Boiler Drum Level Control


Thread Starter

Satish Salankimatt

I have attached the 3 element drum level control drawing, which I got from this site. But I have few doubts.

1. First of all what is the formula used to calculate the Pressure and temperature compensated steam flow.

2. What are the formulas used in the blocks LY1, FY1, FY2 and FY3.

3. Also as seen in figure, the pressure signal from PT2 is connected to FY2 and LY1. Connection to FY2 is for calculating compensated steam flow but why is PT2 signal connected to LY1.

If anybody has worked on any project involving 3 element drum level control, please help me by answering all my doubts and also can advice me on additional points to be considered in this matter.


Satish Salankimatt
Problem: my PC does not want to open Word, New !!!
Understanding is not easy as one variable works backwards. I answered at least one year ago. Look in the web, there is a site by Josephson (Sweden).If you don't find let me know. You can reply by mail, BUT BE CAREFUL: detail your reference line so that I recognise without doubt. Instead of Word (virus prone) rather use Excel.


Satish Salankimatt

Can u kindly give the site address. to go tro. Meanwhile I am also searching for that site.

Satish Salankimatt

Ravi Nambiar

Answers to your questions are
1) The Mass flow conversion is normally done by a flow computer function block if you are using a DCS or similar system. Otherwise look at the Steam table to find out the SG to Pressure/temperature relation or formula.
2) The FY2 is mass flow computer for steam/Water
The LY1 is Density correction for Level measurement and again shall be read from the steam table, FY1 is a simple adder, and if you need a sort of feed forward action try putting in a dx/dt( derivative Function) before the adder,
FY3 is again a mass flow computation function.
3) For density correction, further instead of simply saying compensated it will be better to undersatand for what parameters and how.