Installing pipes for carrying steam involves certain considerations not necessarily applicable to other piping systems. Of course, the major difference is the heat steam generates. Although water’s boiling point is 212 degrees Fahrenheit, steam is often “superheated” to much greater temperatures. Boiling water under greater than normal atmospheric pressures results in steam reaching 300, 400 or even 500 degrees Fahrenheit. Installing pipes to normally handle these temperatures and pressures involves special considerations.
Steam pipes must be insulated so the generated heat is not lost while traversing the length of the pipe. Creating sufficient insulation is part of the pipe system designer's and pipefitter’s responsibility to produce an efficient process. Insulation can be a sheath of material ranging from low-density fiberglass (similar to household “pink” insulation) or high-density foam. Any insulation, however, is not going to be perfect. What’s important is to keep the heat loss to a minimum and account for the heat loss in the system design. If an application for a steam turbine requires superheated steam at 350 degrees F, the system must produce steam of greater heat and allow for heat loss. So the turbine may need steam at 350 degrees, but the anticipated heat loss through an insulated pipe is 50 degrees. This means the boiler must produce steam of at least 400 degrees to ensure optimum system performance.
Piping systems involve “hanging” pipe both horizontally and vertically. When installing steam pipes, the pipe supports (hangers) need to be able to not only resist the tremendous heat in the system but also be large enough to contain any additional insulation. It’s important the insulating sheath be of a consistent diameter. Ordering 1,000 hangers to run steam several hundred feet only to learn the pipe and insulation are 1/2 inch too large to fit in the available hangers can lead to a wasted day on the job. Hangers too large can also lead to problems if the steam pipes are allowed to move or sway. This can lead to issues with chafing and corrosion. A properly sized hanger is an integral part of a steam pipeline.
Steam pipes can produce tremendous vibrations. Heating and cooling cycles as steam is turned on and off cause rapid expansion and contraction. Steam requires tremendous pressure or it will simply cool and become water again. Controlling the pressure involved can cause steam pipes to rattle, flex and vibrate. The hangers, fittings and insulation all need to be able to control and facilitate the pipe’s action while containing the steam.