GB2346672A

GB2346672A - Valve testing apparatus and method

Info

Publication number: GB2346672A
Application number: GB9902933A
Authority: GB
Inventors: Derek Mark Essam
Original assignee: DRALLIM IND
Current assignee: DRALLIM IND
Priority date: 1999-02-10
Filing date: 1999-02-10
Publication date: 2000-08-16
Also published as: ITMI20000209A0; ITMI20000209A1; IT1316622B1; GB9902933D0

Abstract

Test apparatus is disclosed for a valve controlled by a piston moveable in a cylinder, between first/second positions in which the valve is open/closed. An electrically controlled valve 22 is provided to supply gas pressure to one side of the piston 13 to maintain the piston in the first position. An electrically controlled valve 21 is provided for supplying a lower pressure gas to the one side of the piston and an electrically controlled valve 39 is provided for sealing the cylinder on the one side of the piston when the lower pressure gas is supplied to the one side of the piston. The piston is urged to move from the first position to a third position intermediate the first and second positions against the lower pressure gas when the one side of the piston is sealed by the electrically controlled sealing valve 39. The urging force for the piston may be provided by gas pressure or a spring The higher and lower pressure gas may be provided from a common source, the lower pressure via a pressure reducer 46. Valve 21 may be a selector valve.

Description

MEANS FOR TESTING A FLUID VALVE AND METHOD THEREFOR The present invention relates to means for testing a fluid valve and a method therefor.

The invention will be described with reference in particular to emergency shut down valves which are used, for example, in processing industries such as oil refineries or oil rigs, the valve being provided in an oil pipeline, the arrangement being such that in the event of an emergency, the valve will close and isolate the process.

Thus whilst we shall describe the invention with particular reference to valves for use in isolating the flow of oil, it will be understood that other valves controlling the flow of any fluid comprising a liquid or gas may be tested according to the invention.

One of the difficulties with such emergency shut down valves is that particularly where an oil refinery is in continuous operation, in view of the cost of shutting any particular line whilst carrying out maintenance work, the shut down valves are not moved between maintenance intervals which may be several years. As a consequence, over that period of time, because of the deposit of dirt or other material, the valve may become stuck and not be operable in an emergency. It is highly desirable to be able to test the valves at more frequent intervals to ensure that they are operable and it is preferable that the valves should be tested without closing down the oil pipeline in which they are mounted.

The emergency shut down valves may comprise a variety of forms, for example, gate valves, butterfly valves, rotary or ball valves, but the normal method of operation of the valve to open and close it is by applying gas pressure (usually air pressure) to one or other side of a piston in a closed cylinder, the piston being connected to the valve operating mechanism.

We shall describe hereafter an arrangement in which the emergency shut down valve may be tested for operation by only partially closing the valve, it being ascertained that so long as the valve begins to close, it is not necessary to close it fully since the initial movement of the valve is only necessary to prove that the valve is free to move and provides evidence that the valve would close completely.

One aspect of the invention provides, for a valve of a type controlled by a piston in a cylinder, the piston being moved between a first position in which the valve is open/closed and a second position in which the valve is closed/open, gas pressure always being supplied to one side of the piston to maintain the valve in first position, a testing apparatus including a first electrically controlled control valve for diverting, when in a first position, a high gas pressure to one side of said piston and in a second position, a lower pressure gas to said one side of said piston, and a second electrically controlled control valve for sealing said cylinder on said second side of said piston, whereby the gas pressure on said one side of the piston may be reduced from a first, higher pressure to a second, lower pressure, that side of the piston is then sealed so that gas may not pass to or from the first side of the piston, and means is provided to urge the piston to move from the first position to a third position intermediate the first, and second positions.

Other aspects of the invention will be apparent from the description.

The invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a first embodiment of an emergency shutdown valve and control system in accordance with a preferred embodiment of the invention in a normal mode, Figure 2 shows the system of Figure 1 in a preparatory stage 1 test mode, Figure 3 shows the system of Figure 1 in a test mode, Figure 4 shows the system of Figure 1 in an emergency mode, Figure 5 is a diagrammatic view of a second embodiment of an emergency shutdown valve and control system in accordance with a preferred embodiment of the invention in a normal mode, Figure 6 shows the system of Figure 5 in a test condition I mode, Figure 7 shows the system of Figure 5 in a test condition 2 mode, Figure 8 shows the system of Figure 5 in an emergency condition mode.

