CROSSFLOW（NEW CROSSFLOW SERVERS・DOUBLE VALVE）
AIR FLOW PATHS
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Parallel flow paths develop equal forces on the valve elements in the actuated and deactuated modes. This enables both valve elements to respond equally to pilot pressures and promotes synchronous movement of the valve elements. The air flow paths for the valves in different operating modes are shown below. |
VALVE ELEMENTS DEACTUATED
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With both inlet poppets closed, inlet air pressure holds each poppet firmly against its seat. Exhaust poppets are open to an oversized exhaust port, and sensing pressure signals are zero. Sensing passage (shown as dashed lines) transmit pressure signals upward or downward depending on the location of the monitoring device being used. |
VALVE ELEMENTS ACTUATED
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With the valve elements in the actuated position, inlet air is free to flow past the two inlet poppets and theough the two crossflow passages to the outlet port. The exhaust poppets close off the exhaust port, and sensing pressure signals become equal to inlet pressure. When the valve is returned to the deactuated position(see figre at top of this page), the design of the spool remaining in the sensing or crossflow passages to be exhausted through the open exhaust port. |
DETECTING A MALFUNCTION
A malfunction in the system or in the valve itself could cause one valve element to be open and the oter closed. In this event inlet air from the open and the other closed. In this event inlet air from the open inlet poppet is substantially blocked from the outlet port by the spool on the closed valve element. The large size of the open exhaust passage serves to keep the pressure at the outlet port below two percent of the inlet pressure.
The sensing pressure signal from the open valve element is equal to inlet pressure, while the sensing signal from the closed valve element is very small. The internal or external monitor senses the difference between these two pressures and uses this information to shut down the valve and inhibit further valve action. After the cause of the malfunction has been corrected and the electrical signal has been removed from the pilot solenoid, the monitor can be reset and noemal operation can resumed.
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