A study of hydraulic impacts caused by condensate in steam distribution systems

Abstract

This paper describes an investigation into a problem associated with steam distribution systems where condensate is swept through a pipeline by high-velocity steam, causing considerable damage when it impacts upon an obstruction. Two cases have been considered. The first is where an isolated slug of water is swept through a pipeline by high-velocity steam and impacts against an orifice plate. In experimental tests compressed air was used to propel a slug of water through a pipeline 13 m in length and 50 mm in diameter; impact pressures of up to 300 bar were generated. The second case was more specific and considered the damage that occurs in steam traps. Tests were carried out in which damage was inflicted upon a float trap and a bucket trap by slug impact and by water hammer generated in the main pipeline. Although direct impacts by water slugs are often blamed for steam trap failures, the damage inflicted by this mechanism was not consistent with that found in practice and it has been concluded that they are not responsible. Water hammer in the main pipeline could, however, be the cause of failure. During the tests it was observed that the internal design of the body of the trap could produce a beneficial cushioning effect and this, together with the improved construction techniques for float traps, may overcome the problem of collapsing floats.