GB2185287A

GB2185287A - Pressure relief systems

Info

Publication number: GB2185287A
Application number: GB08700501A
Authority: GB
Inventors: David Applegate
Original assignee: THERMAL TECHNOLOGY Ltd
Current assignee: THERMAL TECHNOLOGY Ltd
Priority date: 1986-01-09
Filing date: 1987-01-09
Publication date: 1987-07-15
Also published as: GB8700501D0; GB8600441D0

Abstract

A pressure relief safety system for a pressurised calorifier (10) included in a steam boiler system, comprises a bursting disc (17) in the wall of the calorifier connected by a duct (20) to a receiver chamber of large cross-section and volume. The chamber has an open upper vent pipe (22) and an open outlet (24) at its lower end.The receiver chamber may be designed for use with two separate bursting discs and preferably has tangential inlets to create a vortex. The bursting disc is preferably scored on radial lines and may be formed of stainless steel for example or delanium graphite. <IMAGE>

Description

SPECIFICATION Pressure relief systems This invention relates to pressure relief safety systems as applied for example to pressure generators, steam boilers and the like.

One method of protecting any partofa pressure system is by means of pressure reliefvalves, but these valves may baunreliable particularly if they are inoperable for long periods. An alternative system involves a so called "bursting disc" of the type having a thin wall or membrane designed to rupture if the pressure in the system exceeds a predetermined value. Having no moving pa rts these rupturable discs are reliable but suffer from other disadvantages. For example when a disc bursts open it results in a heavy pressure wave which may cause damage to components ofthe system and can be offensive or dangerous to personnel. Accordingly it is an object of the invention to provide an improved pressure relief system which will avoid such problems.

Broadly stated the invention consists in a pressure relief system for a pressure conduit, vessel, or circuit, comprising a rupturablefluid closure and a relatively large cross-section relief chamber communicating with the downstream side of the closure.

Preferably the closure is a "bursting disc".

The closure may be located on or adjacent to a pressure vessel and is connected to the relief chamber via a pressure conduit; and in any case the relief chamber is preferably vented to atmosphere or exhaust.

When applied to a steam boiler or steam pressure conduit or vessel the closure is preferably located on or in communication with one ofthe steam pressure conduits orvessels, and is connectedtoa relief chamber having a vent outlet, and a further blowdown drain outlet.

The invention may be performed in various ways and one specific embodiment with some possible modifications will now be described byway of example with reference to the accompanying drawings, in which Figure lisa diagram illustrating the main components of a pressure relief system according to the invention, Figure 2 is a side elevation of a pressure relief chamberfor use with the invention, Figure3isa planviewofthereliefchamber, Figure 4 is a sectional side elevation through a bursting disc, and Figure 5 is an end view ofthe disc.

Inthisillustrated examplethe invention is applied to a pressure relief system for one or more calorifiers forming part of a steam boiler system. The calorifier 10 shown in Figure 1 has a high temperature hotwater inlet 1 and outlet 12 connected to a heat exchange tube 13canada lowtemperature water inlet 15 and outlet 16 The calorifier acts as a heat exchanger and has normal internal heat exchange tubes.

To protectthecalorifierand its related fluid conduits against excess pressures a "bursting disc" 17 is located in the top wall, comprising a thin rupturable steel disc or membrane exposed to the internal pressure of the calorifier on one side. In accordance with the invention the bursting disc is directly connected by a duct 20 to a relief vessel or receiver chamber 18 of appreciable cross-section, preferably greaterthan the calorifier itself. The volume ofthe receiver chamber 18 is determined in relation to the maximum pressure of the fluid in the calorifier and the accepted maximum volume of steam orwaterwhich may pass the disc if it bursts. The receiver chamber acts as a pressure accumulator or damperto cushion the effects ofthe pressure shock if the disc bursts.The chamber has a normally open uppervent pipe 22 leading to an exhaust head 23, and is also provided with a normally open outlet 24 at it's lower end leading via a valve or cock 26 to a drain conduit 27. The inlet 28 from the calorifierto the receiver chamber is preferably tangential or oblique.

