The Pressure Equipment Regulations 1999

10.  Equipment comprising casings or machinery where the dimensioning, choice of material and manufacturing rules are based primarily on requirements for sufficient strength, rigidity and stability to meet the static and dynamic operational effects or other operational characteristics and for which pressure is not a significant design factor, such equipment may include:

• engines including turbines and internal combustion engines,

• steam engines, gas/steam turbines, turbo-generators, compressors, pumps and actuating devices;