Abstract:
A prover includes a piston supporting rod extending longitudinally through a cylinder, which cylinder receives and discharges a fluid to measure the volume and flow rate of the fluid by translation of the piston from the fluid receiving end to the fluid discharging end. Motive means includes at least one element for drawing the rod and piston toward the fluid receiving end of the cylinder. Travel of the piston in the direction from the fluid receiving end to the fluid discharging end of the cylinder is sensed at discrete locations to provide an indication of the quantity of fluid therebetween and the related flow rate. Each of a plurality of switches, linear encoder or laser detector provides position sensing signals reflective of the volume and rate of fluid flowing in the cylinder. These signals, representative of this volume and flow rate, are compared with preset parameters to determine the degree of equivalence. Thereby, self testing and validation occurs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part application of an application entitled “METHOD FOR MOUNTING A PROVER”, filed Jan. 6, 2010 and assigned Ser. No. 12/652,820, which is a divisional application of an application entitled “UNIDIRECTIONAL CAPTIVE DISPLACEMENT PROVER” filed Jan. 10, 2008, and assigned Ser. No. 11/972,530, now U.S. Pat. No. 7,650,775. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to the field of measuring fluid flow and, more particularly, to self testing and validating apparatus for a prover. 
     BACKGROUND OF THE INVENTION 
     In order to obtain accurate readings from a flow meter or prover, it must be calibrated periodically by determining its characteristic or K-factor. The K-factor is a constant of proportionality between the flow rate of the fluid flowing through the flow meter and the response provided by the flow meter to the flow rate. A typical turbine type flow meter develops electrical oscillations proportional in number to the volume of flow through the flow meter. The characteristic is expressed in terms of the number of pulses generated by the flow meter per unit volume of fluid passing through the flow meter. Moreover, the characteristic is a function of the type of fluid as well as the fluid temperature, pressure, flow rate and varies as the flow meter parts wear in the course of use. An apparatus for determining the characteristic of a flow meter while in an operating fluid system is called a ‘prover.’ An apparatus for determining the characteristic of a flow meter on a test stand and not in a fluid system is called a ‘calibrator.’ 
     It is well known to determine the characteristic of a flow meter by comparing its response to a ballistic flow calibrator or prover connected in series with the flow meter. A prover uses a piston that travels in a cylindrical chamber in synchronism with a fluid traveling through the flow meter. By measuring the time interval required for the piston to travel through a known volume of the chamber, an average flow rate can be calculated. These calculations may be used to determine the characteristic (K-factor) of the flow meter. 
     In existing provers, the release and return of the piston involves many difficult mechanical problems which have not been regularly overcome. These mechanisms tend to be complex and the prover itself bulky and costly to construct. Some provers utilize complex reverser valves to reverse the direction of flow in a cylinder and thereby return the piston to its original position. Other embodiments utilize devices to retract a piston and restrain it in the upstream position or bypass the flow of the piston by means of a poppet or bypass valve when the prover is not being used in a proving test. Provers utilizing valves to reverse the direction of flow are known as ‘bi-directional provers’ because the proving test may be made with the piston traveling in either direction. Provers utilizing devices to retract and restrain the piston are known as ‘unidirectional provers’ because the fluid and piston always travel in the same direction in the cylinder during a test. 
     Numerous patents have issued disclosing various types of provers. U.S. Pat. No. 3,492,856 discloses a ballistic flow calibrator in which the piston has a passage through it. A valve seals the passage when it is closed and permits fluid flow through the piston when it is opened. U.S. Pat. No. 4,152,922 discloses a ballistic flow calibrator with an auxiliary piston and an auxiliary cylinder to control a fluid displacement measuring piston which moves through a fluid measuring cylinder as a fluid barrier the same distance as the auxiliary piston moves through the auxiliary cylinder. U.S. Pat. No. 3,492,856 describes a unidirectional flow meter calibrating apparatus employing a piston within a conduit where the piston is restrained in the upstream position by means of a complex motor, clutch and cable assembly located upstream of the conduit. A poppet valve, held open by the cable, provides a fluid passage through the piston when the apparatus in not being used for flow measurements. Releasing the cable permits fluid pressure to close the poppet valve setting the piston in motion. U.S. Pat. No. 4,152,922 discloses a prover in which a measuring piston is returned and restrained in its upstream position by means of a second control piston. The control piston travels through a separate control cylinder and is linked to the measuring piston by a rod. A source of pressurized air is used to move the control piston. U.S. Pat. No. 4,794,783 discloses a similar prover wherein the control cylinder is moved by pressurized hydraulic fluid. 
