Diaphragm valve actuator is most commonly used for globe valve applications, although it can be used with ball and butterfly valves. Their operations and construction features are relatively simple to understand, but they do not always function in the same manner. Generally, they are used to control the flow of process water. The actuator consists of a diaphragm that is placed between a split housing. The diaphragm is made from a reinforced rubber compound, and usually is supported by, or attached to, a plate. The plate not only reinforces the diaphragm, but also provides an area on which the return springs can rest. The location of the springs is determined by the valve operation. If the valve is a normally open style, the springs are placed beneath the diaphragm. If the valve is of the normally closed type, the springs are placed on top of the diaphragm. However, there are exceptions to this general design, and spring placement depends upon the construction features of the valve.