Mechanical admissible gaps

[Chillermaster]

Hello everyone,
I have a 4G.2 (piston open type) Bitzer compressor with more than 15 years of intense work.
I am now retrofitting from R22 to R407c and i observe a gap between shaft and main (front) bearing of 0.20mm.
Do anyone know if this gap is ok?
Where can i find literature about machanical gaps for Bitzer compressors.

Thanks.

[The Viking]

Not sure where/how you measure this gap.

But generally there shouldn't be any gap what so ever between the shaft and the bearing.

Good practice when you retrofit these old beasts is to always replace the bearings and seals.
Especially when going from old mineral oil to modern syntetic oil, Bitser's old shaft seals didn't like syntetic oil and would start to disintegrate after a few days or weeks with syntetic oil.

[Josip]

Hi, Chillermaster

Hello everyone,
I have a 4G.2 (piston open type) Bitzer compressor with more than 15 years of intense work.
I am now retrofitting from R22 to R407c and i observe a gap between shaft and main (front) bearing of 0.20mm.
Do anyone know if this gap is ok?
Where can i find literature about machanical gaps for Bitzer compressors.

Thanks.

assume you are speaking about axial clearance ... it is possible to adjust this clearance with different gasket thickness ..

http://www.bitzer.de/eng/productservice/p3/470

then go to document Maintenance Instruction KW-520 ...

http://www.bitzer.de/download/downlo...3.pdf&ccode=DE

hope this will be of some help to you....

Best regards, Josip

[Chillermaster]

Thank you both by your quick reply.

Josip,
Is not the axial clearance, thanks. I already see the literature you kindly advised.
The clearance i messure is when i try to move the crancshaft up or down. Between the bearing bush and cranckshaft is there a gap of 0.20mm

I need to know if bearing bush and cranckshaft are ok or need to be replaced. I think it's all OK but i rather to be sure.

I mean literature about the cranckshaft OEM messurements and admissible clearance.


The Viking,
I always change all o'ring or rubber seals for new ones on retrofits. The old ones don't like the new syntetic oil.


I hope have made me understand, sorry my english.

[RANGER1]

Until someone finds correct measurement, clearance sounds on the high side of things.
Do the parts appear worn & what is the journal or bearing size.

[Josip]

Hi, Chillermaster

Thank you both by your quick reply.

Josip,
Is not the axial clearance, thanks. I already see the literature you kindly advised.
The clearance i messure is when i try to move the crancshaft up or down. Between the bearing bush and cranckshaft is there a gap of 0.20mm

I need to know if bearing bush and cranckshaft are ok or need to be replaced. I think it's all OK but i rather to be sure.

I mean literature about the cranckshaft OEM messurements and admissible clearance.


The Viking,
I always change all o'ring or rubber seals for new ones on retrofits. The old ones don't like the new syntetic oil.


I hope have made me understand, sorry my english.

No problem, all clear ...


I do not know for this compressor but 0,2 mm for me sounds toooo much ...

hope some member will come with exact values ...

Best regards, Josip

[Grizzly]

Hello everyone,
I have a 4G.2 (piston open type) Bitzer compressor with more than 15 years of intense work.
I am now retrofitting from R22 to R407c and i observe a gap between shaft and main (front) bearing of 0.20mm.
Do anyone know if this gap is ok?
Where can i find literature about machanical gaps for Bitzer compressors.

Thanks.

Hi Chillmaster.

If my cross calculation is correct then you have approx. 8 thou clearance on your crank journal bearings.

Way to much, after 1,5 thou the oil surface seal between two machined surfaces, cannot be guaranteed.
Irrespective of bearing size.
I would recommend fitting of oversize bearings and a crank regrind.
I have rebuilt recips where you could literally wobble the crank up and down. At a guess the oil galleries etc
are partially clogged giving sufficient oil back pressure to keep the comp going.
If you clean it up and re-assemble then it won't like it!

