The Supaflex Division of Interflex Hose and Bellows is always keen to promote new ideas on bellows technology to building services engineers.
Rubber bellows with tie bars are bulky and not particularly good for dampening noise and vibration even with large rubber isolators under the tie bars. Untied bellows are much better. However, tie bars do restrict the growth in length under increasing pressure in the larger sizes and it is quite common to go into plant rooms and find loose tie bars on bellows fitted to small pumps and equipment.
So, the industry has done something about it, with a material developed by Dupont called Kevlar. This is a far superior material to nylon reinforced bodies in rubber bellows and also steel cord reinforcing. Nylon becomes brittle with age and steel cord, whilst better, eventually corrodes and fails. Kevlar reinforced bellows used in building services rarely need tie bars. The vast majority of LPHW, MPHW and CHW systems don’t often exceed 8 bar working pressure, with most working on half this, or even less. Elongation is minimal, so too is temperature resistance and ageing resistance is also high.