Vibration

[torque]

Hi Guys

A customer of mine has recently carried out a refrigerant retrofit from R22 to R422D and is saying since the retrofit was completed he has noticed increased vibration at his compressors.
Has any body encountered similar problems and if so other than fitting vibration eliminators what is the solution, if any ?

[Grizzly]

Hi Torque.
I have heard that when swapping over to 422D the Head Pressures are higher and duty drops!
Could the potential extra load have an effect?
Grizzly

[hookster]

Hi Torque
Has system been overcharged on retrofit as there is usually a reduction with R422D. Or as Grizzly says above. The oil return should be checked is compressor suffering? R422D has a higher mass flow it would be worth collecting some operating data on the system pressures, temperatures, superheat etc. to make sure system has been commissioned for new refrigerant.


There is no such thing as a direct drop-in replacement!

Note:
R422D has a GWP of 2729
From 1st January 2020 the use of F Gases with GWP > 2500 for service will be prohibited for systems which
contain more than 40 tonnes CO2 equivalent. This is approximately 18Kg of R422D

[torque]

Thanks for coming back to me with your thoughts.
I was thinking along the same lines with the change in operating conditions, mass flow and density of R422D opposed to R22.
Unfortunately I do not have the answers to some of the questions you have asked.
Before the site services team changed the refrigerant, I was only asked to carry out major overhauls of there Sabroe compressors.
If any base line data was recorded I have not seen it.
I was only called back into site to check over one of the compressors to see if there was anything a miss with my rebuild. Once proving all was ok mechanically with the machine.
They have now asked me to find out why they are experiencing increased vibration and what can be done to reduce it.

You will see from the attached photo of a repair on a cracked weld on top of the oil separator carried out by the customer.

I have suggested discharge line vibration eliminators but this is attempting to deal with a problem not addressing the route cause. Vibration.jpg

[Glenn Moore]

Hi Torque
The comments from Grizz and hookster are both relevant, as with a retro fit.
R422D has been found to lose between 20 to 30% capacity which Ive experienced several times. The TEV is not compatible with this refrigerant, and most companies also change the oil from mineral to POE as standard due to suspect oil return problems. To recover this capacity loss ive had to fit electronic expansion valves which can be programmed for operating with this refrigerant which tends to bring the suction condition back to where it was prior to the retro.
As the lads have said this gas has a different mass flow pressures etc, so this may well have change the natural frequency of the gas flow and increased the pressure pulsations in the system. From the photo it looks like you have fitted a new oil seperator to this system , where the out let pipe weld has fractured. I can tell you that any vibrations via the compressor are being transmitted into the seperator and the weld repair will fail again unless the problem is rectified. From the photo I cant see how the seperator is mounted but i assume it is solid mounted to the floor. You could try adjusting the expansion valves to see if the superheat can be controlled better and if the increase of the suction pressure improves the level of vibrations. Also check that the unloading sequence on the compressor is as design as this could also cause mechanical vibrations as against gas pulsations, both of which can be distructive Kr Glenn

[RANGER1]

Torque, assume you have checked base, compressor & motor hold down bolts.
Could also check coupling & alignment as well as pipework bracketing (maybe loose or broken).
Also assume you checked unloader operation & bumper clearance!
On a machine like this can't see why vibration would increase unless something wrong like above.

What rpm in motor?
Did you check unloaders & bumper clearance with plug all the way in?

[Grizzly]

Cannot see a non return valve in that discharge line Torque.
Is there one out of picture?
Have you checked the working levels of you refrigerant only pulsing gases will set up very destructive vibrations.
As we have discussed before on the forum.

Which is were many above are going / been..
Have you considered the increased compression from you servicing the comp?
Which is again only repeating what has already been said.
Grizzly

[hookster]

All of the above are good relevant checks, I have also experienced a vibration on an SMC being transmitted from run out of the motor bearings under load. Have you checked drive coupling for correct assembly after overhaul?

Take a picture of the interconnecting discharge lines if you can?

[Gaz22]

Hi Torque
Has system been overcharged on retrofit as there is usually a reduction with R422D. Or as Grizzly says above. The oil return should be checked is compressor suffering? R422D has a higher mass flow it would be worth collecting some operating data on the system pressures, temperatures, superheat etc. to make sure system has been commissioned for new refrigerant.


There is no such thing as a direct drop-in replacement!

Note:
R422D has a GWP of 2729
From 1st January 2020 the use of F Gases with GWP > 2500 for service will be prohibited for systems which
contain more than 40 tonnes CO2 equivalent. This is approximately 18Kg of R422D

Danfoss site states that Servicing systems with 1,3kg or more R404A will be banned
from 2020.
Replacment refrigerant for supermarkets at the moment is r407f which has gwp of 1824
The only bad thing is that it has a temprature glide of around 6c compared with r404a's 0.5c

[Magoo]

as per all the above, any increase in compression ratios will accentuate any coupling alignment deviations.
Get coupling lazer aligned to be sure as to eliminate that possibility. Do a cold alignment first and re-check as operational/ hot alignment.

