Suction pipe explosion!!

[Martin Davies]

Hi All,

I'm new here and just looking for anyone who may have seen what I did a week or so ago.

I was called into work by security who said an evaporator had exploded. I didn't know what they meant until I got to work and found gas in the air and oil all over the floor underneath the evap in question. These are big evaps for a huge warehouse holding fruit.

I got the scissor lift out and made my way up to inspect and found the suction pipe coming off the evap had exploded and no longer even looked like a pipe. This on teen caused the entire system to lose its charge (460kg) and so I had a very long day ahead of me.

I want to try find out any information from anyone who may have seen this sort of issue before or know what may have caused it as even the manufacturer has no clue.

Any questions are welcome and if I can I will post a picture of the pipe on here (I'm new)

Kind regards, Martin.

[hookster]

Hi Martin
Is there electric defrost on the evaporator? I have seen this happen before with a banana storage facility.
The evaporator had hydraulic locked with oil and when excessive heating was applied to maintain temperatures oil and gas ruptured manifold connections.

[Martin Davies]

Hi thanks for the reply, yes there is electric defrost. The holding temperature is about 4 degrees, can you explain anymore?

[Martin Davies]

I have only been here for a few months and the equipment that failed is about 3 years old. I've looked back through the worksheets for callouts and faults to the plant from the previous contractor and almost all of them are for oil related issues!

They have been pumping the system down (four 40kw comps) for months, to bring the oil back when a low oil alert has been raised. Obviously there is something fundamentally wrong with the design of the system as the oil seems to be flooding the evaporators and getting trapped there.

I think what hookster posted is accurate and is the result of way too much oil being added to the system and getting trapped in the evaporators and building up for months and months.

What I need to know now is how to find out how much oil is in the system/if its overcharged and if the other evaporators in the system are also flooded!? Any help is greatly appreciated, the HSE are getting involved and want to know why it happened/if it could of been prevented and if it will happen again!

[hookster]

Do you have any more plant detail? Some photos of the plant too would be useful.

With no gas in the system you are in a very good position to now flush and clean system. I would probably advise bringing in an external consultant as there are some serious design issues here. (especially if your company installed/designed it)

Prevention and rectification is possible and if design / Install is at fault, designer/installer could still be held responsible for costs even after three years.

Maintenance practices will also be questioned, I would be collecting as much information as possible.

For anyone who is not aware the HSE are now involved because: Schedule 2 of Riddor Dangerous occurencesPART 1GENERALPressure systems2. The failure of any closed vessel or of any associated pipework (other than a pipeline) forming part of a pressure system as defined by regulation 2(1) of the Pressure Systems Safety Regulations 2000(1 (http://www.legislation.gov.uk/uksi/2013/1471/schedule/2/made#f00040)), where that failure could cause the death of any person.

[Martin Davies]

I will get detail and pictures tomorrow if you like. Unfortunately the cooling load affected by the gas leak had over £1m of fruit in so I had to isolate the evap that blew and recharge the system asap.

Not me who designed/installed thank god! I would like to get a consultant in to check over the installation and try to figure out why the oil is making its way to the evaps - can you recommend anybody?

[Grizzly]

Martin.
I can only assume you are new to the coldstore side of things?
Any oil not recovered by the Oil Separator / System will settle in the area that is the coldest and at the lowest System Pressures.
Guess where that is? The Evap / Cooler.
Is this a DX or flooded system?
You need sufficient Gas flow through the cooler and Heat Load to generate movement of the oil back to the comp / suction / wet return etc.
Once your oil has returned it can then be recovered again and again without adding anymore.
Clean coils and free flowing air are essential.
Someone before you has flooded the system with oil without removing any that comes back, I assume?
Basically once lined with oil a cooler / evap will retain more and more oil with less and less heat exchange.
So said engineers will then lower the suction / system set point to drive down the temps!
Cooler temps / pressures drop resulting in thicker oil and less system pressure / gas flow to return oil etc ect
Basically drain oil whenever you can, Incidentally what oil levels are you running within your comps?
More than 1/2 to 5/8ths full on a recip and you turn it into a very efficient oil pump!
Find out which machines are throwing oil over and check when they were last serviced.
Worn comps throw the most oil!
It is all basic stuff really just start with the basics and move from there.
You don't say what comps you have?
£1m of fruit, ( in Hampshire) I bet hookster knows your site better than you?:D
Talk to him!
Grizzly

[chemi-cool]

Hi thanks for the reply, yes there is electric defrost. The holding temperature is about 4 degrees, can you explain anymore?

