GB2100349A

GB2100349A - Bursting discs

Info

Publication number: GB2100349A
Application number: GB8215976A
Authority: GB
Original assignee: Denso Marston Ltd
Current assignee: Denso Marston Ltd
Priority date: 1981-06-12
Filing date: 1982-06-01
Publication date: 1982-12-22
Also published as: GB2100349B

Abstract

A pair of annular holders 12, 13, nest one inside the other so as to define a fixed width gap for the graphite disc which fits exactly into the gap together with its associated gaskets so that on assembly the compressive load applied to the annular holders is taken by the holders themselves rather than being applied to the graphite disc. <IMAGE>

Description

SPECIFICATION Bursting discs This invention relates to bursting discs and has particular reference to holders for bursting discs of the brittle type such as graphite.

A bursting disc and holder assembly essentially comprises a membrane of material which is located across an aperture and held in position by a pair of annular discs. The membrane of material is adapted to withstand pressures up to a certain level but to give way by failure in some mode so as to release pressures developed on one side of the disc above a desired limit.

In many cases the discs are manufactured from metal and may be clamped around their periphery in a suitable pair of holders. However, some discs are made of a brittle material such as graphite which is less able to withstand compressive loads without cracking. In these circumstances it is important that the discs, when assembled in their holders, are not overstressed, lest they become damaged.

By the present invention there is provided a bursting disc and holder assembly comprising a graphite bursting disc having an annular portion of given thickness and a recess in one side to form a blind bore, the bore being surrounded by the annular portion, the bore being located, in use, on the vent side of the disc, the holder being adapted for location and clamping between pipe flanges, the holder comprising a first annular member and a second annular member, the two annular members being adapted and arranged to define therebetween a gap of given width, the width of the gap being equal to or greater than the given thickness of the annular portion of the bursting disc, there being provided gasket means on at least one side of the annular portion of the bursting disc where the given thickness of the annular portion is less than the width of the gap.

The width of the gap is preferably in the range (a) to (b), where (a) is the thickness ofthe annular portion of the disc plus two gaskets and (b) is the thickness of the annular portion of the disc plus one gasket. Optionally the width of the gap is the thickness of the annular portion of the disc plus the thickness of one of the gaskets plus half the thickness of the other gasket.

The two annular members may directly abut one another to define the gap of given width. One of the annular members may have a surface for engagement with the disc and externally of the disc an annular upstanding flange of a height equal to or greater than the thickness of the disc.

Preferably the flange height is greater than the height of the disc and the other annular member has a mating central flange adapted to lie within the bore of the flange of the one member. The graphite may be impregnated with a suitable resin.

By way of example embodiments of the present invention will now be described with reference to the accompanying drawing which is a crosssection of a disc assembly in accordance with the present invention.

Illustrated in the drawing is one embodiment of the invention. The disc and holder assembly generally indicated by 1 is located between faces 2 and 3 on pipe ends 4 and 5. Pressure is applied, in use, to the lower side of the disc, as shown in the drawing, the upper side is the vent side.

Flanges 6, 7 extend from the ends of the pipe and a series of bolts such as 8 and 9 are used to secure the flanges 6 and 7 together. If required gaskets 10 and 11 are used to form an effective seal between the end faces 2 and the disc holder 1. The disc holder itself is formed of a pair of annular members 12, 13. The annular member 13 has a stepped bore with two major stepped regions 14 and 1 5. Located on step 1 5 is a gasket 1 6 which supports a graphite disc external flange 1 7.The external flange 17 is integral with the cylindrical central region 1 8 which forms the bursting disc proper. Located on top of the flange 1 7 is a further gasket 19.

The second holder 12 locates on top of the gasket 19 and has a face 20 which abuts step 14.

The thickness of the gaskets 16 and 19, together with the thickness of the flange 1 7 of the bursting disc, is slightly greater than the gap between faces 15 and 21 (arrowed) so that the clamping load applied by the bolts 9 is taken through the abutment of faces 20 and 14 and not through compression of the graphite disc 1 7, 1 8, obviously there will then be a controlled amount of compression of the assembly to effect a seal via the gaskets.

Where required, a vacuum support 22 can be provided below the disc 18.

It has been found that graphite can be regarded as a virtually incompressible material in the present design of bursting discs. The amount of compression, therefore, relates almost exclusively to the thickness of the gaskets irrespective of the thickness of the disc. The optimum amount of compression can be found by simple experiment but typically would be of the order of half the thickness of one of the gaskets.

It will be appreciated that other means may be provided to prevent over-compression of the graphite discs. Thus each of the holders 12, 13 could be flat but could be provided with an annular thick washer equal in thickness to the total height of the graphite disc and its associated flanges, the thick washer effectively defining the gap of given width between the annular disc support members.

It will also be appreciated that if required the gaskets 16, 19 could be dispensed with and the thickness of the annular portion 1 7 of the bursting disc would then be made exactly equal to the width of the gap of given width between the annular support members, to effect a seal in such a case '0' ring seal would be provided in face 15.

