7/29/2013 7:23 PM  
Posts: 3 Rating: (0) 
HI Guys We are using the Differential Pressure Transmitter as level Transmitter on a surge Vessel for a water application Details of the application is attached; I would like to know whether the caluculations done in the attachment is right or not?? Ansy help is highly appreciated. Regards, Sharath.
Attachmentsurge vessel LT.pdf (118 Downloads) 
7/30/2013 2:05 AM  
Joined: 3/28/2010 Last visit: 9/18/2023 Posts: 976 Rating: (199) 
Assuming the low side is a dry leg (not filled with liquid), then if your LRV = 2.27mH2O and your URV = 8.57mH2O, then those values will work. You might consider scaling the HMI value with a nice even value like06.0 meter, unless the tank actually fits to the top, You should have a drip leg on the low side, to catch condensation so that the condensation does not apply a pressure to the low side diaphragm. 
7/30/2013 5:56 PM  
Posts: 3 Rating: (0) 
Hi Danw thanks for the reply yeah the lower side is a dry leg
you mean to say that the we have to use theLRV = 2.27mH2O &URV = 8.57mH2O but those are the values of height & they dont correspond to the corresponding pressures?? Can u explain the exact concept of measurement in this. Thanks in Advance Sharath 
Last edited by: Mavericks at: 7/30/2013 5:58 PM 

7/31/2013 5:59 AM  
Joined: 3/28/2010 Last visit: 9/18/2023 Posts: 976 Rating: (199) 
I assume that your distances are true elevation differences (with reference to a plumb line) and not horizontal or angular distance values. Therefore, how can "values of height & they don't correspond to corresponding pressures" be true? 2.27m H2O = LRV = 4.0mA = bottom of the tank In your initial query, you provide the conditions for a level measurement with water as the medium, "a surge Vessel for a water application". Water has a specific gravity or density of 1.000, which is taken into account for the engineering units of mm H2O or inches H2O. A column of water is a column of water; it exerts a force on a diaphragm of known area and the result is pressure. Therefore, the height of the water column is the level or the elevation distance. Pressure transmitters measure pressure in various units, several of which are head pressure in water units, for instance, mm H2O, or for us Americans, inches H2O. The LRV and URV are elevation distance values, corrected, if necessary, for specific gravity, but in your case, no correction is necessary because engineering units in water column are used directly for water applications. The level LRV and URV both take into account the mounting of the DP transmitter below the bottom of the tank. Tank volume values are calculations using the level value which is then multiplied by some scaling factor. But tank volume is not a level transmitter's LRV or URV, level is a transmitter's LRV and URV. Usually tank volume calculations are done outside the transmitter in the indicator/HMI/PLC/SCADA/DCS/whatever. 
7/31/2013 8:12 AM  
Posts: 3 Rating: (0) 
Hi Danw, Thank you for your prompt response, Will there be any effect of the compressed air entering into this closed vessel from the top, Will this influence the pressure being exerted on the lp & HP side? Regards Sharath.

8/1/2013 3:33 AM  
Joined: 3/28/2010 Last visit: 9/18/2023 Posts: 976 Rating: (199) 
Solve the algebra equation: P = (A + B)  B Then substitute A = water pressure B = compressed air pressure Which transmitter port is (A + B) ? Which transmitter port is B ? What does P represent ? 
3/21/2014 6:37 PM  
Posts: 342 Rating: (6) 
new question is splittet to polygon shape & my LRV & URV 
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