When Worcester Controls’ valves and Norbro actuators were installed at a fine chemicals manufacturing plant in Middlesbrough in 1997 they had a target to achieve one million uninterrupted cycles. Five years and ten million cycles later, they are still operating under highly demanding conditions, with only one reported gland leak, which was taken up by a minor adjustment. In the application an acidic liquor containing dissolved salts including sulphates and chlorides with a pH of 3.5 is carried at temperatures of up to 50C.
Operation cycles are extremely high – the actuated valves used to control the liquor’s flow are operated every 20s. Given the nature of the liquor, any valve leakages would be highly unpleasant and adversely affect the workplace, so the valves chosen had to be environmentally safe. In seeking an improved solution that would extend the intervals between valve changes, the firm initially evaluated diaphragm valves, before selecting Worcester Controls’ E51 EnviroSafe flanged ball valves. The seven valves, manufactured from stainless steel, feature a unique dynamic dual sealing stem arrangement and are controlled by double-acting Norbro pneumatic actuators, which given their strenuous workload have also remarkably lasted the course.
