GB2196742A - A compact flow prover - Google Patents

Description

GB2196742A 1 SPECIFICATION accuracies may be introduced into the mea

surement and serious disruption of flow may A compact flow prover occur.

A device similar to U.S. Patent 3,021,703 This invention pertains to the volumetric mea- 70 is disclosed in U.S. Patent 3,580,045, also to surement of flow and, particularly, a compact Pfrehm. The device differs from U.S. Patent flow prover useful in periodically calibrating a 3,021,703 in that the mechanical detector continuous flowmeter in a pipeline without in- switches are replaced with external proximity terrupting the flow of fluid therethrough. The switches which detect the passage of a steel compact flow prover of this invention falls 75 band on the piston. The use of a four way generally into that class of flow provers char- spool valve which reduces the complexity of actefized by the measurement of the move- the valving arrangement is also disclosed.

ment of a piston traveling through a cylinder. However, it is believed that the seals of this This invention pertains specifically to a comvalve are subject to wear and leakage and are pact flow prover having the improved qualities 80 not amenable to monitoring of seal integrity.

of accuracy, dependability, infrequent and sim- U.S. Patent 3,273,375 to Howe discloses plified maintenance, simple and light weight another type of flow prover comprised of in construction, low space requirements, and op- ner and outer tubular members and a free erating flexibility. moving piston located in the inner tubular One type of device commonly employed for 85 member. This arrangement allows for a sim- determining the accuracy of a continuous pler valving system and eliminates the need flowmeter is known as a calibrating loop. This for pressure correction. However, the device device typically comprises a long run of pipe uses the same external proximity switches dis through which a free moving plug or sphere is cussed above and it is believed, that the pis propelled by the fluid moving therethrough. By 90 ton seal life is not greatly improved because measuring the time that it takes the object to the piston must move past outlet ports. In move from one detector switch to another, addition, special arresting mean5 are required the rate of fluid flowing through the flow loop to stop the movement of the piston at either can be determined. This type of device is the end of the calibrating barrel. Moreover, it is subject matter of U.S. Patent 2,948,142 to 95 believed the complicated construction makes Zimmerman, U.S. Patent 2,948,143 to Pruitt, assembly and maintenance difficult.

U.S. Patents 3,423,988 and 3,668,923 to U.S. Patents 3,492,856 and 4,152, 922, Grove, and U.S. Patent 3,530,705 to Lathrop. both to Francisco, disclose flow provers from Calibrating loops generally require a substantial which outlet ports on the calibrating barrel are length to maintain a usable accuracy. The high 100 not necessary. These devices utilize a flow cost of these devices prevents their use in all through piston having a poppet valve in the but the most critical situations. piston which may be closed during the prov- The use of positive displacement piston- ing cycle. The poppet valve requires pressur- type flow-meters is well documented. ing means such as gas to close the poppet Examples of this type of flowmeter which are 105 valve at the beginning of the proving cycle.

not particularly suited for calibration purposes The pressure required to keep the poppet include U.S. Patent 1,586,834 to Ormsby, valve closed during the proving cycle results U.S. Patent 2,652,953 to Gray, U.S. Patent in a significant pressure drop across the pis 2,892,346 to Sargent, and U.S. Patent ton. In addition, the mechanical arresting 4,096,747 to Gilson. 110 means which are required to stop the piston An example of a positive displacement pis- at the end of the proving cycle cause perturton-type flow prover useful in calibrating bations in the fluid flow and produce high flowmeters is seen in U.S. Patent 3,021,703 shock loads in the mechanical components.

of Pfrehm which discloses a bidirectional, free- U.S. Patent 3,492,856 uses external proximity moving piston in a calibration barrel. The 115 switches located on the calibration barrel and movement of the piston is detected by two retrieves the piston at the end of the proving detector switches which are mechanical in na- cycle by means of a cable and drum.

