11 replies to this topic

[karan]

What is the requirement of equalisation line in condensate pots? If we close the isolation valve in equalising line then what would happened?
Please clear me about it?

Thank you!

[Bobby Strain]

Best not to close the valve. However, the best way to find what happens is to do it. Let us know the result.

 

Bobby

[karan]

Thank you for reply!
Actually in our condensate pot so much level is fluctuating around 6-7percent so I have closed the equalisation line valve to check what would happen then the level fluctuation reduced to 0 percent and exchanger outlet process side temp also increased and process flow fluctuations also reduced.
I just want to know that if I will remain closed then what would be the other consequences in our system?
Condensate is going to deaerator where pressure is 0.5 kg/cm2g and steam pressure which is coming to exchanger is 51 kg/cm2g.
If u want anything else then let me know that.

Thank you!

[fallah]

Karan,

 

It's to keep the condensate in the exchanger and the pot at the same level. As Bobby mentioned, it shouldn't be closed at normal operation. If is closed the level in the pot would no longer be the indication of the level in the exchanger and the level control system in the pot would be useless...

[karan]

Thanks for ur reply sir!

But our condensate pot is below exchanger.

If by closing the situation improved as I said in above replies then I think there is unconverted steam which is pressurising the condensate pot so if process side heat requirement need more then I think there may be a problem.
Dear sirs,
What you said all about it?

Thanks!

[fallah]

Karan,

 

To get a proper response on your query, please provide all info in detail along with the sketch of the relevant equipment arrangement...

[Bobby Strain]

Many have assumed that the exchanger duty is controlled by varying exposed surface. But this pot with level control functions solely as a steam trap. Karan didn't mention that the duty is controlled through a valve on the exchanger steam supply, if at all. And we were not told that this is a column reboiler. Maybe it is, but is just as likely that the steam is uncontrolled to achieve maximum duty. It's been a while since Karan told us how it continues to perform. Engineers like to apply solutions to problems. Sometimes the solution is not relevant. Best to get the whole story first.

 

Bobby

[Zauberberg]

Karan, please upload a detailed sketch or P&ID as requested by Fallah, in order to receive proper and correct response.

[karan]

Sorry for delay reply.
Thank you so much to all of you for ur valuable comments.
I will post the drawing soon then will tell u the real situation.
Thank you!

[karan]

Hello all,

A very good morning to all of you!

 

Sorry for delay, please find attachment of drawing of what I have talking about.

 

Again I am explaining the real situation which I have faced as follows:

 

When we lined up the equalising line then there is so much fluctuation in condensate pot level around 7- 10 %,and also temperature drop of shell side outlet around 2-5 deg C, and if we open the local vent with equalising line valve lined up condition then all thing normalised or if we closed the vent as well as equalising line valve then all thing normalise and then also level is controlling very smooth and maintaining.

 

My question is can we close the equalising line valve? what would be the other consequences ?

 

The Naphtha which is coming in shell side of HE having variable FBP of around 200-260 deg C and normally we get outlet temperature of 250-260 deg C and HP steam which is coming in tube side having pressure of 50 to 60 Kg/cm2g depending on load.

 

If u need any other data then let me know.

 

 

Thanking you All!

Attached Files

•  Book1.xlsx   13.59KB   328 downloads

[samroo]

On hydrocarbon  service we have Equalizing line between re-boiler channel head and condensate pot top, it works fine

[Art Montemayor]

I’ve lost count of how many equalization line “problems” I’ve resolved in the field in the past 55 years.  It must be around 10 to 20.  In almost every one of these so-called “problems” the cause has always turned out to be a cheap, quick, and last-minute process engineering or piping designer “solution” to a basic process design screw-up.  I’ve resolved the problem as shown in the attached revised sketch.

 

The typical situation is where a process engineer turns over the process design to a mechanical engineering team composed of usually mechanical engineers and piping designers (who are not engineers).  The basic process design package should contain all the process information critical to mechanically designing and fabricating a reliable and controllable piece of equipment.  This involves the correct sizing of attached piping, nozzles, vents, safety valves, drains, and EQUALIZATION lines.  Their locations are also required to be specified.  All this information and its communication should be carefully organized and scheduled according to project needs.  What usually happens in the case where a heat exchanger - especially a steam-heated one - is concerned is that the process engineer turns over his deliverables to a heat transfer engineer who produces the heat exchanger design for fabrication.  The need for an equalization line is left to a piping designer’s decision or criteria.  In this process, there is inevitably an oversight in failing to point out the need to control the production, flow and control of steam condensate produced in the exchanger.  The fabrication drawings for the exchanger go out approved without any thought as to how the condensate flow will be gravity drain-controlled and this become apparent when the exchanger is delivered.  The solution to ensuring that the condensate flow is allowed to drain under gravity to the respective condensate drum: quickly connect the condensate drum to the steam supply line.  This is quick, cheap, and presumably vents the condensate to a pressure “equal” to that where it originates, and it eliminates the need to do a re-work on the exchanger bonnet (possibly requiring an ASME stamp, expensive and time consuming).  WRONG!  The steam supply pressure is NOT equal to the condensate origin pressure - it is higher by the exchanger’s pressure drop.  The term “equalization” means exactly that: the pressure in the drum should equal the pressure at the condensate’s origin.  This allows for free, un-interrupted gravity flow.  The true and correct origin pressure unfortunately exists in the exchanger’s bonnet last tube pass.  This fact should have been specified by the process and exchanger engineers prior to exchanger fabrication.  An inexperienced or flawed engineering design has caused a more expensive, correct modification.  In today’s engineering world, this type of flawed, embarrassing design is becoming more repetitive than engineering houses would like to admit.

 

I have preached this reality countless times on our forums and have probably become an un-welcomed bore.  I promise this will be the last time.  Samroo’s recommendation is the correct answer.

 

Attached Files

•  Condensate Pot Equalization Line.xlsx   14.09KB   449 downloads