GB2034006A - Over Pressure Protection of Pressure Vessels by Drogue - Google Patents

Abstract

A fluid relief system for pressure vessels for use especially under emergency conditions comprises a collapsible drogue 6 which is made of plastics material, connected to the outlet of a pressure relief valve 3. <IMAGE>

Description

SPECIFICATION Over Pressure Protection of Pressure Vessels by Drogue The present invention relates to a fluid relief system for pressure vessels for use especially under emergency conditions.

Circuits in which a fluid moves under pressure from a source to a delivery point normally contain a relief valve to limit the maximum pressure of the circuit and to provide protection for ancillary equipment. In off-shore operations for the production of oil, both pressure control systems and flow control systems are involved.

Similar considerations apply to other pressure relief systems installed in most petrochemical plants utilising flammable, caustic or acidic fluids which are offensive to the environment. The need for containment of such offensive fluids also applies to relatively less hazardous liquids such as the produced water in crude oil which inevitably contains significant quantities of dissolved hydrocarbon gases as contaminants. This contaminated water if discharged into the environment may cause an unacceptable degree of pollution.Hitherto the relief systems used to counter emergencies during the pumping of fluids such as crude oil have either taken the form of expensive surge tanks or have involved complex instrumentation systems with finite reiiability. In the particular case of off-shore platforms for drilling oil, the problem of relief systems is further complicated not only by the environmental pollution hazards but also by the possibility of oil being lost.

Accordingly, the present invention is a pressure relief system comprising a pressure relief valve which is connected to a collapsible drogue.

The pressure relief system of the present invention is suitable used as a part of a circuit in which fluid is conveyed under pressure from a source to a delivery point. The pressure relief system of the present invention may form part of either a conventional pressure control system or a conventional flow control system. In such systems, the pressure relief valve may be any of the conventional types and is particularly useful in systems in which fluid relief is normally to atmosphere. For example, the pressure relief valve may be of the spring-loaded type or a two-stage valve which can be remotely operated or controlled by pilot pressure.

The collapsible drogue connected to the relief valve should be impervious to the fluid in the circuit and should naturally be resistant to attack by that fluid. Thus the drogue is suitably made of a material selected from nylon, synthetic rubber, (reinforced) polyester and any flexible substrate coated therewith. The capacity of the drogue would also be dependent upon factors such as the pressure in the circuit, the volume of fluid being pumped at maximum load of the circuit, the duration of operation of the circuit and the like.

The drogue may be provided with a gas relief valve.

One of the particular advantages of the drogue of the present system is that in its deflated form it can be accommodated in a relatively small space for example on an off-shore drilling platform or its jacket. If a drogue of adequate size is chosen it could accept full fluid throughput for the time required to bring an emergency situation under control. By using the drogue no fluid would be lost, no pollution would be caused and dependence on instrumentation with finite reliability would be avoided at relatively low cost in terms of space and expense.

The pressure relief system of the present invention is further illustrated with reference to the accompanying drawing: The drawing shows a sectional view of a typical pressure relief system. In the drawing a section of a circuit which is the pressure source (1) is connected to a spring-loaded relief valve (2) which is in sealing contact with a valve seat (3).

The outlet (4) of the relief valve is connected to a drogue (6) via the connection (5).

In operation, when the fluid pressure in the circuit is normal i.e. within a predetermined level, the valve (2) is in sealing contact with the valve seat (3). When the fluid pressure in the circuit exceeds the predetermined level, the valve is pushed open against the natural bias of the spring allowing an amount of fluid to flow from the circuit, via the outlet (4) into a drogue (6) so as to normalise the pressure in the circuit. The fluid is collected in the drogue and this may then be recycled, used or treated as desired without loss or damage to the environment.

Claims

1. A pressure relief system comprising a pressure relief valve which is connected to a collapsible drogue.

2. A pressure relief system according to claim 1 wherein said system is part of a circuit in which fluid is conveyed under pressure from a source to a delivery point.

3. A pressure relief system according to claim 1 or 2 wherein the pressure relief valve is a two stage valve which is remotely controlled or operated by pilot pressure.

