GB2171210A

GB2171210A - Meter provers

Info

Publication number: GB2171210A
Application number: GB08603314A
Authority: GB
Inventors: Graham Capper
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-02-14
Filing date: 1986-02-11
Publication date: 1986-08-20
Also published as: GB8503834D0; GB8603314D0; GB2171210B

Abstract

A meter prover comprises upstream and downstream chambers (1), (3), a stationary seal (5) between the chambers, a piston body (6) within and bridging the chambers, said piston body being in sealed sliding engagement with the stationary seal and having an outer diameter less than the minimum inside measurement across each chamber, an independent actuator (9) to initiate a proving run of the piston body (6) from one chamber to the other, a detector unit (10) for signaling the start and end of a proving run, and port openings (17) at one end of the piston body (6) providing fluid communication between the chambers prior to the onset of the proving run. The piston body (6) is attached to a piston rod (7) forming part of the actuator (9). The rod may extend through a seal at the top of chamber (1). Leakage past the seal (5) is monitored by means (21). <IMAGE>

Description

SPECIFICATION Meter provers This invention relates to meter provers for checking the accuracy of turbine and positive displacement flow meters particularly in the petro-chemical industry.

Generally meter provers are relatively expensive pieces of equipment and the reliability of any sealing arrangement within a prover is crucial but constant monitoring for any leakage can be difficult particu larlywhen the sealing arrangement is on a moving part of the equipment.

The object of the present invention is to provide a relatively compact meter prover having a stationary seal arrangement capable of being readily checked for any leakage.

According to the present invention, a meter prover comprises an upstream chamber with a port, a downstream chamber with a port, either port for connection to a meter to be proved, a stationary seal between the two chambers, a piston body within and bridging the chambers, said piston body being in sealed sliding engagement with the stationary seal and having an outer diameter less than the minimum inside measurement across each chamber, an independent actuator to initiate a proving run of the piston body from one chamber to the other, a detector unit for signalling the start and end of the proving run, and port openings at at least one end of the piston body providing fluid communication between the chambers prior to the onset of the proving run.

The piston body may beattached to a piston rod which projects through a sealing means at the end of at least one of the two chambers and is connected to the independent actuator external of the chambers.

Preferably port openings are provided at the opposite end of the piston body, to provide fluid communication between the chambers at the end of the proving run. Thus the meter being proved maybe used continually throughout the proving run.

The stationary seal may comprise a housing having two sealing rings sealing round the piston body and means are provided for detecting seal integrity between the stationary seal and the piston body which are comprised of a groove in the seal housing between the two sealing rings and a bore from the groove to a fluid indicator, which may be a pressure gauge or alternatively a pressure transducer connected to a remote display.

The independent actuator may be a double acting cylinder with a piston therein secured to the projecting end of the piston rod from the piston body. The piston rod may project from the upstream chamber, and a damper unit for the piston body may be provided at the remote end of the downstream chamber.

Alternatively the other end of the piston rod may project through the piston and through a seal arrangement in the downstream chamber and thus the detector unit may then be mounted selectively at either end of the meter prover to cooperate with that part of the piston rod at that end. This construction has the advantage of balancing the pressure in the complete assembly with the pressure drop through the prover being a function of the flow path and not the pipeline pressure as a multiple of the annulus area of the piston shaft. This construction also balances the flow through the prover in that the introduction of the fluid equivalent of the piston shaft coming into the system will be balanced by an equal fluid equivalent of the piston shaft moving out of the system.

Upstream and downstream pipes are preferably connected to the respective ports of the chambers, either of which pipes is adapted for connection to a meter to be proved and a bypass valve in a bypass pipe as preferably provided between the upstream and downstream pipes.

The invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic axial section of the meter prover in its static position; Figure 2 corresponds to Figure 1 but shows the position of the meter prover at the start of the proving run; Figure 3 corresponds to Figure 1 but shows the position of the meter prover during the proving run; Figure 4 corresponds to Figure 1 but shows the position of the meter prover at the end of the proving run; Figure 5 corresponds to Figure 1 but shows the position of the meter prover during the return; and Figure 6 corresponds to Figure 1 but shows an alternative method of supporting the piston.

In Figure 1 a meter prover has an upstream chamber 1 with a port 2, a downstream chamber 3 with a port 4, a stationary seal 5 between the chambers 1 and 3, a piston body 6 within and bridging the chambers said piston body attached to a piston rod 7 and being in sealed sliding engagement with the stationary seal 5, a further seal 8 is provided at the end of the upstream chamber 1 through which the piston rod 7 passes, and an independent actuator 9 for the projecting end of the piston rod 7. A detector unit 10 is mounted in the independent actuator 9 for measuring the linear movement of the piston body 6, and to signal the start and end of a proving run.A damper unit 11 at the remote end of the downstream chamber 3 is adapted to arrest the downstream momentum of the piston body 6, and a bypass pipe 12 is provided with a valve 13 between upstream and downstream pipes 14 and 15 connected to the respective ports 2 and 4 of the chamber 1 and 3 either of which pipes 14 and 15 is adapted for connection to the meter (not shown) to be proved. Relief ports 16 and 17 are provided respectively at the upstream and downstream ends of the piston body 6.