     SUMMARY OF THE INVENTION 
     The prover of the present invention includes a rod supporting a poppet valve formed as part of a piston within a cylinder having a fluid inlet and a fluid outlet. A pair of motor driven pulleys are used to wind thereupon a pair of belts having their ends secured to a shuttle fixedly attached to the rod. Upon actuation of the motor driving the pair of pulleys, the belts are wound thereupon to draw the rod and piston toward the inlet. The force exerted by the rod upon the poppet valve and the piston opens the poppet valve to permit fluid flow therethrough. To conduct a test, a clutch disengages the motor from the pulleys to accommodate rectilinear translation of the rod, closure of the poppet valve, and movement of the piston in response to the flow of fluid into the cylinder through the inlet. Various limit switches responsive to the position of the rod (piston) may be used to provide information related to the volume displaced in the prover and the flow rate, which information is compared to preset parameters. Alternatively, linear encoders or lasers may be used to determine the position and translation of the shuttle and hence the piston. An encoder may also be used to reflect translation of the belt or cable attached to the shuttle. These encoders or lasers provide signals reflective of the degree and rate of translation of the piston and corresponding volume of fluid. If there is not equivalence between the volume and rate of flow of the fluid with preset parameters, an error signal to that effect will be generated. In the absence of an error signal, validation of the prover will have been accomplished. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
         FIG. 1  is an isometric view of the prover horizontally mounted on a framework; 
         FIG. 2  is a graphic illustration of the fluid flow attendant the prover; 
         FIG. 3  is a side elevational view of the prover showing the fluid inlet and outlet; 
         FIG. 4  is a partly cutaway view showing the poppet valve and piston disposed within the cylinder; 
         FIG. 5  is a rear view of the prover showing the motive apparatus for achieving rectilinear translation of the rod supporting the piston and the poppet valve; 
         FIG. 6  is an isometric view of the motor driven apparatus for translating the rod; 
         FIG. 7  is a detail view of the shuttle interconnecting the rod and a pair of belts; 
         FIGS. 8A and 8B  illustrate the use of a linear encoder to determine the position of the shuttle; 
         FIG. 9  illustrates the use of a linear encoder for sensing travel of the shuttle and connected belt or cable; 
         FIG. 10  illustrates the use of a laser detector to determine the position of the shuttle; 
         FIGS. 11A ,  11 B and  11 C illustrate the generation of pulses as a function of the displacement of the piston within the cylinder of the prover; 
         FIG. 12  is a schematic diagram showing the functions for calculation of validation or error signals of the operation of the prover; 
         FIG. 13  illustrates the piston and associated poppet valve; 
         FIG. 14  illustrates the mechanism for manually opening the poppet valve to perform maintenance and/or repair on the poppet valve; 
         FIG. 15  illustrates the piston and the interconnection between the disk of the poppet valve and the rod sections; 
         FIG. 16  illustrates the frame interconnecting the cylinder and the motive means for translating the piston; 
         FIG. 17  is an isometric view illustrating the lower framework for supporting the prover horizontally and the upper framework for mounting the prover vertically; 
         FIG. 18  is an isometric view illustrating the other side of the prover shown in  FIG. 12 ; and 
         FIG. 19  is an end view of the prover illustrating the lower and upper frameworks for supporting the prover. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is illustrated a unidirectional captive displacement prover  10 . The prover includes a cylinder  12  having a rectilinearly translatable piston with a poppet valve disposed therein and mounted on a rod  14 . Motive means, generally identified by reference numeral  16 , is supported upon a frame  18  attached to and extending from cylinder  12 . The motive means imparts a force to rod  14  to cause translation in one direction of the piston within the cylinder. A clutch accommodates free translation of the rod and piston in the other direction. 
