Once the information regarding the HP and LP side of an orifice plate is lost, how to reinstall it in a pipeline?

 

Typically the plate is inspected and all dimensions re-measured, the transmitter can be recalibrated once you have and idea of the nominal flow requirements, and the details of the piping layout and pipe dimensions.

 

It is not real clear what is being asked. If it is regarding the direction that the orifice plate is to be installed in, the tag and orifice size is normally stamped on the high side (faces upstream). If this information is not available, if it is a sharp edge orifice, the sharp edged faces upstream.

It seems that there is some uncertainty regarding the orifice. The orifice should be replaced with the proper identification (and dimensions verified) on it so that this won't happen again.

A little more information might be nice.

William (Bill) L. Mostia, Jr. PE
ISA Fellow, SIS-TECH Fellow,
FS Eng. (TUV Rheinland)
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.

 

> Once the information regarding the HP and LP side of an orifice plate is lost, how to reinstall it in a pipeline?

HP side of orifice is the pump side. check the inner angle of the orifice. LP is no angle, HP is angled. just remember where the medium is coming from. its the HP.

 

> LP is no angle, HP is angled. just remember where the medium is coming from. its the HP.

I agree that the HP side is on the side "the medium comes from", what I call the upstream side.

But I have to disagree on which side is which.

On every concentric OP I've encountered, the beveled angle is on the downstream LP side of the orifice plate; and the straight bore, sharp edge is on the upstream HP side of the orifice plate.

A 1995 Oil and Gas Journal article, "Backward orifice plate causes major gas flow measurement error", documents the significant error that occurs when an orifice plate is installed backwards, link below.

http://tinyurl.com/nm36cea

As a heads-up, I have observed over the years that although the vast majority of orifice plates are stamped on the upstream side of the plate, that there orifice plates with ID data stamped or engraved on the downstream side of the plate.

 

Placing the beveled surface on the HP side definitely reduces the discharge coefficient and throws off meas. accuracy.

It is a common occurrence and the major manufacturers have the flow coefficient for both directions.