Environmental Engineering Reference
In-Depth Information
4.12.4 Tubing fittings and Connections
Tubing is connected by brazed or welded flange fittings, compres-
sion fittings, and flare fittings. The
welded flange
connection is a reli-
able means of connecting tubing components. The flange welded to the
tube end fits against the end of the fitting. The locknut of the flange is
then tightened securely onto the fitting. The
compression fitting
con-
nection uses a ferrule that pinches the tube as the locknut is tightened
on the body of the fitting. The
flare fitting
connection uses tubing flared
on one end of the tubing that matches the angle of the fitting. The flared
end of the tube is butted against the fitting, and a locknut is screwed
tightly onto the fitting, sealing the tube connection properly.
Other fittings used for flanged connections include
expansion
joints
and
vibration dampeners
. Expansion joints function to com-
pensate for slight changes in the length of pipe by allowing joined sec-
tions of rigid pipe to expand and contract with changes in temperature.
They also allow pipe motion, either along the length of the pipe or to
the side, as the pipe shifts around slightly after installation. Finally,
expansion joints also help dampen vibration and noise carried along
the pipe from distant equipment (e.g., pumps). One type of expansion
joint has a leakproof tube that extends through the bore and forms the
outside surfaces of the flanges. Natural or synthetic rubber compounds
are normally used, depending on the application. Other types of expan-
sion joints include metal corrugated types, slip-joint types, and spiral-
wound types. In addition, high-temperature lines are usually made up
with a large bend or loop to allow for expansion. Vibration dampeners
absorb vibrations that, unless reduced, could shorten the life of the pipe
and the service life of the operating equipment. They also eliminate line
humming and hammering (water hammer) carried by the pipes.
4.13 valves
Any wastewater operation will have many valves that require atten-
tion. A maintenance operator must be able to identify and locate differ-
ent valves to inspect them, adjust them, and repair or replace them. For
this reason, the operator should be familiar with all valves, especially
those that are vital parts of a piping system. A
valve
is defined as any
device by which the flow of fluid may be started, stopped, or regulated by
a movable part that opens or obstructs passage. As applied in fluid power
systems, valves are used for controlling the flow, the pressure, and the
direction of the fluid flow through a piping system. The fluid may be a
liquid, a gas, or some loose material in bulk (such as a biosolids slurry).
Designs of valves vary, but all valves
have two features in common: a pas-
sageway through which fluid can flow
and some kind of movable (usually
machined) part that opens and closes
the passageway (
valves
, 1998).
Key Point:
It is all but impossible, obviously, to
operate a practical fluid power system without
some means of controlling the volume and pressure
of the fluid and directing the flow of fluid to the
operating units. This is accomplished by incorporat-
ing various types of valves.
Whatever type of valve is used in a system, it must be accurate in
the control of fluid flow and pressure and the sequence of operation.
Leakage between the valve element and the valve seat is reduced to a
