Although water and steam are the ideal media for heat transfer, there are often situations when other heat-transfer fluids are called upon to perform this function in the chemical process industries (CPI). The high temperature ones require particular attention as regards selection, design and maintenance.

Rotary valves are widely used for feeding bulk solids into pneumatic conveying systems. When sizing such a system, leakage of conveying gas through this valve must be accounted for, because such leakage can cause gas flow in the conveying line will to increase or decrease, thereby affectation conveying velocity and pressure.