Does anyone have experience/knowledge with measuring saturated steam flowing vertically down using an orifice plate?
If you can get 20 to 30 diameters of straight run, or can use a flow straightener like Vortab, use a standard vortex meter. Otherwise, use a swirl meter... ABB TrioWhirl is the only one made outside of China and Korea, and I don't know how to get the ones made there, unless you are in Asia. ABB is really proud of their swirl meter, pricing wise, but it is the best meter for lousy steam applications I know of.
Of course, your mileage may vary and CONTROL magazine does not endorse products for specific applications. This is me, personally, talking, as the co-author of "The Consumers Guide to Vortex and Fluidic Flow Meters."
Editor in Chief
Read my blog, SOUND OFF! at controlglobal.com or
direct at http://waltboyes.livejournal.com
Sorry, i have another question about orifice plates: what will be the error if i use flow calculation equations for flange taps and the real taps are 2 1/2 and 8 diameters.
Thanks a lot.
Generally, Orifice Plate Vertical installation for saturated steam is not suggested by any orifice or flow meter manufacturer.
We have used flow nozzle and not orifice plate for steam flow measurement and flow was vertically downwards. We never faced any problems with that.If you refer to SHELL flow meter engineering handbook it says,for those meters mounted in vertical pipe it is desirable , but not essential,that a wet gas or saturated steam flow is vertically downwards through flowmeter,and vapour containing liquid flow is upwards through the flow meter.
Vertical installations are easily corrected by manifolding the taps to eliminate the distance between flange taps which introduces measurement error if not corrected. I have seen many installations in Refineries I've worked where this is a common problem. This error is constant throughout the measurement range if not corrected, therefore causing problems for Process Engineers trying to do mass balance.
Averaging Pitot Tube or ACCELABAR could be an alternative technology to be deployed against Vortex on Saturated Steam application. Orifice is pressure drop moreover its reliability depends on wear and tear of its edges. ACCELABAR is a proprietary product but referring it in the discussion as it has advantages over traditional devices and a perfect product on Saturated Steam.