Environmental Engineering Reference
In-Depth Information
figure 4.6 Flanged assembly.
necessary to accommodate maintenance needs or process changes), and
high leakage integrity at low pressure and temperature where vibration
is not encountered. Screwed construction is commonly used with galva-
nized pipe and fittings for domestic water and drainage applications.
4.8.5.3.3 flanged joints
As shown in Figure 4.6, flanged joints consist
of two machined surfaces that are tightly bolted
together with a gasket between them. The flange is a
rim or ring at the end of the fitting, which mates with another section.
Flanges are joined by either being bolted together or welded together.
Some flanges have raised
faces and others have plain
faces, as shown
in Figure 4.7. Steel flanges generally have raised faces, and iron flanges
usually have plain or flat faces.
Key Point:
A flange with a raised
face should never be joined to
one with a plain face.
Flanged joints are used extensively in water/wastewater piping sys-
tems because of their ease of assembly and disassembly; however, they
are expensive. Contributing to the higher cost are the material costs
of the flanges themselves and the labor costs for attaching the flanges
to the pipe and then bolting the flanges each other. Flanged joints are
not normally used for buried pipe because of their lack of flexibility to
compensate for ground movement. Instead, flanged joints are primarily
used in exposed locations where rigidity, self-restraint, and tightness
are required (e.g., inside treatment plants and pumping stations).
Plain faces
Raised faces
figure 4.7 Flange faces.
