MIL-HDBK-1138
a)
Ductile iron pipe, both lined (cement-mortar) and
unlined.
Coatings and cathodic protection may or may not be
required.
b)
Steel pipe, generally lined with coal-tar epoxy.
Buried steel pipe usually requires external coatings,
supplemented with cathodic protection.
c)
Carbon steel structural.
Always requires
protective coatings.
d)
Aluminum used in most atmospheric exposures, such
as ladders, grating, handrails, and covers. Protective coatings
are normally not required.
e)
Stainless steels, usually Type 304 or Type 316.
If there are high chlorides in the wastewater, Type 316 is
usually required. If considerable fabrication is involved,
specify the low-carbon (L-grade) stainless steel. Coatings are
generally not required, unless the steel is buried.
f)
Stainless steel fasteners, preferred because a
WWTP's environment is wet and corrosive.
8.2.3.2
Nonmetals. Most nonmetals may be used with
success in nearly all areas of a WWTP. In addition to concrete,
plastic materials, such as thermal plastics and thermal-sets, are
used extensively. Such materials as polyvinylchloride (PVC),
chlorinated polyvinylchloride (CPVC), polyethylene (PE), and
fiberglass-reinforced plastics (FRP) are used in many
applications.
From a maintenance standpoint, the nonmetallic
materials require different skills to install, maintain, and
repair. PVC and CPVC are joined with special cements, PE is
joined usually by heat fusion, and FRP is joined with reinforced
resin layup. Maintenance of PVC, CPVC, and FRP can usually be
performed by in-plant crews. Repair of PE requires special
tooling that is not usually available onsite.
83
Previous Page