Thats remind me of something I have seen a while ago, a crack in the suction line just after the evaporator outlet.
Checking the controls and found out defrost time was set for 45 min, set it for 10 min as the room temp was set to 4C, never heard from them again.
Electric defrost should only start after pump down has finished. could easily set by using NC contact on compressor contactor to activate defrost.

[Martin Davies]

Hi Grizzly thanks for responding.

Yes I'm new to the industrial side, I've been in the commercial side since starting and am picking it all up as I go! However it's hard when there isn't much in the way of records on work done previously.

They are bitzer compressors and it's a DX system. The comps are half filled with oil but the reservoir seems to be completely full all the time even after the explosion and gas/oil leak. I started to remove some of the oil today from the reservoir and then pumped down the system to try retrieve some of the oil stuck down the line.

Without sounding like an idiot I need to know how to remove any oil that could be trapped in the remaining evaps?

[monkey spanners]

I read once of a guy who left some refrigerated cases on defrost while he went to get parts, when he returned and turned the system back on to cooling the evaporator burst. I presume the evaporator had got so hot during the extended defrost that the refrigerant pressures went very high very quickly once the solenoid valve was opened, so high that the pipework ruptured.

[hookster]

Hi Martin
What refrigerant is the system operating on?
Unfortunately with a live system removing entrained oil is not an easy piece of work as lot is determined by the system pipe work design, fittings, system pressure drops and layout.
Oil return requires the correct velocity of refrigerant.

We normally start with an oil analysis to determine contamination levels because if your refrigerant charge, pipe layout is correct there will normally be another underlying factor eg. sludge build up, moisture etc.

Then you also need to consider compressors are they carrying over excessive oil.

Sorry there are a lot of variables to consider before a solution can be reached.

[hookster]

Sorry doubled up really on your post Grizzly. I reread and you covered most of the salient points before me.:)

[Grizzly]

I read once of a guy who left some refrigerated cases on defrost while he went to get parts, when he returned and turned the system back on to cooling the evaporator burst. I presume the evaporator had got so hot during the extended defrost that the refrigerant pressures went very high very quickly once the solenoid valve was opened, so high that the pipework ruptured.

What no Defrost termination stat?
Martin you will get there. But you do, as you suggest need a second opinion from shall we say "A more experienced Industrial engineer"!
As long as your oil level in your comps is maintained keep draining.
Manually defrost evaps if necessary to allow the oil to be warmed up and it will return.
At +4c it is difficult to visualise why the oil return is so poor, what's the state of the air flow through the evaps?

"Pumping the systems down to get the oil back" Nah! Lower temp = lower Pressure and thicker oil.
Bitzers are very reliable and positively bullet proof. But even they wear and need tlc sometimes.
There are so many variables here I could go on forever!
What is the condenser / discharge system pressure ect. To low a condensing temp can have a huge effect elsewhere in the system.
Incorrect Superheat set-up can cause liquid carry over which will increase oil loss at the comp ect ect.
Time to enlist help!
Which in fairness to you is what you are doing on here in a round about way!
Good Luck Grizzly.

[Grizzly]

Sorry doubled up really on your post Grizzly. I reread and you covered most of the salient points before me.:)

Hi hookster.
Your point about the oil is just as relevant though as if grades have been swapped the Bingo a recipe for Oil logging.

More info needed.

[Grizzly]

Martin,
Just a wild Question!
Why do you need defrosts with a control Temp of +4c.
Unless the coolers are blocked or sized incorrectly? Something is not right!
Depending upon what you have it might be possible to do away with electric defrosting or at least minimise them.
Grizzly

[Martin Davies]

Morning! Well lots for me to answer so bare with me...

The system is running on 407c. I have been following instructions left from the previous company who I will not mention at this time but no doubt what so ever you have heard of them. The work sheets they have filled out on callouts to this system in the past couple of years say things along the lines of; 'Found comp(s) tripped on low oil fail, pumped system down to bring oil back'. (no doubt before this method was adopted they dumped more and more oil in the system)

This has happened on many, many occasions but after talking to my manager about it all yesterday, it's very clear a 'new' (built in 2013) system should not need this sort of treatment and obviously it does not work anyway!

Another 'top tip' left by them, bearing in mind I'm new to this side of things, was; 'Set the electronic expansion valve controller to -5 degrees lower than the room set point'. Is that right?? That is assuming the required superheat for the evap will be -1 degree.

