CPM is an acronym for Constant-Pressure Modulating Valve. There are two types of CPM valves, -O (outlet) & -I (inlet). The CPM-O valves go before the separator (in place of a balance tank), and the CPM-I valves goes after the separator.
CPM-I Valves are more common. The I valve maintains a constant pressure in the process line at the the inlet side of the valve. Typical applications are after separators, heat exchangers, etc. and as overflow valves.
The CPMO maintains a constant pressure in the process line at the outlet side of the valve.
Typical application of CPMO valves are before filling/bottling machines, etc. The round bottom of the CPM valves means it is 3A. There is also a “-2″ after the I or O, to denote that it is sanitary. CPM valves are typically 2”.
There is a “freak” 3″ CPM that was made by Alfa Laval – the CPM-I-D60 valve – this valve consists of upper and lower valve bodies, an inlet tube, a cover, a valve plug with diaphragm unit and clamps. The diaphragm unit consists of two flexible diaphragms supported by 12 stainless steel sectors between them.
These valves are remote-controlled by compressed air and operate without a transmitter in the product line and require only a pressure regulating valve for the compressed air and pressure gauge in the product line. A diaphragm/valve plug system reacts immediately to any alteration of the product pressure and changes position so that the preset pressure is maintained.
NOTE: The inlet valve opens at increasing product pressure and vice versa, while the outlet valves closes at increasing pressure and vice versa as well.
STANDARD DESIGN: CPM valves consist of a valve body w/ valve seat, cover, and a valve plug with a diaphragm unit and a clamp. The diaphragm unit consists of a stainless steel disc which is divided into sectors and of flexible diaphragms which are placed on each side of the sectors. The cover and the valve body are clamped together. The valve body and seat are welded together.
When sizing these valves pressure drop and flow are very important, you always want to get as near as possible to the 50% open curve when sizing these.