saturated steam 5

[shoubaki]

Dear ALL:

I have saturated steam line using in distillation unit with pressure 5.3 so the expected temperature is about 160 C , but actually the temperature is 140 C

what is the possibles causes for this case? can any body help me ???

 

[katmar]

I assume the units for your pressure of 5.3 are bar gauge. Are you measuring pressure and temperature at the same point? If you are measuring the temperature after the steam has passed through a valve and the pressure has dropped the temperature would drop too.

If you are measuring both parameters at the same point then there are 3 possibilities:

1. Your pressure gauge is faulty
2. Your temperature gauge is faulty
3. Your fluid is hot water

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[shoubaki]

thank you Katmar


I've measured at the same point
your assumption is correct it is bar gauge.
I've calibrated the pressure and temperature gauges and its working correct.

for more explanation:
the line is filled with purified water and its heated by industrial steam (heat exchanger)
the industrial steam temperature is 175 C and about 8 bar

it is possible that the line is pressurized and thus the Boiling point increase , so it still hot water ???

 

[ione]

Where are you exactly measuring temperature and pressure?

 

[katmar]

If there is both steam and water in the line then the temperature has to be the saturation temperature that you find in the steam tables. It seems that in your case all the steam has been condensed in the purified water and what you have in the line is only hot water i.e. no steam or vapor.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[shoubaki]

I measure the temperature and pressure at the top of the line.( at the same point)

I check that there is a steam raised from the output of the line

I still searching for the exact reason !!!!

 

[katmar]

Can you post a photo or drawing of the installation. Can you also describe the process. Do you start with the line filled with water. At what temperature. Is the steam fed from the top or bottom. At what rate. How do the temperature and pressure change while the steam is being added.

What you have described is impossible, so you need to give a more accurate and complete description. One of the joys of science is that Nature's laws are always obeyed. Unlike human laws.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[zekeman]

"I check that there is a steam raised from the output of the line"

Please explain how you determined that there is steam under pressure?.
If you did this properly you would have drilled a probe hole for the pressure and temperature gauges measured near the pipe center you would have NO way of visually knowing whether there was steam inside the pipe.
Obviously,if you see steam escaping it is under ambient conditions and it is flash over.
Bottom line, if you accurately measured the temperature and pressure (you posted) inside a closed pipe, there is NO doubt that you have pure water, no steam.

 

[zekeman]

Also, exactly how does the high pressure steam heat the water in the pipe to make steam in the pipe?

 

[shoubaki]

 

[shoubaki]

I try to explain my case in a simple drawing ,
you will note that the position of temp and pressure gauges
not the inlet purified water (PW) temperature (70 C)

 

[shoubaki]

can anyone Help ??

 

[ione]

Is this the first time that pressure and temperature are measured?
I cannot understand whether this situation has been noticed before or weather this is the first time you have those readings for temperature and pressure gauges.
What you can be sure of, as stated by others above, with those readings you have only hot water.

 

[Jboggs]

I encountered a similar situation many years ago in a tire manufacturing plant. For some reason the saturated steam line supplying a line of tire presses was at the right pressure but the temperature was low and we could not figure out why. After much research we discovered that one valve at one of the tire presses was allowing high pressure nitrogen to leak back into the steam line, creating a partial pressure situation. So the the steam line actually contained a mixture of nitrogen and steam instead of 100% steam. Afer we fixed that valve and installed shuttle valves at each tire press to prevent nitrogen from entering the steam lines, the steam temperature rose back to the proper level. This story gave me a much better understanding of partial pressures in mixed gases.

 

[zekeman]

What steam rate are you getting out of the final tank?

If only hot water enters this tank (as we all think) you should be getting very little steam output.

And why is this suddenly a problem? Or is this a startup facility

 

[BDJohnson]

Make certain that you have considered the atmospheric pressure.

 

[hopper112233]

how is pw into the distillation process measured and balanced?

 

[hacksaw]

what is the pressure and temperature of the steam to the first vessel?

 

[flash3780]

Is there air in the system? If so, you'll need to look at the partial pressures of air and steam in your calculations.

 

[rmw]

Air meaning any form of non condensables. EM, Hopper has asked a legitimate question for this thread. Shoubaki, two possibilities, one is non-condensables where the partial pressure of the water vapor has to be taken into consideratoin or (2) if this temperature sensing device is in fact above the calandria, you might be getting some wetting of the bulb or whatever is exposed to the flow stream from carryover from the boiling process. Do you have any way of measuring where your "evaporated PW" arrow points? I strongly suspect the latter. Are there any kind of demisters in the upper portion of the vessel, and is this temperature measuring device upstream or downstream of the demisters? Remember that even down stream of the demisters, some fine mist particles can still be present.

rmw