Recips plod on for ever, but eventually the need some TLC as well.
Good luck Grizzly

[Chillermaster]

Meanwhile I've have contacted Bitzer hoping they can help me someway.

Grizzly,
Thank you for clarification.
On my company we only use new parts to ensure a good job and closest possible to the perfect compressor functioning.

Thank you again for your help.

[RANGER1]

Please let us know, my guess is 0.08 to 0.11mm.
max 0.14mm.
Any other calculated guesses?

[Chillermaster]

Eh he, Bitzer reply:
"Clearances for such parts are only for internal use and I cannot communicate them."

But advise to change cranckshaft and bearings.

I think I'll have to buy the set if I want to know what I need.

[RANGER1]

Rule of thumb is 0.001" to 0.0015 per inch clearance for each inch of journal size.
or approx 0.025 to 0.0035 mm per 25.4mm.
If the crank looks good might just be bearing worn, if not both journal & bearing could be worn.
Bitzer may have undersized bearings, but I doubt it, would have to be aftermarket.
Hardchrome journal is one option.

[Chillermaster]

Ranger1,
Thank yo for your reply.
This clearance is more in line with what I think for new compressor.

[GHAZ]

hi before you open the compressor ,what was it oil pressure ok ,if so then there ok,but any way the crank size on N D end is "1.770"-"1.768 and on the drive end is "2.756"-"2.754". change the main oring inside the suction housing and on the oil pump cover,sight glass oring,and the shaft seal internal oring , any problems lets us know.

[Chillermaster]

Sorry for my late reply.
GHAZ, I'm not sure of oil pressure value. But I never observe abnormal values and the equipment as an oil pressure differential switch attached who never disarm, so I assume that the oil pressure is ok.

I will check the cranks measurements you indicated.
Regarding the O'rings matter, I usually change all them on retrofits. But I am not sure if they are the correct ones. Can you tell me the correct material built of O'ring for R407c, R404a, and similar mixtures?

Thank you in advance.

[GHAZ]

The orings you need are viton 75

[Chillermaster]

Have you tried it yet?
Because my supplier says that the ester oils are aggressive to viton.

Thanks.

[GHAZ]

I've use viton orings all the time on ester,alkaline,mineral, oils

[mbc]

In our work shop we repair
Between the bearing bush and crankshaft is 0.006 mm to 0.008 mm
between connecting rod and crankshaft is 0.005 to 0.007
for oil pressure check gear of oil pump and should be loose shaft of oil pump.
hosing of gear should be clean and smooth surface
check oil pressure check value and also casket of oil pump
after you repaired ---start Comp. for 2 minuets with second hand oil ((should be clean )) and measure oil pressure then clean up oil filter and change the oil with new one.
for cleaning do not use fibers fabric and cloth .
in old comp. rotation is important. ((DWM & BITZER ))

[Chillermaster]

I've use viton orings all the time on ester,alkaline,mineral, oils

Thank you GHAZ,
I will now test a viton silicone coated o'ring, my supplier advise, at the oil pump cover to be easier to change in case of a failure test.

In case of failure test will test a silicone one like you mean.

[Chillermaster]

In our work shop we repair
Between the bearing bush and crankshaft is 0.006 mm to 0.008 mm
between connecting rod and crankshaft is 0.005 to 0.007
for oil pressure check gear of oil pump and should be loose shaft of oil pump.
hosing of gear should be clean and smooth surface
check oil pressure check value and also casket of oil pump
after you repaired ---start Comp. for 2 minuets with second hand oil ((should be clean )) and measure oil pressure then clean up oil filter and change the oil with new one.
for cleaning do not use fibers fabric and cloth .
in old comp. rotation is important. ((DWM & BITZER ))

Thanks for your data and advise.
All care with impurities are taken usually on my work shop too.

I will consider your, and all of you, instructions on assembling process.

Thank you all.