Which appropriate equipment should I use to get water level signal at PLC?

[AB2005]

Hi,
I am working on automating an industrial fabric shrinkage tester to replace its outdated electronics with a PLC.
To get the tank's water level signal to the PLC, I am considering designing a tube connected to the nozzle at the bottom of the tank. I plan to install a water level probe/sensor in this tube. Could you please suggest which kind of level sensor would be best for this application?
The required specifications are:

• Range: 1 meter
• Output: 4-20mA

Thank you for your expert opinion!

 

[parky]

More information is really needed, for example are you thinking of a continuous water level ?, what sort of temperature range i.e. is it hot ?. are there any chemicals or steam give some idea of the environment.
Can you fit for example a radar sensor in the top of the tank or a pressure type in the bottom.
There are many options for example pressure type that fits in a boss at or near the bottom of the tank, simple only requires someone to cut a hole & weld a threaded boss in the bottom, a differential where there are two sensors one in the bottom & one in the top, a radar type (not good for hot water as the steam may affect the sensing.
There are probe types although have never used them these rely on conductivity along the probe but have to be ordered at the length required.
Endress & hauser have a good range but not cheap.
RS do an ultrasonic sensor never used them in a water sensing application but is cheap & may work for you.

 

[AB2005]

More information is really needed, for example are you thinking of a continuous water level ?, what sort of temperature range i.e. is it hot ?. are there any chemicals or steam give some idea of the environment.
Can you fit for example a radar sensor in the top of the tank or a pressure type in the bottom.
There are many options for example pressure type that fits in a boss at or near the bottom of the tank, simple only requires someone to cut a hole & weld a threaded boss in the bottom, a differential where there are two sensors one in the bottom & one in the top, a radar type (not good for hot water as the steam may affect the sensing.
There are probe types although have never used them these rely on conductivity along the probe but have to be ordered at the length required.
Endress & hauser have a good range but not cheap.
RS do an ultrasonic sensor never used them in a water sensing application but is cheap & may work for you.

Hi,

Thank you for your response and interest.

There is no continuous water level; at initial start-up, the system will insert water as per the given parameter. The temperature can go up to a maximum of 95°C.
There are no chemicals or steam, only detergent is used.
Since the drum of this machine is enclosed and the agitator rotates inside it, we cannot insert from the top. At the bottom, there is just a nozzle.
I have found two types of level transmitters, the pictures of which are below. For KSR KUEBLER, which has float, I would have to create an SS tube and fit it at the level of the drum, then insert the probe into it. The tube will connect with the nozzle of the drum by a pipe.

The other one, WIKI S-10, will connect directly to the nozzle with a siphon between them.

I prefer the KSR KUEBLER, but it is more costly. The WIKI model is cheaper.

Your expert opinion will be great for me.

 

[parky]

Did you mean Wika S-10 not wiki, I have used the Wika for vacuum in a vessel the product temperature was 95 Deg c & one failed after a few weeks I have no idea if it was the temperature, just a faulty sensor & no idea if it was replaced with the same model I did assume it was but apart from that little episode it seemed to work well, I do know in my application the product tended to go thixotropic & the direct steam injection would blow through small batches so it is possible that the sensor was hit by 150 Deg steam I do remember removing the PID & had a recipe mod that changed the steam pressure as the product thickened, it was the only way that stopped the blow through i.e. when the product reached a certain temperature it became quite thick so the injectors would blow the steam through & this meant that the product would not rise in temperature reducing the pressure as the temp rose cured the problem.

 

[OkiePC]

If you are going to use a regular pressure transmitter, I would recommend IFM Effector. You can specify a temperature range to narrow the search results. When I did that and set it to 100C, it eliminated those with 1/4" MNPT process fittings which is common in North America, but you may have a different preference in your country. I use one of their sensors to measure the level of a small drum of polymer that has an agitator in it, and the model I got with a built in display also has dampening features to take the noise out of the signal before it even gets to the PLC. I was impressed with its accuracy and repeatability for such a small pressure range of a tank less than 4 feet tall.

They have a pretty wide variety of other types of level sensor to consider as well.

Homepage US

Homepage US

www.ifm.com

 

[AB2005]

Sorry.

