GB2332939A

GB2332939A - Testing fluid valves

Info

Publication number: GB2332939A
Application number: GB9800050A
Authority: GB
Inventors: Derek Mark Essam
Original assignee: DRALLIM IND
Current assignee: DRALLIM IND
Priority date: 1998-01-02
Filing date: 1998-01-02
Publication date: 1999-07-07
Anticipated expiration: 2018-01-02
Also published as: GB2332939B; GB9800050D0

Abstract

A testing apparatus for a valve (10) of a type controlled by a piston (15) in a cylinder (14), the piston being moved between a first position in which the valve is open and a second position in which the valve is closed, comprises means to supply gas at a first higher pressure to one side of the piston to maintain the valve in the first position. Means are provided to reduce the gas pressure on the one side of the piston from the first, higher pressure to a lower pressure, and to then seal the one side of the piston so that gas may not pass to or from that side of the piston. Means are also provided to then pass gas at a second higher pressure to the opposite side of the piston to urge the piston to move from the first position to a third position intermediate the first, and second positions.

Description

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

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 din 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 and method in which the gas pressure on said one side of the piston is 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 a higher pressure gas, for example, at said first pressure, is passed to the opposite side of the piston to urge the piston to move from the first position to a third position intermediate the first. and second positions.

As the piston moves to said third position, gas at said one side of the piston is compressed by the higher pressure on the opposite side of the piston until the pressure on the two sides are in equilibrium.

There may be provided one or more selector valves which control supply of pressure gas to the valve, the selector valve(s) being moved from a first position in which the first higher pressure is supplied to said first side of the piston to a second position in which said first gas pressure is applied to the opposite side of the piston to close the valve and said second lower pressure is applied to the first side of the piston.

Means may be provided to provide said second, lower, gas pressure from said supply of said first pressure, said means comprising a pressure reducing means.

The invention will now be described by way of an example and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of an emergency shut down valve and control system in accordance with a preferred embodiment of the invention in a first position, Figure 2 shows the arrangement of Figure 1 in a second position, Figure 3 shows the arrangement of Figure 1 in a third position. and Figure 4 is a perspective view of a rotary valve arrangement for use with the apparatus of the invention.

Referring to Figure 1, there is shown an emergency shut down valve 10 for insertion, for example, in an oil 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 lower port 16 which connects with a first, lower, side of the piston 13. Similarly an upper port 18 connects with the upper part of the cylinder 14 and with a second, upper side 19 of the piston 13.

The lower port 16 is connected via a first selector valve 21 (to be described later) with a control valve 22. The control valve 22 is controlled by a solenoid 23 which moves the control valve 22 between a first and second position, the first position (shown in Figures 1 and 2) connecting the first selector valve 21 with an air supply 27 at a first upper pressure P1 and the second position (shown in Figure 3) connecting the first selector valve 21 with an exhaust port 40.

In detail, port 16 is connected to a port 28 of selector valve 21 by a line 24 and a line 26 interconnects a port 29 of selector valve 21 with a port 31 of control valve 22. A port 25 is connected to the air supply 27.

Power is provided from a powerline 45 to the solenoid 23 via an electrical line 46 connected to a first terminai 47 of a rotary switch 48, a second terminal 49 of the rotary switch 48 being connected to the power line 45 there being provided a third terminal 51 and a fourth terminal 52.

The upper port 18 is connected by a line 32 to a port 33 of a second selector valve 34, a second port 36 of selector valve 34 is connected to a second port 37 of control valve 22 by means of line 38. The air supply 27 is connected via line 39 to a pressure reducing regulator 41 which supplies air at a reduced pressure (P2) to a port 42, and port 42 of the pressure reducing regulator 41 is connected by line 43 to a third port 30 of the selector valve 21. The pressure reducing regulator maybe a self-venting pressure regulator.

The pressure air supply 27 is also connected via line 52 to a third port 53 of the selector valve 34.

The selector valves 21. 34 and rotary electrical switch 48 may be connected to one another to be rotated in synchronism with one another as is well known in respect of a range of such rotary selector switches sold by the applicant, Drallim Industries Ltd of Bexhill, East Sussex, England, under for example, the code number PIV Series 40. Such a combination of two selector valves and a rotary electrical switch is shown in Figure 4.

Referring to Figure 4 it will be seen that the selector valves 21, 34 are mounted above one another and at the base of the apparatus is mounted the rotary electrical switch 48. Not shown in Figure 4, but illustrated diagrammatically at 58 in Figures 1 to 3, is a shaft which passes through from the top of the stack through the selector valves 21, 34 to the switch 48, and each of the valves and switch is connected to the central shaft so as to be rotated with the central shaft. Inside each selector valve 21 is provided a rotatable block (shown diagrammatically at 59A, 59B in Figures 1 to 3) with one or more selective passages there through, the arrangement being such that the passages connect in an air tight manner with the ports of that switch, rotation of the shaft rotating the block and thereby changing the relative connections between the various ports of each selector valve. A somewhat similar arrangement pertains to the rotary electrical switch 48. The construction of the selector valves 21, 34 and the rotary electrical switch 46 are well known in the field. Also shown in Figure 4 is a key operating mechanism 56 comprising a key 57 and lock 58. The key 57 is removable and allows only selected personnel to operate the apparatus by rotating the shaft by means of key 57. Such an arrangement is generally well known in fieid.

