Downstream steam pipe pressure
Downstream steam pipe pressure
(OP)
Can anyone point me in the right direction for the following:
I have steam in a 6" pipe at a pressure of 64 barg and a temperature of 400 C with a mass flow rate of 100 tons per hour.
The 6" pipe is connected to a 10" pipe by means of a reducer and the 10" pipe is open to atmosphere.
What pressure can I expect to see in the 10" pipe?
What diameter would I need to increase the 10" pipe to see a pressure of 30 barg?
Any help greatly appreciated.
I have steam in a 6" pipe at a pressure of 64 barg and a temperature of 400 C with a mass flow rate of 100 tons per hour.
The 6" pipe is connected to a 10" pipe by means of a reducer and the 10" pipe is open to atmosphere.
What pressure can I expect to see in the 10" pipe?
What diameter would I need to increase the 10" pipe to see a pressure of 30 barg?
Any help greatly appreciated.





RE: Downstream steam pipe pressure
RE: Downstream steam pipe pressure
There is 1 x 6" elbow, 20 metres of 10" pipe and 1 x 10" elbow
Thanks
Paul
RE: Downstream steam pipe pressure
Good luck,
Latexman
RE: Downstream steam pipe pressure
There is only 1 elbow on the 6" source, then a reducer to get to 10".
RE: Downstream steam pipe pressure
Good luck,
Latexman
RE: Downstream steam pipe pressure
RE: Downstream steam pipe pressure
Good luck,
Latexman
RE: Downstream steam pipe pressure
Or has it already been designed and controlled. Please explain.
RE: Downstream steam pipe pressure
Good luck,
Latexman
RE: Downstream steam pipe pressure
Usually blowdown is related to a TDS control and it is scheduled at precise time and for a set duration (if the valve is suitable for the purpose 5-10 seconds each 8-10 hours of working can be enough).
If the boiler works at such a pressure 64 barg, and blowdown valve discharge to atmosphere, flash is undoubtedly an issue. It is a quite common practice to use a blowdown vessel to separate flash steam (reusable in low pressure applications) and dirty condensate.
Take a look at the link below to get further info.
h
RE: Downstream steam pipe pressure
The discharge at the 10" outlet to atmosphere would be choked at the speed of sound; the pressure immediately upstream of the 10" discharge is caculated as with safety relief valve exhaust stacks- see the Bechtel Laio mehtod defined in the asme B31.1 code appendix II. Knowing the pipe diamenter, flow, and ehtnalpy, the pressure can be caclualted.
The flow is defined by the choked conditions at the smallest open flow area betseen the base reservoir at 64 barg and the 6" pipe, likely a valve. You can use the ISA handbook of valves to compute the choked flow thru the valve knowing its Cv, Xt, and upstream fluid properties.
RE: Downstream steam pipe pressure
Good luck,
Latexman
RE: Downstream steam pipe pressure
I used the Spirax Sarco website, and together with a colleague we calculated the expected pressure drop through the piping system.
RE: Downstream steam pipe pressure
Below the procedure I follow to evaluate an intermittent blowdown:
B = (Q * S)/(Ca – S)
B = flow rate of water for blowdown [kg/h]
Q = boiler capacity [kg/h]
Ca = admissible water conductivity [μS/cm]. It depends on boiler working pressure
S = Feed water conductivity [μS/cm]
Once B has been calculated there are sizing charts available for blowdown valves that show the discharge capacity of hot water [kg/s] vs boiler pressure [barg].
For a boiler operating at 64 barg the TDS should not exceed 625 ppm (ABMA Recommended Feedwater source).
Even if a precise conversion factor to turn ppm of TDS into μS/cm of conductivity requires the chemical composition of TDS, it is possible (acceptable from an engineering point of view) to use the following correlation:
(TDS) ppm * 0.67 = Conductivity µS/cm
RE: Downstream steam pipe pressure
The blowdown flowrate you've quoted goes on puzzling me. For automatic blowdown, managed by water conductivity controllers, there are available valves (2") capable to discharge up to 30 ton/hour (with 100 bar pressure differential), which is less than one third the value you've quoted. Would it be possible to know the way you've calculated 100 ton/h of hot water blowdown?