dwm copeland

[Stevonz]

I'm a new member.
Has anybody had any experience with discus valve type copelands running on r404a on low temp application dx system. We have had more than one failure and have noticed the pins that locate the suction valves have flogged out the casting allowing the suction valve to move in a sideways direction. The suction valve ultimatley fails(terminal). This has happened on different blast freezers. Pumpdown operation. Poly oil.

[Renato RR]

Does valve look like they are "biten" or burned.Do you have some picture of felior.

Renato

[Peter_1]

Liquid slugging? The fact that the compressor is pumping R404a - you haven't said that, it was just additional information you gave us - has nothing tho do with the broken pins.

[Stevonz]

Liquid slugging? The fact that the compressor is pumping R404a - you haven't said that, it was just additional information you gave us - has nothing tho do with the broken pins.
i guess it could be liquid but would have to be repeated liquid floodback. The pins don't break they flogg out the compressor housing and become very loose.
I haven't seen this type of thing on the older refrigerants.

[Stevonz]

Does valve look like they are "biten" or burned.Do you have some picture of felior.

Renato

Sorry didn't get a picture. The valve ring show no signs of heat.

[monkey spanners]

Have seen suction valve pins fired through the valve plate leaving a shiney mark on the cylinder head (like it had been tinned with solder) due to liquid pumping. No use to you, but i thought i'd share it.

Cheers Jon

[taz24]

The pins don't break they flogg out the compressor housing and become very loose.



I don't think I have heard of the term flogg?:)
in what contex do you mean flogg?

cheers taz.

[Stevonz]

i guess being flogged or flogging is somthing that is normally associated with english rugby when playing the allblacks not compressors but what i mean is the hole that the pin is located in opens up considerably and the pin is free to move around in the hole.

[Below 0]

Hi Stevonz
I have seen what you describe many times.I worked on reefer containers for quite some time and found this to happen on r134a units.The compressor would run very hot and have a ticking noise associated with it, and of course, be slow to pull down.We would pull the compressor and remove head and find what you describe.On most occasions we would replace reed valves gaskets etc and return to service.More often than not this was done in the ships hold,on deck or somewhere inhospitable.If the damage was too bad then of course a compressor change was required.As to the cause,well this was always explained as liquid flood back by our compressor rebuilders.Me i am not so sure because on the odd occasion just one reed would be broken. If it was liquid there would have been more damage wouldnt there?My opinion is that it is caused by a number of things all adding up to culmanate in the damage described.On the compressors i repaired they nearly all had very dirty/acidic oil and Incorrect tx super heat.Some were even quite short of gas.I found that copelands dont like getting too hot, and down in a ships hold the temps often rose above 40C around the tropics.Anyway enough of my raving this is just some of the things i found and thought you might find of interest.
Cheers

[taz24]

I'm a new member.
Has anybody had any experience with discus valve type copelands running on r404a on low temp application dx system. We have had more than one failure and have noticed the pins that locate the suction valves have flogged out the casting allowing the suction valve to move in a sideways direction. The suction valve ultimatley fails(terminal). This has happened on different blast freezers. Pumpdown operation. Poly oil.

I now know what you mean about flogging.
Thankyou for relateing it to us getting beaten by the All Blacks:)

I am still confused though when you mention the pins and then state that they were on a discuss comp.
as below0 explained about the R134a comps on the reefer ships they are assosiated with reed valves.
I'm not dim honest just slow on the uptake somtimes;)
Could you confirm if it is a discuss valve or a reed type. I have had a lot of experience with copeland comps with both systems and found that the discus ones were very reliable as long as the oil was ok. Even liquid coming back short term should not be to problematic. I found the oil was the biggest culprit for most of the woes with the comp. one thing they don't like is long term liquid flooding back. It flushes the oil and refrigerant does not lubricate very well.
Not much help to you maybe:)

Is it one comp or a series of them?

Cheers taz.

[old gas bottle]

hi matey,have they got suction accumilators fitted!! i think there a must on blast freezers due to the low temp application,realy need a oil sep to go with it though, not had any problems like your s unless it has been flooding back.

[Stevonz]

i have seen it on discuss type valves only. i aren't working on that many copelands on blast freezer applications so don't have too many comparasons to make. in one case the compressor is a singe 30hp. The other cases have been two 60hp connected to common suction so three stand alone blast freezers. All compressors have danfoss mp55 oil failure protection and have no history of oil failure tripping. All have suction accumulators. i could say the accumulators are not overly generous in size on the larger units.
i was mainly curious to know if this has been seen as a common type of failure with the valve pins.

all your ideas are appreciated.

Cheers Stevonz.

[winfred.dela]

This has happened on different blast freezers. Pumpdown operation. Poly oil.


Hi Stevonz and welcome to RE forum.

Thanks for sharing your experience.

Have designed and build a couple of Tuna fish fillet/loins blast freezers with 30KW motor for minus 55C Tevap (two stage semi) and minus 35 Tevap (single stage open & semi).
I have not come across these type of problems. I usually use Bitzer though.

My questions are:
(1) Are these compressors single stage or 2 stage?
(2) Does the system have complete components: oil separator, suction accumulator, pressure reducing valves etc.?

Would like to really know why this happens and learn from it.
Is this due to compressor make/design/brand not being applicable?
Or is it due to system incomplete/design components?

Regards
Winfredy :)

[Stevonz]

i have heard from a company that specializes in overhauling copland semihermetics that they have seen quite a bit of this. Apparently the latest models have changed the way the suction valve is located. i understand it is now attached to the valve plate.

[donhoban]

i have heard from a company that specializes in overhauling copland semihermetics that they have seen quite a bit of this. Apparently the latest models have changed the way the suction valve is located. i understand it is now attached to the valve plate.

As a former distributer we had several instances of this, where the pins became loose and effectively the entire compressor was then knackered - you can't fit new plates or heads without these locating pins. I thought they's solved this problem when the switched form the A to B 3-cylinder Discus, and to the '4' gen 4,6-cylinder models.

Having said that, overall the Discus models were and are very good compressors, just try not to get liquid in them!