In the particular construction of receiver vessel illustrated in Figures 2 and 3the vessel is designed-for use with two separate bursting discs, associated with two differentcalorifiers. The receiver vessel 30 has two inlets 31,32 each of which is nearlytangential or oblique as illustrated in Figure 3 thereby encouraging a swirling movement or vortex of any incoming fluid.

In addition the chamber hasan upperventtube 33 which dips down a short distance 34 into the vessel and is connected to the vertical vent pipe 22. The bottom drain pipe 35 is fitted directly to the rounded bottom endorsump36and leadstotheexhaust conduit 27. The vessel is not intended to contain any water or other liquid The bottom drain is always open, there is no outlet pipe dipping intothevessel,no internal wear plate, and the design parameters are sufficientto withstand any expected fluid surges arising from bursting of the disc, which may in turn be caused by a rupture in the primary system.

In the actual bursting disc construction illustrated in Figures 4 and 5 the disc40 is a dome shaped member ofthin sheet material positioned between two shaped annular rings41,42 with its edge clamped to form a positive fluid tight seal. The clamping is effected by means oftwo end rings43, 44 held by heavy bolts 45 and the inlet and outlet connections 46,47 are tightly secured to the end fittings by heavy duty sealing rings 48,49. The bursting disc itself is preferably formed with radial score lines 51 whose function is to cause the disc two burst only at an accurate overload pressure and in such a way as to give a clear break along the score lines.

The disc may be formed of a variety of different materials. For example, it may be a metal such as aluminium, nickel, monel or stainless steel or it may be of a non-metallic material such as delanium graphite.

1. A pressure relief system for a pressure conduit, vessel, or circuit, comprising a rupturablefluid closure and a relatively large cross-section reliefchamber communicating with the downstream side of the closure.

2. A pressure relief system according to claim 1, in which the closure is a "bursting disc".

3. A pressure relief system according to claim 2, in which the closure is located on or adjacent to a pressure vessel and is connected to the relief chamber

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

Claims

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

SPECIFICATION Pressure relief systems This invention relates to pressure relief safety systems as applied for example to pressure generators, steam boilers and the like.

One method of protecting any partofa pressure system is by means of pressure reliefvalves, but these valves may baunreliable particularly if they are inoperable for long periods. An alternative system involves a so called "bursting disc" of the type having a thin wall or membrane designed to rupture if the pressure in the system exceeds a predetermined value. Having no moving pa rts these rupturable discs are reliable but suffer from other disadvantages. For example when a disc bursts open it results in a heavy pressure wave which may cause damage to components ofthe system and can be offensive or dangerous to personnel. Accordingly it is an object of the invention to provide an improved pressure relief system which will avoid such problems.

Broadly stated the invention consists in a pressure relief system for a pressure conduit, vessel, or circuit, comprising a rupturablefluid closure and a relatively large cross-section relief chamber communicating with the downstream side of the closure.

Preferably the closure is a "bursting disc".

The closure may be located on or adjacent to a pressure vessel and is connected to the relief chamber via a pressure conduit; and in any case the relief chamber is preferably vented to atmosphere or exhaust.

When applied to a steam boiler or steam pressure conduit or vessel the closure is preferably located on or in communication with one ofthe steam pressure conduits orvessels, and is connectedtoa relief chamber having a vent outlet, and a further blowdown drain outlet.

The invention may be performed in various ways and one specific embodiment with some possible modifications will now be described byway of example with reference to the accompanying drawings, in which Figure lisa diagram illustrating the main components of a pressure relief system according to the invention, Figure 2 is a side elevation of a pressure relief chamberfor use with the invention, Figure3isa planviewofthereliefchamber, Figure 4 is a sectional side elevation through a bursting disc, and Figure 5 is an end view ofthe disc.