Referring to Figure 1, there is shown in diagrammatic form an emergency shut down valve 10 for insertion, for example, in an oil or gas pipeline, said shut down valve comprising a valve member 11, a control rod 12 to move the valve member between a first, open, position and a second, closed, position, the control rod 12 being connected to and driven by a piston 13 mounted in a closed cylinder 14. The cylinder 14 includes a first port 16 which connects with a first side 17 of the piston 13 and a second port 18 which connects with the second side 19 of the piston 13.

The first port 16 is connected via a first control valve 21 (to be described later) and a second control valve 22 with a pressure air supply 23. Each control valve 21,22 is controlled by a respective solenoid 26,27 which causes the control valve 21,22 to move between a first and second position, the first position (shown in Figures 1 and 2) connecting the port 16 with the pressure air supply 23 at a first upper pressure PI.

In detail, first port 16 is connected to a port 28 of control valve 21 by a line 24 and a line 29 interconnects a port 31 of control valve 21 with a port 32 of control valve 22.

A port 33 of selector valve 22 is connected to the air supply 23.

The second control valve includes a third closed port 34. The first control valve 21 includes a third port 36 which is connected by line 37 to port 40 of a third control valve 39, the third control valve 39 including a second port 41 and a third port 42.

The third control valve 39 is controlled by a solenoid 43, and the port 42 is connected by a line 44 to the output of a pressure reducing regulator 46. The pressure reducing regulator 46 is connected by line 47 to receive pressure air from the air pressure supply 23. The pressure reducing regulator 46 provides on line 44 an intermediate pressure P2 which is lower than the pressure PI in the pressure air supply 23.

The second port 18 of the valve 10 is connected by line 48 to a first port 49 of a fourth control valve 51 controlled by solenoid 52, a port 53 of fourth control valve 51 is connected to exhaust and a third port 54 is connected by line 56 to the pressure air supply 23.

Pressure indicators 57,58,59 are connected respectively to lines 24 and 29, and port 41.

An electrical control system 61 is provided to supply power to the solenoids 26, 27,43 and 52, to control operation of respective control valves 21, 22, 39, 51, in the case of solenoid 43, via a limit switch 62 in the form of a switch which changes when the piston 13 reaches a predetermined position in the cylinder 14. Control valves 21 22 are rotated to their different positions by actuation of the solenoids 26,27 bv the electrical control system 61.

The system operates as follows.

In the drawings, in respect of the control valves 21,22, 39, 51, the relevant ports which are open are indicated by clear triangles and the ports which are closed are indicated by black triangles. Similarly, with regard to the cylinder 14, the side of the piston which is under high pressure PI is indicated in black, the side of the piston which is connected to exhaust is indicated in white, and the side of the piston which is connected to an intermediate pressure is cross-hatched.

In use of the apparatus the normal positions of the valves is shown in Figure 1. In this position, air under pressure from supply 23 is passed from port 33 to port 32 of second control valve 22, via line 29 to port 31 of first control valve 21, and thence to port 28, and via line 24 to first port 16 of the cylinder 14. This causes the piston 13 to be held at the lefthand end (when viewed in Figure 1) of the cylinder 14. Note that the port 18 is connected to atmospheric pressure via ports 49 and 53.

In this position, the valve member 11 is in its normal open position.

In an emergency, as shown in Figure 4, electrical control system operates the solenoids 27 and 52 to switch the second and fourth control valves to their opposite orientation in which ports 32 and 34 are interconnected and ports 54 and 53. In this position, therefore, first port 16 is connected via line 24 port 28, port 31, line 29, port 32 port 34 to atmosphere. Second port 18, however, is connected via line 48, ports 49 and 54, and line 56 to air at pressure PI from pressure air supply 23. This moves the piston 13 from the left position shown in Figure 1 to the right hand position shown in Figure 4 which closes the valve number 11.

Movement of the piston away from the limit switch 63 will be recorded by the electrical control system.

When it is required to test the actuation of the shut down valve without closing the shut down valve, it is desired to move the piston 13 from its position of Figure 1 to a position intermediate Figures 1 and Figure 4. This is carried out in the following manner.