ture, located toward either end of the calibrat- U.S. Patent 4,152,922 discloses a piston ing barrel. In order to obtain usable accuracy, retracting means comprised of a rod con a considerable run of pipe is required. For 120 nected to a measuring piston which has at its example, if the accuracy of the detector other end a retracting piston located in a hy switch is 0.1 cm, a run of pipe of 13m or draulic cylinder. The movement of the measur more is required to yield desired accuracy of ing piston is detected by proximity switches 0.02%. In addition, since the detector which detect the movement of the retracting switch protrudes into the calibrating barrel and 125 piston in the hydraulic cylinder. In this prover, the outlet ports are connected to the calibrat- the measuring piston seals may be damaged ing barrel, the piston seals will be subject to by the presence of entrained solids such as wear each time they pass the switches and grit or sand which may be in the measured the outlet ports. Because valves must be fluid and become trapped between the cali opened and closed simultaneously, further in- 130 brating barrel and the piston seals, If this pro- 2 GB2196742A 2 ver is operated in a horizontal position, the displacer is released by the fluid actuator, the situation is aggravated since the solid particles flow of fluid through the inlet section cause will tend settle along the bottom of the cylin- the displacer to move toward the main cylin der. der. The guide means ensure a smooth entry A further problem associated with the flow 70 of the displacer into the main cylinder by provers heretofore mentioned is that horizontal maintaining the displacer in axial alignment operation results in reduced piston seal life with the main cylinder. Once it enters the along the bottom of the piston because of the main cylinder, the displacer is propelled there weight of the piston. through by the flow of the measured fluid.

It is a feature of this invention to provide a 75 As the displacer moves through the main compact flow prover which does not have the cylinder, the time required for it to move a disadvantages associated with the devices predetermined longitudinal distance corre heretofore known. A further feature is to pro- sponding to a known volume is measured and vide a compact flow prover with improved ac- may be used to calculate the rate of fluid curacy and dependability, reduced space and 80 flow. The downstream section guide means weight requirements, simplified construction maintain the displacer in axial alignment with and maintenance, and operating flexibility. the main cylinder as it exits therefrom and These and other features will be apparent to enters the downstream section. The flow of those skilled in the art in the following de- fluid through the housing is terminated or by scription of the invention. 85 passed and the return means are used to The compact flow prover can be used to bring the displacer from the downstream sec- determine the rate of flow by measuring the tion, through the main cylinder and into its time in which a piston travelling through a launch position in the inlet section. The com cylinder displaces a known volume of fluid. pact flow prover is then ready to begin The invention provides a compact flow pro- 90 another proving cycle.

ver comprising: a housing including an inlet The flow of fluid past the displacer while it section having a fluid inlet, a main cylinder, is disposed within the inlet and downstream and a downstream section having a fluid out- sections provides a cleansing of the displacer let, the said sections being greater in diameter seals which tends to remove any solid ma than the main cylinder; a piston movable 95 terial which my be deposited therein. This through the main cylinder as a fluid barrier; a cleansing extends the useful life of the displa fluid actuator for acting on the piston, includ- cer seals. Another advantage is that fluid ing an enclosure and a member reciprocatable flows through the entire cross-section of the within the enclosure, the said member being main cylinder along its entire length so that no connected to the piston by a first, axially ex- 100 dead spots develop which would tend to al tending shaft, the piston being returnable from low suspended particles to settle, especially the downstream section to the inlet section when the prover is operated in the horizontal by means of the fluid actuator; guide means position. Still another advantage is that the for limiting radial movement of the piston displacer may be of light weight construction while in the inlet section and the downstream 105 resulting in less wear on the displacer seals in section the guide means including a piston pi- the interior surface of the main cylinder. The lot terminating in a free end contained within single barrel construction also facilitates as the housing and axially extending from the sembly and maintenance accessibility.

face of the piston, and an axial sleeve located In a specific implementation of the compact in the inlet section, the sleeve being axially 110 flow prover of this invention, fluid is intro aligned with the pilot such that the pilot may duced into the inlet section of the measuring extend into the sleeve; and means for detect- housing by means of an inlet conduit. The ing the displacement of the piston along the fluid leaves the measuring housing through an main cylinder. outlet conduit in communication with the The cross-sectional area of the inlet and 115 downstream section of the measuring housing.

