Safety Valves and Inward Relief Valves

Safety Valves and Inward Relief Valves

Mountings, pipe unions, electrical actuator where fitted, (and its connections) should be checked for signs of damage, deterioration and security.

Leak tests and functioning tests should be made after installation, when the serviceability of valves is suspect, during cabin pressure testing, and at the periods specified in the Approved Maintenance Schedule. The requirements for functional testing of inward relief valves is normally restricted to checking freedom of movement.

Valve faces and seats should be inspected and deposits of dust and nicotine tar removed in the same manner as that specified for discharge valves. After cleaning, a check should be made to ensure that valve faces and seats make good contact.

Electrical and manual override controls should be checked for security and tested for correct operation, particular attention being paid to the settings of actuator limit switches, lost motion in linkages, cable tension and static friction. Where specified, moveable parts should be lightly lubricated using only the specified lubricants.

Certain types of safety valves can be adjusted in situ, but before any attempt is made to alter the relief pressure setting it should be established that any error in the pressure at which the valve relieves is not due to a defect in the valve mechanism. After making adjustments to a valve its operation must be checked by repeating the appropriate cabin pressure and functional test.