- The H.P. Delivery Valve can be tried by taking out the H.P. suction valve then putting on the air back from the receiver to the compressor. If the H.P. delivery valve is tight, no air will leak out of the suction valve hole.
- The H.P. Suction Valve can be tried by first taking out the H.P. delivery valve, then the pipe between the cooler and the H.P. suction valve. Now open the valve from the receiver, and if the H.P. suction valve is tight, no air will pass back through the pipe hole in the compressor head.
- The other valves can be tested similarly, after first removing the H.P. suction and delivery valves to allow the air to pass through.
- When under running conditions, if the L.P. compressor gauge shows a tendency to drop, the L.P. valves may be out of order. On the other hand, if the L.P. gauge rises, the intermediate valves may be out of order. Leaky H.P. valves cause the pressure to rise in both of the lower stage
Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole is lesser in size than the corresponding circular hole. More over it is prime concern to have a smoothed generous radius at the corners to eliminate stress concentration. Hence other geometrical shapes like rectangle and square are ruled out. To compensate for the loss of material in the shell due to opening, a doubler ring has to be provided around the opening. The thickness of the ring depends on the axis length along the dirrection in which the stresses are maximum and the thickness of the shell. It is important to align the minor axis along the length of the vessel, as the stress in this direction is maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t= thickness of the shell plating Circumferential stress: Pd/4t More over a considerable material and weight saving is achieved as minor is along the direction of maximum stress.