downstream sections is larger than that of the Means for bypassing the measuring housing is main cylinder so that fluid may flow past the provided which includes a valved bypass con piston - referred to hereinafter as the displacer duit fluidly connected to the inlet and outlet - when it is disposed within either of these conduits. In a preferred implementation, an im sections. The fluid actuator can be used for 120 proved bypass valve is provided which has a encouraging the displacer to enter the main simpler construction and operation than by cylinder from the inlet section at the start of a pass valves heretofore known. Since the by proving cycle, as well as functioning as return pass valve does not have to anticipate differ means for returning the displacer from the ential pressure across the valve equal to the downstream section to the inlet section at the 125 rated internal pressure of the flow prover, the end of a proving cycle. valve can have a simple poppet construction With the displacer held in the inlet section, rated for considerably lower pressure, thus of- flow of the fluid to be measured is initiated fering an economical advantage over conven into the inlet section and through the main tional valves. The improved bypass valve pro cylinder and downstream section. After the 130 vided also has the advantage of enabling mon- 3 GB2196742A 3 itoring of its seal integrity without an external space formed between the seals is also com pressure source which is required to monitor pressed. If the seals are functioning properly, the seals of known bypass valves. the pressure of the fluid trapped - between the In another implementation, the displacer re- seals will be higher than the fluid in the main turn means comprise a hydraulic cylinder and 70 cylinder and this pressure differential will not piston. The hydraulic cylinder is connected to dissipate until the displacer exits the main cyl the displacer by a rod or shaft extending inder. Thus, by comparing the pressure in the through the housing in axial alignment with the annular space with the line pressure, the in main cylinder. Following the proving cycle, the tegrity of the displacer seals may be verified.

displacer is returned to its launching position 75 Means are provided for verifying the integrity by introducing a hydraulic fluid under pressure of the displacer seals statically and while the into the hydraulic cylinder. The inlet section displacer is in the proving mode. Thus, the guide means comprise the rod connecting the integrity of the displacer seals may be verified displacer to the hydraulic piston and a journal without removing the prover from operation.

bearing located in the wall of the housing 80 Since the integrity of the prover seals is which slidably engages the rod. The rod may quickly ascertained, error introduced by leak be of relatively small diameter and low weight. age of fluid past the seals is easily eliminated.

Another implementation provides an encour- In another implementation, the compact flow aging means comprises a compression spring prover is operated in a vertical position and is in the inlet section of the housing. The spring 85 provided with pliable, spring loaded displacer encourages the displacer to enter the main seals. This specific implementation is capable cylinder when the return means is released, or handling very dirty fluids such as crude oil.

thus eliminating the need for a pressurized gas In another implementation, the compact flow or hydraulic fluid to encourage the displacer at prover is operated in a horizontal position and the beginning of the proving cycle. 90 is provided with less pliable displacer seals Another implementation provides a down- which are capable of supporting the weight of stream section guide means comprising a dis- the displacer. This specific implementation placer pilot extending from the downstream provides a seal which is capable of handling face of the displacer and an axial sleeve bear- low lubricity fluids.

ing located in the downstream section. The 95 Optionally, means are provided for monitor- axial sleeve bearing the pilot are in axial ing the integrity of the seals of the detector alignment with the main cylinder and the rod and displacer rod.

sleeve slidably engages the pilot as it enters A control system is optionally provided to the downstream section. These downstream simplify the proving sequence. The use of per section guide means maintain the displacer in 100 missive actions minimizes and identifies prob axial alignment while it is disposed within the lems with the prover. For example, the displa downstream section, allowing for a smooth cer cannot be launched unless it is in the fully exit and entry of the displacer between the retracted position and the bypass valve closed main cylidner and the downstream section. with positive seal integrity. When the displa- In another implementation, the detecting 105 cer is at the end of its stroke, the bypass means comprise a rod connected to the dis- valve will open after a predetermined time de placer, a journal bearing located in the wall of lay. Once the valve is opened, the displacer is the housing slidably engaging the rod, a de- permitted to return. The bypass valve cannot tector'flag positioned at the other end of the close until the displacer is in its launch posi rod, and a plurality of detector switches which 110 tion.

