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Old January 24th, 2018, 02:11 AM   #1
Theboss
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Boiler steam pressure

Good day Gents,

Does atmospheric pressure have an influence of a boiler steam pressure.
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Old January 24th, 2018, 07:41 AM   #2
John Morris
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Try this, fairly basic

http://www.narrowgauge.iform.com.au/steam4.html
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(I should probably look into this)
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Old January 24th, 2018, 12:13 PM   #3
dwoodlock
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It would depend on exactly how your boiler is configured. Higher atmospheric pressure = higher boiling temperature and vice versa.
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Old January 24th, 2018, 12:18 PM   #4
Theboss
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And if the boiler is a closed system, using the steam to create vacuum and steam tracing. Should we be measuring gauge pressure or absolute pressure of the steam?
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Old January 24th, 2018, 12:31 PM   #5
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I am no boiler expert at all. Hopefully someone who has more experience can chime in.

I suspect a absolute gauge would yield a wider range of information for you to consider.
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Old January 24th, 2018, 02:31 PM   #6
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Boiler pressure is not affected by atmospheric pressure - it is a closed loop. The pressure is usually stated in gauge pressure.

That being said most steam tables are in absolute pressure. If any calculations are to be made convert the boiler operating pressure to absolute first.

Many good online steam tables.

http://www.spiraxsarco.com/Resources...am-tables.aspx
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Old January 24th, 2018, 02:55 PM   #7
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Why should the boiler pressure (gauge) be converted to absolute pressure for calculations?
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Old January 24th, 2018, 03:19 PM   #8
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What is your operating pressure?

Most times the slight difference in atmospheric pressure isn't going to make much difference.
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Old January 24th, 2018, 03:21 PM   #9
Theboss
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17bar out of the boiler but downstream we getting 14bar line pressure which is gauge pressure.
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Old January 24th, 2018, 03:43 PM   #10
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you do not have to calculate in absolute pressure. Just every printed steam table I have used works in absolute.

What are you trying to figure out?

The online steam tables work for gauge or absolute.
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Old January 24th, 2018, 03:55 PM   #11
Theboss
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Yeah I noticed that as well.

I'm trying to understand why does absolute pressure hv to be measured for pressure compensation on a flowmeter.
The boiler is a closed system and atmospheric pressure has no influence on the steam pressure from the boiler.
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Old January 24th, 2018, 04:03 PM   #12
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I believe you just need to convert the gauge pressure to absolute for the flowmeter.

The flowmeter my be able to work at below atmospheric. Maybe the built-in calculations want to work in absolute.
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Old January 24th, 2018, 04:08 PM   #13
Theboss
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I believe so too.

Is there any reason why absolute pressure is the preferred method?

Maybe I'm thinking about it incorrectly but since the boiler is a closed loop, gauge pressure(line pressure) should be measured instead. Please correct me if I'm wrong.
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Old January 24th, 2018, 04:19 PM   #14
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Not sure why it wants absolute.

Maybe the built in calculations are based on absolute. You should be able to just add 14.7 psi or 101.3 kPa to your gauge reading. Or I guess 1.013 bar.
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Old January 24th, 2018, 04:26 PM   #15
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That's exactly what I did.

But if absolute is what is needed, surely it's for an open loop system (eg. Kettle) where the steam is open to atmosphere
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