The EEV is controlled via a Danfoss EKC 316A with a suction pipe temperature probe and transducer to measure the superheat. But it has not been fitted with the S3 probe which tells the controller the room temp - Which I have been questioning from day 1. Another point which I was unsure about when I first started was the lack of solenoid valves - there aren't any at all on the liquid line. They are using the EEV as a solenoid to each evap controlled via a digital input from the main evap controller - Danfoss CC210.

However what I thought (I may be wrong) is, as the EEV controller does not have the S3 probe installed (the company who installed this system has argued with me that is the correct way) it is relying on the superheat value to charge the evap and as there is clearly an oil build up in the evap it will be reading a higher than actual/normal value due to the warmth of the oil.

On top of these controls, each evap also has a suction optimisation valve controlled via a Danfoss EKC 361 which I have been told is also set to -5 degrees lower than the room set point. This controller does have the S3 probe fitted. I will measure the pipe runs today to give you an understanding of the size of the system.

Defrosts;
When I took the reins on this site the defrosts were scheduled in to each controller (even on the banana sheds where the store temp is 14 degrees!) The schedule for the system in question here was every 6 hours for 30 minutes with a cut out of 15 degrees which is read from the S5 probe located inside the coil.

I thought this was way too many for too long, too frequently etc.. and the danfoss system we have (SC355 front end unit) is very clever and has a 'defrost on demand' function which uses the S5 probe to calculate if and when a defrost is necessary. I deleted the schedules a few weeks ago and adopted the defrost on demand. None of the evaps I tested it on had a defrost. I didn't know if this was a good or bad thing though as the oil will need heating to allow it to return??

All agreed I need help and am more than willing to get someone in to assess the system and control set up, I fear there are many issues with the design of the system that will be very hard and expensive to rectify but as mentioned earlier - the company who designed and installed it may be liable.

[Martin Davies]

Sorry 407A not C

[Grizzly]

Martin.

I suspect you need a "Glenn Moore!

Just out of interest what Bitzer comps are they?
Why has anyone not looked at why the oil carried over in the first place?
Correct me if I am wrong Guys, but pumping a system down does not necessarily remove the oil. It empties the evap of refrigerant.
Creating bubbles and generating heat exchange / load with the resultant increased gas flow does remove oil however.
Grizzly

[Martin Davies]

Bitzer model is 6H-35.2Y-40P

[Grizzly]

Thanks for that Martin.
What oil is being used?
Grizzly

[redroge]

Sounds like fitting oil separators is the only answer as for getting the oil back switch off the compressor and add hot gas to the suction once the pressure is fairly high shut off the hot gas and start the compressor this might help to bring the oil back, like others have said you need higher pressure/velocity to get the oil back

[Martin Davies]

The oil is BSE32, there is an update if anyone is interested.

We heard back from the design/install company today on their thoughts of why it happened. This is what they said

"In my opinion the only way you can have excessive pressure in the coil is if both the expansion valve and ICM valve both shut down trapping refrigerant and oil in the coil, if then the heaters were to come on either initiated by defrost or heating cycle the refrigerant gas would boil and its pressure increase, without being able to release this pressure through the suction valve, the pipe work will likely burst.

Therefore I can only conclude that both valves were closed, trapping the refrigerant.

Our control philosophy would not allow this to happen, and the ICM should either be modulating or fully open when on heating or defrost.

We have installed this control throughout the stores over the last 3 years and in that time have never encountered this problem".

After reading this I thought I would test the theory and go check the valves opening position whilst putting the evap into manual defrost. The system is connected to the server and so I can control it through my iPad. The ICM valve has a digital display on the top to show opening degree. When I set manual defrost the valve will fully close - the opposite to what the email had said. After this I check all the evaps on the system (11 including the currently switched off evap) They are all the same - closed during defrost.

This then means if the evap is completely saturated with oil and hits a defrost and both the EEV and ICM close shut the liquid, gas and oil mix is trapped inside. Obviously with heat from the defrost this mixture will expand and will want to move but can't!

[Grizzly]

Hi Martin.
I think you have identified why it went bang! Well Done!
There is still the question of the oil trapping but that is relevant to how the cooler control you describe been set up?
Someone has ****ed up the set-up of the ICM methinks!
And I think it's been happening for a long time. I would set a minimum opening asap.

Polyolester Oil is what you should have so no problem there then.
A good day at the office for you then Martin!
Grizzly

[Martin Davies]

Thanks, I'm learning a lot and quickly because I have to but enjoying it a lot too! My findings have been sent off to the design company so will wait to here back. I also have a consultant booked in for week after next to look over the system and produce a report for us.