detect the passage of the detector flag and The compact flow prover may be used to simultaneously provide a signal. Since the de- calibrate a continuous flowmeter connected in tector flag and detector switches are located series with the flow prover. The accuracy of outside the housing, extremely precise optical the continuous flowmeter is determined by detector switches or magnetic detector swit- 115 comparing electrical pulses therefrom with ches may be used. Another advantage of ex- high frequency electrical pulses generated by ternal placement of the detecting means is the flow proving system as the displacer that maintenance and calibration of the com- moves a predetermined distance within the pact flow prover are greatly facilitated. Still main cylinder. The volume of fluid displaced another advantage is that the detecting means 120 thereby may be corrected for temperature and may be made insensitive to temperature varia- pressure expansion of the cylinder.

tions of the flowing fluid, eliminating the need Figure 1 is a side sectional view of the for correction of the distance between the decompact flow prover in the launch position.

tector switches due to thermal expansion. Figure 2 is a side sectional view of the In another implementation, the main cylinder 125 compact flow prover in the proving cycle.

is charnfered at either end and the displacer is Figure 3 is a side sectional view of the provided with a plurality of compressible compact flow prover at the end of the proving seals. As the displacer enters the main cylin- cycle.

der, the seals are circurnferentially com- Figure 4 is a side sectional view of the pressed. The fluid trapped in the annular 130 compact flow prover in the displacer return 4 GB2196742A 4 mode. from the center of the downstream face of Figure 5 is an expanded view of an imple- displacer 7, and axial sleeve bearing 14, lo- mentation of the bypass valve. cated in downstream section 10 and in axial Figure 6 is an end view of the invention of alignment with displacer pilot 13.

Figs. 1-4 along the lines 6-6. 70 Compression spring 12 is located in axial Figure 7 is an expanded view of an imple- alignment around shaft 8 in inlet section 6 to mentation of the downstream section guide aid in encouraging displacer 7 to enter main means. cylinder 9 during the launch mode.

Figure 8 is an expanded view of the displa- In the specific implementation shown in Fig, cer in the main cylinder. 75 5, bypass valve 4 is of a simple poppet de- Figure 9 is a sectional view of an implemen- sign and is positioned in bypass conduit 3.

tation of the displacer as seen in Fig. 8 along Poppet 60 is shaped as a conical frustum and the lines 9-9. is connected to actuator stem 63. Poppet 60 Figure 10 is a sectional view of a specific is shown abutting valve seat 68 positioned implementation of the displacer seals. 80 between upstream flange 61 and downstream Figure 11 is a sectional view of another flange 62. Poppet 60 is provided with seals specific implementation of the displacer seals. 64 and 65. Annular space 66 between seals Figure 12 is a side sectional view of the 64 and 65 is in fluid communication with volume compensator. channel 67 formed in valve seat 68. Channel Figure 13 is a block diagram of typical hy- 85 67 may be connected to a pressure element draulics. (not shown).

Figure 14 shows a block diagram of a spe- Fig. 6 shows an end view of the compact cific implementation of control circuitry which flow prover of Figs. 1-4 as seen along the may be provided. lines of 6-6. The figure shows shaft 8 sli- Specific implementations of various operat- 90 clably engaged by journal bearing 15 and de- ing modes of the compact flow prover of this tector rod 19 sliclably engaged by journal invention are shown in Figs. 1-4. The com- bearing 20. Inlet conduit 1 is bifurcated to pact flow prover shown includes inlet conduit allow fluid to enter inlet section 6 through 1 and outlet conduit 11 in fluid communication fluid inlet ports 26 and 27. This arrangement with housing 2, and bypass conduit 3. Bypass 95 allows fluid to enter inlet section 6 in a sub valve 4 is located in bypass conduit 3 and is stantially longitudinal direction, reducing or el operated by bypass valve actuator 5. iminating radial and angular forces on displacer Housing 2 includes inlet section 6, main cyl- 7 and permitting shaft 8 to have a reduced inder 9, and downstream section 10, all in diameter and weight. Monitoring means (not axial alignment. Inlet section 6 is in fluid com- 100 shown) may be provided for monitoring the munication with inlet conduit 1 and main cylin- integrity of the seals (not shown) in journal der 9. Downstream section 10 is in fluid combearings 15 and 20.

