Wastewater Conveyance - Wastewater Operators - page 150

4.3 definiTions
Key terms related to wastewater conveyance are listed and defined
in this section.
absolute pressure— Gauge pressure plus atmospheric pressure.
alloy— A substance composed of two or more metals.
annealing— Heating and then cooling a metal to make it softer and
less brittle.
asbestos— Fibrous mineral form of magnesium silicate.
Backsiphonage— A condition in which the pressure in the distribu-
tion system is less than atmospheric pressure, which allows con-
tamination to enter a water system through a cross-connection.
Bellows— A device that uses a bellows for measuring pressure.
Bimetallic— Made of two different types of metal.
Bourdon tube— A semicircular tube of elliptical cross-section, used
to sense pressure changes.
Brazing— Soldering with a nonferrous alloy that melts at a lower tem-
perature than that of the metals being joined; also known as hard
soldering .
Butterfly valve— A valve in which a disk rotates on a shaft as the valve
opens and closes. In the full open position, the disk is parallel to
the axis of the pipe.
Carcass— The reinforcement layers of a hose, between the inner tube
and the outer cover.
Cast iron— A generic term for the family of high carbon-silicon-iron
casting alloys including gray, white, malleable, and ductile iron.
Check valve— A valve that is designed to open in the direction of nor-
mal flow and to close with a reversal of flow. An approved check
valve has substantial construction and suitable materials, is posi-
tive in closing, and permits no leakage in a direction opposite to
normal flow.
Condensate— Steam that condenses into water in a piping system.
diaphragm valve— A valve in which the closing element is a thin, flex-
ible disk; often used in low-pressure systems.
differential pressure— The difference between the inlet and outlet
pressures in a piping system.
double-line diagram— Pictorial view of the pipes, joints, valves, and
other major components similar to an electrical wiring diagram.
ductile— A term applied to a metal that can be fashioned into a new
form without breaking.
expansion joint— Absorbs thermal expansion and contraction in pip-
ing systems.