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jumacao (Chemical) (OP)
14 Feb 12 15:11
If we have saturated steam at 97 % quality.  If we are measuring a temperature 2 degrees lower than the saturated temperature.  What could cause that?  We are measuring the pressure and the temperature.   
ash9144 (Chemical)
14 Feb 12 16:33
Measurement errors.
MiketheEngineer (Structural)
14 Feb 12 17:17
Or out of whack or non-calibrated instruments
DRWeig (Electrical)
15 Feb 12 7:59
Agree with ash9144's and MikethEngineer's answers.

What is the accuracy of your temperature sensor/transmitter combination? Thermal effect? What about the pressure transmitter? At what temperature and pressure were they calibrated? What was the accuracy of the calibration standard? Do you have a calibration report?

What pressure/temperature steam are you working with? If 1000°F, being off by 2°F is trivial considering you are working with two sensors that both have error bands.

Is your temperature sensor insertion well insulated the same as the rest of the pipe or vessel? Your sensor probe may be conducting heat to the surroundings. Is the vessel well-insulated? The probe may be radiating to the vessel wall.

Lots of possibilites.

Good on ya,

Goober Dave

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chicopee (Mechanical)
16 Feb 12 9:42
Perhaps, altho I doubt it, an erroneous steam table?
rmw (Mechanical)
16 Feb 12 21:36
So if you aren't able to measure you steam temperature accurately, how do you know that the quality is 97%?

StoneCold (Chemical)
17 Feb 12 10:30
Did you compensate the pressure measurements for altitude?
Drexl (Chemical)
29 Feb 12 16:11
Are you sure you have no air or other gases in there at the time of measuring?
EdStainless (Materials)
15 Mar 12 15:17
What do the tips of your pressure sensing lines look like?
Zero flow velocity? are you sure that there is never any water in the lines?
This is a sensor issue.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

rmw (Mechanical)
16 Mar 12 20:47
The OP's keyboard seems to have gone dead.

ports394 (Mechanical)
22 Mar 12 14:20
Is there a thermowell involved?
msquared48 (Structural)
22 Mar 12 20:20

I guess the OP is steamed from the comments.

Mike McCann
MMC Engineering

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