munication with main cylinder 9 and outlet Fig. 7 shows an implementation of the conduit 11. The inside diameter of main cylin- downstream section guide means. Displacer der 9 is substantially uniform. The cross secpilot 13 is secured to displacer 7 by means of tional areas of inlet section 6 and downstream nut 69. Displacer pilot 13 and shaft 8 may be section 10 are larger than the cross sectional of unitary construction. Displacer pilot 13 is area of main cylinder 9. shown sliclably engaged by bushing 70 in axial A d i splacer/ piston 7 is movably disposed sleeve bearing 14. Axial sleeve bearing 14 within housing 2. Displacer seals 28, 29 are 110 and displacer pilot 13 are in axial alignment positioned on the periphery of displacer 7. with main cylinder 9. Axial sleeve bearing 14 Shaft 8 is connected to the center of the up- is provided with channel 71 to allow fluid to stream face of displacer 7. Shaft 8 extends escape from axial sleeve bearing 14 as displa through journal bearing 15 in inlet section 6 cer pilot 13 enters. This displacement of fluid and is connected to hydraulic piston 16 which 115 from axial sleeve bearing 14 provides a gentle is sliclably disposed in hydraulic cylinder 17. arresting mechanism to slow the movement of Detector rod 19 is connected to displacer 7 displacer 7 as it enters downstream section and extends from inlet section 6 through jour- 10.

nal bearing 20. At its other end, the detector Figure 8 shows an enlarged view of displa- rod 19 is provided with detector flag 21. De- 120 cer 7 in main cylinder 9. Main cylinder 9 is tector unit 22 is provided with precision de- shown chamfered at either end to facilitate the tectors 23, 24 and 25 to detect the passage smooth entry of displacer 7. For example, a of detector flag 21. The detectors can be op- 4' chamfer of 5 cm gives suitable results with tical detectors such as photomicrosensors, a 32.385 cm inside diameter cylinder. The in Model EE-SH3M, available from OMRON. Mag- 125 terior surface of main cylinder 9 is preferably netic detectors would also be acceptable if plated with a corrosion resistant material and detector flag 21 is appropriately modified. Al- honed smooth. The main cylinder 9 must have ternatively, a linear transducer may be used. a substantially uniform inside diameter to pro- The downstream section guide means are vide accurate measurement and provide long comprised of displacer pilot 13, extending 130 displacer seal life. For example, it has been GB2196742A 5 found that a 32.385 cm 0.001 inside dia- implementation of control circuitry which may meter cylinder, with a 0.1 mm hard chrome be used to control the compact flow prover of plate and a 12 RMS or better finish, gives this invention. This circuitry is comprised of suitable results. The particular diameter and control box 53, prover controller 56, and prin length of the cylinder are chosen based on the 70 ter 75. Control box 53 is electrically con flow rates to be measured and the accuracy nected to detector 23, any seal monitoring required. means which are provided, prover controller Displacer 7 is comprised of conical portion 56, and the hydraulic system. Prover control- 72 and ring portion 73. Seals 28 and 29 are ler 56 is electronically connected to detectors prevented from slipping off displacer 7 by re- 75 23 and 24, continuous flow meter 57 and taining rings 36. Annular space 32 formed be- printer 75.

tween seals 28 and 29 is in fluid communi- The operation of this specific implementa- cation with channel 58. Volume compensator tion of the compact flow prover of this inven 37 is provided in fluid communication with tion is best described by reference to Figs.

channel 58 to prevent excessive pressure in 80 1-4. The flow of fluid through the compact annular space 32. flow prover in the launching mode is shown Fig. 9 shows a view of the displacer seen by solid arrows in Fig. 1. The fluid enters inlet in Fig. 8 along the lines 9-9. conduit 1 and flows into housing 2. Fluid is Fig. 10 shows an expanded view of displaprevented from flowing through bypass con- cer seals 28 and 29. Displacer seals 28 and 85 duit 3 during the proving cycle by closing by 29 are comprised of resilient outer layer 34 pass valve 4 by means of bypass valve actua and metallic energizer 35. The material of tor 5. Fluid enters inlet section 6 of housing outer layer 34 may be any material typically 2, flows through main cylinder 9, and exits used for seals such as polyletrafluoroetheylene housing 2 through outlet conduit 11.

