BCAS 2018

www.bcas.org.uk 25 Technology Guide seal in some form of housing against either the inner or outer surface of the piping system. Box section modular aluminium pipes are connected to each other and fittings employing a double ‘O’ ring seal and dovetail clamping and jointing system. Screwed Joints Where pressure-tight joints are made on the threads – the BCAS publication “Pipe Joint Guide” identifies the thread types used for this type of jointing technique and the practices to adopt to ensure a satisfactory air-tight joint. Welded Joints The integrity of this type of joint rests solely with the quality of the welded joint. Therefore, a qualified and certificated welder in accordance with BS EN ISO 9606 should perform the welding procedure ‘Press-fit’ Joints This is a mechanical pressed joint using an O-ring to make it fluid tight. The joint can be made by either hand force crimping tools or powered hand tools. Where flexibility is required, other systems may be more suitable. Hydraulic Friction Joints These are popular for pressures above 20 bar and extend into regions of 450 bar. The use of these fittings to make a joint with a pipe should follow the joint manufacturers’ instructions in every detail. Flanged Joints This type of joint relies upon a sealing material being adequately clamped between faces whose surface is suitably prepared to prevent leakage. The flanges are secured to the pipes by threaded or welded joints and the flanges are bolted together with a sealing gasket between them. Rigid Plastic Joints The integrity of this type of joint, usually fusion bonded, also rests solely on the quality of the jointing procedure. Air main location This is another area that causes confusion and dispute. The air mains can be sited at any level from under-floor ducting to overhead. For ease of servicing and draining and for access when connecting to service points, the overhead main is often used. Some general guidance: ● Pipes must not be allowed to sag or hog, especially at threaded or flanged joints, since the bending stress could result in leakage and possibly to pipe fracture. Follow manufacturer’s instructions for support spacing. ● The air main should be supported throughout its length so that the correct fall to the drain points is maintained and condensate cannot collect in the pipe itself. ● Allowance must be made for thermal expansion and contraction. This allowance will vary with the material used. ● Compressed air piping should not be attached to (i.e. hung from), other utilities such as gas mains. Your contractor Under Regulation 6, The Pressure Systems Safety Regulations 2000 Approved Code of Practice, the owner/user of the system must ensure that those doing the installation have the required training, skills and experience. It is important that the user selects a supplier that can demonstrate competence through experience and evidenced training in pipe installation and jointing. The user should also check that the supplier: ● Is conversant with the safety issues surrounding compressed air ● Will carry out the work in a safe manner ● Holds the appropriate insurance ● The Pressure Systems Safety Regulations 2000 do not specify piping types or specific installation procedures. Like other health and safety legislation such detailed recommendations are beyond its scope. ● Therefore to demonstrate compliance with the law, users (and their contractors) should follow that “good industry practice” during the installation process. Examples of “good industry practice” are trade bodies’ codes of practice, for example: ● the BCAS installation Guide, and ● BCAS Pressure & Leak Testing Best Practice Guide (BPG 103). For full detail these two publications cover the selection of equipment, correct installation and commissioning prior to use and are available to download at: www.bcas.org.uk