Answer / jitendra patel

It is good question

Generally in orifice plate when upper side hole is called
as went hole. It is generally used in liquid flow measure
ment and bootom side(drain hole) hole is used in gas flow
measure ment.

went hole is for remove gas trap and drain hole used for
unwanted liquid removing

Answer / ripul ghosh

i think it should be vent hole and not went hole used for
liquid service..
otherwise the answer is perfectly correct.

Answer / ripul gosh

Hi Varadharajan,
It can't be vice versa because vent hole is used for liquid flow in pipes. If any gas gets trap being lighter in density it will go towards upside of the orifice plate. For this reason vent hole is on the upper side.
Drain hole-which is located towards the lower side of the orifice plate used for gas flow in industrial pipes. It is obvious that any particle will higher in density than gas and will always try to be on the lower side of the pipe. So drain hole provision is made so that the trapped solid or liquid particle will easily go out of the orifice plate.
Both the holes are provided so that the trapped material can't cause any erroneous reading in the differential pressure measurement.

Answer / jitendra patel

thanks ripul for this comments

ya,it is vent not went sorry for that

Answer / chandraveer singh

In Orifice Plate Thera are Two Holes.One Is In Upper Side
And Another One Is In Bottom Or Lower Side.
Upper Side Hole- Also Called Vent Hole ,Used When Liquid
Services Is there for Removing Any unwanted Gas traps.
Bottom Side Hole- Also Called Drain Hole ,Used When Steam
Services Is there for Removing Any unwanted liquid or any
oil contaminant or steam condensate.

Answer / varadharajan

can you explain me more in detail please, why cant it be
vice-versa.

Answer / tyrkrv83

Vent goes up.
Drain goes down..
Vent is generally for removal of air bubbles & Non condensable gases & drain to remove condensates like in pneumatic air,liquids

Answer / arun george

hi all,
Thought that the answers require and little more add on. It is correct that vent is provided for liquid service orifice assemblies and drain for gas/vapour service orifice assemblies. The reason, if no drain hole is given in a gas/vapour service assembly the liquid droplets gets accumulated at the bottom.This keeps on happening till the liquid level reaches the bore of the orifice.Now the liquid starts overflowing through the bore causing sudden pressure drops causing unstable transmitter readings and may also damage it. In the case of vent holes in liquid service orifices the vice-versa happens.

Answer / varadharajan

Thanks alot ripul. Then i have one more question how we are
designing multi-stage trims to avoid cavitation in control
valves. how we come to know cavitation occured.

I have a problem with a valve (air to close). When it is fully closed and try to open 1% it doesn't responce till 3% open suddenly more than 3% then back to 3%. I tried to tune positioner then removed it, the problem still exist. Any idea

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