or polybutylene and is selected based on the 90 The proving cycle is commenced by allow- chemical resistance of the material to the fluid ing hydraulic fluid to drain from hydraulic cylin being measured, the lubricity of the fluid, and der 17 as discussed below. Displacer 7 is horizontal or vertical orientation of the com- encouraged to enter main cylinder 9 by com pact flow prover in operation. The material of pression spring 12 and the flow of fluid energizer 35 is preferably a metallic alloy. The 95 through inlet section 6. As displacer 7 enters seals are prevented from slipping off of displa- main cylinder 9, fluid is displaced from main cer 7 by retaining rings 36 and held in place cylinder 9 into downstream section 10 and by bands 33 which may be made of steel or out of housing 2 through outlet conduit 11 as aluminum. Base portion 34 of seals 28 and shown in Fig. 2. Detectors 24 and 25 provide 29 extends beyond rings 36. Lip 74 is 100 signals as detector flag 22 passes there pressed outward by metallic energizer 35. through. The rate of flow is determined by Fig. 11 shows an alternate implementation measuring the time between signals.

of displacer seals 28' and 29'. Base portion Fig. 3 shows displacer 7 at rest in down- 34' is shown. not extending beyond rings 36. stream section 10 after the proving cycle is However, lip 74' is pressed out beyond rings 105 completed.

36 by metallic energizer 35'. Displacer 7 is returned to the launching poFig. 12 shows a side sectional view of vol- sition by opening bypass valve 4 and applying ume compensator 37. Volume compensator pressure to hydraulic cylinder 17. Fluid dis 37 is comprised of housing 38, inner element placed by the movement of displacer 7 enters 39, outer element 41, compression spring 40, 110 housing 2 through outlet conduit 11 and exits and seal 42. Inner element 39 is slidably en- through inlet conduit 1 as shown in Fig. 4.

gaged by seal 42. The chamber formed be- Positioning outlet conduit 11 on the side of tween inner element 39 and outer element 41 downstream section 10 is preferred for sev is in fluid communication with the fluid sur- eral reasons. As displacer 7 exits main cylin rounding volume compensator 37. 115 der 9, displacer pilot 13 engages axial sleeve TvFig. 13 shows a block diagram of typical bearing 14 to keep displacer 7 in axial hydraulics used with the specific implementa- alignment with main cylinder 9. Displacement tions. This system is comprised of hydraulic of the fluid from downstream section 10 and pump 43 driven by motor 47, lift selector axial sleeve bearing 14 serves as a natural valve 48 operated by lift actuators 49, and 120 arresting mechanism to stop the movement of reservoir 44. The supply and return of hydrau- displacer 7, eliminating the need for any spe lic fluid to hydraulic cylinder 17 is controlled cial arresting means. Also, it is impossible for by displacer release solenoid 45 and displacer displacer 7 to block the flow of fluid from return solenoid 46. Similarly, bypass valve ac- downstream section 10 after displacer 7 en tuator 5 may be controlled by means of by- 125 ters downstream section 10 since fluid exits pass close solenoid 50 and bypass open sole- therefrom in a radial direction. A more signifi noid 51. The hydraulic system is protected cant advantage is that suspended solids, such from overpressure by means of relief valve as sand or grit, which may be present in the 52. fluid will be less likely to adhere to displacer Fig. 14 shows a block diagram of a specific 130 seals 28 and 29 because of the cleansing ac- 6 GB2196742A 6 tion by the flowing fluid. the use of a more rigid seal material is notShaft 8 and journal bearing 15 function as recommended for use with fluids having a an inlet guide means while displacer 7 is dis- high content of suspended solids as particu posed within inlet section 6. It can be readily late matter will be more likely to remain em appreciated, however, that other guide means 70 bedded in the seals.

