Sensor for reading water in steam environment

[James Mcquade]

Hi all,

i have an application in which i need to read the water level in a 1 1/2" diameter tube that is 24 in. tall. the sensor will be mounted on top of the tube and the water level will be approx. 6in. below it. the 6" level is the tank full setting and 8 to 10 in. lower will be the tank low and empty setting.
where i am having an issue is because the water is heated to 200 degrees F and there is steam in the tube.
i have tried an ifm ultrasonic sensor which worked for a while, but is now reading the steam and giving readings all over the place because the building is not as hot because of the fall weather.

does anyone have a sensor they have used or any suggestions?
thank you in advance,
james

 

[OkiePC]

Maybe a guided wave radar?
https://www.automationdirect.com/ad...a-_controllers/radar_level_sensors/gwr-1600-p
I believe that one is a rebranded IFM

 

[drbitboy]

is the tube under pressure?

 

[goghie]

For example with autoclaves, Magnetic Level Gauge with is usually used. There is often 4-20mA output option.

 

[drbitboy]

and when you say steam in the tube, do you mean something visible i.e visible water droplets, or steam i.e. clear H₂O vapor?

 

[robertmee]

Is the tube a sight glass? Can you drop a float in it? A metallic float and a couple of prox switches if the tube is plastic and all you care about is high and low.

 

[drbitboy]

if it is the fall temperatures that are the source of the change in behavior of this system, then insulating the tube may return it to its previous behavior.


Another possible option would be to continuously vent the vapor space of the tube.

 

[MaxK]

differential pressure

 

[drbitboy]

differential pressure

obvious solution, but involves tapping into a vessel near water's boiling point. perhaps there is a tap already available elsewhere on the tank, or the tap for the tube could be used and the tube removed.


I mentioned insulating the tube; another option might be going in the opposite direction by cooling the tube so there is negligible steam or water droplets above the liquid surface.

 

[JesperMP]

I think you are looking for a 'magnetic float level sensor'.

 

[robertmee]

I think you are looking for a 'magnetic float level sensor'.

Yeah, that's what I said....by the description of a 1 1/2" diameter tube, sounds like a sight glass to me off a much larger reservoir.

 

[goghie]

Magnetic Level Gauge=Magnetic Float Level Sensor=Sight Glass with magnet floating on top.
There are versions with analog output.

https://www.youtube.com/watch?v=1ft1ypJNO9w&ab_channel=HileControls,Inc.

 

[James Mcquade]

this is the process.
we have an open stainless steel water tank that is about 20 ft long x 3 ft wide x 16 inches deep (best guess) that is heated to 200 degrees F. the tank is covered with doors so we can clean the tank as required.

the product enters the tank on one end and is lowered into the water. the product is heated up and then exits the tank on the other end.

in order to measure the water tank level, we have a 1 1/2" pipe welded to the
side of the tank at the bottom. it comes out a couple of inches and then makes a 90 degree bend and goes approx. 6 in. above the tank and has a flange top so we can bolt a sensor to it and look down at the water level.
there is a 2" standoff between the sensor and the flange of the tube.

this is not a pressurized vessel.

we have been using a turck rod sensor with a magnetic float which has now gone bad after only a few months and the delivery time is 6 months. we then went with an ultrasonic sensor which worked well for a few weeks. last week the readings were eratic, bouncing all over the place. the water level in the tube only varies 1/2" and is stable. the sensor when not placed over the tube gives stable readings. the only thing we can figure out is that the steam in the tube being seen as the water level. as it goes to the top of the tube, the sensor no longer sees the steam.

thanks again for all your help.
james

 

[George Graziano]

James, On/Off for 2 levels? Or continuous. Madison has both. madisonco _Com

 

[g.mccormick]

Ultrasonics will not really work in steam applications (or dusty, etc) since the sound waves will be reflected off of the steam, dust, etc.

Guided radar will work well for a 2phase like this.

You can also use differential pressure measurement to measure vapor space at top vs liquid pressure at bottom. There are a few caveats with DP measure for level measurement thorugh:
1. You need to ensure that the top "dry" line is not allowed to condense/collect water.
2. There will be error in the calculated level if you do not account for volume/density change in the fluid. The same mass of water will create a taller column if it is at 200F than if it is at 40F due to expansion of the fluid.

Float type level transmitters are available with 4-20MA output. This type would work well since the float would sink through the steam and float on-top of the water.

Many ways to skin the cat.