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YOUR COMPLETE GUIDE TO VALVE TERMINOLOGY
Our comprehensive guide to valve industry terminology is a valuable resource, whether you’re learning about the industry for the first time or refreshing your knowledge.
HANDWHEEL
A manual override device used to stroke a valve or limit its travel. The handwheel is sometimes referred to as a hand jack. It may be top-mounted, side-mounted, in-yoke mounted or shaft-mounted and declutchable.
HARD FACING
A material that is harder than the surface to which it is applied. It is normally used to resist fluid erosion or to reduce the chance of galling between moving parts. Hard facing may be applied by fusion welding, diffusion or spray coating the material. Stellite is a common material used for this purpose.
HIGH RECOVERY VALVE
A valve design that dissipates relatively little flow stream energy due to streamlined internal contours and minimal flow turbulence. Therefore, pressure downstream of the valve vena contracta recovers to a high percentage of its inlet value. These types of valves are identifiable by their straight-through flow paths. Examples are most rotary control valves.
HYDROSTATIC TEST
Pressure tests that are carried out on every valve when built to test the integrity of the pressure-containing parts.
HYSTERESIS
The difference between up-scale and down-scale results in instrument response when subjected to the same input approached from the opposite direction. Hysteresis can be caused by a multitude of variables, such as packing friction, loose linkage and pressure drop.
