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from the Instrumentation and Control department...
Ammonia Tank Level Measurement
Continuous process industries, DCS questions. topic
Posted by Shafqat Iqbal on 26 February, 2005 - 4:16 pm
Dear friends I just joined the Fertilizer company and i want to measure the level of liquid ammonia tank a closed tank. I want to know what kind level instruments should be used for it that best suit.

The tank is 22 m high and 21 m dia. Now pleas give me the suggestion about it and help me in this regards thanks.
Well i chosed the buoyancy type level transmitter but i dont will it be useful for so much high tank. Or u suggest me some dp pressure transmitter.

Regards


Posted by Gary on 27 February, 2005 - 2:21 pm
At 22 meters, I would suggest a DP. This is the easiest and most cost effective route. Pay attention to material, and take the other side through a capillary.

GWoods@CrossPointEngineering.com
GTW


Posted by Bud Buyer on 28 February, 2005 - 9:04 pm
Web sources list ammonia dielectric constant > 16, which means industrial radar can shoot from the top (no side mounting), ignore the vapors and probably give you 8-10mm accuracy. Higher accuracy possible at 3-4x cost.

DP works, too.

Bud


Posted by Daniel Vila on 1 March, 2005 - 9:41 pm
It depends not only on tha measurement range, but also on tha accuracy you are looking for.

As a measurement principle you have made the right choice due to the type of product you are measuring.

Regards,


Posted by Troy Hammerbeck on 6 March, 2005 - 11:33 pm
If your looking for a non contact maintenace free solution try using ultrasonic level transmitters by Pulsar. If you just want to monitor level with no display and have a 4-20ma output with two alarm relays I suggest the low cost Pulsar Blackbox level transmitter with a Db25 transducer. For more advanced funtions and a display, try the Level Star 110 with the Db 25 tranducer. For more info please visit the website http://www.pulsarus.com. If you wish to discuss further call me personally @(678)296-7269

Good Luck!
Troy Hammerbeck


Posted by ashley on 11 March, 2005 - 8:25 pm
the best and most reliable is using a dp cell, just remember, you will need a wet leg installation. you can use antifreeze or something of that source. nh3 is corosive and will dammage the cell if this is not done.


Posted by Amir on 14 March, 2005 - 1:39 pm
I have worked on construction of an ammonia plant and Installation of instrumentation on the tank.

I think that the best way to measure the level is to use two devices...

The DP is a good measure but you will have to look into the existing tank drawings to establish if there are spare nozzles at the top of the tank. If not then the best bet will be to take an existing tap from an already installed pressure device at the top of the tank.

However, for high level accuracy, I suggest usinf a level transmitter called the ENRAF. This is a level that is flanged to the top of the tank and the measurement is via a servo motor and a dispacer that actaully is inserted into the tank and floats on the top of the liquid. The principle of measurement is base on Archimedes Principle and the accuracy is amazing - in the order of 1mm or so. The only problem with commissioning of the device is that you will either need an already exisiting level for reference calibration or an empty tank. Either way you cannot lose.

Good Luck!


Posted by Anonymous on 26 April, 2005 - 10:35 pm
I recomend the Garnet SeeLevel System Model 900D2 system with a polyethylene sender bar.

You can contact them at garnet4@itexas.net


Posted by Daniel Vila on 29 April, 2005 - 7:54 pm
You may use the servo level gauge. We have used it with success in ammonia tanks in different countries.

Check http://www.enraf.com


Posted by Thotakura Venkat Ramanjulu on 20 July, 2005 - 5:07 pm
Hello,

you can very well go for ENRAF Servo Gauge for measuring the liquid level of the closed Ammonia Tank. Even you can go for NIVO (Indian) MEchanical Level Gauges which can be used for local indication and even come with remote indication options presently. We are using these and very satisfied with their performance.

With regards.
Thotakura Venkat Ramanjulu


Posted by Level Headed on 17 August, 2007 - 12:04 am
It appears you are getting advice from some people who are less than familiar with this difficult to measure material. Ammonia does not have a hard reflective surface. Hence, standard devices employing radar and ultrasonic technology do not yield a usable reflection. However, low frequency radar (~6 GHz) can be used successfully if used in conjunction with a full length stilling well. The diamater of this stilling well should be less than 6" (150mm). This technology is probably the best solution for vessels where a stilling well already exists.

I personally have not tried the GWR/TDR technology but I believe it stands a chance on this tough application.

Regarding DP, I would not want another hole in the bottom of my vessel and would certainly not want to find out what product antifreeze and ammonia produce.


Posted by Wet Leg on 25 September, 2007 - 11:41 pm
We're using d/p transmitters at our facility to gauge NH3 storage tanks. The low side is heat traced to maintain vapor. It must be taken into consideration the opportunities one may have to repair the devise if something inside the tank fails. In the Enraf unit, what are the consequences of the float sticking in the down position and there is no opportunity to evacuate the tank? As Level Headed posted, NH3 is a difficult application for radar. I doubt the d/p is the best application but it does work and can be isolated.

While we're on the subject of NH3, what do you folks use to measure level in your syn loop NH3 separators? We recently installed a couple of diaphragm/capillary d/p's on our primary separator and they're working great.

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