The statutory seal 5 is provided with two sealing rings 18 sealing round the piston body 6 and the means for detecting seal integrity comprises a groove 19 in the seal housing 5 between the sealing rings 18 and a bore 20 from the grooves to a fluid indicator 21.

In the operating sequence the meter prover is initially in the static position of Figure 1 with fluid flowing from the upstream pipe 14 between the upstream chamber 1 and the downstream chamber 3 through the ports 17 in the piston body and also through the open valve 13 in the bypass pipe 12. The valve 13 is then closed, as shown in Figure 2 allowing fluid flow through the ports 17 only.

In Figure 3 the proving run is initiated by applying pressure to the actuator 9 which moves the piston body 6 forward until the ports 17 have passed the seal housing 5 and fluid pressure in the upstream line carries the piston body 6 forward into the downstream chamber and therefore via the downstream pipe 15 through the meter (not shown) being proved. Downstream movement of the piston body 6 continuies until, in the position shown at the end of the proving run in Figure 4, the relief ports 16 pass the seal housing 5 and relative the fluid pressure on the piston body 6 and the damper unit 11 arrests its downstream movements. Gate detection signals generated by the detector unit 10 at the beginning and end of the proving run are analysed by the meter prover computer (not shown) together with pulses from the meter being proved to give a readout of a correction factor immediately upon completion of the proving run.

In Figure 5 the piston body is returned to the starting position of Figure 1 after opening the valve 13 allowing fluid flow from the upstream pipe 14to the downstream pipe 15, by applying pressure to the actuator 9 to draw the piston body 6 into the upstream chamber 1.

In the alternative construction shown in Figure 6 the piston rod 7 projects through the piston body 6 and through a seal 22 in the remote end of the downstream chamber3 and the detector unit 10 is mounted at the end of the meter prover to coperate with that end of the piston rod 7.

Claims

1. A meter prover comprising an upstream chamber with a port, a downstream chamber with a port, either port being for connection to a meter to be proved, a stationary seal between the two chambers, a piston body within and bridging the chambers, said piston body being in sealed sliding engagement with the stationary seal and having an outer diameter less than the minimum inside measurement across each chamber, an independent actuatorto initiate a proving run of the piston body from one chamber to the other, a detector unit for signalling the start and end of the proving run, and port openings at at least one end of the piston body providing fluid communication between the chambers prior to the onset of the proving run.

2. A meter prover as in Claim 1, wherein the piston body is attached to a piston rod which projects through a sealing means at the end of at least one of the two chambers and is connected to the independent actuator external of the chambers

3. A meter prover as in Claim 1 and Claim 2, wherein means are provided for detecting integrity of the seal between the stationary seal and the piston body.

4. A meter prover as in any one of Claims 1 to 3, wherein port openings are provided at the opposite end of the piston body providing fluid communication between the chambers at the end of the proving run.

5. A meter prover as in any one of Claims 3 and 4, wherein the stationary seal comprises a housing having two sealing rings sealing round the piston body, and the means for detecting seal integrity comprises a groove in the stationary seal between the two sealing rings and a bore from the groove to a fluid indicator.

6. A meter prover as in Claim 5, wherein the fluid indicator is a pressure gauge.

7. A meter prover as in Claim 5, wherein the fluid indicator is a pressure transducer connected to a remote display.

8. A meter prover as in any one of Claims 2 to 7, wherein the independent actuator is a double-acting cylinder with a piston therein secured to the projecting end of the piston rod from the piston body.

9. A meter prover as in any one of Claims 2 to 8, wherein the piston rod projects from the upstream chamber, and a damper unit forth piston body is provided at the remote end of the downstream chamber.

10. A meter prover as in any one of Claims 1 to 8, wherein the piston rod projects through the piston and through a seal arrangement in the downstream chamber.

11. A meter prover as in any one of Claims 2 to 10, wherein the detector unit is mounted selectively at either end of the meter prover to cooperate with that part of the piston rod at that end.

12. A meter prover as in any one of Claims 1 to 11, further provided with upstream and downstream pipes connected to the respective ports of the chambers, either of which pipes is adapted for connection to a meter to be proved, a bypass pipe between the upstream and downstream pipes, and a shut-off valve in the bypass pipe.

13. A meter prover substantially as hereinbefore described with reference to Figures 1 to 5, or as modified as in Figure 6 of the accompanying drawings.

14. A meter prover substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.