GB2280705A - Lock disabling pressure safety device - Google Patents

Abstract

A fluid actuator 31, to which fluid pressure is communicated from a region accessible by means of a key 17, urges a latching member 22 to cooperate with a key retainer 27 and thereby prevent release of the key 17 until the pressure is at a safe level. The key 17 may be used to unlock a clamp embracing pipe flanges which are bolted together. <IMAGE>

Description

Pressure Safety Device This invention relates to a safety device for releasably retaining a key which can be used to enable an operation in a region which may contain a fluid (gas or liquid) under pressure. The key may be used, for example,to gain access to such a region or to unlock a valve at a safe operating pressure.

The invention provides a safety device comprising a key retainer for retaining the key, a latching member which cooperates with the key retainer and which is movable between a latching position for preventing release of the key and an unlatching position for allowing release of the key, a fluid actuator arranged to urge the latching member towards one of its positions when fluid pressure exceeding a threshold value is applied to the fluid actuator, return means for urging the latching member to its other position in the absence of a pressure exceeding the threshold value, and fluid connection means for communicating fluid pressure to the fluid actuator from the said region.

If the key is to be used to gain access to a region which may contain a fluid under pressure, the said one position will be the latching position. In the case of hazardous (e.g. explosive, hot, or toxic) fluids, the threshold value may approximate to atmospheric pressure. In other cases, the threshold value may be a safe pressure above atmospheric pressure. The key may be used to unlock a hatch, for example, or to release a clamping device inhibiting separation of flanges in a pipeline, or to release a further key or keys which allow access to the said region. Access to a pressure vessel may be controlled, in this way, by using the key to release a clamping device applied to the bolts of an access hatch. Alternatively, the key may be used to unlock an access lock on a pressure-vessel door or hatch.

The released key may instead be used, for example, to unlock a valve to enable operation of the valve at a safe pressure. If operation of the valve at a pressure above a prescribed limit would be hazardous, the said one position will be the latching position and the threshold value will be less than or equal to the prescribed limit. Conversely, if operation of the valve at a pressure below a prescribed limit would be hazardous, the said one position will be the unlatching position and the threshold value will be greater than or equal to the prescribed limit.

The invention also provides apparatus for providing safe access to a region which may contain a fluid under pressure, comprising flanges connected by bolts which are releasable to permit separation of the flanges, thereby allowing access to the said region, a lockable clamp which embraces the flanges and is removable only when unlocked by a key, and a safety device comprising a key retainer for releasably retaining the key, a latching member which cooperates with the key retainer and which is movable between a latching position for preventing release of the key and an unlatching position for allowing release of the key, actuating means for urging the latching member towards one of its positions in response to a fluid pressure exceeding a threshold value and urging the latching member towards its other position in response to the absence of a fluid pressure exceeding the threshold value, and means for communicating fluid pressure to the actuating means from the said region.

This is particularly applicable to the flange joints in a pipeline (e.g. valve flanges). The clamp physically prevents and/or warns against the loosening of the bolts, and it can only be unlocked when the pressure in the pipeline is at a safe level.

Usually the key will be releasable when the pressure is at or below the threshold value. However, in certain circumstances, it may be desirable to provide for key release only at or above the threshold value (e.g. if the region in question is normally at sub-atmospheric pressure or must not be contaminated by ambient atmosphere).

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front elevation of a safety device for releasably retaining a key; Figure 2 is a section on line II-II in Figure 1; and Figure 3 is a part-sectional fragmentary side elevation of a pipeline and an associated valve.

One branch of the valve 1 shown in Figure 3 has a flange 2 which is fixed to a flange 3 on a pipeline section 4 by bolts 6 and nuts 7. A lockable clamp 8 embraces the flanges 2,3 and also inhibits release of one of the bolts 6. The clamp 8 includes a lock 9 which rigidly locks together two arms 11, 12 bearing respective caps 13, 14 which cover the bolt head 16 and the nut 7.

The clamp 8 is unlocked by a key 17, allowing the arm 12 to be released and re-inserted as indicated by the double-headed arrow in Figure 3. The valve 1 has two other branches (not shown) with associated flanges and clamps unlocked by respective keys 18, 19 (Figures 1 and 2).

The pipeline carries a fluid (e.g. natural gas, petroleum, live steam, or another inorganic or organic gas or liquid) under pressure. The pressure may be greatly in excess of the ambient atmospheric pressure.

In order to inhibit loosening of the bolts 6 while the pipeline is in use, the keys 17, 18, 19 are retained by a safety device 21 as shown in Figures 1 and 2, which only allows the keys 17-19 to be released when the pressure in the pipeline has fallen to atmospheric pressure.

Furthermore, the keys 17-19 cannot be released until a primary key (not shown) is inserted into the safety device, which primary key is only available when operation of the pipeline has been shut down.

The primary key (not shown) and the keys 17 to 19 are received by respective retainers 26,27,28,29 each comprising a fixed body and a rotary cam 26a,27a,28a,29a. The keys 17 to 19 are trapped in the retainers 27 to 29 in the first rotary position as shown and are freed when turned (together with the cams 27a to 29a) are turned to second rotary positions (not shown) in which arcuate recesses 27b,28b in the cams 27a,28a are in register with the cams 28a,29a. The cam 27a cannot be turned to its second rotary position until the first cam 26a is turned to bring one of its recesses 26b into register with the second cam 27a, whereupon the primary key is trapped.

