Vertical vs. Horizontal Orifice Plate Install 2

[lacajun]

Some guys I am working with have an old Shell Refining Handbook that states orifice runs are best installed in vertical runs. Flowing up for liquids and down for gases and steam.

This is counter to everything I have learned in my 18 years about flow metering with orifice runs. The Chilton/CRC/ISA Measurement Handbook says horizontal runs. From an engineering perspective, it doesn't make sense for accuracy either.

Have any of you heard of this before? Know where this thinking came from? What are your thoughts about installing orifice meters in vertical runs and horizontal runs?

 

[Ashereng]

Is this a forum to read only?

This forum is interactive. Everyone is invited to read, write, ask, answer, explain and otherwise participate in all discussion.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[JLSeagull]

Many lack an understand of how poorly the orifice plate and dp transmitter correspond to flow.obvious this fact. Orifice plates are used for lots of flow rate measurement including a very large amount of custody transfer. Lots of custody transfer contracts are still based upon integrating the circular charts from wind-up seven-day chart recorders. Almost every other type of measurement is superior to orifice plate flow measurement.

The orifice plate and dp combination are based upon one set of physical properties for pressure, temperature and density. This is not a really big deal for liquid. It is a really big deal for gas. The orifice meters can include pressure and temperature compensation based upon the ideal gas laws or AGA corrections. Measurements that include a GC can also provide calculated compensation for the density.

Coriolis meters are limited to smaller applications by the size of the meter. A Coriolis meter compensates for density automatically in liquid. The gas meters provide a mass flow rate but cannot provide a density signal. A dual chamber quick change orifice installation (senior fitting) is rather large too.

 

[dcasto]

JLS, with the advent of the cheap flow computer, the orifice meter is no longer a chart recorder. I've been using flow computers since 1979 and with the new API measurement equations, its almost impossible to do chart integration with the new equations. Yes, you either need an on line GC to get a gas density, use a composite sampler or use a desitometer with an orifice. The same is true with a turbine meter.

With a mixed fluid, you'll need a GC or sampler even with a coriolis meter to get componet breakdown. As for size, 250,000 lb/hr is easily done with a micromotion.

 

[Scotsinst]

Commonly liquid feed and product to and from a refinery unit is measured via orifice plates on a 5m high pipe rack. Typically the contractor ignores the horizontal tapping requirement and uses 45° down taps, the close-coupling requirement is ignored and you end up with 20 metres of impulse tubing, causing all kinds of error, especially feed from storage. Since the feed/product control valve is at grade and the piping comes down from the rack giving a nice meter-run of straight pipe, I can sympathize with those who would mount the orifice in the vertical line just upstream of the control valve, high enough to meet the downstream straight-run requirement. The transmitter could easily be close-coupled and accessed for maintenance. I've never seen it done this way but it would be better than the long impulse lines I've seen at most battery limits.

 

[JLSeagull]

I have not been exposed to the windup circular chart in a while either. However, I have applied flow computers across the same orifice taps with the contract based upon a circular chart and the FQI being a check meter.