Estimate Flow Rate to DA
Estimate Flow Rate to DA
(OP)
I have a faulty pressure regulator that was not designed for the service it is in and I must replace it. I was requested to find a proper control valve, rather than a regulator.
The regulator was to maintain pressure on a DA. The DA is fed by a condensate drum, going from 20 psig to 5 psig. The DA also has makeup water from an RO system.
How do I estimate the flow needed to maintain pressure on the tank so I can size a replacement pressure control valve?
Thank you for your help!
The regulator was to maintain pressure on a DA. The DA is fed by a condensate drum, going from 20 psig to 5 psig. The DA also has makeup water from an RO system.
How do I estimate the flow needed to maintain pressure on the tank so I can size a replacement pressure control valve?
Thank you for your help!
Onwards,
Matt





RE: Estimate Flow Rate to DA
Parameters should include steam flowrate and pressure, cooling water flow rate and temperatures (inlet and outlet temperatures).
RE: Estimate Flow Rate to DA
RE: Estimate Flow Rate to DA
The condensate coming back has no flow measurement, and is at temperature. The RO water, likewise, has no flow measurement and comes in cold/ambient. I can estimate the flows based on the CVs of the level controllers, and I do have a flow meter on the line to the boiler, so perhaps I can get a balance on the drum.
The pressure regulator is on a tee on the 300# steam line, which drops the pressure directly to 5 psig to the deaerator (DA).
Onwards,
Matt
RE: Estimate Flow Rate to DA
You just need to do an ethalphy balance around the DA (H of the 30 psig steam and the h of the two water streams) to estimate how much steam is required to achieve this plus the purge rate.
RE: Estimate Flow Rate to DA
RE: Estimate Flow Rate to DA
so to hold 5 psig, you'll need steam enough to heat the maximum make-up flow to saturated liquid at 5 psig, convert the btu to #'s steam and you're done,
undersized regulators create a ton of problems
RE: Estimate Flow Rate to DA
The boiler has a BTU or lb/hr value, this can tell you how much steam is being made which will be how much water the DA will put through.... EXCEPT you have to add blowdown, and in a perfect world the blowdown amount will equal the water make-up from the RO(some estimate it a 10-20% but this depends on water quality). of course you will not have this perfect world 100% condensate return.
Then you do the BTU calcs as mentioned above and don't forget the amount of steam for the vent.