[Martin Davies]

Grizzly - what would be an acceptable min OD?

[Grizzly]

Thanks, I'm learning a lot and quickly because I have to but enjoying it a lot too! My findings have been sent off to the design company so will wait to here back. I also have a consultant booked in for week after next to look over the system and produce a report for us.

Ouch! Light blue touch paper and stand back.
There is no better way of learning than getting involved.
Well done Rep point awarded for a good and interesting post!
Grizzly
Grizzly

[Martin Davies]

Thank you, Thank you very much :cool:

[Glenn Moore]

Hi Martin
I believe I know this job as I was involved in the selection of the Danfoss equipment used on this site. (I assume its full of seamen down there). The CC210 controls just give a digital GO signal to the EKC 316A +ETS expansion valves. The EKC 361 driving the ICM+ICAD motors is basically a stand alone controller acting as an evaporator temperature regulator. During defrost the coil gets warm and the S3 sensor detects this and forces the ICAD to open the valve (Why it is being closed is probably due to the DI on the EKC 361 being open circuited) this is a control set up error.
The EKC 316A does not need an S3 sensor if it is only being used as a superheat control . The 316A has a built in thermostat function which if switched ON (parameter r14) then will need the S3 sensor fitted. But in your case the CC210 does the thermostat function . In theory the ETS valves can act as both expansion valve and solenoid valve. As when the D1 contact is broken on the 316A the ETS valve is driven down on to its seat, and the small overcurrent drive maintains the seat tightness during the off cycle. , which is great but if the ETS motor bearings fail or wear over time and the motor fails then the valve will say open or partially open during the OFF cycle or Defrost cycle, so I always fit solenoid valves as 100% shut off , as ive seen liquid damaged compressors caused by the motor failing open a filling the compressor with liquid during the OFF Cycle.
The parts selected where for energy efficiency and product safety ie Low temperature fail safe (EKC361) Heat and thermostat control (CC210) EKC 316A superior superheat control.
I am very surprised by the situation but I never saw the wiring schematic to make sure that the controls inter reacted correctly and was never involved in the system commissioning , apart from the set up of the SC 355 monitoring system along with a colleague.
Some of the superheat settings you mentioned don't make sense at all and Im concerned that the ICM valve is forced to close rather than as should be forced to OPEN during defrost. This is a very Dangerous practice as to have set this up this way.

If I can guide or help at all in any way , but really I need a list of parameter settings for the Danfoss controllers to help determine where the root cause may be. Someone with no prior knowledge of the controls and there intereaction will be lost trying to sort this as the many safeguards for the product in the design have probably been changed to protect the innocent. Kr Glenn

[Grizzly]

Hi Martin.
I said you needed Glenn!
What's with the KR!
You will be saying OK Yah! Next.
Grizzly

[Grizzly]

Hi Martin.
I said you needed Glenn!

What's with the KR!
You will be saying OK Yah! Next.
Grizzly

[Martin Davies]

Hi glenn thanks for your reply,

Everything you've said makes sense and is basically what I've seen. It just took me up until today to realise the icm is being forced closed on defrost which above all is the main issue. I've tried to set a minimum opening degree (n33) but even after setting this at 10% it still made its way to 0% on defrost not sure why. I'm going to have to switch the EKC 361 controllers off tomorrow and prevent the icm from working at all.

I've been removing oil all day I'll try post a picture if I can figure out how?

The front end in this store is now a SC355 as I had it changed recently to match the rest of the site, it was originally a CS model which is built for convenience stores, which is obviously not right for the site.
13750

[Martin Davies]

But yes I would expect to see solenoid valves in place for the off chance the expansion valve decided not to fully close when requested, this may have to be adopted in the future once I've installed the new evap (3-4 week lead time)

[Glenn Moore]

Hi Martin
Please send the parameter settings for the EKC 316A controllers as this may be part of your problem . If the superheat settings are wrong or several other parameters then this will cause liquid overfeed to the evaps , this liquid will then return to the compressors causing the oil to foam and increase your compressor oil carry over rate. This can then overwhelm the oil seperators making them u/s Glenn

[Martin Davies]

Glenn, what I would love to know is the correct set point of both the EKC controllers? If the store set point is 4 degrees what should the set point be for both and what is the calculation behind it?

