Steam self operated press./temp regulating valve

[morojlu]

Dear all,
I have used self operated pressure/Temperature regulating valves (ERV) in superheated steam line to reduce the pressure or temprature.
Do you know any type of ERVs that I can use in saturated steam line?
I think if the pressure of saturated steam is decreased, the steam condition will be superheated and this is not good for my application.

Best regards,

Mehdi Orojlu

 

[rmw]

Pressure reduction of medium to low pressure saturated steam will always result in the steam superheating to a small degree.

Unless your pressure reduction is great, the superheat should not be so bad so as to be a problem.

This is not an issue related to the type of valve that you use, but it is related to the laws of thermodynamics.

If having no superheat is absolutely critical to your process, then you should consider a steam conditioning valve that reduces the pressure and desuperheats it in the same valve body.

Even at that, most desuperheaters can't control right at saturation and have to control 5-10-20°F of superheat.

I have used plenty of self contained regulators to pressure reduce saturated steam, and would not hesitate to do so again.

rmw

 

[quark]

I agree with RMW. The superheat, I observed, varies between 5 to 10F. You can use desuperheater(water injection into steam) after Pressure Reducing Valves. Check with Spirax Sarco. If the steam flow rate is huge, you can use back pressure turbines that use the superheat and generate power. Finally you get saturated steam out of it.

Regards,

 

[JimCasey]

RMW brings up some good points. You can control the temperature of superheated steam with an attemperator/desuperheater. Once the steam crosses the saturation line, you can add a lot of water without changing the temp,so any control system to a certain moisture content would be very complicated.

OTOH, as RMW points out, you don't get much superheat by adiabatic isenthapic throttling through a valve. 250 psi saturated steam throttled to 100 psi only comes out 20 degrees superheated, if the insulation of the valve is perfect. Once you lose 12 BTUs per pound (almost nothing), you are back down to saturation.