Pressure Drop (Condensate)

[C26M13]

Hi,

I would like to have some ideas about pressure drop calculation for gas (condensate). Does the elevation (the different elevation is 18 m) and the sudden enlargement and contraction affect the pressure losses along the pipe? if it does, how to determine the total pressure drop?
Can somebody please give me advise?

Thanks,

 

[georgeverghese]

Okay. So here again, you have to make an assesment whether the trays will withstand the diff pressure created when the gas blowby stream blows through it.

So the calc is as follows, for a first pass estimate:

a) Obtain the wide open Cv for this control valve
b) Assume flow is critical across the control valve. Then compute the critical flow across the valve using the max normal MP steam pressure upstream of the valve.
c) Now check if the assumption for critical flow is correct. Tally up all the equivalent lengths. Then work backwards from the PSV relieving pressure ( set press + 10% ) for each line size to get the correspondinf upstream press. Keep moving backwards till you reach downstream of the control valve. At the appropriate locations, you need to add the additional press drop for the de aerator trays and the flash drum wiremesh demister.
d) Check if the total computed pressure obtained from (c) at the control valve is less than the critical pressure for steam for the given upstream pressure and the specific heat value for steam.
e) If the press downstream of the control valve is found to be > critical pressure, redo steps (b) to (c), using the other flow formula across a control valve for subcritical flow. As a first assumption for subcritical flow calc, you can use the pressure obtained from the critical flow assumption above.
(f) Check if the total recalculated backpressure at the control valve is the same as the one used in this trial. If not, redo the calc again ( step e ) until the backpressure at the control valve = the pressure used in this trial.

If you need help with any of these steps, ask a senior process engineer to help. Many of the formulas for some of these steps may be found in Crane publication 410, but you may need to search elsewhere for some others. When calcs are completed, you have to get the calc documented and checked / signed off. In the calc , you have to state the risks involved with the wiremesh demister and the trays. Ask your senior engineer to advise the mechanical engineers to devise some means to strenghthen the wiremesh pack and the trays to withstand the dp during gas blowby.

 

[C26M13]

@georgeverghese: Thanks a lot for you kind support and input. I will let you know after doing the calculation (hand calculation and HYSYS)

Thanks again

 

[racookpe1978]

So. How many questions have YOU brought up to your boss or supervisor?

YOU are responsible for getting YOUR company's training and experience from their sources (ref library, shelf-in-the-back-closet, technical library in the next floor, headquarters building across the quad, or the shelf-behind-George's-desk). In no case should YOU be basing your calc's strictly on internet sources - no matter how much I trust and respect the guys giving YOU advice here! - because ultimately, your boss is responsible for your company's design to your company's customers about your company's future business and reliability.