[torque]

Thanks for all your input.

Compressor

The comp had a major overhaul and as part of that the motor / compressor was laser aligned before been put back into service.
Due to new main bearings and replacement crank been fitted all clearances have been checked and are within tolerance.
I am currently waiting for prices for new vibration mounts for the skid.

By the looks of the oil separator on the unit, non are original supply. Mounting of the separator is not very substantial either. ( Not Sabroe Spec )
The discharge pipe work is all steel,well bracketed and there are no NRV's fitted !!!.

System

I suspect the problem to be more a system issue than a compressor fault, I will contact the customer to suggest they check out the points raised that are associated with the change in refrigerant.
Even though the suction / discharge pressure appears to be stable, there was a distinct audible change as though they are experiencing gas pulsation.

I will keep you informed and give feed back.

Thanks again

[chemi-cool]

Vibration in that size compressors is usually from faulty discharge or intake valve or a damaged rod inside.

If the oil is clear, I would go to see how the valves are doing in all 3 heads.

[torque]

Hi Chemi

That's what the customer had me back to site for in the first instance, to check over the compressor and I found nothing mechanically wrong with it.

[RANGER1]

Thanks for all your input.

Compressor

The comp had a major overhaul and as part of that the motor / compressor was laser aligned before been put back into service.
Due to new main bearings and replacement crank been fitted all clearances have been checked and are within tolerance.
I am currently waiting for prices for new vibration mounts for the skid.

By the looks of the oil separator on the unit, non are original supply. Mounting of the separator is not very substantial either. ( Not Sabroe Spec )
The discharge pipe work is all steel,well bracketed and there are no NRV's fitted !!!.

System

I suspect the problem to be more a system issue than a compressor fault, I will contact the customer to suggest they check out the points raised that are associated with the change in refrigerant.
Even though the suction / discharge pressure appears to be stable, there was a distinct audible change as though they are experiencing gas pulsation.

I will keep you informed and give feed back.

Thanks again

Out of interest, what was wrong with old crank.
Was it a genuine one you replaced it with?

I would have thought you would have to try pretty hard to damage one!

All the Sabroe's I have seen, from memory, the discharge leaves from the side of the oil
separator, which is mounted solidly off compressor base.
Having no non return valve on oil separator should be noted strongly for your protection.

You could also run motor separate to make sure it run smooth.

Trouble is it sucks up all your profit!

[chemi-cool]

Hi Chemi

That's what the customer had me back to site for in the first instance, to check over the compressor and I found nothing mechanically wrong with it.

If there was nothing wrong with it, it wouldn't be vibrating....

[torque]

Hi Ranger

I carried out major overhauls on four Sabroe SMC 108 on this site. All are 1995 machines and 3 out of the 4 required replacement crank shafts.The fourth had the crank undercut and over sized bearings fitted.
All Parts supplied and fitted were genuine Sabroe parts.
Looking are some of the things I came across on stripping these compressors, they have suffered from poor maintenance in the past and limited resources due to some non genuine parts been fitted.

Good point about the oil separator pipe configuration. I never paid much attention until you mentioned it.

I will see if I can return to site and check the model numbers of the oil separators.

Chemi

Having worked for JCI for a number of years and knowing our own compressor models and having considerable experience on the SMC range I am confident there is nothing wrong mechanically with this machine.

[RANGER1]

Hi Ranger

I carried out major overhauls on four Sabroe SMC 108 on this site. All are 1995 machines and 3 out of the 4 required replacement crank shafts.The fourth had the crank undercut and over sized bearings fitted.
All Parts supplied and fitted were genuine Sabroe parts.
Looking are some of the things I came across on stripping these compressors, they have suffered from poor maintenance in the past and limited resources due to some non genuine parts been fitted.

Good point about the oil separator pipe configuration. I never paid much attention until you mentioned it.

I will see if I can return to site and check the model numbers of the oil separators.

Chemi

Having worked for JCI for a number of years and knowing our own compressor models and having considerable experience on the SMC range I am confident there is nothing wrong mechanically with this machine.

Thanks Torque,
Have you checked all hold down bolts etc.
Sometimes if you go around package checking for vibration, using you finger against areas that can be affected like
compressor feet to base
motor feet to base
base to plinth
number of hold down bolts base to plinth (should be at least 3 per side)
in between bolt holes base to plinth
mounted solid on plinth, no gaps, as can act like a trampoline
soft feet on compressor & motor causing tension on all components.

You are obviously experienced so only giving ideas.

Also is discharge pipe piped so to rigid (see Sabroe manual) direction changes & length of pipes to give flexibility.
They are all belt drive?
Are they all vibrating, or only one with broken pipe on oil separator?

You would have to admit all those new cranks & wear is extremely abnormal on a Sabroe!