and other displacer return means are possible. For operation of the compact flow prover in The bifurcated arrangement of inlet conduit the vertical position, seals 28' and 29' shown 1 shown in Fig. 6 is preferred because fluid is in Fig. 11 are suitable. Since seals 28' and 29' introduced into inlet section 6 in a substan- do not have to support the weight of displa tially longitudinal direction, thereby reducing or 75 cer 7, only lips 74' need to contact the in eliminating radial and angular forces on displa- terior surface of main cylinder 9. Seals 28' cer 7 and permitting shaft 8 to have a re- and 29' may be made of a more resilient ma duced diameter and weight. The reduced terial such as VITON. Solids entrained in the weight of shaft 8 results in lengthened seal fluid measured are less likely to remain em life when the compact flow prover is posi- 80 bedded in seals 28' and 29' and are more tioned horizontally. The reduced diameter of likely to be removed by the flow of fluid past shaft 8 results in a lower pressure drop the seals while displacer 7 is disposed within across displacer 7 while it is disposed within either inlet section 6 or downstream section main cylinder 9. It is readily appreciated that 10. Hence, seals 28' and 29' are suitable for other arrangements of inlet conduit 1, such as 85 use with a dirty fluid such as crude oil. How three, four or more ports, are possible. ever, the softer seal material will cause a It is also desirable to have a minimal pres- higher friction to develop and its use with sure drop in the fluid flowing past displacer 7 fluids having low lubricity is not rec while it is disposed within inlet section 6. The ommended.

diameter of inlet section 6 should therefore be 90 In a preferred implementation of the inven- substantially larger than the diameter of displa- tion, the integrity of displacer seals 28 and 29 cer 7. The conical shape of displacer 7 aids in is verified by monitoring the pressure in annu reducing the pressure drop by reducing turbu- lar space 32. If there is no decrease in pres lence in the fluid flowing therepast. It can be sure as displacer 7 moves from one end of readily appreciated, however, that other displa- 95 main cylinder 9 to the other, the dynamic in cer shapes are possible. tegrity of displacer seals 28 and 29 is veriAs displacer 7 enters main cylinder 9, dis- fied. A pressure element, such as a trans- placer seals 28 and 29 are compressed as ducer, can be located internally sending a sig they contact chamfers 30 or 31. This circum- nal electronically through wiring in either de ferential compression of displacer seals 28 100 tector rod 19 or displacer shaft 8. The pre and 29 causes the pressure to increase in ferred method is fluidly connecting annular annular space 32, resulting in a seal which space 32 with an externally located pressure does not require conventional external block element (not shown) by means of channel 58 and bleed pressuring. A more significant ad- connecting annular space 32 with conduit 59 vantage is that there is only a low pressure 105 formed in detector rod 19.

drop across the displacer 7 as it moves The static method of determining seal integ- through the main cylinder 9 because the seals rity involves positioning displacer 7 within cause only minimal friction as they slide main cylinder 9 with bypass valve 4 in the against the interior surface of main cylinder 9. open position. The pressure in annular space Depending on the type of fluid to be mea- 110 32 may thus be observed for a longer period sured, the compact flow prover may be oper- of time using the static method. This method ated in either a horizontal or a vertical orienta- may be preferred at times since minimum du tion. Fig. 10 shows displacer seals which are ration of the proving cycle can be as low as suitable for use in a compact flow prover op- 1/3 second orless.

erated horizontally. As displacer 7 slides 115 In larger embodiments of the invention through main cylinder 9, gravitational forces which are used for higher flow rates, the dia acting on the weight of displacer 7 will tend meter of the main cylinder 9 and displacer 7 to pull it toward the bottom of main cylinder may be substantial. The volume of fluid com 9, If the seals could not support the weight of pressed in annular space 32 may be therefore the displacer, metal to metal contact would 120 quite large, exceeding several cubic centi occur with the disastrous consequences of meters or more. Hence, the pressure in annu damaging the finish of main cylinder 9. Thus, lar space 32 would become excessive without seals 28 and 29 are provided with a base some modification. For this situation, a volume portion 34 which extends beyond rings 36. compensator 37 as shown in Fig. 12 may be To ensure long life of seals 28 and 29, it is 125 provided to allow for expansion of the fluid preferred that they are made from a more ri- volume. As the fluid in annular space 32 is gid seal material, such as for example polytet- compressed, inner element 39 compresses rafluoroetheylene. The use of a more rigid seal compression spring 40 against outer element material allows the seals to be used with a 41. Fluid between inner element 39 and outer fluid having a low lubricity. On the other hand, 130 element 41 is expelled from volume compen- 7 GB2196742A 7 sator 37 while seal 42 forms a fluid barrier integrity or indicating possible error in the which prevents the fluid compressed in annu- measurement caused by the escape of fluid lar space 32 from escaping into main cylinder past any of these seals. If desired, the prover 9. controller 56 may be equipped with a printer In the launch and proving modes, displacer 70 58 to provide a hard copy of data and calcurelease solenoid 45 shown in Fig. 13 is lations.