Inthisillustrated examplethe invention is applied to a pressure relief system for one or more calorifiers forming part of a steam boiler system. The calorifier 10 shown in Figure 1 has a high temperature hotwater inlet 1 and outlet 12 connected to a heat exchange tube 13canada lowtemperature water inlet 15 and outlet 16 The calorifier acts as a heat exchanger and has normal internal heat exchange tubes.

To protectthecalorifierand its related fluid conduits against excess pressures a "bursting disc" 17 is located in the top wall, comprising a thin rupturable steel disc or membrane exposed to the internal pressure of the calorifier on one side. In accordance with the invention the bursting disc is directly connected by a duct 20 to a relief vessel or receiver chamber 18 of appreciable cross-section, preferably greaterthan the calorifier itself. The volume ofthe receiver chamber 18 is determined in relation to the maximum pressure of the fluid in the calorifier and the accepted maximum volume of steam orwaterwhich may pass the disc if it bursts. The receiver chamber acts as a pressure accumulator or damperto cushion the effects ofthe pressure shock if the disc bursts.The chamber has a normally open uppervent pipe 22 leading to an exhaust head 23, and is also provided with a normally open outlet 24 at it's lower end leading via a valve or cock 26 to a drain conduit 27. The inlet 28 from the calorifierto the receiver chamber is preferably tangential or oblique.

In the particular construction of receiver vessel illustrated in Figures 2 and 3the vessel is designed-for use with two separate bursting discs, associated with two differentcalorifiers. The receiver vessel 30 has two inlets 31,32 each of which is nearlytangential or oblique as illustrated in Figure 3 thereby encouraging a swirling movement or vortex of any incoming fluid.

In addition the chamber hasan upperventtube 33 which dips down a short distance 34 into the vessel and is connected to the vertical vent pipe 22. The bottom drain pipe 35 is fitted directly to the rounded bottom endorsump36and leadstotheexhaust conduit 27. The vessel is not intended to contain any water or other liquid The bottom drain is always open, there is no outlet pipe dipping intothevessel,no internal wear plate, and the design parameters are sufficientto withstand any expected fluid surges arising from bursting of the disc, which may in turn be caused by a rupture in the primary system.

In the actual bursting disc construction illustrated in Figures 4 and 5 the disc40 is a dome shaped member ofthin sheet material positioned between two shaped annular rings41,42 with its edge clamped to form a positive fluid tight seal. The clamping is effected by means oftwo end rings43, 44 held by heavy bolts 45 and the inlet and outlet connections 46,47 are tightly secured to the end fittings by heavy duty sealing rings 48,49. The bursting disc itself is preferably formed with radial score lines 51 whose function is to cause the disc two burst only at an accurate overload pressure and in such a way as to give a clear break along the score lines.

The disc may be formed of a variety of different materials. For example, it may be a metal such as aluminium, nickel, monel or stainless steel or it may be of a non-metallic material such as delanium graphite.

1. A pressure relief system for a pressure conduit, vessel, or circuit, comprising a rupturablefluid closure and a relatively large cross-section reliefchamber communicating with the downstream side of the closure.

2. A pressure relief system according to claim 1, in which the closure is a "bursting disc".

3. A pressure relief system according to claim 2, in which the closure is located on or adjacent to a pressure vessel and is connected to the relief chamber via a pressure conduit.

4. A pressure relief system according to any ofthe preceding claims, in which the relief chamber is vented to atmosphere or exhaust.

5. A pressure relief system for a steam boiler or steam pressure conduit or vessel, according to any of the preceding claims, in which the closure is located on or in communication with one ofthe steam pressure conduits or vessels, and is connected to a relief chamber having a vent outlet, and a further blowdown drain outlet.

7. A pressure relief system substantially as herein described with reference to the accompanying drawings.