I've just seen your last reply about the parameters, I'll send the info to you tomorrow when I'm back in front of the PC

[PaulZ]

Hi Martin
I would be adding a pressure relief valve around the ICM. If an evap can be completely shut off as in your case it creates a very dangerous situation.
If you are running +4 room an air defrost is probably all you need, it might be worth shutting off the heaters and trying it.
The oil carry over is a big issue, I take it there is a separator and the oil return is working properly, no blocked strainer or line.
As Grizzly said you appear to getting on top of it and learning along the way.
Let us know when you resolve the problems.
Regards

[RANGER1]

It would be interesting to know how oil return system is set up & can it be proven to work at some stage.
Maybe oil stil no correct pressure, sump floats blocked etc.
Also any lines returning to sump that could pressurise it with hot gas or whatever.

Coalescer loose , missing.
Just thoughts to add to everyone else

[Martin Davies]

Good Morning everyone,

Yes each comp has an oil separator linked to the oil reservoir. Since I've been here the reservoir has been full to capacity and there have been no low comp oil fails, (obviously because of the amount of oil in the system) shame there isn't a high comp oil alarm.

However....the second pack which controls a different area of the same store has 3 comps and 1 of these is continuously tripping (the only inverter run comp in system) on low oil - even though the reservoir is almost full to capacity also. Now, I'm assuming from the previous comments there could be a blocked filter or line connecting the reservoir to the comps which could be causing the original problem. Instead of fixing this issue someone along the line has added oil every time the comp trips and along with the ICM closing problem that is a recipe for disaster - hydraulic lock, busting pipe and complete loss of refrigerant into the store.

Ranger1 is right, I need to test to oil flow from oil reservoir to oil regulator. Any help with this would be appreciated

[Martin Davies]

Glenn - The problem with not having an S3 sensor connected to the 316A is the front end unit cannot display a temperature so it looks like this;
13751

I've asked someone who you will almost certainly know in the Danfoss industry if it is possible to change the internal software of the controller so that the front end can show me either the superheat value or opening degree of the EEV instead of a generic value which is totally useless. This would also be useful for the 361 controller so that the user can see the opening degree of the ICM from afar rather than having to trek up to the top of the cold-store.

EEV Parameter settings;

13752137531375413755

[Martin Davies]

Not sure if anyone is still interested but a new update today after I've been playing around with the controllers all day!

The digital input from the CC210 controllers on ground floor up to the two EKC controllers in the roof space above the evaps is literally just an on/off relay. So the two EKC's are told when to power up and down if cooling is required or not/and when a defrost comes on. The design was meant to allow the ICM/ICAD to stay open when on defrost or when the store is at set point.

HOWEVER - as the digital input is just a single on/off relay it is not possible to have the EEV off at the same time as the ICM on - in the instance of a defrost. They two EKC controllers do the same thing at the same time.

I have now moved the control signal for the ICM controller - EKC361 to the common side of the relay so it is permanently on and now I am able to set the minimum opening degree to whatever I want and it actually works instead of completely closing when the signal is dropped.

The two controllers now work well together, ideal superheat is being achieved and the ICM will stay open at 10% during off cycle and defrost - allowing the oil to be drained from the evaps and back to the comps.

[Grizzly]

Your having a good week Martin.
It's nice when things go well is it not!
Now it will be interesting to see the actual oil carry over/ return.
I bet you will be oil draining for a while yet!

Now don't forget to assist others on the forum whenever you can.
Grizzly

[Martin Davies]

Yea good week, will be checking the oil levels tomorrow and probably draining more.

Yes I will help if I can, I'm still getting used to how it all works - how do the rep points work?

[hookster]

This has been a great thread and really enjoyed the updates Martin, been a hectic week for me so only just caught up on your scenarios.
Getting Glens saliva levels up to drooling levels again is fun to see! :D

[Glenn Moore]

