Pneumatic Rolled Diaphragm Actuators
When using old style unloader actuators customers commonly experience:
• Leakage of the process gas past the shaft and cover seals
• Old OEM membrane diaphragms leaking which prevents them from actuating the unloaders
• Problems with insufficient stroke length of old OEM membrane diaphragms that occur after the valves are reconditioned and the unloader finger travel height changes
• Inability of hand operated unloaders to be used with automated control systems
Read the full case study here:
CPI Unloader Actuators with upgraded seals reduce emissions, and when combined with a CPI valve upgrade, increases overall reliability.
New CPI actuators prevent seal leakage with upgraded O-rings and shaft seals. As an extra precaution, a vent connection is supplied for the collection of any leaking process gas to the flare or disposal system.
The flat membranes commonly used in old OEM diaphragm actuators are based on old material technology which results in high stresses when the diaphragm is stretched when actuated. Over time this can lead to failure of the diaphragm which prevents the actuator from stroking the actuator shaft. This can be difficult to diagnose in the field and requires the compressor to be shut down for replacement. The rolled diaphragms are manufactured with a geometry that allows them to flex without creating high stresses.
Another advantage of these rolled diaphragm actuators is their extended stroke capability – often more than 3 times traditional membrane actuators. As the valves are reconditioned their seat thickness changes which often requires the adjustment of finger unloader travel on the suction valves. If this is not done properly, the fingers can either not unload the valves at all or they can hold the valves open all the time. Both of these conditions can only be identified with the compressor running which leads to time wasted during troubleshooting and the need for shutting the unit down for re-adjustment. The CPI actuator with extended stroke prevents the actuator stroke from causing adjustment problems.