Spirax Sarco has been providing valves for processing solid rocket propellant at Roxel UK in Kidderminster for the last three years. With production continuing round the clock, 365 days per year, the reliability of the three valves is crucial. Each valve controls the curing temperature of batches of different propellants by modulating steam flow into air heater batteries in specially built curing buildings. Each curing process lasts up to four days and calls for temperatures of 45C, 60C and 65C to be maintained to within +/2C. Subsequently, each curing house was fitted with separate shutdown valves to prevent any possibility of overheating of the propellant. "The product can explode if it gets too hot," says Mr Laing. "We initially had problems with the shutdown valves sometimes closing unnecessarily." Spirax Sarco solved the problem by changing the control system programme to ramp up the heating, avoiding a temperature overshoot when first bringing each batch up to its temperature, rather than just switching the control valves full on.
