Dear Sir,

Now days Boiler water level calculation is compensated by making use of the boiler drum pressure corresponding water density and steam density according to the Boiler pressure.

Example the boiler drum tap to tap distance was 770 MM, operating pressure was 42 bar, the calibration range traditional method was 0 to 595 mm with elevated zero.

The question is transmitter calibration. while drum pressure corresponding steam density algorithm in place the transmitter calibration is actual Tap to tap distance say 0 to 770 mm or calibration is 0 to 595 MM?

(the actual calibration can be treat as -770 mm to 0 or -595 mm to 0)

Regards
Rakesh

 

What is important is to set the range on your smart transmitter as follows; [Upper Measuring Scale - Lower Measuring Scale] = Transmitter tap to tap distance. In your PLC or DCS you can then set your calibration offset by say 10mm e.g my transmitter can be scaled 0 to 350mm, whereas in the DCS I calibrate as -170mm to 170mm from the datum, so that I have a range of 340mm.

 

The physical distance between taps is 770 mm, and if your boiler drum always contained water at room temperature the transmitter range would be 0-770 mm WC.

But you need to use the density of water at normal operating pressure and temperature to determine the actual head from 770 mm of water at operating conditions. That is your actual transmitter range.
You can then decide if your range will be 0-max range or -min -0-max range with 0 at your normal operating range.

 

I would think this is correct. The water density will change slightly at the operating conditions.

 

Thanks sir,
I understand this information clearly.

The main reason that i am asking this question, the change boiler pressure is having impact on the water level. if we incorporate the drum pressure into consideration, automatically the drum pressure makes the water level compensates and give the corrected drum level indication.

This is the theory, i need some help practically how to implement this in realty.

regards
Rakesh