How to calculate flow Rate with pressure differential

How to calculate flow Rate of water and Steam ton per hour with pressure differential.

Differential pressure is one of the most common methods for measuring flow of fluids, and is one of the fundamental principles of process flow measurement.

Before asking a PLC-specific version of your question, I strongly recommend you do some basic research on the principles of differential pressure flow measurement. Typing "differential pressure flow meter" into Google results in dozens of good tutorials, mostly from companies who produce differential pressure flow metering devices.

The classic "Instrument Engineer's Handbook" edited by Bela Liptak is on the shelves of hundreds of thousands of engineers worldwide and includes very good descriptions of the principles and practices of differential pressure flow metering.

The supplier of the orifice or primary device should have the formualas available. The ASME also has standards that show the calculations.

Ken must be a very good teacher, because he wants to force you to do your own research. If you're in a hurry to get this implemented, then you should know that the root of this issue is exponential.

The pressure drop across the constriction is proportional to the square of the flow rate.

Bit_Bucket_07 said:

then you should know that the root of this issue is exponential.

Click to expand...

I see what you did there.

The flow element drops a certain pressure at a certain maximum flow rate, according to the conditions provided for a calculation.

Any commercial differential pressure flow element (orifice plate, averaging pitot tube, venturi, Taylor wedge, V-cone) comes with a 'sizing sheet' that gives the differential pressure at maximum design flow rate.



Good news: If the DP pressure transmitter has a square root extractor, there's no need to perform a calculation because

0 to max DP (square rooted) = 4 to 20mA = 0 to max flow,

according to the numbers on the sizing sheet.

If the DP pressure transmitter does not have a square root extractor (or it's not used), then the receiver can scale the 4-20mA 0-to-100% (or 0-to-1.00 as shown below) and square root the percentage value, which is the percentage of maximum flow rate.

@ 100% max differential pressure, Sq rt of 1.00 = 1.00 = 100% of max flow rate at design conditions
@ 81% of max pressure; Sq rt of 0.81 = 0.900 = 90% of max flow
@ 50% of max pressure; Sq rt of 0.50 = 0.707 = 70.7% of max flow
@ 25% of max pressure; Sq rt of 0.25 = 0.500 = 50.0% of max flow
@ 20% of max pressure; Sq rt of 0.20 = 0.447 = 44.7% of max flow
@ 15% of max pressure; Sq rt of 0.16 = 0.400 = 40.0% of max flow
@ 10% of max pressure; Sq rt of 0.10 = 0.316 = 31.6% of max flow
@ 5% of max pressure; Sq rt of 0.05 = 0.227 = 22.7% of max flow

I want to calculate water flow in ton per hour from Differential pressure

What flow rate units is the primary flow element sized for?
pounds per minute? Kg per sec? liters/min?

Are you successfully reading those flow rate in those units in your controller/HMI?

tom is right

Knock yourself out:

http://www.asme.org/products/codes---standards/flow-measurement

http://www.engineeringtoolbox.com/orifice-nozzle-venturi-d_590.html

(Why do so many posters, particularly offshore and youngsters, resist contacting their suppliers with questions?)