Abstract: A method of creating a burst groove in a burst member is provided. The burst groove following a path, wherein: the groove is created in a plurality of laser scoring stages which are performed in succession to thereby successively increase the depth of the burst groove during each stage; each laser scoring stage involving laser scoring the burst member along at least a portion of the path. The laser scoring in each stage involves laser-energizing a respective region of the burst member with a respective energization width measured perpendicular to the path. In at least one stage the energization width is smaller than the energization width in the immediately preceding stage.

Abstract: The bursting disc assembly has a primary bursting disc (10) and a secondary bursting disc (20) immediately behind and supporting the primary bursting disc. Each of the said discs (10,20) is made of metal and is gas impermeable, and the bursting strength of the assembly is derived from both of the bursting discs acting in combination. The primary and secondary bursting discs are in contact over the whole of the operating area of the disc, and are shaped together as a pair. The materials of the two discs can be chosen suitably for their functions. The primary disc is for example corrosion-resistant.

Abstract: A pressure relief bursting disc has a flange portion, a sloping portion interior of the flange portion and a dished portion interior of the sloping portion. The sloping portion has its wider end joined to the flange portion and slopes up from the flange portion in a first direction and is joined at its narrower end directly to the dished portion. The dished portion has its concave side facing in the first direction. In use pressure is applied to the concave side of the dished portion. The disc has a line of weakness, in the sloping portion. This shape achieves reliability of the burst strength, because the sloping portion buckles at the burst strength.

Abstract: A safety pressure relief device comprises an annular flange portion (22), a concave/convex dome portion (24) and a transition portion (26) between the flange portion (22) and the dome portion (24), the transition portion (26) comprising a linear extent (28) extending from the annular flange portion (22) at a first acute angle (?1) to the plane of the flange portion (22), a tangent to the dome portion (24) at its junction with the transition portion (26) making a second acute angle (?2) with the plane of the flange portion (22) which is greater than said first angle (?1), a line of weakness being formed in and around part at least of the linear extent (28) of the transition portion (26).