Air Components Used On Air-Over-Hydraulic Panels
Relay Emergency Valve
EE Bleed Down Type Relay Emergency Valve J58860
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This valve controls pressure to the service brake pressure cluster on
type A/H, A/H-HRC, and A/H-ERC systems. It applies pressure from the
right half of the horizontal reservoir. Whenever emergency port E is
pressurized above 50 psi, reservoir port R pressure is poised for
application to delivery port D at whatever pressure is applied to
service port S. Without pressure at the service port, no pressure is
applied to the delivery port. Whenever emergency port pressure drops below 40 psi, pressure at the reservoir port is applied to the delivery port. Hence the valve applies pressure to |
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the service brake pressure cluster in "emergencies", although
a tiny "bleed down by-pass" bleeds delivery port pressure
through the service port. After several hours the "emergency"
brake pressure is fully released. |
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SYSTEM IDLE In the idle condition, emergency port pressure is off, reservoir port is open to delivery port. Service brake pressure cluster is applied if reservoir pressure is available. The check valve has no function and is closed permanently. With no emergency pressure, the emergency piston and valve cartridge is held in by spring force and the exhaust poppet closes service port while the inlet poppet opens a passage to the relay piston. Pressure on the relay piston forces it down against spring force, sealing the inlet-exhaust poppet and opening reservoir port to delivery port. A bleed down by-pass slowly vents reservoir pressure to the service port to prevent service pressure cluster application for extended periods. SYSTEM NORMAL When emergency port is pressurized, 65-80 psi compressor pressure forces the emergency piston and valve out against spring force, pulling the exhaust poppet open and the inlet poppet closed. With no pressure at the service port, the return spring forces the relay piston up, allowing relay inlet-exhaust poppet to seal reservoir port and open delivery port to exhaust port. Service pressure cluster is released. SERVICE STOP When service port is pressurized pressure strokes the relay piston against spring force. The piston picks up the relay inlet-exhaust poppet valve, first closing the exhaust passage and then unseating the poppet to open reservoir port to delivery port. When the force on the relay piston balances opposing spring forces, the piston is forced to lap, permitting the spring loaded relay inlet-exhaust poppet to close while holding the exhaust passage sealed. The valve remains poised in this "hold" position, relaying delivery port pressure equal to service port pressure. EMERGENCY STOP Reduction of emergency port pressure below 40 psi triggers the valve to apply reservoir pressure, as described in SYSTEM IDLE section above. |
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SERVICING THE EE BLEED DOWN TYPE RELAY EMERGENCY VALVE
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The valve should be replaced or overhauled using both seal and maintenance kit
should any abnormal symptoms occur. A. On A/H, A/H-HRC or A/H-ERC Systems
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SERVICE PARTS INFORMATION
EMERGENCY VALVE SECTION
RELAY VALVE SECTION
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