GB2190992A

GB2190992A - Flame arrester

Info

Publication number: GB2190992A
Application number: GB08710783A
Authority: GB
Inventors: Peter James Yapp
Original assignee: IMI Amal Ltd
Current assignee: IMI Amal Ltd
Priority date: 1986-05-22
Filing date: 1987-05-07
Publication date: 1987-12-02
Anticipated expiration: 2007-05-07
Also published as: GB2190992B; GB8710783D0; GB8612538D0

Abstract

A flame arrester with an element comprising a crimped metal strip interleaved with an uncrimped metal strip to form a core, and a casing with a bar passing through the metal core and the casing. The bar is retained to the casing by a steel ball forced into a recess in the end of the bar, deforming the wall of the recess into engagement with the casing. The arrester element may be circular in cross section, and the bar may be retained by a ball at each of its ends. <IMAGE>

Description

SPECIFICATION Flame arrester This invention relates to flame arresters which are also sometimes known as "flame traps".

The function of a flame arrester is typically to prevent or delay the spread of a flame into a conduit carrying flammable gas or vapour. It may be mounted on a vent to a conduit or in-line within a conduit so as to prevent flash-back of flame from one side of the flame arrester to the other. Modern types of flame arrester comprise a cellular construction metal element mounting in a housing across the direction of flow of any gas or vapour. Crimped metal strip interleaved with uncrimpred metal strip may be spirally wound around a central pin to form a cylinder which is retained in a spun casing in the case of a circular section flame arrester element. In the case of a rectangular flame arrester element the crimped metal strip may run in parallel lengths interleaved with uncrimped metal strip.

Flame arresters are frequently installed on a permanent basis with regular inspection to ensure that they are not blocked or damaged. As well as being required to resist heat damage for a period of time, they need to have certain physical properties to resist mechanical damage which could cause distortion of the element and thereby result in premature failure. The resistance to deformation of the element as a result of loading at points across the diameter of the element is thus an important parameter.

It is an object of the invention to provide a flame arrester of increased mechanical strength and resistance to deformation.

According to one aspect of the invention we provide a flame arrester having an element made of crimped metal strip interleaved with uncrimped metal strip and retained in a casing, a bar arranged transversely across the element so that it passes through orifices in both the casing and the metal strip, the bar being provided with a cylindrical recess at at least one end, into which recess is forced a ball having an initial diameter greater than the diameter of the cylindrical recess, the diameter of the recess, the dimensions of the bar, the dimensions of the orifice in the casing and the diameter of the ball being such that the exterior of the bar surrounding the recess is deformed into engagement with the wall of the orifice in the casing by the action of the ball being forced into the recess in the bar.

The flame arrester element may be circular in section, and the interleaved crimped and uncrimped strip may be spirally wound around a central pin.

The bar is suitably circular in cross-section, and may be solid or hollow. The orifice in the casing will typically be of the same shape as the bar but slightly greater in dimension. The orifice in the casing may be chamfered at its exterior, as may be the entry to the recess. The casing may be a metal casting which has been machined to receive the interleaved crimped and uncrimped strip.

In the case of circular section arrester element, the bar may pass through a centrally located pin and through the casing at two points on a diameter of the casing. The bar may be recessed at both ends and a ball forced into each recess to deform the exterior of the bar surrounding each recess into engagement with the wall of an orifice in the casing. For certain diameters of flame arrester element, the bar may extend only across a radius of the element into a blind hole in the central pin and be retained at its outer end by the action of a single ball forced into a recess in the bar at its casing end. There also may be constructions of circular or rectangular elements where the bar traverses the element, and is retained in a blind hole at one end, with the other end being held in place by having a single ball forced into a recess in the bar.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic side elevation in cross-section of a flame arrester element within a housing, Figure 2 shows in partial cross-section a detail of Fig. 1.

