Selection Between Ball and Globe Valve
What is the criteria used when selecting a ball or globe valve in the
piping system of propane bulk storage installation? Such valves would be
2", 2-1/2" and 3" size fitted in the liquid and vapor transfer lines
(loading and unloading). Forged Steel ValvesIf you had said "the choice between ball, gate, and plug valves seems to
be a matter of opinion or availability" this would have been a
reasonable question, but the valves you mentioned have very different
purposes. Filter to be frankly , a ball valve is intended for service and should not normally be throttled .because of the terrible throttle chractaristics .A globe valve is designed for throttling .If a particular line should always be fully open or fully shut, then a
ball valve is often a very good choice (the further choice between a
floating ball and a trunnion ball depends on the process).Bellow Seal ValvesAutomatic Control Valves A valve to
control flow within a stream should have good throttling
characteristics--if the required position changes frequently then a
regulator is a better choice, but if it changes infrequently then a
manual globe valve can occasionally be the best choice.If you are just speaking about isolating valves (on-off) the globe valve is at a disadvantage on almost every parameter. Convenience: Globe valve requires 4 or 5 turns of the handwheel to open
or close. Ball valve: 90-degrees. (Ball valves were initially
developed for USNavy. Tactical advantage to being able to yank a valve
shut while at a dead run, vs having to stop and grind away at a
handwheel.) Somebody over-eager to close a ball valve may yank it shut
too quickly and cause liquid-hammer.
In fairness: Larger ball valves need a gear-operator. Position of a ball valve is easy to read. Lever is aligned with the pipe
when the valve is open. Position indication of a globe valve is on a
small plate inside the yoke.
Environmental: Rising stem in
globe valve drags packing particles out, and environmental dirt
in, every time the valve is cycled. ALso if you figure 4 turns to Needle Valves
open, globe valve packing sees 16 times the wear on each stroke. Ball
valve packing stays tighter-longer. Oil pumpsInstallation: Globe valve is taller and heavier and usually longer F-F, than a ball valve of the same size.
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