1. Why whole head lift arrangement is provided?
Modern valves are of Reed or disc type of high grade alloy steel valve sitting on a stainless steel with a usual lift of 2mm. The discharge valve retainer is normally held down to a set position by heavy springs, thus it gives a requirement to provide a spring load arrangement on the discharge valve cage to lift the whole head in case of liquid ingress. REEDS
Aluminium piston with 2compr rings n one scraper ring
Con rod aluminum
Crankshaft is CG Iron in Vee block and spheroidal graphite CI for W configuration.
Body close grained casting of Iron or steel
Nickel bursting disc allowing excess pr from discharge to suction side
Head lift arrangement for liquid ingress
Differential oil press cutout
4. Plate type valves why
Large diameter and very small lift offers least resistance and have low inertia