4. A pressure relief system according to any one of the preceding claims wherein the drogue is of a material selected from nylon, synthetic rubber, (reinforced) polyester and any flexible substrate coated therewith.

5. A pressure relief system accrding to claim 1 substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Over Pressure Protection of Pressure Vessels by Drogue The present invention relates to a fluid relief system for pressure vessels for use especially under emergency conditions. Circuits in which a fluid moves under pressure from a source to a delivery point normally contain a relief valve to limit the maximum pressure of the circuit and to provide protection for ancillary equipment. In off-shore operations for the production of oil, both pressure control systems and flow control systems are involved. Similar considerations apply to other pressure relief systems installed in most petrochemical plants utilising flammable, caustic or acidic fluids which are offensive to the environment. The need for containment of such offensive fluids also applies to relatively less hazardous liquids such as the produced water in crude oil which inevitably contains significant quantities of dissolved hydrocarbon gases as contaminants. This contaminated water if discharged into the environment may cause an unacceptable degree of pollution.Hitherto the relief systems used to counter emergencies during the pumping of fluids such as crude oil have either taken the form of expensive surge tanks or have involved complex instrumentation systems with finite reiiability. In the particular case of off-shore platforms for drilling oil, the problem of relief systems is further complicated not only by the environmental pollution hazards but also by the possibility of oil being lost. Accordingly, the present invention is a pressure relief system comprising a pressure relief valve which is connected to a collapsible drogue. The pressure relief system of the present invention is suitable used as a part of a circuit in which fluid is conveyed under pressure from a source to a delivery point. The pressure relief system of the present invention may form part of either a conventional pressure control system or a conventional flow control system. In such systems, the pressure relief valve may be any of the conventional types and is particularly useful in systems in which fluid relief is normally to atmosphere. For example, the pressure relief valve may be of the spring-loaded type or a two-stage valve which can be remotely operated or controlled by pilot pressure. The collapsible drogue connected to the relief valve should be impervious to the fluid in the circuit and should naturally be resistant to attack by that fluid. Thus the drogue is suitably made of a material selected from nylon, synthetic rubber, (reinforced) polyester and any flexible substrate coated therewith. The capacity of the drogue would also be dependent upon factors such as the pressure in the circuit, the volume of fluid being pumped at maximum load of the circuit, the duration of operation of the circuit and the like. The drogue may be provided with a gas relief valve. One of the particular advantages of the drogue of the present system is that in its deflated form it can be accommodated in a relatively small space for example on an off-shore drilling platform or its jacket. If a drogue of adequate size is chosen it could accept full fluid throughput for the time required to bring an emergency situation under control. By using the drogue no fluid would be lost, no pollution would be caused and dependence on instrumentation with finite reliability would be avoided at relatively low cost in terms of space and expense. The pressure relief system of the present invention is further illustrated with reference to the accompanying drawing: The drawing shows a sectional view of a typical pressure relief system. In the drawing a section of a circuit which is the pressure source (1) is connected to a spring-loaded relief valve (2) which is in sealing contact with a valve seat (3). The outlet (4) of the relief valve is connected to a drogue (6) via the connection (5). In operation, when the fluid pressure in the circuit is normal i.e. within a predetermined level, the valve (2) is in sealing contact with the valve seat (3). When the fluid pressure in the circuit exceeds the predetermined level, the valve is pushed open against the natural bias of the spring allowing an amount of fluid to flow from the circuit, via the outlet (4) into a drogue (6) so as to normalise the pressure in the circuit. The fluid is collected in the drogue and this may then be recycled, used or treated as desired without loss or damage to the environment. Claims

1. A pressure relief system comprising a pressure relief valve which is connected to a collapsible drogue.

2. A pressure relief system according to claim 1 wherein said system is part of a circuit in which fluid is conveyed under pressure from a source to a delivery point.

3. A pressure relief system according to claim 1 or 2 wherein the pressure relief valve is a two stage valve which is remotely controlled or operated by pilot pressure.

4. A pressure relief system according to any one of the preceding claims wherein the drogue is of a material selected from nylon, synthetic rubber, (reinforced) polyester and any flexible substrate coated therewith.

5. A pressure relief system accrding to claim 1 substantially as hereinbefore described with reference to the accompanying drawing.