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DESCRIPTION

The INVALCO Model CDM is a diaphragm-operated Pressure Switch for pneumatic or hydraulic control. The unit is equipped with one or two snap-acting three-way Micro Valves® to provide on/off output to one or more controlled circuits. Since the Micro Valves® are completely isolated from the diaphragm, and also isolated from each other, various control output pressures and media may be used in the same CDM pilot.

Specifications

Diaphragm Case and Case	Aluminum
Micro Valve®	Aluminum body, stainless trim, Buna-N inserts and seals. Other materials available on special order.
Stem and Bushing	Stainless and brass
Micro Valve® Flow Characteristics	Type 38F1, 1/8” Orifice: 26 cfm @ 100 psi.
Maximum Working Pressure	Micro Valve: 100 psig Actuator: 30 psig - limited by spring range.

OPERATION

Process pressure is applied to the upper diaphragm chamber, causing the stem to lower against the spring. When the upper drive collar has been dropped sufficiently, the Micro Valve® will snap, thereby reversing the control circuit. As process pressure decreases, the lower drive collar will raise, contacting the toggle arm which causes the Micro Valve to snap to its “normal” position.

ADJUSTMENT

Operating adjustments are very simple on the CDM Pressure Switch. The range spring fixed and requires no adjustment. The process pressure required to trip and release the Micro Valve will depend on the spacing of the drive collars. The adjustable drive collars provide a convenient means of adjusting the span of output valve action within the operating range. Tripping pressure can be adjusted from approximately 6 to 20 psig, with release pressure varying from approximately 2 to 8 psig.

SPECIAL APPLICATIONS

Where manual reset is required, simply remove one of the adjustable drive collars. The CDM pilot lends itself to lock up or alarm service since either application, or loss of process pressure, can cause the Micro Valve to trip with manual reset required by removing either the lower or upper drive collar. The clear plastic cover permits visual indication of the Micro Valve position as well as the approximate process pressure.

Differential pressure control is another process variable which can cause actuation of the Micro Valve. In this application, the lower process pressure is applied below the diaphragm with the higher pressure above the diaphragm. The Micro Valve will now be tripped by a change in the differential between two process pressures. In this application, the maximum static pressure applied to either side of the diaphragm must be limited to 100 psig.

ADDITIONAL INFORMATION

Note: Dimensions – Inches to the nearest tenth (millimeters to the nearest whole mm), each independently dimensioned from respective engineering drawings.