Environmental Engineering Reference
In-Depth Information
4.12 PiPe and Tube fiTTings
The term
piping
refers to the overall network of pipes or tubing,
fittings, flanges, valves, and other components that comprise a conduit
system used to convey fluids. Whether a piping system is used to simply
convey fluids from one point to another or to process and condition the
fluid, piping components serve an important role in the composition and
operation of the system. A system used solely to convey fluids may con-
sist of relatively few components, such as valves and fittings, whereas a
complex chemical processing system may consist of a variety of compo-
nents used to measure, control, condition, and convey the fluids. This
section describes the characteristics and functions of various piping
and tubing fittings (Geiger, 2000).
4.12.1 fittings
The primary function of fittings is to connect sections of piping and
tubing and to change direction of flow. Whether used in piping or tubing,
fittings are similar in shape and type, even though pipe fittings are usu-
ally heavier than tubing fittings. Several methods can be used to connect
fittings to piping and tubing systems; however, most tubing is threadless
because it does not have the wall thickness required to carry threads. Most
pipes, on the other hand, because they have heavier walls, are threaded.
With regard to changing direction of flow, the simplest way would
be to bend the conduit, which, of course, is not always practical or pos-
sible. When piping is bent, it is usually accomplished by the manufac-
turer in the production process (in larger shops equipped with their own
pipe-bending machines), but not by the maintenance operator on the
job. Tube bending, on the other hand, is a common
practice. Generally, a tubing line requires fewer fit-
tings than a pipeline; however, in actual practice
many tube fittings are used.
Key Point:
Recall that improperly
made bends can restrict fluid flow
by changing the shape of the pipe
and weakening the pipe wall.
Fittings are basically made from the same
materials (and in the same broad ranges of sizes) as piping and tubing,
including bronze, steel, cast iron, glass, and plastic. Various established
standards are in place to ensure that fittings are made from the proper
materials and are able to withstand the pressures required; they are
also made to specific tolerances, so they will properly match the piping
or tubing that they join. A fitting stamped “200 lb,” for example, is suit-
able (and safe) for use up to 200 psi.
4.12.2 functions of fittings
Fittings in piping and tubing systems have five main functions:
•
Changing the direction of flow•
•
Providing
branch connections
Changing sizes of lines
•
•
Sealing lines
•
Connecting lines
