Steam pipeline pressure drop

Question

Steam pipeline pressure drop

doomster (Chemical)

(OP)

21 Sep 20 13:33

A main steam line is operating at most 7 bars, and one of the end user only uses 2 bars. From the main steam line of 200mm there is a pressure relief valve to make the steam pressure reduced to 2 bars before entering to a 100mm steam line.
Now my question is that, will the mass and rating of the steam changes after it passes through the PRV?

Thanks Doomster

TiCl4 (Chemical) · Answer 1 · 2020-09-21 13:50:18

For clarity - Do you mean a pressure reducing valve?

MJCronin (Mechanical) · Answer 2 · 2020-09-21 13:52:10

What is "rating of the steam" ?

MJCronin
Sr. Process Engineer

danschwind (Mechanical) · Answer 3 · 2020-09-21 13:55:05

I'm pretty sure he meant a pressure reducing valve.

Doomster, when pressure is reduced through a valve you may consider it an isenthalpic process. Basically, calculate the enthalpy of your steam upstream of the valve, then find your new steam properties with the same enthalpy and new pressure downstream of the valve.

Daniel
Rio de Janeiro - Brazil

Latexman (Chemical) · Answer 4 · 2020-09-21 14:04:54

Quote (doomster)
will the mass and rating of the steam changes after it passes through the PRV?

I will clarify by rewording this to, will the pressure, temperature, and density of the steam change after it passes through the PCV?

Yes, as danschwind has pointed out.

Good Luck,
Latexman

LittleInch (Petroleum) · Answer 5 · 2020-09-21 14:23:56

Try this https://www.spiraxsarco.com/learn-about-steam/stea...

You do need to know temperature of your steam as well as start pressure - i.e. saturated steam or super heated?

Mass will not change either side of the valve.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

FacEngrPE (Mechanical) · Answer 6 · 2020-10-03 23:50:07

The Sarco website is a good place to start. The Sarco site has the steam tables you need to find the answer. Enthalpy across a valve is constant like danschwind indicates.

Things to consider -
If you reduce the pressure at the front end of a pipeline, the user will see more pressure droop than if you reduce the pressure close to the end user.
You can get the same effect by reducing the boiler pressure setpoint.

Check your pipeline pressure drop, at lower pressures the volume (keeping the mass constant) increases, so velocity increases and the pressure drop increases. If the velocity gets to sonic, the flow will choke.
https://www.engineeringtoolbox.com/steam-pressure-...

Fred

MortenA (Petroleum) · Answer 7 · 2020-10-08 17:16:17

Use a steam table and use constant enthalphy. Or use the links provided above

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Steam pipeline pressure drop