GB2028973A - An explosion protection device - Google Patents

Abstract

An explosion protection device comprises a cylindrical housing 10 which is connectable at one end 13 to a primary unit and which has openings at both ends 13, 14 and, in between, a circumferentially extending inwardly directed shoulder. The protection device also comprises a closure 12 supportable with respect to the housing and being movable under the influence of a rise in pressure resulting from an explosion in the primary unit from a normally open position in which it is spaced from said shoulder to a closed position in engagement with the shoulder. Fins 18 are arranged to rotate the closure during normal use. The closure may be supported on a spindle 17 or hung from its apex by e.g. a chain. <IMAGE>

Description

SPECIFICATION An explosion protection device This invention relates to an explosion protection device.

It is known to provide an explosion protection device within the body of a unit of plant or vessel (hereinafter referred to as a primary unit), the device when fitted in combination with an explosion venting arrangement, such as a fragile panel or diaphragm, ensuring within its own limitations, the evacuation of the effects of the explosion via the venting arrangement and thus, minimising the risk of spreading of the explosion to adjacent areas or to other primary units. Such explosion protection devices have particular advantage where one or more primary units are connected by common services, such as conveyors, ducts, piping, etc., in that the consequent risk of sequence explosion will be minimised.

In a common form, such known explosion protection devices comprise rotary valves.

However, rotary valves have rotating/rubbing parts, bearings, seals etc., require motive power and an indication that they are functioning. They also involve a relatively high initial cost and, in particular with abrasive products, regular maintenance to ensure that the close tolerances of the moving faces remain within the limits required to ensure a seal.

Alternatively, a form of explosion suppression system extensively used employs pressure sensors connected to pressurized containers of inert gas, which at a signal from the detectors, discharge their contents into the source of the explosion.

This method relies on indirect sensing and can (fairly readily) be subject to mis-operation.

Moreover, the gas containers have to be replaced, the system purged and re-set all of which is time consuming and expensive, particularly when used in conjunction with primary units which are processing food which may be contaminated.

It is an object of the present invention to provide an explosion protection device in an improved form.

In one aspect, the present invention provides an explosion protection device comprising a cylindrical housing which is connectible at one end to a primary unit and which has openings at both ends and between its ends a circumferentially extending inwardly directed shoulder, and a closure supportable with respect to the housing and being movable under the influence of a rise in pressure resulting from an explosion in said primary unit from a normally open position in which it is spaced from said shoulder to a closed position in engagement with the shoulder, the closure having a shape which converges in the direction of movement thereof from said open to said closed positions and which in cross-section conforms with the cross-sectional shape of the shoulder.

Preferably, the closure is conical and the shoulder is frusto-conical.

Conveniently, the closure has an axially directed aperture therein or in a part secured thereto, said aperture slidably receiving a spigot fixedly supported with respect to the housing so as to project coaxially therewith. The aperture may be defined by a sleeve projecting axially from the smaller diameter end and towards the larger diameter end of the closure. Alternatively, the closure is suspended by a flexible elongated element, such as a metal chain, connected to the housing which in use has its axis vertically orientated. Advantageously, the outer surface of the closure has projecting therefrom a plurality of blades so that material or fluid passing through the housing when the closure is in an open position will cause the closure to undergo rotational motion.

In a further aspect the invention provides a primary unit having connected thereto an explosion protection device as hereinbefore described, and a further normally closed closure capable of opening if and when an explosion occurs to thereby vent the unit.

The invention will now be more particularly described with reference to the accompanying drawings, wherein: Figure 1 is a part sectional view of one embodiment of an explosion protection device, according to the invention, showing the closure in a normal open position, Figure 2 is a part sectional view of the device shown in Figure 1, but with the closure in a closed position under the effect of an explosion.

Referring to the drawings, the explosion protection device shown therein comprises a cylindrical open-ended housing 10, which is of circular cross-section and which is stepped between a first larger diameter end and a second smaller diameter end to define a frusto-conical shoulder 1 and a closure 12. The first and second ends of the housing are provided with radially outwardly directed flanges 13, 14 respectively, the first end being sealingly engageable with a primary unit, i.e. a unit of plant or vessel and a second end being sealingly engageable with a pipe or duct.

The closure 12 is a hollow cone open at its larger diameter end. A sleeve 1 5 is secured to the apex of the closure 1 2 and projects axially towards the larger diameter end of the cone 12.

A support bar 1 6 diametrically bridges and is secured, preferably removably such as by bolting, to the larger diameter end of the housing 10.

