Sabroe HPC 106 on CO2

[Dober49]

First things first hi all,
Now down to business, I've been looking after fridge systems for 25 years, at the moment I look after only one site, which is of a reasonable size consisting of 2 Stal mini screws S24 and a R5 MK2 for the vertical scrape coolers. 1 frigoscania plant with a Sab 163 hf and a CO2 plant with a SMC 116 e and 2 HPC 106s's both suppling cooling for 2 Samifi's plate freezers. A coldstore with 2 bitzer screw on NH3 and A/C for the production area being supplied by 2 Grasso recep's. I took part in the commisioning of the the CO2 plant while working for York and to be honest was never overly impressed with the plant. The oil recovery was always an arse on the CO2 side. I have since modified and has been proven to be ok for the last 8 months, plus other minor problems I've had to sort. The plant is now about 2 1/2 years old and since being employed by the site I've kept on top of all the servicing. First I carried out an inspections on all of the comps, a top end service and an oil change on the NH3 comp after finding 3 broken suction valves and numerous valve spring broken. After completing the oil change and top inspections on the CO2 comps everything looked in order. Well I thought, today after being able to shut the plant down I took the opportunity to carry out a oil filter change and top end service on the No1 CO2 comp. All was going well untill I took the last valve out to find mild pitting in the piston's crown, thinking a suction valve was broke but no, so I pulled the liner out to find the rings shattered, plus the ring grooves on the piston looked like they had melted in a fuuny way. Being curious I pulled out all the other liners to find every single piston ring had shattered. I mean each ring in about 6 or 7 pieces, no valves were broken not even a spring, all the liners are ok except for the melted one. York had previosly replaced a comp due to failure, not this one though. I was just wondering if there was anyone out there that has had much to do with HPC106's comps on CO2 and there experiences of them.

Cheers for looking Dober49.

[Dober49]

Hi all again
Looking into it my basic conclusions are, that the discharge limits are set to high resulting in high discharge pressures. Due to the nature of the application, basicaly the site have been putting to much product loading on to the plant. At commisioning York run the plant at -10 condensing on the cascade cooler, I did lower this to -18, at the time to save on energy. After looking at things I see this should be the norm. At the moment discharge limiting is at 33 barg and the high alarm is at 35 barg. I think I'll be lowering this to 27 barg limiting and 30 barg on the high alarm to save the compressors from this happening again.
Any additionaly info would be greatly recieved.
Cheers Dober49

[Andy]

Hi all again
Looking into it my basic conclusions are, that the discharge limits are set to high resulting in high discharge pressures. Due to the nature of the application, basicaly the site have been putting to much product loading on to the plant. At commisioning York run the plant at -10 condensing on the cascade cooler, I did lower this to -18, at the time to save on energy. After looking at things I see this should be the norm. At the moment discharge limiting is at 33 barg and the high alarm is at 35 barg. I think I'll be lowering this to 27 barg limiting and 30 barg on the high alarm to save the compressors from this happening again.
Any additionaly info would be greatly recieved.
Cheers Dober49

Hi Dober

It is the general accepted that Co2 recips need a 10000 hours overhaul each year, all but a shaft out, shell bearings and piston rings along with piston rings.

If this is carried out each year the compressor will run well.

The Co2 is a very dry refrigerant causing frictionwearing rings and linners quickly.

Also the high pressure causes a lot of load on the bearings, so they need changed at a shorter interval.

Hope this helps.

Kind Regards Andy

[Dober49]

Hi Andy
Thanks for that, i'll be keeping a closer eye things from now on.
The only thing that concerns me, is that it looks like the piston ring grooves worn down causing the rings to shatter.
I can only think of high discharge pressures causing this or liquid but I know thats not the case, i've spoken to sabroe who will be coming back to me with the correct spec for this comp.
As I said before I havn't got a great confidence in the york office I was dealing with.
Heres a little pic.
Note the groove wear.
By the way want would you call excessive discharge pressure on CO2 plant ?