... , 4.Self relieving seats, 5.DBB 1,Cast steel ball valves made by our company can be divided into handle ... ball type, trunnion ball type, high, middle and low pressure, high, middle and low temperature, sulphur-resistant and non-sulphur- resistant valve by valve ... manufacturing technique. 3,Valve teat is so strict that each valve is tested, measured,and the results are recorded for quality-tracing. We ...