broken crankshafts

[just chilling]

HI Guys.

i am interested to find out if many of you have had broken crankshafts on your list of problems to solve?

for now i do not wish to name the machine as i do not believe that is fair or proffesional.

the system in question has suffered approximately 6 failures over a twenty year period.

not all failures have been accompanied by piston and valve plate assembly failures.

the machine is belt driven open drive on R22 marine installation one run and one standby configuration. no1 comp closest to suction accumulator has suffered 4 failures and no2 comp a little further down the suction line has had 2 failures.

the system presently has another failure(no6) and the crank is broken clean in half midway along its lenghth.

has any one seen a similar scenario?

[monkey spanners]

I've not seen any broken crankshafts, but have seen many broken con rods and smashed valves.
These have all been accompanied by either a lack of oil or oil dilution in the sump or liquid slugging, either oil or liquid refrigerant returning due to poor system design, faulty metering devices or low refrigerant charge.

These have all been in small 5hp and under machines, i know many of the bigger compressors such as i suspect you are running have recommended sevice inervals for valve plates etc.
Maybe worth getting a report done on the old compressor to diagnose the root cause of the failures.

[chemi-cool]

My last broken crankshaft was in a 60 hp open drive Vilter.

The poor machine had a flood back, every thing was broken inside, rods, crankshaft, intake valves, head covers had cracks on them.

Flood back is the worst damage to the internal parts

Was the crank case heater on?

Is there any procedure of changing from one compressor to another?

Did it happened during regular work or only when changing between the compressors?

Is the suction valve kept close when on compressor is at rest?

[just chilling]

Chemi cool

hi thanks for your response. I am going to attend the vessel again next week and travel with it for a period. presently i believe change over from lead to lag is done manually. so an operator should be present during start up i have already put heaters on my list of things to check. suction valve closed at rest is a good point but the failure would have been on start up. i think the failures have occured when machines are unattended?

[just chilling]

monkey spanners.
thanks also for the reply. this is a fairly large system i do suspect the fault lies with the system some how. but i am open to new ideas i do not want to give away all my ideas in a hurry. as they my taint other peoples ideas.

[chemi-cool]

Working or standby, crank case oil temp should not go below 35°C.

Start up is the worst time for any compressor, especially after long standby, low body temp, no oil on the bearings, cold liquid streaming in.

Most failures occurred on start up.

If you keep the suction valves closed and open them very slow at start up, you will help the poor machine oil itself and get some heat from the friction as there is no electric motor to heat it.

Can you give some more details of the system? working temps, refrigerant, ambient?

[mad fridgie]

Do you have oil level/pressure protection.?
Do you clean oil filters?
Presume yes to both.
Is the comp marine rated (deep sump)?
Being marine it is likely that you could be getting some liquid carry over out of your suction pot (Acc) as the boat bobs around.
Add a second suction pot (does not need be large) to protect against occassional carry over

[Jase]

Probably the chief engineer has been tinkering with a few things when the ship is at sea.
They do like to adjust TEV's so it may be that there is liquid carryover to the comps.
What's the compressors serving? Galley coldstores?
Are there oil separators fitted? May be that the float is a bit iffy and whilst the comps are off on temp/defrost, the comps may be cycling on/off by the LP as the separators could be passing.
Any problems with power supplies on board? Could be problems with phase rotation.

regards,
Jase

[just chilling]

I join the vessel on friday and sail with it for a week, during the next week we shall observe the system in action. you have raised a few more items for me to check that were not on my list of things to check. so many thanks for that. I shall write back I rerurn. but if you have any more ideas before i depart friday then please share them with me.

many thanks just chilling

[alan wolf]

Hello

Just 1 sugestion to back up point that TEVs get abused, Can system not be pumped down prior to changing compressors?

Regards
AWW

[Mark II]

Just Chilling,

I went up to look @ a vessel a few years back with a similar problem..
Someone had fitted a Carel IR32 to the scallop room. The room was on hot gas defrost & the control was set to Hot gas defrost. Problem was: the compressor contacts were wired to the liqiud solenoid.. Standard pumpdown set up / In this case to just activate & de-activate the freezer coil as the compressor ran continous.. Because the defrost was set for Hot Gas, the liquid solenid would remain energised during defrost & smash the occasional compressor..

I don't think you need to worry about protecting the Manufacturers identity. It wouldn't matter what was in there they'd be smashed to.. Sump heaters are a biggy & there should also be non returns on both discharge lines..
Good Luck.. Hope you get some fishing in

[just chilling]

chemicool and mark11. thanks for all ideas. for chemicool the system is the HT or posistive temp rooms, compressors and condensers are located on 1 deck and some bars as high as 12 deck. some of the remote bars have been removed from the system during succesive refits, leaving dead legs that can log up with oil or liquid refrigerant. the owners have been advised this can be dangerous. the LT/ negative temp side is operating on a different compressor model and has never had crankshaft failures.
as already ststed the fridge plant is on 1 deck and the port main propeller shaft runs close by. shipping manouvres in and out of port may be causing bad vibration?
the defrost one from mark11 needs further investigation. that is now on my list of checks to be made.

[just chilling]

found a very likely contender for the broken crankshafts this week on the ship. 10 years after the ship was built a DX fan coil was fitted into the adjacent workshop. it has been tee'd into liquid line and tee'd into suction line for sump oil cooler. when staff left the workshop the fan gets unplugged via ext lead. liquid ref still races through as no solenoid fitted. floods accumulator and superheat drops from 8k to 1 k in about 30 mins.

thanks for your ideas. Just Chilling

[Jase]

found a very likely contender for the broken crankshafts this week on the ship. 10 years after the ship was built a DX fan coil was fitted into the adjacent workshop. it has been tee'd into liquid line and tee'd into suction line for sump oil cooler. when staff left the workshop the fan gets unplugged via ext lead. liquid ref still races through as no solenoid fitted. floods accumulator and superheat drops from 8k to 1 k in about 30 mins.

thanks for your ideas. Just Chilling

Ah! These bespoke systems

Jase

[Magoo]

Good result, but why did you not live the problem ten /what ever crankshafts ago.
magoo