opened and hydraulic fluid allowed to drain While I have described above the specific into reservoir 44 as it is displaced from hy- implementations of my invention, many other draulic cylinder 17 by hydraulic piston 16. Dis- variations will occur to those skilled in the art.

placer 7 is returned to its launch position by 75 It is intended that all such variations which fall closing displacer release solenoid 45, opening within the scope of the appended claims be displacer return solenoid 46 and filling hydrau- embraced thereby, lic cylinder 17 with fluid from reservoir 44 by The compact flow provers described above hydraulic pump 43. are also described and claimed in our co- Hydraulic pump 43 is driven by motor 47. 80 pending application No. 8427074 (GB-A-2 The rate of hydraulic fluid pumped is deter- 149 125), from which the present application mined by lift selector valve 48 which is oper- has been divided.

ated by lift actuators 49. The hydraulic sys

Claims (3)

1. tem is preferably used to also control bypass CLAIMS valve 4 by means of

   bypass close solenoid 85 1. A compact flow prover comprising:

   50, bypass open solenoid 51 and bypass a housing including an inlet section having a valve actuator 5. fluid inlet, a main cylinder, and a downstream The internals of control box 53 shown in section having a fluid outlet, the said sections Fig. 14 are arranged to allow certain permisbeing greater in diameter than the main cylin sive actions. Thus, displacer 7 can be pre- 90 der; vented from being launched unless a signal a piston movable through the main cylinder from bypass valve 4 indicates closed and a as a fluid barrier; signal from bypass valve seal monitor 54 indi- a fluid actuator for acting on the piston, cates that the pressure in bypass valve seal including an enclosure and a member recipro 55 is higher than line pressure. Detector 23 95 catable within the enclosure, the said member can also be required to indicate that displacer being connected to the piston by a first, axi 7 is in launch position before closing bypass ally extending shaft, the piston being returna valve 4. ble from the downstream section to the inlet 4As displacer 7 travels through main cylinder section by means of the fluid actuator; 9, detector flag 21 will pass through detector 100 guide means for limiting radial movement of 24 which provides a signal to prover control- the piston while in the inlet section and the ler 56. Upon receiving this signal, prover con- downstream section, the guide means includ troller 56 internally generates a series of high ing a piston pilot terminating in a free end frequency electrical pulses which are counted contained within the housing and axially ex until detector flag 21 passes through detector 105 tending from the face of the piston, and an 25. For even greater accuracy, the prover axial sleeve located in the inlet section, the controller determines fractional pulses using sleeve being axially aligned with the pilot such the dual chronometry method which is well that the pilot may extend into the sleeve; and recognized in the industry, although other well means for detecting the displacement of the known methods, such as the four counter 110 piston along the main cylinder.

   method or the phase lock loop method, will
2. 2. A flow prover as claimed in claim 1, work equally well. wherein the second shaft is adapted to extend The volume of fluid displaced is determined externally of the housing, the said detecting from the distance between detectors 24 and means including a second shaft connected to 25 and the diameter of main cylinder 9, cor115 the piston and extending axially through the rected for pressure and temperature expan- main cylinder, the second shaft including sion. In a preferred implementation, the detec- means for enabling the position or given posi tors will be mounted on a shaft made of a tions of the piston to be detected, and a de material with a low thermal expansion coefficitector, mounted externally of the housing, ent, such as Invar, so that no temperature or 120 adapted to detect the position or given posi pressure correction will be required for the tions of the portion of the second shaft ex distance between detectors 24 and 25, the tending externally of the housing.

   measured length. From the elapsed time and
3. 3. A flow prover as claimed in claim 2, the volume so determined, the flow rate can wherein the piston includes a seal means for be calculated. The flow rate is then compared 125 forming a fluid barrier within the main cylinder, with the output generated by continuous flow the second shaft including means for monitor meter 57. ing the integrity of the seal means.

   It is also preferred that seal monitoring means for displacer 7, hydraulic shaft 8 and detector rod 19 provide a signal verifying seal 8 GB2196742A 8 Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD.

   Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.