual pumping rate to be accomplished for at least one of the pump units, and wherein the transition steps are ordered by decreasing magnitude of alternating increasing and decreasing individual pumping rate adjustments. The at least one of the pump units for which the total individual pumping rate adjustment is to be accomplished in each transition step may be a first pump unit, and at least one of the transition steps may further include a temporary adjustment to the individual pumping rate of a second one of the pump units to compensate for a temporary dip or spike in the cumulative pumping rate that would otherwise be caused by the total adjustment of the individual pumping rate being accomplished for the first pump unit in that transition step. The ordered transition steps may include a first transition step and subsequent transition steps, and: if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is less than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest decreasing individual pumping rate adjustment; and if the cumulative pumping rate change is an increase from a first cumulative pumping rate to a second cumulative pumping rate, and the magnitude of the largest decreasing individual pumping rate adjustment is greater than the first cumulative pumping rate, then the first transition step may include the total adjustment to be accomplished for the pump unit corresponding to the largest increasing individual pumping rate adjustment. 
     The foregoing outlines features of several embodiments so that a person having ordinary skill in the art may better understand the aspects of the present disclosure. A person having ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. A person having ordinary skill in the art should also realize that such equivalent constructions do not depart from the scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure. 
     The Abstract at the end of this disclosure is provided to permit the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.