Getting the grey cells working again. Been wracking my brains over this one as it was an overcomplicated control strategy hmmm. Anyway Martin the settings for the EKC 316A look OK , but from memory the control strategy is as follows. The Compressor pack controller runs the system suction pressure somewhere about minus 3 Deg C (3.5Bar) on R407A. This would give a room temperature of say minus 2 Deg C. The room temperature is controlled by the EKC 361 controllers driving the ICM evaporator pressure regulators to throttle the suction pressure at the evaporators to maintain approx. 4 Deg C . (EKC 361 Set point 4 deg C) via its S3 sensor.
The CC210 controllers are set approx 2 Deg C , with a small Differential.
The Defrost heaters in this case are not actually defrost heaters they are used to heat the room if the temperature drops below the 4 Deg C setpoint of the 361. The CC210 energises the heaters if the room temperature drops below 2 degrees C.
If the temperature drops below 4 Deg C the ICM valve should close to keep the temperature from falling further and damaging the product, if the temperature falls below 2 Deg C the CC210 should stop the EKC 316A and energise the defrost heaters with the evaporator fans running to bring the room temperature back up to the 4 DegC . As the temperature rises the EKC 361 detects the temperature increase and the ICM should start to open causing cooling to start again.
These controls had various inter locks holding bits ON or OFF. I never saw the finished electrical drawing or who set the system up so I am not surprised that it has problems .
The set up is not quite a conventional fridge plant as most of this was done via a consultants demands for belt and braces safety for the Bananas, so I would be interested as to how the plant is actually set up on each control.
Have you got the settings for the CC210, EKC 361 and the pack controllers cant remember if its the PC 530 or the later AK 730/840 type. But their settings will all have relevance to making a good plant or a bad one.

But as the other lads have said if the ICMs are being held closed and the coolers are filling with liquid as the ICM s open liquid will rush back to the compressors causing oil to be pum,ped around the system and then becoming trapped in the closed down evaps. These situations will vary with store loading etc.
The Defrost heaters being used to heat the rooms is due to the cold ambients around the docks area at certain times of the year Please send any further controller data so that I can advise further , Be careful what you change as it could affect something else in the system Glenn

[RANGER1]

Getting the grey cells working again. Been wracking my brains over this one as it was an overcomplicated control strategy hmmm. Anyway Martin the settings for the EKC 316A look OK , but from memory the control strategy is as follows. The Compressor pack controller runs the system suction pressure somewhere about minus 3 Deg C (3.5Bar) on R407A. This would give a room temperature of say minus 2 Deg C. The room temperature is controlled by the EKC 361 controllers driving the ICM evaporator pressure regulators to throttle the suction pressure at the evaporators to maintain approx. 4 Deg C . (EKC 361 Set point 4 deg C) via its S3 sensor.
The CC210 controllers are set approx 2 Deg C , with a small Differential.
The Defrost heaters in this case are not actually defrost heaters they are used to heat the room if the temperature drops below the 4 Deg C setpoint of the 361. The CC210 energises the heaters if the room temperature drops below 2 degrees C.
If the temperature drops below 4 Deg C the ICM valve should close to keep the temperature from falling further and damaging the product, if the temperature falls below 2 Deg C the CC210 should stop the EKC 316A and energise the defrost heaters with the evaporator fans running to bring the room temperature back up to the 4 DegC . As the temperature rises the EKC 361 detects the temperature increase and the ICM should start to open causing cooling to start again.
These controls had various inter locks holding bits ON or OFF. I never saw the finished electrical drawing or who set the system up so I am not surprised that it has problems .
The set up is not quite a conventional fridge plant as most of this was done via a consultants demands for belt and braces safety for the Bananas, so I would be interested as to how the plant is actually set up on each control.
Have you got the settings for the CC210, EKC 361 and the pack controllers cant remember if its the PC 530 or the later AK 730/840 type. But their settings will all have relevance to making a good plant or a bad one.

But as the other lads have said if the ICMs are being held closed and the coolers are filling with liquid as the ICM s open liquid will rush back to the compressors causing oil to be pum,ped around the system and then becoming trapped in the closed down evaps. These situations will vary with store loading etc.
The Defrost heaters being used to heat the rooms is due to the cold ambients around the docks area at certain times of the year Please send any further controller data so that I can advise further , Be careful what you change as it could affect something else in the system Glenn

Glenn do you think a simple ICS with a couple of CVP's & EVM would have done the same job.
Like you say seems very complicated.
As Paul Z mentions, a pressure relief around ICM would be the fail safe in current situation.

