The compressor and delivery valve of air compressor allow the air flow in only one direction .Suction valve allows air flow into the cylinder and prevent back flow and delivery valve vice versa .
To make the action of valve more positive the valve are spring loaded . When the piston makes a suction stroke the pressure behind the suction valve over comes the spring pressure and causes the valve to open .
When ,suction valve opens the extended air flow into the cylinder by virtue of the great air pressure outside the cylinder .During the suction stroke the air with in the cylinder clearence volume expands to some value lower than the outsider.
Pressure difference is necessary is required to get the air flow into the cylinder .Similarly on discharge stroke of the piston the pressure in the cylinder rises to some point at which the discharge valve opens .
After the valve opens the pressure in the cylinder falls slightly then remains approximately constant and valves closes.These valve losses lower the mechanical efficiency of the air compressor .
suction valve :
EFFECTS OF SUCTION VALVE LEAKS :
1.Area of the indicator diagram will be less so work done by the compressor is less.
2.Compressed air can pass through the suction valve due to the leakage as a result compressor delivery /discharge pressure will be low.
3.Air leak through suction valve leads carbon deposit on valve plates and suction plates .
4.Suction valve will be over heated ,so the carbon deposit will be high it restrict air passage and valve can even break .
5.Suction filter will get chocked .
6.Suction pressure will show higher than normal value .
7. Compressor discharge quantity will be low .
8.Compressor will run for long time .
9.The volumetric efficiency of the compressor will be low .
EFFECTS OF DISCHARGE VALVE LEAKS :
1.Low discharge pressure caused due to the leakage in the discharge valve .
2.Volumetric efficiency will be low .
3.Every stroke there is high pressure and high temperature leakage air is available for suction stroke ,so compressed air temperature will raise .
3.High compressed air temperature will effect liner lubrication oil film .The oil may burn Incompletly hence lead high carbon deposite on plates and in piston rings .
4.If carbon deposits traped on valve seat it can lead higher valve lift so loss of air will be more .
5.Compressor will work for more time leads over heating liner ,piston and lube oil etc.
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