This package contains valves of different types.
The valves have been divided into three categories based on how they are used. Each category has its own sub-package.
All valves consist of one or several orifices
often controlled by a spool of some sort from the utilities
Almost all the valve models have a parameter called overlap. The parameter overlap
defines the overlap of the valves. If it is a negative overlap there is always some flow through the ports, and if it is a positive overlap the flow through the ports starts a bit late. Valves with negative overlap are used when the speed of the valve is more important than having a small internal leakage. The valves with positive overlap are slower but have less internal leakage. See the figures below. No overlapPositive overlapNegative overlap