Did you mean Wika S-10 not wiki, I have used the Wika for vacuum in a vessel the product temperature was 95 Deg c & one failed after a few weeks I have no idea if it was the temperature, just a faulty sensor & no idea if it was replaced with the same model I did assume it was but apart from that little episode it seemed to work well, I do know in my application the product tended to go thixotropic & the direct steam injection would blow through small batches so it is possible that the sensor was hit by 150 Deg steam I do remember removing the PID & had a recipe mod that changed the steam pressure as the product thickened, it was the only way that stopped the blow through i.e. when the product reached a certain temperature it became quite thick so the injectors would blow the steam through & this meant that the product would not rise in temperature reducing the pressure as the temp rose cured the problem.

Sorry, that was a typo error. It is WIKA, not WIKI.

I am still wondering whether I should use this pressure transmitter or not. The supplier suggested that I use it with a "U" shaped syphon between the tank and transmitter to reduce the temperature.

 

[parky]

I agree, most sensors are probably only rated to 80 - 90 Deg C

 

[durallymax]

More information is really needed, for example are you thinking of a continuous water level ?, what sort of temperature range i.e. is it hot ?. are there any chemicals or steam give some idea of the environment.
Can you fit for example a radar sensor in the top of the tank or a pressure type in the bottom.
There are many options for example pressure type that fits in a boss at or near the bottom of the tank, simple only requires someone to cut a hole & weld a threaded boss in the bottom, a differential where there are two sensors one in the bottom & one in the top, a radar type (not good for hot water as the steam may affect the sensing.
There are probe types although have never used them these rely on conductivity along the probe but have to be ordered at the length required.
Endress & hauser have a good range but not cheap.
RS do an ultrasonic sensor never used them in a water sensing application but is cheap & may work for you.

With how cheap Radars are now, I can't think of a level application where I'd ever use Ultrasonic (except for hobbiest arduino projects). An 80GHz radar can handle a lot of condensation in the air before it has issues, I've yet to find the limit.

The agitator would likely be an issue for OP (although a short tank witha 3* Radar beam can avoid many obstacles), but a radar can operate in a standpipe outside of the vessel just fine as well.

 

[AB2005]

Hi,

Has anyone had experience using the WIKA A-10 pressure transmitter for measuring liquid level?

 

[robertmee]

You seem fairy resistant to suggestions, and want to use the Wika, so just use it. One or two peoples experience here isn't going to define whether to use it or not, or whether it would be successful in your application. You have a supplier that's guiding you and can offer support, so try it.

 

[OkiePC]

If you add the siphon to isolate it from the heat, it should work for you. I would also use mathematical filtering in the PLC to take noise out of the signal caused by pressure disturbances from the mixer. I typically scale the value to milliamps first, then apply filtering to that result, then apply scaling to desired engineering units. It may seem like overkill, but when there is an HMI that allows you to see all of these settings and apply filtering to a signal in milliamps, see the result on the screen, it is handy for commissioning and maintenance going forward.

 

[robertmee]

If you add the siphon to isolate it from the heat, it should work for you. I would also use mathematical filtering in the PLC to take noise out of the signal caused by pressure disturbances from the mixer. I typically scale the value to milliamps first, then apply filtering to that result, then apply scaling to desired engineering units. It may seem like overkill, but when there is an HMI that allows you to see all of these settings and apply filtering to a signal in milliamps, see the result on the screen, it is handy for commissioning and maintenance going forward.

You mentioned that years ago in one of these threads and I began following that methodology. Any analog module that has scaling capabilities, I scale 4000 to 20000, so I know exactly what the ma signal is. After 35 years, I still learn here all the time

 

[OkiePC]

After 35 years, I still learn here all the time

That's why I am here and I read threads even about topics I have no chance to help on ... so many times I have read about something here and run across it later and at least have a clue where to go to find more answers.

 

[AB2005]

If you add the siphon to isolate it from the heat, it should work for you. I would also use mathematical filtering in the PLC to take noise out of the signal caused by pressure disturbances from the mixer. I typically scale the value to milliamps first, then apply filtering to that result, then apply scaling to desired engineering units. It may seem like overkill, but when there is an HMI that allows you to see all of these settings and apply filtering to a signal in milliamps, see the result on the screen, it is handy for commissioning and maintenance going forward.

Nice.
Thanks a lot.

 

[diat150]

Hi,

Has anyone had experience using the WIKA A-10 pressure transmitter for measuring liquid level?

wika has a bad reputation in my industry. I would use something else.