     Prover  10  is mounted upon a framework  20  that is attached at a location generally adjacent a flow meter  24  (see  FIG. 2 ) to be periodically tested. As particularly shown in  FIG. 2 , a fluid  22  flows through a flow meter  24 , which flow meter is to be tested, and into prover  10 . Outflow from the prover is channeled into a conduit for the fluid, as represented by arrow  26 . The prover includes various sensors and test equipment for determining the flow therethrough. This flow is compared to the indicated flow through the flow meter. Any difference reflects an adjustment to be made to the flow determined by the flow meter. This is generally referred to as a K-factor. Such testing of flow meters is required due to wear and other factors affecting the accuracy of the prover and flow meter over time. Additionally, maintenance or replacement of parts may affect the accuracy of the prover and flow meter and require testing in order to adjust and thereby correct the data provided by the flow meter. 
     Referring jointly to  FIGS. 1 ,  3  and  4 , further details of prover  10  will be described. Cylinder  12  includes an inlet  30  for receiving fluid from the flow meter (see  FIG. 2 ). After fluid passes through the cylinder, it is exhausted through outlet  32  into a conduit for the fluid. A piston  34  is rectilinearly translatable within cylinder  12 . The piston includes a ring  36  in sealed engagement with interior surface  38  of the cylinder, which sealing means accommodates translation of the piston relative to the cylinder without leakage. Ring  36  is supported by three arms  40 ,  42  and  44  extending from a sleeve  46  slidably encircling rod section  48  of rod  14 . A poppet valve  35  includes a disk  50 , configured to mate with opening  52  within ring  36 . Seals are disposed between the disk and the ring to ensure that fluid does not leak therebetween. Rod  14  includes a further rod section  54 . The abutting ends of the two rod sections include annular flanges  56 ,  58  mechanically attached to one another to thereby form rod  14 . Disk  50  is mechanically attached to flange  56  of rod section  44  to ensure that translation of rod  14  causes a corresponding translation of the disk. A coil spring (not shown in  FIG. 4 ) biases the disk against the ring to maintain a seal therebetween. 
     Motive means  16 , as shown in the end view depicted in  FIG. 5 , as well as in  FIGS. 1 ,  3  and  4 , includes an electric motor  60  for rotating a pulley  62  driving a belt  64 . The belt engages a further pulley  66  driving a gear reduction unit  68 . Shaft  70  of the gear reduction unit is connected to a clutch  72 . Output shaft  74  of the clutch is or is not connected to shaft  70  as a function of operation of the clutch. The shaft  74  supports a pulley  76  driving a belt  78  in engagement with a further pulley  80 . Pulley  80  is attached to shaft  82 , which shaft is journaled within supports  84 ,  86  and  88  and supports reels  90 ,  92 . To ensure commensurate rotation of the reels upon rotation of shaft  82 , the interconnection may be splined or otherwise rigidly interconnected. Each of reels  90 ,  92  has attached thereto a belt  94 ,  96 , respectively, which belts extend through opening  98  in plate  100 , a part of frame  18 . 
     It is to be understood that motive means  16  may be not only the electric motor described and illustrated, but could be a hydraulic motor, an internal combustion engine or other power source. Furthermore, the belts ( 64 ,  78 ) driving the associated pulleys ( 62 ,  66  and  76 ,  80 ) in the motive means could be replaced by conventional chains driving sprockets instead of pulleys. Belts  64 ,  78  and their respective pulleys  62 ,  66  may be collectively referred to as ‘driving elements.’ Similarly, belts  94 ,  96  extending from take up reels  90 , 92  could be replaced by conventional chains and take up sprockets, respectively. In a less preferred embodiment, belts  94 ,  96  could be replaced by cables and reels  90 ,  92  would be replaced by suitably configured reels to accommodate the cables. Belts  94 ,  96  and substitutable chains or cables may be collectively referred to as ‘drawing elements.’ 
     Referring particularly to  FIGS. 6 and 7 , the interconnection between motive means  16  and rod  14  will be described. A pair of rods  110 ,  112  are attached to and extend intermediate cylinder  12  and frame  18 . A shuttle  114  includes bearing blocks  116 ,  118  in slidable engagement with rods  110 ,  112 . Thereby, the shuttle is slidable along these rods. Rod section  48  of rod  14  is rigidly clamped to shuttle  114  to ensure that any movement of the shuttle results in corresponding movement of the rod. Ends  120 ,  122  of belts  94 ,  96 , respectively, are clamped or otherwise attached to shuttle  14 . Thereby, any rectilinear motion of the belts will result in commensurate translation of the shuttle. 
