7 replies to this topic

[sprem]

Dear All,

We need 14.2 kg/cm2 steam for a particular heating operation.what are the expected advatage/disadvantage in

1. Tapping this from a 20kg/cm2 header line

2. Tapping from a 17kg/cm2 header line.

Assume 95% steam quality.

Regards,

SP

[djack77494]

Some very general comments -
The higher the steam pressure, the higher the value of the steam. Besides just the pressure itself, this is because the higher pressure steam is (probably) available at higher temperature.

Using steam for heating, I would always prefer saturated steam. Since you list the steam's quality, you don't have to worry about superheat, though it is not clear to me what the 95% quality is due to. If the 20 and 17kg/cm2 headers carry either saturated or superheated steam, then where is the liquid water coming from?

Doug

[JoeWong]

Tap from 17kg/cm2 header line, less pressure drop, less energy lose...less noise...less vibration...bigger steam control valve...steam line size larger as more steam massflow @ 17 kg/cm2 require...

There is just a small pressure different between both pressure level and you won't see big advantage selecting either pressure level...

[sprem]

Sir,

Thank you very much for the reply.I would like to clarify my specific doubt little more.

We observed increased temparature in a given time for the surface heated with higher header pressure ie 20 kg/cm2 when compared to 17kg/cm2 (in both cases 14.2kg/cm2 was the end line pressure).in both cases steam was genarated from the same boiler.what could be the reason?.

Regards

Sp

[JoeWong]

We observed increased temparature in a given time for the surface heated with higher header pressure ie 20 kg/cm2 when compared to 17kg/cm2 (in both cases 14.2kg/cm2 was the end line pressure).in both cases steam was genarated from the same boiler.what could be the reason?.

What do you mean by "increased temparature in a given time for the surface heated with higher header pressure " ?

What surface are you referring to ?

[sprem]

Sir,

we are putting steam in to a rubber membrane and measuring the outer surface (outer surface temparature of the membrane having 9.5 mm thickness). In one case it was found to be 165 °C in 20 minutes, and in the other case it was 172 °C. In both cases all other parameters were the same - except the steam header pressure from which the tapping for 14.2 kg/cm² was taken. Hope the point is clear to you.

Any suggessions?

Regards,
SP

[Padmakar Katre]

Dear,
You dont consider the basic like saturation temperature of the 20 Kg/cm2 g pressure header will be more than the others (as the header pressures are low) which will yield the higher temperature of the end user in this case.
The reply to your first post is ,
1. Check the vibration analysis from your instrumentation and process control department in both the cases ( i.e. from 20 Kg-14.2 Kg and 17 Kg-14 Kg)
2.Check the cost for both the cases for higher pressure drop application control valve size will be smaller resulting into less price.
3.Check the degree of superheat associated with the pressure letdowns in both the cases and their effect on the end application.

Hope this could help you a little.If this is not making any sense please ignore my suggestions.

[sprem]

Dear Padmakar,

I will study your suggession and come back

Thanks

regards,

Sp