[Glenn Moore]

Hi Ranger
The ICM valve with ICAD was selected as the plant is controlled remotely but yes they would have worked but would need manual adjustment for different fruits. This plant is on the dockside and is not easy to access due to heavy traffic and so everything is centrally controlled an d monitored Glenn

[RANGER1]

Hi Ranger
The ICM valve with ICAD was selected as the plant is controlled remotely but yes they would have worked but would need manual adjustment for different fruits. This plant is on the dockside and is not easy to access due to heavy traffic and so everything is centrally controlled an d monitored Glenn

thanks fair enough

[Martin Davies]

Hi Glenn, I'm sorry but either a lot was changed after you selected the equipment or the person who actually installed/commissioned everything decided to change how it all works. The system has been set up as follows;

- Room temp set at 4 degrees for citrus fruit (this is minimum temp possible)
- Room temp is controlled via the cc210 sending a signal to the relay controlling the two EKC's
- The ICM controller EKC361 is set at -1 and has been since I've been here and the old bloke who 'showed me the ropes' when I first started who was from the install company said this as correct as it maintains the desired superheat in the evap.
- The heaters are controlled via the cc210 and due to a minimum allowable diff of 3 degrees (R36) will not activate until the store has got to 0.9 degrees. This is very poor design as by the time the store has dropped to this temp and brought the heaters in, the Testo alarm system has gone mad and the fruit will have frozen. As I said 3 degrees is the minimum value with the cc210 but on the newer controllers which I've just had installed in another store, (cc550) this value starts a 1 degree, which is a lot more reasonable.
- I would absolutely love to say the plant controllers are any model of Danfoss but unfortunately they are not. They are Mercury Pack Controllers - which are not connected to the network, nor the danfoss front end and so are not visible from afar or even up close! I believe to access the settings and values read by the controller I would need a laptop and a program and some idea what I'm doing! ha

Anyway as mentioned yesterday and checked this morning - the 'on' input for the ICM valve has been moved to the common side of the relay and a minimum opening degree of 10% has been added to each evap. Now when in off cycle or defrost, the EEV closes as it should and the ICM is either 100% open or a minimum of 10% depending on the value of S3. This allows the comps to effectively pump all of the oil and gas back, prevents oil build up in the evap and prevents refrigerant slugging.

[al]

Martin

Get Glenn those danfoss settings asap, compressors tripping on oil could be down to liquid flood back, guys add a "bit" of oil to overcome and suddenly you've a 100litres more than you need! Are oil seperators working? Checked suction and liquid line filters?

[Glenn Moore]

Hi Martin
Just to clarify the controls a bit. You say the the EKC 361 is set to -1 Deg C . The EKC 361 +ICM valve has NO relation to the evaporator superheat whatsoever , as the ICM valve is in the suction line between the evaps and the compressors. The ICM valve simply throttles the suction pressure inside inside the evaporator, by controlling the evaps pressure you control its temperature. This part of the system was to be the main temperature control as the ICM modulates keeping a constant air of the coil temperature.
The EKC 316A plus ETS valves control the superheat of the individual evaporators and that is their prime objective.
By setting the EKC 361 to minus 1, basically the ICM will be 100% open as it will never see -1 as the CC210 kills it at +4.
I Knew when this was designed unless they had a good commissioning engineer it would be a disaster, sounds like you had Clint Eastwood or the Sundance Kid commission it. If you have the wiring diagrams for the control panel I would like to have a swift look at them Glenn

[Martin Davies]

Hi Glenn,
I think I know where this has gone wrong but will triple check when I go back in and also send you some wiring diagram however I'm off for a week now. When I was playing around with the controllers and monitoring the values of both controls I noticed the S3 input which should be the air on to the coil appears to be reading the coil air off temp as if an S4 instead. This would make more sense of -1 set point. Either change in design or probe has been put in wrong place?

[Martin Davies]

Hi Al - I mentioned in earlier post that I've recovered a lot of oil from the pack so far I estimate about 15L that was not needed and this was due to the ICM closing during off cycle. However if what Glenn is saying was implemented and the EKC361 was getting its temp input from the S3 then theoretically it would be open during off cycle as the temp would be above 4 degrees - BUT the way it has been wired means both the EKC controllers are getting there on signal from a digital input off of the CC210 and so when the CC210 is in off cycle the relay to both EKC's is powered down and when that happens they both close shut even if a minimum opening degree is set.

[Martin Davies]

Hi Al - I mentioned in earlier post that I've recovered a lot of oil from the pack so far I estimate about 15L that was not needed and this was due to the ICM closing during off cycle. However if what Glenn is saying was implemented and the EKC361 was getting its temp input from the S3 and was set to 4 degrees then theoretically it would be open during off cycle as the temp would be above 4 degrees - BUT the way it has been wired means both the EKC controllers are getting there on signal from a digital input off of the CC210 and so when the CC210 is in off cycle the relay to both EKC's is powered down and when that happens they both close shut even if a minimum opening degree is set.

