adccommunitymod (AutomationDirect) asked a question.
Liquid Level Sensor for Ammonia
Created Date: November 16,2010
Created By: keycoldstorage
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Does anybody have a recommendation for continuous sensing the liquid level in a 4 ' diameter steel horizontal receiver tank containing liquid ammonia at up to 300psi? Ideally it would transmit an analog signal or communicate through modbus. Alternatively, a series of six or so level sensors might also suffice, but I am not a fan of float switches. Could I just stick a capacitive proximity sensor against the side of the tank? edgar
Created Date: September 25,2017
Created by: maxkleiber
Hi Edgar,
Our pressure probes are the way to handle caustic liquids. They are incredibly reliable and robust.
They convert the weight into a current, that is either displayed locally, or can be transmitted remotely.
Might be worth checking into:
https://www.tankmonitoring.net
https://www.tankmonitoring.net/solutions/tank-monitoring-solutions.html
Markus.
Created Date: September 26,2017
Created by: g.mccormick
Danfoss makes level transmitters for liquid refrigerant measurement, i believe that the sensor is a guided radar type.
http://products.danfoss.com/productrange/list/refrigeration/electronic-controls-sensors-transmitters/level-control-components-for-electronic-controls/aks-4100-aks-4100u-electronic-level-transmitter/#/
Other manufacturers offer guided radar sensors aswell. I would venture to guess that float type transmitter would also potentially work as long as the material was compatible with NH3 (stainless steel).
A quick look on Omega's site found
https://www.omega.com/pptst/LVR20_30.html
Created Date: November 16,2010
Created by: keycoldstorage
Does anybody have a recommendation for continuous sensing the liquid level in a 4 ' diameter steel horizontal receiver tank containing liquid ammonia at up to 300psi?
Ideally it would transmit an analog signal or communicate through modbus.
Alternatively, a series of six or so level sensors might also suffice, but I am not a fan of float switches. Could I just stick a capacitive proximity sensor against the side of the tank?
edgar
Created Date: November 17,2010
Created by: ebalarde
I have a differential pressure transmitter in use on a 100psi boiler. It provides a 4-20mA signal based on the liquid level. All you need is a port in the tank below the lowest level the liquid can reach, and a port above the highest level. I don't know if there are issues with liquid ammonia as opposed to water/steam but the unit I have is made by foxboro ( www.foxboro.com ). I'm sure they could help you out. Also Omega Automation ( www.omega.com ) sells differential pressure transmitters. You might want to check them out too.
Created Date: November 17,2010
Created by: Tom Jenkins
You can use almost any pressure or diferential pressure transmitter with the correct range.
What you want is an isolation diaphragm to separate the ammonia from the transmitter. I'd suggest contacting a local vendor of process monitoring equipment. Selection of the proper membrane material will be critical. Usually the membrane is exposed to the process fluid on one side and the other side of the membrane is a chamber filled with silicone or other inert fluid, with the pressure transmitter connected to the filled chamber.
Created Date: November 19,2010
Created by: Shimmy
This might sound silly but you could try a vision sensor on the sight glass. They are fairly inexpensive these days.
Created Date: November 19,2010
Created by: Bob S BN
Edgar,
Our Process Ammonia tank (horizontal mount, round) has a sensor for the filling company to monitor for the need to refill.
It's made by RobertShaw, and called Centeron, http://wirelessmonitoring.centeron.net/
They also sell RF capacitance level sensors, http://www.robertshawindustrial.com/pages/products/rflevel/rflevel.asp
I'm not sure if the RF capacitance technology is what's used in the Centeron system, but if it is, Omega sells some too. I just didn't see a list of compatible chemicals.
Might be worth checking into though,
Created Date: November 19,2010
Created by: ksmith
Hansen Technologies has a Vari-Level for controlling level and a Techni-level that is just a level transducer probe. We have used Hansen for many years on our NH3 equipment.
http://www.hantech.com/products/pages/level.htm#
Created Date: September 26,2017
Created by: g.mccormick
BTW. I'm now second guessing the float transmitter due to nh3 liquid having such a low specific gravity. It is likely that a float will sink, though different float materials may work. Guided radar is great for tough applications that may have different phases present (unlike ultrasonic). I don't believe automation direct has any, but many companies due. I 've used this one from omega on before though not on ammonia.
https://www.omega.com/pptst/LVRD10.html
Created Date: November 17,2010
Created by: keycoldstorage
Thanks all. Unfortunately, due to my operating range and that this is a horizontal tank rather than a vertical one, getting even mediocre accuracy is cost prohibitive with differential pressure measurements on ammonia wetted parts.
Looks like just putting capacitive sensors against my glass sight gauges are going to have to work for now.
Thanks again!