The large-scale contained use of biological agents / Advisory Committee on Dangerous Pathogens.

  • Great Britain. Advisory Committee on Dangerous Pathogens
Date:
1998
Catalogue details

Licence: Open Government Licence

Credit: The large-scale contained use of biological agents / Advisory Committee on Dangerous Pathogens. Source: Wellcome Collection.

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    Couplings 69 When joints in tubing or pipes are necessary, welding is the preferred option. X-ray testing allows examination of the mechanical quality of a weld but does not guarantee that it is leak-tight. The use of gas testing is therefore preferred and should be applied to each joint and then to the system as a whole. Welds should also be subjected to a hydrostatic test of one-and-a-half times the normal working pressure for two hours. Where possible, inspection of welds should take place during fabrication, rather than after delivery of the complete plant to the site of the contained area. 70 ‘It is recommended that pipework for use at Containment Level 3 should be of all welded construction unless another form of joint is justified. It is strongly recommended that pipework for Containment Level 4 be welded and it is recommended that all welds are subjected to both X-ray and gas testing before use. 71 For work at Containment Level 2, a variety of clamped and flanged joints may be used. There are a number of differing types of clamp available, all of which have their own specific advantages. In practice it is the correct fitting, support and testing of gaskets which is the key factor, rather than the type of clamp or flange system. In each case, it is important that the user is able to show that the coupling/gasket system chosen is performing to the design requirement. Of the following, the ring joint type coupling, the international dairy federation and the in-line cleaning coupling are not recommended for use in biopharmaceutical plants. Triclover clamp type joints have become the standard in the UK. e The ring joint type (RJT) coupling - consists of a male part which carries an external thread and sealing groove, a liner, a seal and a hexagonal nut. One problem with this type of fitting is that the gap between the male part and the liner makes cleaning in place and sterilisation difficult. The problem does not arise in those industries, for example dairy and brewing, which favour this type of coupling because pipework is normally dismantled and cleaned manually. e The international dairy federation (IDF) coupling - consists of the same four basic components as the RJT but the ends of the male part and the liner are specially shaped to give a smooth, crevice-free joint. It may be used with a support ring for the seal. This is optional at the smaller sizes, but should be used for couplings of more than 60 mm (2.5 inches) diameter at pressures greater than 10 bar gauge. One disadvantage is that these couplings are only available in sizes of 25 mm (1 inch) and above. © The in-line cleaning (ILC) coupling - this is similar to the IDF coupling but the seal has rounded edges. It also has the advantage that it is available in all sizes and can therefore be used throughout an installation. 72 The above couplings all rely on a hexagonal nut which is screwed onto the matching thread on the male part, in order to apply compression to the seal. © 0) 6) 0) 6) Oh ce: fe” e) <a) in; ei “ai “ee ©: Je) <6) fe lo 0) 10 io io 0) 6) 0) @: ol ee) o) 18) © 0) 6 0) @ (eine (s, 0 10) e710) \e' lelle) le. celielies ‘© lel elle: is
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