     To control operation of rod  14  and poppet valve  35 , a plurality of limit switches responsive, for example, to the position of shuttle  114  may be used. For example, as shown in  FIG. 4 , switch elements  124 ,  125 ,  128  may be mounted on frame  18  to cooperate with a further switch element  130  on shuttle  114 . These switch elements may be mechanical, electrical or optical, as is well known in the art. Actuation of one or another of the switch elements will result in the generation of appropriate command signals relating to operation of motive means  16  and/or the position of the piston, as will be described below. 
     Automated procedures have a number of advantages wherein electrical signals are generated upon actuation of a switch, whether mechanical, optical or electronic. The signal produced by such a switch is used to initiate a process or procedure that may continue until such time as a further switch terminates the operation of the process or procedure. By using such switches to control the operation, such as through a computer program, various data can be generated as a function of the mechanical activity undergoing between operation of start and finish switches. The resulting data may be used for numerous purposes, including monitoring the operation, testing the function of the operation and comparing such function with a preset function to generate an error signal, if appropriate. It may also be used for purposes of self testing the operation and for validation and/or calibration purposes. 
       FIGS. 8A and 8B  illustrate a further apparatus for determining the position of shuttle  114  and hence the position of piston  34  within the prover. An off-the-shelf linear encoder  250  extends from plate  100  to the support for the prover. A bracket  252  extends from shuttle  114  into operative engagement with the linear encoder. Thereby, a signal may be generated as a function of the position of the shuttle (bracket  252 ) relative to the linear encoder to provide an accurate determination of not only the position of the shuttle but the extent and rate of movement of the shuttle. As noted above, the shuttle is in operative engagement with piston  34  through rod section  48 . Thereby, the position of the shuttle is commensurate with the position of the piston within the prover. As noted above, belts  94  and  96  are secured to shuttle  114  to draw the shuttle and the attached piston upstream within the prover and released to permit movement of the shuttle in the opposite direction in response to the flow of fluid into the prover. A rod  110  (switch bar) supports a plurality of switches  126 , as discussed above. 
     As shown in  FIG. 9 , reel  92 , when under power, draws belt  94  toward plate  100  resulting in translation of the shuttle  114  towards plate  100  and piston  34  toward the upstream end of the prover. Thereafter, a clutch releases the belt(s) to accommodate movement of the piston (and shuttle) downstream in response to fluid flow into the cylinder. An off-the-shelf cable reel encoder  260  is secured to plate  100  and includes a cable  262  functionally attached to shuttle. The cable reel encoder provides a signal as a function of the translation of the cable in response to movement of the piston downstream and commensurate movement of the shuttle. This signal is functionally associated with the position of shuttle  114  and hence the position of piston  34  within the prover. Thereby, translation of cable  262  is reflective of and commensurate with the translation of piston  34 . 
     Referring to  FIG. 10 , there is shown a further apparatus for accurately determining the position of shuttle  114  and hence the position of piston  34 . Herein, and off-the-shelf laser detector  270  is mounted on plate  100 . It emits a beam  272  to impinge upon surface  274  of shuttle  114  and reflect a return beam  276 . The distance between laser detector  270  and shuttle  114  is accurately determined by the laser detector. Thereby, an accurate position of the shuttle as it moves toward and away from plate  100  may be reflected in a signal generated by the laser detector. Hence, the commensurate position of piston  34  is similarly calculatable with great accuracy. 
     Referring jointly to  FIGS. 11A ,  11 B and  11 C, the methodology for self-testing and validation of the prover will be described. In general, a microprocessor and associated program measures the time and distance between actuation of position responsive switches or other determinants providing an indication of the position of the shuttle as well as the rate of translation between predetermined fixed locations. As the volume of the cylinder is known, (diameter and length are known), calculation of the time and distance between the switches, or other predetermined positions of the shuttle, the volume and the rate of flow can be determined and compared with information manually entered into the microprocessor. Any differences determined as a result of such comparisons will provide an error signal if there is a variation between the calculated factors and the previously established factors. Thereby, self-testing is accomplished and validation of accuracy or an error will be determinable. Additionally, temperature and pressure sensors may be employed to calculate compensation factors for the flow rate and volume and thereby ensure accuracy of the validation or error signal. 
