We want to install flowmeters as paymeter. The line size is 20 inch and fluid is MP steam. (40 ~ 85 ton/h, 10.5 kg/cm2g, 230 degreeC)

The most two important factor is accuracy(within +- 1.3 %) and rangeability(more than 12:1)

Your suggestion or experience will be greatly helpful to me. Thanks in advance.

 

For steam we mainly use vortex meters and DP pressure transmitters. Vortex meters offer better accuracy but over a limited range. With DP, the range can be extended by using more transmitters to measure the same DP. One can be used for very small flows, another for bigger flows and a third/fourth,... This gives different accuracy's over every part of the range but very good overall accuracy and enormous rangeability. (But it's expensive and requires some extra programming on the DCS). Normally the low range can be quite big as the losses here are not very big even if the accuracy is not so good. (this can also be a reason to go for vortex). It's in the upper part of the measurement that most losses (or gains for the other party) are made.

 

If cost is not a major factor,for the required accuracy & rangability, i guess Vortex flowmeter is the only option.

But you can check up with Rosemount for using their Mass Pro bar Model, which has combined accuracy of 1.8%. But, Rangebility is 8:1. This may work out cheaper than vortex. Also, upstrem/downstream requiremnt for this instrument is much lesser than Vortex.

One major advantage of Mass probar would be you get compensated mass flow from the isntrument.

Good luck.

H.S.Girish

 

Vortex meters are good and will get you a 12:1 turn down in most cases if sized correctly.

You will need 10 - 20 pipe diameters before and 5 pipe diameters after the meter.

The working pressure and pipe diameter define the range. If you have a 12" pipe (largest Vortex
I have data for) and 125 psig saturated steam your minimum reading is 12500 #/hr and your maximum is 188500 #/hr.

If the measurement range you want is given by a smaller meter size then you have to resize your
pipe to that size.

They are affected by vibration. Tap on them with a wrench and they show flow based on the impact
vibration.

You need to a flow computer and temperature or pressure compensation.

There are other options that I have been looking into. Haven't finished doing my investigation
yet.

Contact me if you like.

"[email protected]", mailto:[email protected]

 

Hi,

Orifice flowmeter is the most suitable one in this case. With a single DP, the turndown ratio is about 6:1, but stack DPs, it could meet 12:1 or
better. Other flowmeters like Vortex, Coriolis, etc. are too expensive with line size 20 inch. Vortex flowrate and total flow are effected very strongly by two-phase steam (usually existing in the start / stop steam flow). Two-phase steam just causes some larger error for Orifice or Coriolis meters, but causes an unbelieved flowrate and total flow for normal Vortex meter for steam custody transfer. I heard that some Vortex manufacturers have a special design that they simply stop to measure when detect a two-phase flow.

Regards,

Hung Lam