Danfoss AKS 4100 (coaxial version) problem in NH3 instalation

[Majkee]

Hi,
I have a few AKS 4100 (coaxial version) with the same problem.
There are connected straight to PLC , they reads well in 4-20 till time when without external reason they starts to read 100% level and give 20mA on output but in real the ammonia level is about 40%, sometimes 50%. In effect ICM/ICAD stops in 0% (reaction too high level) and all of ammonia evaporate in short time. Then effect is that the chilling process gets stop. In this moment the only way is to fix it is reset AKS to factory settings or turn off voltgae for a moment. Do You have the same problems like that?

[RANGER1]

Majkee,
Please find link below if you do not already have.
You might have older version that has to be replaced.
Read through to see if anything stands out.
I think I heard of changing range, so where you want to operate level
is the same but calibration is altered 9maybe for frozen value)?

http://files.danfoss.com/technicalinfo/dila/01/DKRCI.PD.SC0.D4.02_Trouble%20shooting_AKS%204100_4100U.pdf


http://files.danfoss.com/TechnicalIn...%20version.pdf

[Majkee]

Hello, thank You for answer. I've already read it, but unfortunately it takes only about relation between HMI and converter. Whole problematic sensors were bought in sets (HMI+sensor) in different parties and are placed in one piece without replacing/changing HMI and sensors. I think it depends on something else. Interesting is that they works fine till starts to "see" max level and give 20mA on output. And it's not depend of chilling process. Strange...

[cricri]

Hi Majkee,
You have probably no display on the sensor head.
Did'nt you open it and check for any amonia smell?
Is it a new one or an older model?
We have some internal leakage experiences on old design AKS4100 and could get replacements from Danfoss.

[RANGER1]

Hello, thank You for answer. I've already read it, but unfortunately it takes only about relation between HMI and converter. Whole problematic sensors were bought in sets (HMI+sensor) in different parties and are placed in one piece without replacing/changing HMI and sensors. I think it depends on something else. Interesting is that they works fine till starts to "see" max level and give 20mA on output. And it's not depend of chilling process. Strange...

We installed a new one last year, same as your set up.
Keeps freezing on something like 70%, allows liquid to keep feeding ICM, then high level.
They say they are super reliable, we hate them, so don't use on our stuff.
If we do we prefer to install a back up liquid level control switch, like Hansen or Parker, when things occasionally go wrong.
Danfoss level switches no better, like a cheap interim thing.
In general their product is good, but not perfect.
One callout or failure could cost more than installing back up level switch.

[Majkee]

Hi Majkee,
You have probably no display on the sensor head.
Did'nt you open it and check for any amonia smell?
Is it a new one or an older model?
We have some internal leakage experiences on old design AKS4100 and could get replacements from Danfoss.

No, there's no Ammonia smell after replacing cover in each of them. Actually i have 8 with HMI display and 5 without it. Those are a brand new - 2017 and newer.
HMI ver. 1.10.03 (troubleshooting say's up to 1.10.00)
SENSOR ver 1.22.03
CONVERTER ver. 1.08.01
so they are not listed in troubleshooting, but randomly there's still a problem. I'm looking for common issue reason for them. Next time when one of them will freeze i will disconnect a HMI and look for effect. Maybe Danfoss didn't report problem officially for this config?

[cricri]

5 years ago when we were facing to our issues, ammonia leaks and frozen display, Danfoss said:

Frozen signal (investigation about to conclude)–
during our investigation we confirmed 2 different symptoms (frozen signal and
unstable readings) related to the same root cause (to be confirmed). The new
symptoms could be triggered by factors including a fast level change in the
upper side of the standpipe (to be validated). As of today, we can replicate
these symptoms in our lab, so a final solution is coming. Solution: We have now
an option to help eliminate this problems by a configuration change, but also
we are working on a solution through a software update which is expected within
8 weeks (currently under validation in a laboratory). When the
investigation/validation finalizes, we´ll share ....

you are probably dealing with piping problems and instable level (NH3 boiling). 22mA is a fault value.
After checkings you finally could talk about that with Danfoss.