1. A bursting disc and holder assembly comprising a graphite bursting disc having an annular portion of given thickness and a recess in one side to form a blind bore, the bore being

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Bursting discs This invention relates to bursting discs and has particular reference to holders for bursting discs of the brittle type such as graphite. A bursting disc and holder assembly essentially comprises a membrane of material which is located across an aperture and held in position by a pair of annular discs. The membrane of material is adapted to withstand pressures up to a certain level but to give way by failure in some mode so as to release pressures developed on one side of the disc above a desired limit. In many cases the discs are manufactured from metal and may be clamped around their periphery in a suitable pair of holders. However, some discs are made of a brittle material such as graphite which is less able to withstand compressive loads without cracking. In these circumstances it is important that the discs, when assembled in their holders, are not overstressed, lest they become damaged. By the present invention there is provided a bursting disc and holder assembly comprising a graphite bursting disc having an annular portion of given thickness and a recess in one side to form a blind bore, the bore being surrounded by the annular portion, the bore being located, in use, on the vent side of the disc, the holder being adapted for location and clamping between pipe flanges, the holder comprising a first annular member and a second annular member, the two annular members being adapted and arranged to define therebetween a gap of given width, the width of the gap being equal to or greater than the given thickness of the annular portion of the bursting disc, there being provided gasket means on at least one side of the annular portion of the bursting disc where the given thickness of the annular portion is less than the width of the gap. The width of the gap is preferably in the range (a) to (b), where (a) is the thickness ofthe annular portion of the disc plus two gaskets and (b) is the thickness of the annular portion of the disc plus one gasket. Optionally the width of the gap is the thickness of the annular portion of the disc plus the thickness of one of the gaskets plus half the thickness of the other gasket. The two annular members may directly abut one another to define the gap of given width. One of the annular members may have a surface for engagement with the disc and externally of the disc an annular upstanding flange of a height equal to or greater than the thickness of the disc. Preferably the flange height is greater than the height of the disc and the other annular member has a mating central flange adapted to lie within the bore of the flange of the one member. The graphite may be impregnated with a suitable resin. By way of example embodiments of the present invention will now be described with reference to the accompanying drawing which is a crosssection of a disc assembly in accordance with the present invention. Illustrated in the drawing is one embodiment of the invention. The disc and holder assembly generally indicated by 1 is located between faces 2 and 3 on pipe ends 4 and 5. Pressure is applied, in use, to the lower side of the disc, as shown in the drawing, the upper side is the vent side. Flanges 6, 7 extend from the ends of the pipe and a series of bolts such as 8 and 9 are used to secure the flanges 6 and 7 together. If required gaskets 10 and 11 are used to form an effective seal between the end faces 2 and the disc holder 1. The disc holder itself is formed of a pair of annular members 12, 13. The annular member 13 has a stepped bore with two major stepped regions 14 and 1 5. Located on step 1 5 is a gasket 1 6 which supports a graphite disc external flange 1 7.The external flange 17 is integral with the cylindrical central region 1 8 which forms the bursting disc proper. Located on top of the flange 1 7 is a further gasket 19. The second holder 12 locates on top of the gasket 19 and has a face 20 which abuts step 14. The thickness of the gaskets 16 and 19, together with the thickness of the flange 1 7 of the bursting disc, is slightly greater than the gap between faces 15 and 21 (arrowed) so that the clamping load applied by the bolts 9 is taken through the abutment of faces 20 and 14 and not through compression of the graphite disc 1 7, 1 8, obviously there will then be a controlled amount of compression of the assembly to effect a seal via the gaskets. Where required, a vacuum support 22 can be provided below the disc 18. It has been found that graphite can be regarded as a virtually incompressible material in the present design of bursting discs. The amount of compression, therefore, relates almost exclusively to the thickness of the gaskets irrespective of the thickness of the disc. The optimum amount of compression can be found by simple experiment but typically would be of the order of half the thickness of one of the gaskets. It will be appreciated that other means may be provided to prevent over-compression of the graphite discs. Thus each of the holders 12, 13 could be flat but could be provided with an annular thick washer equal in thickness to the total height of the graphite disc and its associated flanges, the thick washer effectively defining the gap of given width between the annular disc support members. It will also be appreciated that if required the gaskets 16, 19 could be dispensed with and the thickness of the annular portion 1 7 of the bursting disc would then be made exactly equal to the width of the gap of given width between the annular support members, to effect a seal in such a case '0' ring seal would be provided in face 15. CLAIMS

1. A bursting disc and holder assembly comprising a graphite bursting disc having an annular portion of given thickness and a recess in one side to form a blind bore, the bore being surrounded by the annular portion, the bore being located, in use, on the vent side of the disc, the holder being adapted for location and clamping between pipe flanges, the holder comprising a first annular member and a second annular member, the two annular members being adapted and arranged to define therebetween a gap of given width, the width of the gap being equal to or greater than the given thickness of the annular portion of the bursting disc, there being provided gasket means on at least one side of the annular portion of the bursting disc where the given thickness of the annular portion is less than the width of the gap.

2. An assembly as claimed in Claim 1 in which the width of the gap is in the range (a) to (b), where (a) is the thickness of the annular portion of the disc plus two gaskets and (b) is the thickness of the annular portion of the disc plus one gasket.

3. An assembly as claimed in Claim 2 in which the width of the gap is the thickness of the annular portion of the disc plus the thickness of one of the gaskets plus half the thickness of the other gasket.

4. An assembly as claimed in any one of Claims 1 to 3 in which the two annular members directly abut one another to define the gap of given width.

5. An assembly as claimed in any one of Claims 1 to 4 in which one of the annular members has a surface for engagement with the disc and externally of the disc an annular upstanding flange of a height equal to or greater than the thickness of the disc.

6. An assembly as claimed in Claim 5 in which the flange height is greater than the height of the disc and the other annular member has a mating central flange adapted to lie within the bore of the flange of the one member.

7. An assembly as claimed in any one of Claims 1 to 6 in which the graphite is impregnated with a suitable resin.

8. A bursting disc and holder assembly substantially as described herein with reference to and as illustrated by the accompanying drawing.