Piping connection

Piping systems are defined by the Piping Specification for the particular system or part of a system involved. The locations where things change are called 'spec breaks' for short.

The piping specification will call out what material, what pressure class, what connection procedure, etc. is required for that particular section of piping. The Piping Designer who creates the Pipe Spec has to choose the materials, etc. based on the Materials of Construction flow diagram prepared by the Process Engineers- on which are specified the materials to be used, the temperature and pressures of operation, the material contained by the piping, as well as any non-ordinary, but expected conditions that must be considered in designing the piping.

For instance, piping containing liquid propane is usually ordinary mild carbon steel. However, if there is a situation that would have the propane boiling (evaporating ) in that section, it is possible the temperature could fall as low as -40 due to the refrigerating effect. For those potential conditions, special steel that retains good ductility at low temperatures is necessary to avoid brittle fracture.

ALWAYS follow the Piping Specification. If your are charged with DEVELOPING a piping specification, you MUST greatly increase your body of knowledge. THis is a life safety critical document and your question indicates you have not been trained in this area.