Page 55 - Apollo - Industrial Applications Guide

APPENDIX H – INDUSTRIAL APPLICATIONS GLOSSARY APPENDIX H – INDUSTRIAL APPLICATIONS GLOSSARY

Trunnion Mounted Wire Draw
As opposed to a “Floating Ball”, the ball on a “trunnion” or Erosion damage that reveals itself in the form of a cut that looks
“trunnion mounted” valve is supported by bearings within like a wire has been drawn through the material. In a valve, this
the valve body and the valve’s seats are typically loaded generally occurs when a valve is just about closed or opened
against the ball. Trunnion mounted valves have a few unique slightly causing the media to travel through the opening at
capabilities; the valve seals on the upstream seat, the seats high speeds. Abrasives in the media exacerbate the problem.
tend to be somewhat self-relieving and the valve is generally
capable of double block and bleed, two characteristics not Zero Leakage
normally found in floating ball valves. This term has no real meaning on its own. Most test standards
for soft seated valves allow no leakage for the period of the
UL test, commonly called zero leakage. But, the period of these
Underwriters Laboratories tests is usually measured in seconds, or even occasionally in
minutes. Zero leakage on its own would imply that a device
UL Guide would never leak, and that’s a myth.
These are more properly called category codes.

Union, Dielectric
Dielectric unions are required in some application by code. In
particular on water heaters, in the transition from black pipe to
copper. The basis for their use is to prevent galvanic corrosion
of the black iron pipe. Whether or not they are technically
necessary depends largely on water chemistry. In applications
with dissolved electrolytes their use would be beneficial.

Vacuum
A negative pressure relative to ambient atmospheric pressure
and is often identified as psiv.

Valve
A valve is a device used to control flow of media through a
pipe or tube.

Valve Bore
Referring to the flow passage through a valve.

Valve Trim
See Trim.

Viscosity
A measurement regarding the fluidity of a liquid usually
measured in units of centipoise.

Wetted Parts
Any component of a device subject to contact with the fluids
it contains. For ball valves, the metallic wetted parts are
generally assumed to be the body, retainer or bonnet, ball and
stem. Seats and seals are also wetted parts.

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