[Josip]

Hi,

many years ago we faced similar problem with Danfoss 38E level controller ...

due to fast level change in a vertical pipe .... so we solved it to instal a kind of baffle plate
on the top of vertical pipe (3" or less) before stop valve with a small hole in the middle of baffle
plate with diameter of about 6-8mm to reduce waves within vertical pipe.
We had also a level glass to control level visually ...

One possibility is to reduce speed of refrigerant flow
(increasing and decreasing of refrigerant level)
to manually close hand stop valve by some turns,
but all must be under surveillance until proved good ...
then you can install baffle plate

Of course installing back up level switch is also possible ...

Can be a long game until solved ok ...

Best regards, Josip

[Tycho]

We've been using these since they came on the market, with little to no issues.
Our plants are on ships mostly, so we always fit them with the sleeve to keep the wire straight.

We had one on a land based plant where we didn't use the sleeve and there we had issues almost like yours.
the wire would move because of boiling refrigerant (we think) and it would show weird values, jumping up and down.
It did freeze on a few occasions, but only for a few minutes.

after some hair pulling we took it out and fitted it with a sleeve, and it's worked fine since then.

The only real issue we had, were with the series that would leak ammonia up into the connection box.
After we claimed them the reply from Danfoss was "you can't expect the wire penetration to be 100% leak free"
we solved it by drilling vent holes in the cap, and then when the issue was fixed by danfoss we got new ones.

I think we had maybe 5-10 where this happened.

There was also a software issue (in the sensor head), where if the standpipe was completely full with liquid, the reading would go from 100% to 0%, but i think this was fixed 5 years ago or so.
We had it happen one time, and after danfoss had checked, they sent us replacement heads to replace the ones in the bad batch.

I've never had any issues with these when it comes to boiling or rapid level changes, the older model with the teflon tube was a nightmare.


Is yours fitted with the sleeve, or is it just the bare wire?

[RANGER1]

We've been using these since they came on the market, with little to no issues.
Our plants are on ships mostly, so we always fit them with the sleeve to keep the wire straight.

We had one on a land based plant where we didn't use the sleeve and there we had issues almost like yours.
the wire would move because of boiling refrigerant (we think) and it would show weird values, jumping up and down.
It did freeze on a few occasions, but only for a few minutes.

after some hair pulling we took it out and fitted it with a sleeve, and it's worked fine since then.

The only real issue we had, were with the series that would leak ammonia up into the connection box.
After we claimed them the reply from Danfoss was "you can't expect the wire penetration to be 100% leak free"
we solved it by drilling vent holes in the cap, and then when the issue was fixed by danfoss we got new ones.

I think we had maybe 5-10 where this happened.

There was also a software issue (in the sensor head), where if the standpipe was completely full with liquid, the reading would go from 100% to 0%, but i think this was fixed 5 years ago or so.
We had it happen one time, and after danfoss had checked, they sent us replacement heads to replace the ones in the bad batch.

I've never had any issues with these when it comes to boiling or rapid level changes, the older model with the teflon tube was a nightmare.


Is yours fitted with the sleeve, or is it just the bare wire?

Tycho,
Don't want to hi-jack your thread, but what do you mean by sleeve?
Is it a Danfoss thing, or something you make yourself?

[Tycho]

Tycho,
Don't want to hi-jack your thread, but what do you mean by sleeve?
Is it a Danfoss thing, or something you make yourself?

it's possible to get a pipe you thread the wire through to make it rigid, on ships we need it or else the wire would be moving too much, on land you shouldn't need it, but like I said, it's more stable with the pipe added.

you can get the pipes to specific lengths, or you can cut it to fit.

Danfoss original
AKS-COAXIAL-D14-tegning-300x300.png