In the preparatory stage 1 test mode shown in Figure 2, the control valves are moved to the position shown, in particular the control valves 21 and 22 are moved so as to interconnect ports 28 and 36 and 32 and 34 respectively. In this position therefore, the first port 16 is connected via line 24, ports 28 36, line 37, ports 40 42, to receive the intermediate pressure air at pressure P2 from the pressure reducing regulator 46. The piston 13 will remain at the left hand end of the cylinder 14 as shown.

Under control of the electrical control system 61, the solenoid 52 is operated. The electrical control system 61 applies a signal to solenoid 52 which rotates the fourth control valve 51 so as to interconnect ports 49 and 54 which thereby allows air pressure PI from the pressure supply 23 along line 56 to be applied to the port 18.

Thus the piston 13 will have air at pressure PI applied to the left hand side, and air at intermediate pressure P2 applied to the right hand side so that it moves to the right.

The electrical control system 61 has in the meantime applied an electrical control signal via the limit switch 62 to the solenoid 43 which causes the control valve 39 to rotate so as to interconnect ports 41,42 and shut off port 40. This means that the air at intermediate pressure P2 which is applied to the inlet port 16 is then trapped within the cylinder 14. The higher air pressure of PI will tend to move the piston to the right but because the air to the right of the piston 13 is trapped, there comes a point at which the pressures on the two sides of the piston will equalise before the piston reaches the right hand end of the closed cylinder 14. This position is shown diagrammatically in Figure 3. In this position, therefore, the piston has been moved so as to partially close the emergency shut down valve without it closing completely.

To return to the normal position, the electrical control system 61 switches the various solenoids in the reverse order.

It will be understood that the pressure indicators 57,58 and 59, which may be connected to a remote control point, indicate operation of the apparatus. A bleed device is provided adjacent pressure indicator 59 to allow air trapped in Figure 2 to bleed down to atmospheric pressure. The pressures indicates in the different Figures for the different pressure indicators are as follows: Pressure Indicator 58 Pressure Indicator 57 Pressure Indicator 59 Figure 1 (normal) PI PI 0 Figure 4 (emergency) 0 0 0 Figure 2 (stage 1 test mode) 0 P2 0 Figure3 (test mode) 0 P 1 P2 The system may be manually activated where the electrical control system 61 is local to the valves, or the electrical control system may be situated at a remote control position such as the plant control system.

The first and second control valves may be combined into a single unit, for example, as a single solenoid 5/2 arrangement.

Figures 5 to 8 show a second embodiment of the invention in which the emergency shut down valve 10, rather than being operated by differential pressure applied to opposite sides of a piston 13 (a so called double acting pressure shut down valve) is operated by air pressure applied to one side of the piston, the piston being urged against the air pressure by means of a spring 71. The same reference numerals have been used as with regard to Figures 1 to 4 where appropriate but it should be noted that the closed cylinder 14 does not of course include a second port 18, there is no fourth control valve 51 and associated solenoid and line.

Referring now to Figure 5, it will be seen that as with Figure 1, the pressure air at pressure PI from air pressure supply 23 is passed via first and second control valves 21,22 to the first port 16 of the cylinder 14 which urges the piston 13 to the left against the action of the spring 71.

In the emergency condition shown in Figure 8, second control valve 22 is rotated by solenoid 27 so as to interconnect ports 32 and 34 which thereby allows the pressure air to the right of the piston 13 to pass to atmosphere so that the emergency shut down valve 10 closes by mean of the action of the spring 71.

In order to test the operation of the emergency shut down valve 10, solenoid valve 26 is energised by electrical control system 61 so as to rotate first control valve 21 to the position shown in Figure 6 wherein the ports 28 and 36 are interconnected. In this position, reduced air pressure at pressure P2 is supplied via third control valve 39 and first control valve 21 to the first port 16 of the closed cylinder 14. This lower pressure allows the piston 13 to move somewhat to the right as indicated in Figure 6. As the piston moves av.'ay ay from the Lm. ; t switch 6 is allovvs a ccr. ~cl signal to be passed from the electrical control system 61, via the limit switch 62 to the solenoid valve 43 to rotate the third control valve 39 so as to interconnect ports 41 and 42. In this position, the line 37 is closed by means of the port 40 which prevents exhaustion of the air in the cylinder 14 to the right of the piston 13 so that the piston 13 compresses the air until the force exerted by the spring 61 and the pressure exerted by the air to the right of the piston 13 balance one another. This happens before the valve 10 closes.

