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WHAT IS IT?
 This is a pilot operated, two stage, high temperature pneumatic Valve. It is designed for continuous duty controlling air at 700 degrees F in an ambient temperature of 250 degrees F. All "wetted" surfaces are made of Stainless Steel or protected by compatible plating. There are no overboard or internal seals. Leak paths are match-lapped to minimize by-pass flow.
Pilot flow from the second stage-piston is vented overboard, but could be plumbed to the downstream side. A high temperature Limit Switch is included to act as a positive position indicator.
The Valve is normally open. When actuated closed, the Limit Switch opens a circuit extinguishing a light on the cockpit control panel. |
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HOW DOES IT WORK?
 In the de-energized state, the Valve is open and flowing. Thus, in a loss of power, the unit fails open. Inlet pressure is ported to the face of the second stage Piston and one leg of the Pilot pneumatic circuit. The other leg is connected to the back side of the second stage Piston.
The Pilot stage is positioned by a D.C. Solenoid. While it remains de-energized, pressure is bled from the back side of the second stage Piston. When energized, the Solenoid positions the Pilot to close off that bleed flow. The resulting pressure build-up, together with a Spring, overcomes the opposing pressure forces, closing the Valve. De-energizing the Pilot Solenoid vents the Piston cavity permitting inlet pressure operating on the face of the Piston, to overcome the Spring force, opening the Valve. |
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| HOW IS IT USED? |
This particular model is used to control the flow of the fourth stage Turbine Engine Compressor gas. The Valve is connected to a manifold system which delivers the high temperature air to both the Engine Nacelle Inlet Ring and the Turbine Hub (Bullet). Both surfaces are thereby maintained at a temperature well above that at which ice can form. The Valve concept can be packaged in almost any form to accommodate various manifold or plumbing schemes. Flows of up to 15 lb./min at 700 degrees F and 100 psig inlet pressure are feasible with this basic design. The practical high temperature limit is 850 degrees F set by the tolerance of the electrical insulating materials in the Solenoid.
See the link below for additional information: |
| Tech Data Bulletin - Pilot Operated, Anti-Ice Valve (PDF) |
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