Before describing the operation of the arrangement of Figures I to 3 it may be useful to refer to the arrangement of emergency shut down valve control system which is used at present. In prior art arrangements, selector valves 21, 34, rotary electrical switch 48. and pressure reducing regulator 41 are not provided. Thus port 31 of control valve 22 is directly connected to port 16 of the valve 10. and port 18 of valve 10 is directly connected to port 37 of control valve 22. Thus in normal operation there is provided an electrical signal on line 46 which maintains the control valve 22 in the position shown in Figure 1 whereby air pressure P1 from the air supply 27 is supplied directly to the port 16 and thence to the lower part first side 17 of the piston 13, second side 19 being connected via line 32 and control valve 22 to exhaust port 40.

When the electrical signal on line 46 is interrupted, the control valve 22 moves to the second position (the position shown in Figure 3) in which rhe pressure air supply is connected from inlet port 25 to port 37 and thereby along line 32 to the upper part 18 of the cylinder 14 and similarly the port 16 is connected via line 26 and control valve 22 through to the exhaust port 40. In this position the piston 13 is driven downwards to close the valve member 11.

The valve member 11 may be reopened by reapplying the electrical signal to line 46 which moves the control valve 22 back to the position shown in Figure 1.

The apparatus as described above is operated as follows and as shown in the Figures 1 to 3.

Referring to Figure 1, this shows the arrangement during normal operation. In this arrangement, the solenoid valve 23 is in a position whereby the port 25 is connected to outlet port 31 so that the pressure air supply 27 supplies pressure at pressure P1 via selector valve 21, port 28 and line 26 to the port 16 of the emergency shut down valve 10. This maintains the piston 13 at its uppermost position as shown in Figure 1 and in this position the valve member 11 is in its normal position (which in this example is normally open). Air at pressure P1 from the air supply 27 is also passed to the pressure reducing regulator 41 and reduced air pressure is provided by that regulator 41 to line 43 at a lower pressure P2.

This is passed to the port 30 of selector valve 21 which, as is clear from Figure 1, is not connected by the selector valve to any other port.

It will be noted that in the position of the selector valves 21. 34 and rotary electrical switch 48 shown in Figure 1 that the selector valve 34 connects a second side 19 of the piston 13 via upper port 18 and line 32 to port 37 of control valve 22 which is the exhaust port 40 connected. Similarly the electrical switch 48 connects the power inlet terminal 49 to an outlet terminal 47 which is connected to line 46 and hence to solenoid 23 maintaining the control valve 22 in the position shown in Figure 1.

When it is intended to tese the operation of the shut down valve 10 without completely closing the shut down valve, the selector valves 21 34 and rotary electrical switch 48 are rotated in synchronism from the positions shown in Figure 1 to the positions shown in Figure 2. In this position, the immediate effect is to maintain the control valve 22 in its normal position (as the power inlet terminal 49 is connected to line 46 via terminal 51) but the line 26 is no longer connected by the selector valve 21 to the first side 17 of the piston 13 but is isolated. However, the selector 21 now allows connection between the port 30 and the port 28 and thereby applies the reduced air supply at pressure P2 from the pressure regulator 41 via line 43 to port 16 to the first side 17 of the piston 13 so that the pressure is reduced from the normal high pressure P1 to the lower pressure P2. The second side 19 of the piston is still isolated via selector valve 34. This lower pressure P2 is sufficient to maintain the piston 13 in the same position as in Figure 1.

The selector valves 21, 34 and rotary electrical switch 48 are tlien rotated in synchronism to the position shown in Figure 3. and the situation changes. In this position, the input terminal 49 is no longer connected to the output terminals 47 or 51 and thus the electrical power to the line 46 and to the solenoid 23 is cut. As a result. the control valve 22 moves to the position shown in Figure 3. (ie line 26 is connected to exhaust port 40 and line 38 is connected to pressure P1 by port 25).

In the position of the selector valves shown in Figure 3, the selector valve 21 isolates the first side 17 of the piston 13 as the port 28 is no longer connected to another port in the selector valve. This means that the air at pressure P1 within the cylinder 14 on the first side of the piston cannot be evacuated. With the solenoid controlled valve 22 in the position shown in Figure 3, air pressure from the air supply 27 at pressure P1 is provided along the line 52 to the port 53 and the selector valve 34 connects port 53 with port 33 thereby providing this high pressure air supply P1 via the line 32 and the port 18 to the second side 19 of the piston 13. The effect of this is to drive the piston downwards and this partially rotates or moves the control rod which at least partially closes the valve member 11. During this downward movement of the piston 13 the air inside the lower part of the cylinder 14 is compressed and the piston 13 comes to rest at a point at which the air in the lower part is compressed to a pressure substantially equivalent to the higher pressure Pi. This position will of course be intermediate the upper most and lower most possible positions of the piston 13 so that the valve 10 is not completely closed but is open at all times.