The system may be reset by operating the solenoid valves in the opposite sense to return to the arrangement of Figure 1.

The pressure indicators will indicate the following pressures : Pressure Indicator 58 Pressure Indicator 59 Figure 5 (normal) PI 0 Figure 8 (emergency) 0 P2 Figure 6 (test condition 1) 0 0 Figure 7 (test condition 2) 0 P2 The invention is not restricted to the details of the foregoing examples.

Claims

CLAIMS 1. Test apparatus for a valve of a type controlled by a piston in a cylinder, the piston being moveable between a first position in which the valve is open/closed and a second position in which the valve is closed/open, means being provided to supply gas pressure to one side of the piston to maintain the valve in said first position, the test apparatus including means for supplying a lower pressure gas to said one side of said piston and means for sealing said cylinder on said one side of said piston when said lower pressure gas is supplied to said one side of said piston, and means is provided when said one side of said piston is sealed by said sealing means to urge the piston to move from the first position to a third position intermediate of the first and second positions against said lower pressure gas.
2. A test apparatus as claimed in claim 1 in which said urging means comprises means to supply gas at a higher pressure to a second side of the piston opposite said first side.
3. A test apparatus as claimed in claim 1 in which said urging means comprises a spring.
4. A test apparatus as claimed in any of claims 1 to 3 in which said lower gas pressure supply means comprises a pressure reducing means connected between a higher gas pressure supply means and said one side of said piston.
5 A test apparatus as claimed in claim 4, in which the higher gas pressure supply means is also connected to said one side of said piston, and selector means is provided to select either the higher pressure gas from the higher gas pressure supply means or lower pressure gas from the lower gas pressure supply means.
6. A test apparatus as claimed in claims 2 and 5, in which further selector means is provided to selectively connect said higher gas pressure supply means to said second side of the piston opposite said first side, said fLrthei selector means providing said urging means.
7. A test apparatus as claimed in claim 5 or claim 6, in which each of said selector means comprises an electrically controlled selector valve.
8. A test apparatus as claimed in claim 1 substantially as hereinbefore described with reference to Figures 1 to 4.
9. A test apparatus as claimed in claim 1 substantially as hereinbefore described with reference to Figures 5 to 8.
10. A test apparatus for a valve of a type controlled by a piston in a cylinder, the piston being moveable between a first position in which the valve is open/closed and a second position in which the valve is closed/open, means being provided to supply gas pressure to one side of the piston to maintain the valve in said first position, the testing apparatus including a first electrically controlled control valve for diverting, when in a first position, a high gas pressure to one side of said piston and in a second position a low pressure gas to said one side of said piston, and a second electrically controlled control valve for sealing said cylinder on said one side of said piston, whereby the gas pressure on said one side of the piston may be reduced from a first high pressure to a second lower pressure, that side of the piston is then sealed so that gas may not pass to or from the first side of the piston, and means is provided to urge the piston to move from the first position to a third position intermediate of the first and second positions.
11. A method for testing operation of a valve of a type controlled by a piston in a cylinder, the piston being moveable between a first position in which the valve is open/closed and a second position in which the valve is closed/open, means being provided to supply gas pressure to one side of the piston to maintain the valve in said first position, for supplying a lower pressure gas to said one side of said piston and sealing said cylinder on said one side of said piston when said lower pressure gas is supplied to said one side of said piston, and when said one side of said piston is sealed by said sealing means urging the piston to move from the first position to a third position intermediate of the first and second positions against said lower pressure gas.
12. A method as claimed in claim 11 comprising supplying gas at a higher pressure to a second side of the piston opposite said first side to urge said piston to move from the first position to the third position.
13. A method as claimed in claim 11 in which said urging means comprises a spring.
14. A method as claimed in any of claims 11 to 13 in which said lower gas pressure supply is provided via a pressure reducing means connected between a higher gas pressure supply means and said one side of said piston.