Surge Drum sizing 1

[Nova N]

Hi Engineering Colleagues,

How do you calculate size of surge drum for steam condensate if you have all design flows?

Cheers
Nov

 

[MJCronin]

I would first ensure that the surge drum/receiver is safe and has passive devices to relieve pressure build-up. This can be done with relief valves or even rupture disks.

Second, I would ensure that the receiver has a HLL set at 90% of Full Volume

Third, I would size the receiver to have a minimum sufficient size to hold a condensate volume equivalent to that evaporated by the boiler in a one-third to one-half hour period at the normal firing rate.

Since we have only begun our long journey of Vague Questions with Insufficient Details...

....the ball is now in your court, Najeeb ...

MJCronin
Sr. Process Engineer

 

[Nova N]

Hi Najeeb,
I wanted to be concise and focussed, and not vague.

Your third point is what I am focussed on now. Is this somewhere in API-650? If not where can this be located.

Thanks Again for your response.

Regards
Nov

 

[georgeverghese]

@MJC
"Third, I would size the receiver to have a minimum sufficient size to hold a condensate volume equivalent to that evaporated by the boiler in a one-third to one-half hour period at the normal firing rate."

Would this condensate surge volume equivalent to 20-30min of max normal steam generation rate be held up between normal control level and Level Alarm High?
or
between level alarm high and level alarm high high ?

 

[MJCronin]

George, buddy ....

You are asking a question that cannot be definitivly answered in all cases ...
Sometimes engineering can be more of an art than a science...

Since, as usual, we ge almost zero details from the 3rd world OP .... We have to guess at the configuration of the rest of the steam and condensate system ..

Let us consider CASE #1 --Surge Drum for a very small boiler/Small steam distribution system

In this case, where there are minimal system losses, minimum distances for the steam distribution system - 20 minutes holdup time would be a reasonable engineering estimate

Now consider CASE #2 --Surge Drum for multiple boiler extensive steam distribution system (District heat system)

In this case, where there are significant system losses and significant "condensate return rush" as the DH system heats up, - a 40-60 minutes holdup time would be a reasonable engineering estimate. Larger Surge Drums are better !!!

As is most typical, because he has no experience, the OP wants a rule that will cover surge drum sizing for ALL CASES !!!

Cannot be done, IMHO ....

MJCronin
Sr. Process Engineer

 

[georgeverghese]

In more recent designs, flash condensate return is minimised. This is done by installing LP condensate flash drums at suitable local areas which receive LP condensate from multiple local sources without having to go through elevated pipe rack risers. Preflashed condensate is then pumped out in single phase liquid conditions through the elevated pipe racks to the plant de aerator. Flash steam from local area flash drum is either vented out locally or returned to the central surge drum via the plant racks through insulated lines. In such plants, surge volume provisions at the central surge drum would be much smaller.

I would interpret your design thumb rule as surge volume holdup between LAH and LAHH.

Another approach would to be list out the large dia 2 phase flash condensate return lines ( leading out to the central surge drum) and rank them based on line id. Select the largest say 30% of these lines, calculate their vertical riser volumes and sum them up. Assuming that these largest lines slug through these risers at the same time, use this sum total as the surge volume.

 

[MJCronin]

NOVA has lost interest in this thread.... so we will never get any other details

I will ask the site Admin to retire this thread ....

MJCronin
Sr. Process Engineer