     As shown in  FIG. 11A , switch S 1  may be actuated by a representative trigger  290  mounted on rod (switch bar)  110  to release the reels or pulleys supporting the belts or cables and thereby permit shuttle  114  and piston  34  to translate from the upstream end to the downstream end as a function of fluid inflow through inlet  30 , as represented by arrows  280  and  282 . The inflowing fluid will close poppet valve  35  by translation of disk  50  into sealed engagement with ring  36 . When trigger  290  reaches a position corresponding with volume 1 (Vol 1), a start pulse is initiated, as illustrated in  FIG. 11B . At a position corresponding with volume 2 (Vol 2) or volume 3 (Vol 3), a stop pulse is generated by trigger  290 . The time between the start and stop pulses provide data to determine the volume of fluid existing within cylinder  12  and positionally corresponding with the distance represented between Vol 1 and Vol 2 or 3. Thereafter, the above-noted calculations can be made to validate the operation of the prover or to generate an error signal. 
     Referring to  FIG. 12 , there is a schematic representation of the above-described operation. As represented by block  294 , initial data is provided to the microprocessor including the ID and OD of cylinder  12 , the material of rod (switch bar)  110  supporting a plurality of switches along with pressure and temperature indicia. A prover interface module  296  receives a signal representative of the start pulse count and the stop pulse count, which may be generated by the mechanical switches, the encoders or the laser described above. A flow computer  298  receives data from a temperature sensor  300  providing an input of the present temperature of rod (switch bar)  110 . A temperature sensor  302  provides the temperature of cylinder  12 . A pressure sensor  304  provides an indication of the pressure within the cylinder. Through computations within the flow computer, these three signals may modify the data received from the power interface module to provide an accurate output. Such output may be displayed as indicia on a screen  306  of a computer or the like. Other devices may be used to provide a signal representative of the output from the flow computer. It is to be understood that the output from the flow computer may confirm validation of operation of the prover or may provide an error signal. In the latter event, corrective action may be taken by operating personnel. 
       FIG. 13  is a detailed view of piston  34  and poppet valve  35  generally shown in  FIG. 4 . An annular flange  140  is secured to sleeve  46  and arms  40 ,  42  and  44 . This flange includes three passageways  142 ,  144  and  146  (not shown) equiangularly disposed in flange  140 . A coil spring  148 , or the like, is disposed about rod section  48  to urge movement of disk  50  toward ring  36  and into sealing engagement therewith. A plurality of annular seals  150  are disposed about disk  50  for sealing engagement with opening  52  in the ring. Disk  50  includes a plurality of threaded apertures  152 ,  154  and  156  (not shown) equiangularly displaced in the disk radially external of spring  148  and in alignment with apertures  142 ,  144 , and  146  (not shown), respectively. 
     Referring jointly to  FIGS. 14 and 15 , details attendant displacement of disk  50  from ring  36  to perform maintenance/repair on the disk or the ring will be described. Rods  160 ,  162  and  164  slidably engage apertures  142 ,  144 , and  146 , respectively, and into threaded engagement with threaded apertures  152 ,  154  and  156 , respectively. The rods include nut-like elements  166  formed as part of or affixed to the rods to ensure that any rotation of these nut-like elements results in commensurate rotation of the respective rods. By rotating the nut-like elements clockwise (for instance), the threaded engagement with disk  50  will draw the disk toward annular flange  140  and compress coil spring  148  therebetween. Such movement will result in axial displacement of disk  50 , as shown in  FIGS. 14 . The resulting space between the disk and ring  36  may provide the necessary space to perform any maintenance or repair on the disk or the disk engaging parts of ring  36 . 
     As particularly shown in  FIG. 15 , rod section  54  includes an annular flange  58  attached thereto. A similar annular flange  56  is attached to the end of rod section  48 . A plurality of bolts  178  interconnect the annual flanges whereby rods sections  48 ,  54  form rod  14  discussed above. It may be noted that upon disengagement of annular flanges  56 ,  58 , rod sections  48  and  54  become separable and, with appropriate disassembly of other components, permit replacement of piston  34  or its components, such as ring  36  and disk  50 . To maintain a seal between piston  34  and interior surface  38  of cylinder  12  (see  FIG. 4 ), annular seals  170  may be disposed about ring  36 . During disassembly, these seals are also readily replaced. 
