(h)Working cylinders of steam engines or prime movers, feed pumps and steam traps; turbine casings; compressors cylinders; steam separations or dyers; steam strainers; stream de-super heaters; oil separators; air receivers for fire sprinkler installations; air receivers or monotype machines provided the maximum working pressure of the air receiver does not exceed 1.33 kg.f/cm 2 (20lb/sq.inc.) and the capacity 84.95 liters (3cu.ft.); air receivers of electrical circuit breakers; air receivers of electrical relays; air vessels on pumps, pipe coils accessories of instruments and appliances, such as cylinders and piston assemblies used for operating relays and inter-locking type of guards; vessels with liquids subjected to static head only; and hydraulically operating cylinders other than any cylinder communicating with an air and accumulator.