SPECIFICATION | RUBBER BELLOWS BELLOW EXPECTATIONS The consequences of specifying low-grade rubber bellows for pump systems can be costly and dangerous. Eddie Warren, of Supaflex Agencies, says a British Standard is long overdue Example of a burst rubber bellow A high-grade EPDM tied unit with polyester ether keytone reinforcing in the body. Produced by Elaex/Continental, it meets DIN 4809 those specifying rubber bellows can use German DIN 4809, as there is no BS EN standard. Rubber bellows, which are used for flexible connections to pumps, are mostly ethylene propylene diene monomer (EPDM) with steel-collar reinforcing and nylon reinforcing in the body. The degradation of the nylon at high temperature is substantial; it deteriorates with age, and this also applies to the EPDM. High-grade rubber bellows are not reinforced with nylon in the body. In the mid-1970s full steel cord mesh was used, but this was found to fret through the EPDM wall. Kevlar (aramid fibre), developed by Dupont, was then used for many years, to be superseded by polyester ether keytone (PEEK). Only a very small number of rubber bellows manufactures are approved under DIN 4809. The formation of the Rubber Bellows Manufacturers Association has been instigated to only allow membership from manufacturers of high-grade rubber bellows. EDDY WARREN is the owner of Supaex Agencies Here is the new design. Any enquires should be sent to: INTELLIGENT, YET SIMPLE. Here is the new design. Any enquires should be sent to: sean.austen@ksb.com T he failure of rubber bellows in pumps and plant can have serious consequences. A flooded plantroom where hot water is kept to 65C to avoid legionella is dangerous to personnel, and the damage to plant and the building can be costly. Low-pressure and medium-pressure hotwater boilers are particularly prone to sudden burst failure. I have seen numerous examples of burst bellows, and been involved in wellknown projects that have had to replace all their rubber bellows. Where working temperatures of the systems are much lower such as on chilled water and closed cooling water systems failure is less likely, but with poor maintenance, it can still happen. Standard IE BS 6129-1 for metallic bellows, was published in 1981. The global standard for metallic bellows is covered by the Expansion Joint Manufacturers Association. In the UK, Quality products from KSB last longer and work better. Thats a promise. Find out more about KSB and our efficient solutions now. www.ksb.co.uk - 01509 231872 Pumps Valves Service 62 October 2020 www.cibsejournal.com CIBSE Oct20 pp62 Rubber bellows.indd 62 25/09/2020 16:50