       FIG. 16  illustrates frame  18  for interconnecting the cylinder (reference numeral  12 ) with motive means (reference numeral  16 ), as shown in  FIG. 3 . In particular, it includes a box frame  190  for attachment to the upstream end of the cylinder. Plate  100  is located is located at the opposite end of frame  12  for supporting the motive means. A pair of longerons  192  and  194  interconnect box frame  190  and plate  100 . To minimize flexing of frame  18  and to ensure positional stability between box frame  190  and plate  100 , a pair of diagonal braces interconnect the upper end of box frame  190  with the lower end of plate  100 . Moreover, C-channels  200 ,  202  are secured to plate  100  and to each of longerons  192 ,  194  and diagonal braces  196 ,  198 . Thereby, flexing of plate  100  is essentially precluded. Furthermore, a horizontal brace  204  extends intermediate the midpoint of box frame  190  and plate  100  to further stabilize the box frame with the plate. It may be noted that the exact configuration of frame  18  may be varied from that described above, depending upon various factors. For example, frame  18  may be configured similarly to the functionally equivalent frame  206  shown in  FIGS. 17 and 18 . It may include vibration damping elements  207  of rubber or plastic composition disposed between frame  206  and lower framework  20 . Suitable attachment devices well known to those skilled in the relevant vibration damping art provide the requisite physical interconnection. 
     At most locations, the footprint of a prover is of minor concern and the prover is usually mounted horizontally by means of framework  20  described above. For certain locations, such as the platform of an offshore oil rig, the surface area for equipment is at a premium. As the prover described above is of relatively significant size to perform its intended function, the footprint required for horizontal mounting is of some concern. To reduce the footprint required, a support structure may be added to framework  20  to permit vertical mounting of the prover. Because of the configuration of the prover, as described above, routine maintenance and repair can be performed whether the prover is mounted horizontally or vertically. 
     Referring jointly to  FIGS. 17 ,  18  and  19 , there is shown a prover  10  mounted upon framework  20 . This framework may include a plurality of flanges (such as flanges  210 ,  212 ) for penetrably receiving bolts in threaded engagement with an underlying supporting surface. It may be defined as a lower framework. To provide an upper framework  208 , each corner of framework  20  includes a length of square tubing  214 ,  216 ,  218  and  220  for receiving vertical stanchions  222 ,  224 ,  226  and  228 , respectively. These stanchions are attached to the respective square tubings by bolts, welding or other robust attachment means. Stanchions  222 ,  224  support a horizontal I-beam  230 . Stanchions  226 ,  228  support a similar I-beam  232 . The attachment of these I-beams is the conventional manner well known to ironworkers. To provide further robustness to the upper framework, a further I-beam  234  is attached to the underside of I-beams  230 ,  232 . Thereby, any sway or movement of the stanchions extending upwardly from framework  20  is unlikely to occur upon imposition of normal and expected loads. Additionally, I-beam  234  may be used as a support for hoisting components of prover  10  during maintenance and/or repair thereof. Additional stability is provided by an angled I-beam  236  extending from one end of I-beam  230  to a location along stanchion  226 . A yet further I-beam  238  extends from opposed sides of I-beam  234  for various purposes. As particularly shown in  FIGS. 18 and 19 , a cabinet  240  may be attached to stanchion  222  to support various gauges and control elements relating to operation of prover  10 . 
     For normal operation of prover  10  at most land-based locations, a footprint of a horizontally oriented prover is acceptable. At such locations, the lower framework is attached to supporting structure to prevent movement of the prover relative to pipes and conduits connected thereto. For offshore oil rigs and other locations wherein the size of the footprint of the prover is of concern, upper framework  208  may be used. It is attached to appropriate and corresponding structures associated with the main platform of an offshore oil rig. Thereby, the prover is oriented vertically and the resulting footprint is significantly smaller than if the prover were mounted horizontally. Appropriate pipes and conduits would be employed to interconnect the prover with the flow meter being measured. Whether the prover is mounted horizontally or vertically, access to the prover for repair and maintenance purposes is essentially unimpeded by either the lower or upper framework. Thereby, there is little need to dismantle or otherwise disturb either the lower or the upper framework for these purposes and irrespective of the orientation of the prover at the location of use.