Furthermore, the cam 27a cannot be turned from its first rotary position (and the keys 17 to 19 cannot be released) until a latching member 22 is withdrawn from a notch 23 in the rotary cam 27a. The latching member 22 in this embodiment is an integral part of a piston rod 24 extending from a fluid actuator 31 in the form of a piston-and-cylinder device. The piston rod 24 is extended to the latching position, as shown, when fluid pressure in excess of a threshold value (e. g.

approximating to atmospheric pressure) is applied to the actuator 31 via a connector 32. The rod 24 is urged to an unlatching position by a spring (not shown) acting on the piston of the actuator 31.

The safety device 21 has a connector 33 which is to be fluidly connected (directly or indirectly) to the pipeline upstream of the valve 1 so that the fluid pressure at the connector 33 is proportional to the pressure in the pipeline. Tubing 34 (e.g. of nylon or copper) communicates between the connector 33 and a branch coupling 36, one branch of which is connected to a pressure gauge 37 and the other branch of which is connected to the connector 32.

Thus, once the pipeline has been shut down and the primary key inserted into its retainer 26 and turned, the key 17 cannot be turned and released until the pressure in the pipeline has fallen to a safe level at which the actuator 31 withdraws the latching member 22 from the notch 23 in the cam 27a.

A particular advantage of the above-described safety device is that it can be used in potentially explosive atmospheres, where electrical devices would be unacceptable.

Various modifications may be made within the scope of the invention. For instance, one or more of the key retainers 26, 28, and 29 may be omitted, since a single releasable key 17 may provide sufficient security. The latching member 22 may be separate from and kinematically connected to the actuator 31. The actuator 31 is arranged to withdraw the latching member 22 when the pressure applied to it falls to a given level, but its operation could be reversed so that the latching member 22 is withdrawn when the pressure applied to the actuator rises to a given level. The clamp which embraces the flanges 2,3 may be fabricated of sheet metal (e.g. steel), rod, or cast sections. It may cover more than one bolt or all of the bolts.

Alternatively, it may leave the bolts exposed but act as a hindrance to release of the bolts. At the very least, the presence of the clamp acts as a visual warning against loosening or removal of the bolts.

Claims (13)

Claims:-

1. A safety device for releasably retaining a key which can be used to enable an operation in a region which may contain a fluid under pressure, the device comprising a key retainer for retaining the key, a latching member which cooperates with the key retainer and which is movable between a latching position for preventing release of the key and an unlatching position for allowing release of the key, a fluid actuator arranged to urge the latching member towards one of its positions when fluid pressure exceeding a threshold value is applied to the fluid actuator, return means for urging the latching member to its other position in the absence of a pressure exceeding the threshold value, and fluid connection means for communicating fluid pressure to the fluid actuator from the said region.

2. A safety device as claimed in claim 1, in which the fluid actuator is a piston-and-cylinder device.

3. A safety device as claimed in claim 1 or 2, in which the key retainer traps the key in a first rotational position and frees the key in a second rotational position, the latching member preventing rotation of the key away from the first rotational position when in the latching position.

4. A safety device as claimed in claim 3, in which the key retainer includes a rotary member which rotates with the key, rotation of the rotary member being blocked by the latching member when the key is in the first rotational position and the latching member is in the latching position.

5. A safety device as claimed in any preceding claim, including a pressure gauge connected to the fluid connection means.

6. Apparatus for providing safe operation in a region which may contain a fluid under pressure, the apparatus comprising locking means for selectively inhibiting and allowing operation in the said region, a key for unlocking the locking means, and a safety device according to any preceding claim.

7. Apparatus as claimed in claim 6, for providing safe access to the said region, further comprising closure means for selectively inhibiting and allowing access to the said region, the locking means selectively inhibiting and allowing opening of the closure means.

8. Apparatus as claimed in claim 7, in which the closure means comprises flanges connected by releasable bolts, and the locking means comprises a lockable clamp which embraces the flanges and is removable only when unlocked.

9. Apparatus for providing safe access to a region which may contain a fluid under pressure, comprising flanges connected by bolts which are releasable to permit separation of the flanges, thereby allowing access to the said region, a lockable clamp which embraces the flanges and is removable only when unlocked by a key, and a safety device comprising a key retainer for releasably retaining the key, a latching member which cooperates with the key retainer and which is movable between a latching position for preventing release of the key and an unlatching position for allowing release of the key, actuating means for urging the latching member towards one of its positions in response to a fluid pressure exceeding a threshold value and urging the latching member towards its other position in response to the absence of a fluid pressure exceeding the threshold value, and means for communicating fluid pressure to the actuating means from the said region.

10. Apparatus as claimed in claim 8 or 9, in which the clamp inhibits release of at least one of the bolts.

11. Apparatus as claimed in claim 10, in which the clamp covers both ends of at least one bolt.

12. A safety device substantially as described with reference to, and as shown in, Figures 1 and 2 of the accompanying drawings.

13. Apparatus for providing safe access, substantially as described with reference to, and as shown in, the accompanying drawings.