Secured to the centre of the bar 1 6 is a spindle 17 which projects axially towards the smaller diameter end of the housing 10. The sleeve 1 5 is mounted on the spindle 1 7 for both axial and rotational motion relative thereto.

The outer surface of the closure 12 has secured thereto and projecting therefrom a plurality of equiangularly spaced angled blades 18 for the purpose which will become more apparent hereinafter.

Normally, the apex of the cone 12 rests on that end of the spindle 17 remote from the support bar 1 6 and in this position the closure is spaced from the shoulder 11 so that an annular passage is defined between the closure 12 and the housing 10.

In use, the explosion protection device is connected to a primary unit at any point of open entry thereto and when used at a point of feed, the feed material will pass over the external surface of the closure, the action of the flow on the angled blades 1 8 serving to impart a slow rotary movement to the closure. This action is designed to maintained the freedom of movement of the closure 12 on the spindle 17.

When used at an extraction point of the primary unit, i.e. dust collection connection, the air movement past the angled blades will impart the rotary movement to the closure.

When the pressure within the primary unit rises during the initial stages of an explosion within the unit, the closure 12 will be forced axially along the spindle 1 7 until it is forced into sealing engagement with the shoulder 11 (see Fig. 2). The closure will be retained in sealing engagement with the shoulder 11 so long as pressure is maintained within the primary unit and the speed of action of the protection device will vary with the velocity of the pressure rise. Thus, the device utilises the explosive pressure to seal off other connected items of plant and since the pressure wave of an explosion is usually followed by a flame front, the device will also contain the latter.

A primary unit fitted with such an explosion protection device should also have a venting arrangement, such as a diaphragm which will burst or a fragile panel which will fly off when an explosion occurs.

It will be appreciated that a device as described above will operate in a vertical, horizontal or any intermediate position. This device acts in direct response to the initiation of an explosion, that is to say, it does not require any intermediate sensing or signalling to initiate protection. It provides positive pressure resistant sealing which seals more firmly as pressure increases. It has inherent reliability over long periods of "no action", with little or no attention, and yet will operate without failure when needed. It is capable of repeated action and at least when operated vertically or at a small acute angle to the vertical, will automatically reset without the need for any work other than visual inspection. It will permit passage of infeed material without causing restriction or interruption. It is qf simple construction, having a minimum of working parts and does not require power or energy from an external source. It is also compatible with being in contact with food products.

For explosion protection devices which are to be vertically orientated, the closure may be suspended at its apex by means of a flexible elongated element, such as a metal chain, which is anchored to a bar bridging the smaller diameter end of the housing. In this case, the bar 16 and spindle 17 will be omitted.

Claims (10)

1. An explosion protection device comprising a cylindrical housing which is connectible at one end to a primary unit and which has openings at both ends and between its ends a circumferentially extending inwardly directed shoulder, and a closure supportable with respect to the housing and being movable under the influence of a rise in pressure resulting from an explosion in said primary unit from a normally open position in which it is spaced from said shoulder to a closed position in engagement with the shoulder, the closure having a shape which converges in the direction of movement thereof from said open to said closed positions and which in cross-section conforms with the cross-sectional shape of the shoulder.

2. A device as claimed in claim 1, wherein the closure is conical.

3. A device as claimed in claim 1 or claim 2, wherein the shoulder is frusto-conical.

4. A device as claimed in any one of the preceding claims, wherein the closure has an axially directed aperture therein or in a part secured thereto, said aperture slidably receiving a spigot fixedly supported with respect to the housing so as to protect coaxially therewith.

5. A device as claimed in claim 4, wherein the aperture is defined by a sleeve projecting axially from the smaller diameter end and towards the larger diameter end of the closure

6. A device as claimed in any one of claims 1 to 3, wherein the closure is suspended by a flexible elongated element connected to the housing which, in use, has its axis vertically orientated.

7. A device as claimed in claim 6 wherein the flexible elongated element is a metal chain.

8. A device as claimed in any one of the preceding claims, wherein the outer surface of the closure has projecting therefrom a plurality of blades so that material or fluid passing through the housing when the closure is in an open position will cause the closure to undergo rotational motions.

9. An explosion protection device substantially as herein described with reference to and as shown in the accompanying drawing.

10. A primary unit having connected thereto an explosion protection device as claimed in any one of the preceding claims, and a further normally closed closure capable of opening if an when an explosion occurs to thereby vent the unit.