The large-scale contained use of biological agents / Advisory Committee on Dangerous Pathogens.
- Great Britain. Advisory Committee on Dangerous Pathogens
- Date:
- 1998
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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![Static seals ULCER OT oeoaistk ei oiiel ‘stileln.e) Left i=litel [oleh ed op toluzeute) |e! collie, (6ire) (6) el) 10) “ol e's) ei 6) fe: 0; Je) (ele. ei ce 6) (0, fe: je ie) je :0; © fe e- 'e) ie) :6 10) 56 e Triclover clamp type joints - an alternative method is to use a clamp to force together two liners, each of which is grooved to locate a shaped seal. The seal, which is usually flanged and contoured, can be made to give a crevice-free joint in the pipework. Such couplings can be dismantled easily, particularly if the clamp is tightened by a quick-release clip. These clamps cannot be accidentally over-tightened unless they are designed to be tightened using a locking bolt, in which case the use of excessive force can result in a cut seal. It is essential to use a torque wrench for such applications. 73 Alternatively a pair of flat flanges can be made perfectly gas-tight when used with a suitable seal, the dimensions of which are arranged to produce a crevice-free joint. Care should be taken to ensure that the flange faces are smoothly machined and do not contain any radial scratches which could cause leakage paths. It is also preferable that the bolts which join the flanges are tightened with a torque wrench to avoid distortion to the flanges. 74. Theuse of screwed pipe is not recommended at Containment Level 2, because of difficulty in sterilisation and decontamination. The use of screwed pipe is not acceptable at Containment Levels 3 or 4. 75 Whatever method of coupling is used, it is essential that the pipework is adequately supported to prevent distortion of the couplings and gives good pipe alignment. This support should also take into account the dimensional changes introduced by thermal expansion during sterilisation cycles. Failure to make such provision can result in distortion or cut seals. 76 The choice of materials for seals and gaskets depends on the specific process conditions and factors such as temperature, exposure to steam, temperature cycles, chemical resistance and other factors. Some of the typical materials commonly used are: General temperature range (°C) Ethylene propylene diene modified —50 to 150 Isobutylene isoprene —30 to 130 Butadiene acrylonitrile —40 to 100 Fluoroelastomer —30 to 175 Silicone —60 to 230 static (175 dynamic) 77 Polytetrafluoroethylene (PTFE) This exhibits a very broad range of chemical and thermal serviceability. However, the effects of temperature, pressure and absorption of chemicals on PTFE and their interactions should be considered. A modified PTFE, developed for use where intermittent steam sterilisation is used, provides improved resistance to creep and elevated steam temperatures. Pr a-ha ctl cect od oft oY ols) oh ion ol (of to) olyeMoMe MU Glsoy (of Lael ot is)ii61-9h 0] (OF 0) (0) 0/16) (6) (60), .0, eC 10) le (ej (eye 8 8) [011% (0 0: @](https://iiif.wellcomecollection.org/image/b32230163_0025.jp2/full/800%2C/0/default.jpg)