Correct operation of the valve 10 can be determined either by watching rotation or other movement of the control rod 12 or, alternatively. by remotely checking the pressure in the line 24. It is conventional to check the pressure in this line so as to determine operation of the valve in any case and during normal operation in Figure 1 the pressure in line 24 will be at P1; when the test procedure starts and the position in Figure 2 is reached the pressure will drop to P2: and when the test procedure continues to the position shown in Figure 3, then the pressure will rise from P1 up to P2 if the valve moves properly. If the pressure does not rise to P2, then it is clear that the piston 13 has not moved downwardly so as to compress the fluid in the lower part 16 of the cylinder 14 and thus the valve 10 is jammed and remedial action is required.

To return to normal operation, the selector valves 21, 34 and rotary switch 48 are rotated back to the position shown in Figure 2 and then to the position shown in Figure 1 when normal operation is resumed although it is necessary to provide sufficient time between movement from the position in Figure 3 and Figure 2 to allow the piston to move.

In addition to detecting the pressure on line 24 and thereby determining correct operation of the device, as is clear from Figure 3, when the rotary electrical switch 48 is in the position shown in Figure 3, the input signal is passed from input terminal 49 to a third output terminal 52 which is connected to a recording device whereby rotation of the rotary switch 48, and hence the selector valves 21 and 34 to the position shown in Figure 3 is duly recorded.

The invention is not restricted to the details of the foregoing example.

Claims

CLAIMS 1. A testing apparatus 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 neniclosed and a second position in which the valve is closed/open, said testing apparatus comprising means to supply gas at a first higher pressure to one side of the piston to maintain the valve in said first position, means to reduce the gas pressure on said one side of the piston from the first, higher pressure to a lower pressure, means to then seal said one side of the piston so that gas may not pass to or from the first side of the piston, and means to then pass gas at a second higher pressure to the opposite side of the piston to urge the piston to move from the first position to a third position intermediate the first, and second positions.
2. A testing apparatus as claimed in claim 1 wherein said first and second higher pressures are the same pressure.
3 A testing apparatus as claimed in claim 2 wherein there is provided means to provide said higher pressure gas and means to provide said lower pressure gas, said means to provide said lower pressure gas comprising a pressure reducing means connected to said means for supplying said higher pressure gas.
4 A testing apparatus as claimed in claim 3 wherein a first selector valve is connected to said one side of said piston, said means to provide higher pressure gas, and said means to provide lower pressure gas, said first selector valve being moveable between three positions; in a first position selectively connecting said one side of the piston to said means to provide higher pressure gas; in a second position, connecting said one side of the piston to said means to provide lower pressure gas; and, in said third position isolating said one side of the piston so that gas may not pass to or from said one side of the piston.
5. A testing apparatus as claimed in claim 4 wherein a second selector valve is connected to said opposite side of said piston, said means to provide higher pressure gas, and an exhaust outlet, said second selector valve being moveable between three positions; in a first position, selectively connecting said opposite side of the piston to said exhaust outlet; in said second position, isolating said opposite side of the piston so that gas may not pass to or from said opposite side of said piston; and, in said third position connecting said opposite side of the piston to said means to provide higher pressure gas.
6. A testing apparatus as claimed in claim 5 wherein said first and second selector valves are connected to move together between their respective first, second and third positions.
7. A testing apparatus as claimed in claim 6 wherein a rotary electrical switch is provided and connected to move with said first and second selector valves between first, second and third positions and there is provided an electrically controlled valve connected to said rotary electrical switch, said valve being moveable between a first position in which it connects said means to provide higher pressure gas to said first selector valve and a second position in which it connects said means to provide said higher pressure gas to said second selector valve, said rotary electrical switch in said first and said second positions providing an electrical signal to said electrically operated valve to maintain said valve in said first position, and when said rotary electrical switch is in said third position, interrupts the electrical signal to said valve to thereby allow said electrically operated valve to move to said second position.
8. A testing apparatus as claimed in claim 7 wherein said rotary electrical switch includes means whereby, when said switch is in said third position, an electrical output is provided to an output line
9 A method of testing 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, gas pressure normally being supplied to one side of the piston to maintain the valve in said first position, said method comprising reducing the gas pressure on said one side of the piston from a first, higher pressure to a lower pressure, sealing said one side of the piston so that gas may not pass to or from said one side of the piston, and passing a gas at a second higher pressure to the opposite side of the piston to urge the piston to move from the first position to a third position intermediate the first and second positions.
10. A method as claimed in claim 9 wherein said first and second higher pressure are the same pressure.