Steam receivers that must be registered with MOM include:

• Any vessel or apparatus (other than a steam boiler, steam container, steam pipe or coil that serves the sole purpose of conveying steam from one point to another, or a part of a prime mover) used for containing steam under pressure greater than atmospheric pressure.
• Equipment that contains chemical or hydrocarbon material on the shell side and steam on the tube side.

You do not have to register equipment where the safe working pressure does not exceed 0.5 bar or the product of its safe working pressure and volume does not exceed 100 bar litres.

This information is sourced from MOM