The safe isolation of plant and equipment (HSG253) - Health and ...

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Technique Brief description Primary devices Physical disconnection Specialist techniques Remove spool and install blank flange (blind) Squeeze off Pipe is squeezed together to stop flow using a mechanical or hydraulic clamp Foam bagging Foam is injected into a semi-porous bag, previously inserted into the pipework Typical use (process plant or pipelines) and pressure ■ ■ ■ ■ ■ Standard use for process plant and pipelines Suitable for all fluids over a range of pressure ratings Ideal for extended term, infrequent isolation Specialist technique – temporary isolation of low and medium pressure gas network polyethylene pipework Specialist technique – low and medium pressure gas network for cast iron, ductile iron and steel mains Health and Safety Executive Features – pros Features – cons Comments, refs to industry codes ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Positive isolation Indication of presence Clear indication of even minor failure No specialist training or materials required Continual attendance or monitoring not usually required Blank flanges can incorporate valves etc for bleeding/ venting and monitoring purposes Low component cost Simple technique Location of isolation flexible Relatively cheap Can be used when insufficient room to carry out a conventional mains isolation A useful means of flow – stopping tapered, vertical or non-standard diameter pipe Can be inserted without decommissioning the pipeline Low cost option for abandoning mains or services Requires intervention into the process to break and make joints Requires temporary isolation for insertion and removal – such isolations may be remote from the worksite, making control more difficult Care is needed when installing and removing blanks as pressure can build up behind them Slow to install and reinstate Flanges may not be in optimum position, especially in welded pipework, resulting in large inventories beyond the isolation The safe isolation of plant and equipment Page 54 of 81 ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Only suitable for use on polyethylene pipework Causes physical deformation hence further squeeze offs should not be carried out within specified limits along the same length of pipe Low differential pressure technique For permanent abandonment only – not suitable for temporary isolations A second method of isolation must be used if the technique is to form a permanent isolation, eg end cap or blank May require specialist equipment and training Blanks to be compatible with the service fluid and rated to the maximum operating pressure IGE/TD/3 23 IGE/TD/3 23
Technique Brief description Specialist techniques Pipe plugs A single multi-seal plug or a number of plugs in combination See Figure 9 Typical use (process plant or pipelines) and pressure ■ ■ Suitable for process plant and pipelines Normally used for short- term isolations CONTROL UNIT Health and Safety Executive Features – pros Features – cons Comments, refs to industry codes ■ ■ ■ Can provide an effective leak-free barrier Isolation scheme can comprise a single multi-seal plug or a number of plugs Medium cost control umbilical driving cups end closure gripping unit Figure 9 Pipeline plug If used as primary isolation technique, sufficient redundancy and independence should exist within or between plugs so that failure of a part of the sealing system does not cause total loss of sealing capability Care must be exercised to ensure correct fitment for the full duration of the isolation – continuous monitoring required Requires open end to access pipeline – limited choice of location If control lines are damaged, pipe plugs can get stuck within the pipe Specialist technique, requires specific training main line valve pressure seals The safe isolation of plant and equipment Page 55 of 81 ■ ■ ■ ■ ■ Pipe plugs must be suitable for use with the fluid and rated to the required pressure – consultation with manufacturer necessary
Page 1 and 2:
The safe isolation of plant and equ
Page 3 and 4: Contents Foreword 4 Introduction 5
Page 5 and 6: Introduction Scope and target audie
Page 7 and 8: Overview of isolation hazards Healt
Page 9 and 10: Health and Safety Executive 30 The
Page 11 and 12: 43 Human failures can be grouped in
Page 13 and 14: Figure 1 Responsibilities of key pe
Page 17 and 18: Setting performance indicators for
Page 19 and 20: Health and Safety Executive 82 In a
Page 21 and 22: Health and Safety Executive Key sta
Page 23 and 24: Health and Safety Executive Hazards
Page 25 and 26: Health and Safety Executive 110 Sec
Page 27 and 28: Health and Safety Executive 120 As
Page 29 and 30: Figure 5 Flowchart for selection of
Page 31 and 32: Health and Safety Executive for ret
Page 33 and 34: Level of security Methods Typical a
Page 37 and 38: Health and Safety Executive 173 Imm
Page 39 and 40: Health and Safety Executive 187 Use
Page 41 and 42: Health and Safety Executive An exam
Page 43 and 44: Health and Safety Executive Offshor
Page 45 and 46: Hazards associated with electrical
Page 47 and 48: Isolation scheme examined: Date: Ap
Page 49 and 50: 3 PLANNING and IMPLEMENTING Risk as
Page 51 and 52: Valve type Sealing ability Ball Goo
Page 53: Technique Brief description Primary
Page 57 and 58: Technique Brief description Special
Page 59 and 60: Substance Pressure Appendix 6: Exam
Page 61 and 62: Health and Safety Executive 8 For m
Page 63 and 64: Release factor Health and Safety Ex
Page 65 and 66: Summary of considerations when usin
Page 67 and 68: Health and Safety Executive A secti
Page 69 and 70: valving to provide double block and
Page 71 and 72: Health and Safety Executive 19 You
Page 73 and 74: Venting or flaring activities Healt
Page 75 and 76: Appendix 9: Isolations for instrume
Page 77 and 78: Health and Safety Executive Referen
Page 79 and 80: Glossary Health and Safety Executiv
Page 81: Further information Health and Safe
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