A circular section element, indicated generally by arrow 10 is mounted in a circular housing 11 and secured by the heads of retaining bolts 12. Element 10 comprises metal strip crimped perpendicular to its length interleaved with uncrimped strip spirally wound around a central pin 13. This type of honeycomb construction, well-known for many years in the "AMAL" (Registered Trade Mark) flame arresters manufactured by IMI Amal Limited, is particularly effective in heat dissipatation and resistance to heat damage. The strip may be cupro-nickel or stainless steel or other metal/alloy in the case of special applications, and is retained in a cylindrical casing 14 made of cast and machined stainless steel with a retaining edge 15 stepped inwardly at one end.

Once so assembled, element 10 is drilled completely through across a diameter, the bore passing through the spiral of metal strip, the central pin 13 and the casing 14 at two diametrically opposite points. The holes in the casing may have chamfers 16 at their exterior ends. A circular cross-section stainless steel bar 17, of the same length as the diameter of casing 14 and which has previously been drilled to form a circular recess at each end, co-axial with bar 17, is then inserted through the bore. The diameter of the bar is chosen to be substantially identical to that of the bore through the casing and the spiral, the tolerances of the bar and the bore being selected to ensure that the bar can be inserted into the bore.A stainless steel solid ball 19 is then forced into each recess 18, such that the wall of the recess 18 is deformed into engagement with the wall of the hole drilled in the casing 14 (see Fig. 2).

The diameter of the hole in the casing 14, the diameter of the bar 17, the diameter of the recess 18 and the diameter of the ball 19 are selected for a particular material eg stainless steel so that the deformation caused by the ball 19 being forced into recess 18 is sufficient to rigidly hold bar 17 in place in casing 14. The recess is typically slightly deeper than the diameter of ball 19.

Typical dimensions of the following parameters are as follows: Example No 1 2 3 Bar Diameter 0.1875 0.250 0.3125 Diameter of bore through casing 0.1875 0.250 0.3125 Recess diameter 0.149 0.209 0.209 Ball diameter 0.156 0.219 0.219 All dimensions are in inches.

There may be more than one bar passing through the casing and spiral, depending on materials and dimensions of the flame arrester required. The bar is typically positioned about half way up the element.

Claims

1. A flame arrester having an element made of crimped metal strip interleaved with uncrimped metal strip and retained in a casing, a bar arranged transversely across the element so that is passes through orifices in both the casing and the metal strip, the bar being provided with a cylindrical recess at at least one end, into which recess is forced a ball having an initial diameter greater than the diameter of the cylindrical recess, the diameter of the recess, the dimensions of the bar, the dimensions of the orifice in the casing and the diameter of the ball being such that the exterior of the bar surrounding the recess is deformed into engagement with the wall of the orifice in the casing by the action of the ball being forced into the recess in the bar.

2. A flame arrester as claimed in claim 1 in which the flame arrester element is circular in cross section and the interleaved crimped and uncrimped strip is wound spirally around a central pin.

3. A flame arrester as claimed in claim 1 or claim 2 in which the orifice in the casing is of the same shape as the exterior of the bar.

4. A flame arrester as claimed in any preceding claim in which the orifice in the casing is chamfered at its exterior.

5. A flame arrester as claimed in any preceding claim in which the casing is a metal casting.

6. A flame arrester as claimed in claim 2 or in any of claims 3 to 5 when dependent upon claim 2 in which the bar passes through a centraliy located pin and through the casing at two points on a diameter of the casing.

7. A flame arrester as claimed in claim 6 in which the bar is recessed at both ends and a ball is forced into each recess to deform the exterior of the bar surrounding each recess into engagement with the wall of a respective orifice in the casing.

8. A flame arrester as claimed in claim 2 in which the bar extends only across a radius of the element into a blind hole in a centrally located pin, said bar being retained at its outer end by the action of a single ball forced into the recess in the bar at its outer end.

9. A flame arrester as claimed in claim 1 in which the bar traverses the element and is retained in a blind hole in the element casing at one end with the other end being held in place by having a single ball forced into a recess in the bar.

10. A flame arrester substantially as described herein with reference to and as shown in the accompanying drawings.