Glenn I can't stop thinking about what you said about the ICM having no relevance to the superheat control.... Surely the opening degree of the valve which is controlled via the air off probe is maintaining the superheat in the evap? The 316 uses the S2 pipe probe and transducer on the suction line between the evap and ICM to calculate the superheat so this means the two controllers are working together?? I'm really sorry if I have this wrong but if the ICM isn't controlling the superheat then what is?

It's my understanding that the 361 is set 5 degrees lower than room set point as this is the optimum air off temperature to achieve target superheat? Thus allowing all refrigerant to be boiled off before heading back to comp and flooding it. The 361 controlling the superheat like this allows the 316A to calculate the superheat and allow in as much refrigerant as required. They have to work together like this because they are only getting an on signal from the cc210 they are not directly controlling the room temp. Again sorry if my refrigeration theory is incorrect but I'm sure this is the way it's working. Can anyone else say if they think this sounds correct?

[al]

Martin

Not sure how many evaps are off the pack, but if the suction valve was closing on defrost, unless the coolers are all defrosting at same time then room temps must be all over the place?
From a super heat perspective, the suction transducer would be S2 with S1 being a probe strapped after the EEV, but am open to correction on that as it's a good while since i worked on danfoss aKV's.

Have there been many compressor failures?

[Martin Davies]

There are 6 evaps off the pack but each has its own ICM and each are separately controllable so 1 can be in defrost at a time. The EEV is calculating the superheat from S2 pipe probe and transducer both located on the suction line between the evap and ICM

[Glenn Moore]

Hi Martin
The idea of the control was similar to the older plant on this site. If you ignore the CC210 controls and concentrate on the Pack controllers, the EKC316A 's and the EKC 361's and the ambient temperatures around the stores summer and winter.
The pack controllers control the systems minimum evaporator pressure/temperature say at -4 Deg C by switching compressors on or off to match the desired system capacity requirements to maintain the suction condition at -4.
The EKC316A controllers driving the ETS valves with information from the S2 Sensor and the suction pressure transducer control the liquid injection into the evaporators and control the Superheat in the evaps at around the design set point of between 4 and 7 Deg K superheat. These controls try to operate the evaporators with maximum efficiency and lowest stable superheat.
The EKC 361 with the ICM/ICAD motor simply modulates the suction(evaporator) condition inside the evaporator. The pack is running at -4 Deg C so the EKC 361 modulates the evaporator pressure/temperature so that the air OFF the coil cannot drop below 4 Deg C (EKS 361 setpoint). At this time the EKC 316A is still controlling the S/heat between 4-7 Deg K.

During the warm months with the ambient higher than 4 degrees , the cold store will absorb heat through the fabric of the store , and the product respiration load etc, so the pack still runs some compressors keeping the suction at -4 C , the EKC 361's are running holding the evaporator condition up at 4 Deg C .

During the cold winter months the cold store temperature will fall below the desired 4 Deg C .At this point the EKC 361 controls will force the ICM valves to close trying to raise the store temp up to the design 4 DegC. But the ambient outside the store is still very cold dragging the in store temperature below the 4 Deg. The pack now switches the compressors Off. At this point the CC210 thermostats come into play , as the in store temperature plummets below 1 Deg C the EKC 316A controller is switched OFF and the Defrost heaters are now energised with the Evap fans still running.
As the temperature rises above the CC210 differential setting the heaters switch OFF , the EKC 316A is restarted and the EKC 361 starts to open the ICM valves. The suction pressure starts to rise above the set point of the pack controller and the compressors now start to cycle in, and so on.

The EKC 361 when it starts to throttle to close the ICM, this changes the pressure and the temperature of the evaporator the temperature S2 and the pressure converted to temperature (S1) of the EKC 316A begin to equalise to 0 superheat or slightly negative -1 superheat. This causes the ETS valve to be driven closed (No more liquid injected.)
Sounds complicated but is easy when you understand the demands of the system. As I said only myself and one other understood how it was designed to work but like the design for a racehorse its lost in translation and you get a donkey . Send me your Mobile and Ill text you my contact details Glenn

[Martin Davies]

If the 361 was set at 4 and was reading the air on, all of what you just said would make sense :) and I believe that's how it should be but as I said earlier whoever installed the probes has put them infront of the air off and so the 361 cannot be set to 4 as it would shut the ICM as soon as the evap started cooling as the evaporating temp is about 0. This must be why it is set to -1?? I really need you, the commissioning engineer and the electrician in a room together to sort all this out! My number is (phone number removed to stop the spammer, sent to Glenn via PM, Brian_UK)