INSTALLATION OF PIPING
Edward F. Gerwin, P.E.
The term fabrication applies to the cutting, bending, forming, and welding of individ-
ual pipe components to each other and their subsequent heat treatment and nonde-
structive examination (NDE) to form a unit (piping subassembly) for installation.
The term installation refers to the physical placement of piping subassemblics,
valves, and other specialty items in their required final location relative to pumps,
heat exchangers, turbines, boilers, and other equipment; assembly thereto by weld-
ing or mechanical methods; final NDE; heat treatment; leak testing; and cleaning
and flushing of the completed installation.
Depending on the economics of the particular situation, fabrication may be
accomplished in a commercial pipe fabrication shop, or a site fabrication shop,
where portions of the piping system are fabricated into subassemblies or modules
for transfer to the location of the final installation.
Commercial pipe shops have specialized equipment for bending and heat treat-
ment which is not normally available at installation sites. They also have certain
types of automatic welding equipment which permits welding to be performed more
efficiently and economically than in field locations where fixed position, manual
arc welding is most often employed.
As a general rule piping NPS 2¹⁄₂ (DN 65) and larger for nuclear and fossil
power plants, chemical plants, refineries, industrial plants, resource recovery, and
cogeneration units are most often shop fabricated. Piping NPS 2 (DN 50) and
smaller is often shop fabricated where special heat treatment or cleaning practices
may be required; otherwise it is field fabricated. Pipelines and other systems involv-
ing long runs of essentially straight pipe sections welded together are usually
In recent years, the infusion of new bending technologies, new welding processes,
new alloys, fracture toughness limitat