Tribological failure analysis of ball valve seals

The ball valve seals are exposed during their use to thermal gradients (alternating the flow of cold and hot water), static loading (clamping force) and cyclic loading (alternating opening and closing) which can be sources of valve failures. The ball valves usually fail as a result of different failure modes such as wear, plastic deformation and corrosion. In order to describe these modes a failed ball valve which was belonged to a sanitary installation is investigated. The investigation of the failure was carried out by using several experimental tests including optical microscopy and Scanning Electron Microscopy (SEM). Tests were performed on a specific reciprocating tribometer for ball valve seals application. Experimental results revealed that the friction behaviour of polymeric seal depends strongly on the clamping load of seal and the manipulation frequency of counterface ball. Optical microscope observation of the worn surface showed that strong adhesion of the polymeric transfer layer to the counterface ball.