Steam heat exchanger control

[MatiasMech]

Good afternoon,
I have the following problem:
The steam heat exchangers i work with, are controlled by regulating the condensate flow.
When the tubes get dirty or the exchanger reaches its maximum capacity, steam flows through the exchanger, doesnt condensate, and therefore messes with the flowmeter located after the exchanger.
There is no barrier that preventes steam passage through the condensate line.

I read about condensating pots with level control, but it seems cheaper to install a level control in the heat exchanger with a control logic.

A level control is enough to prevent steam passage?
When is a condensating pot mandatory?

Thank you.

 

[georgeverghese]

There is usually hardly any room at the bottom of the shellside of the HX to enable level control; hence use an external level boot or condensate pot with sufficient volume to enable level control / temperature control. An external pressure equalising line at the pot which connects with the top vapor space of the HX shellside is required also.
If steam is on the tubeside, there is no way you can enable level control without an external level pot.

 

[pierreick]

Hi,
You know already when you have to clean your HX ( flowrate are fluctuating) , what is the benefit of your proposal ?
My 2 cents
Pierre

 

[MatiasMech]

Hello, thank you for your replies.
Georgeverghese, i understand that you are talking about volumen as the variable that makes the pot better than the level transmitter only solution.
The increase in volumen would guarantee more time to react to level changes. Is this correct?

The flowrate through the exchanger can fluctuate as a result of different things. This exchanger in particular is a reboiler located at the bottom of a depropanizer column. Changes in the NGLs composition that feed the column should alter the flowrate.

Thank you.

 

[georgeverghese]

If this deC3 reboiler is a kettle type, then steam must be on tubeside - the liquid volume in the tubeside channel + a few flooded tubes is simply inadequate to enable temperature - level control. Control valves will oscillate a little around the control point and flooded area changes must be kept minimal with these oscillations, so a condensate pot provides the volume buffer as capacitance.

 

[Latexman]

When the tubes get dirty or the exchanger reaches its maximum capacity, steam flows through the exchanger, doesnt condensate, and therefore messes with the flowmeter located after the exchanger.
There is no barrier that preventes steam passage through the condensate line.

Could the exchanger be accumulating / building up non-condensable gas? This will prevent steam from condensing.

Good Luck,
Latexman

 

[pierreick]

HI,
To support your query consider the links attached :

https://www.driedger.ca/ce3_stx/CE3_STX.pdf

https://www.driedger.ca/ce4_sh/CE4_SH.pdf

Good luck
Pierre