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DHP
28-10-2014, 01:24 AM
Hi,

This is my first thread on here although I have been a member for a few years.

I work for a company in Australia that services mechanical seals. I deal with all makes of compressors from Grasso, Mycom, Stal and Howden to name a few.

Over the years we have experimented with a few different o-ring materials. We generally use neoprene, super neoprene from Parker to be exact. We still find the o-rings take set and is the main cause of premature failure of the seal.

We find Grasso compressors to be the most problematic. Recently, one of our clients had 2 failures within 24 hours! Anhydrous Ammonia and Suniso mineral oil were being used.

I would like to get peoples opinions and experiences with o-ring materials.

Also is there known issues with Grasso compressors that affect the performance and life of the seals? Could there be a reason they run hot?

Thanks in advance.
Dean.

Magoo
28-10-2014, 02:51 AM
Hi DHP.
welcome to the forum. Your experience with o/rings etc.. will be invaluable.

RANGER1
28-10-2014, 03:59 AM
Dean, how hot are they running?
Ask what oil temp is, should be around 50 deg C
Some stationary faces do not have anti-rotation
pin, if "0"ring not the right size, could spin in housing.
We use "Kalrez" in problem seals or in plants very isolated.
They are expensive, but cheaper than having to do it twice.
A lot of Euroean stuff, SAbroe etc use HNBR.

DHP
28-10-2014, 04:31 AM
Thanks Ranger1. We modify the OEM seals to use a pinned stationary on the Grasso's but its up to the client to fit a pin to the housing. We also machine the o-ring grooves in the rotary to take an imperial BS size o-ring. We did use use Kalrez on one problematic compressor in the past. The boss doesn't want to use Kalrez because of the cost factor. There is nothing more frustrating than having a seal let go because of o-rings that cost under $10 each. If it was up to me I would certainly go the Kalrez way.
Our next step is to use Parker grade N1195 or N1173 HNBR and see if it gives longer life.
As for oil temp. I am told that the seal is only seeing 50 C. Where they are measuring that I'm not sure.
I suspect its the oil that is affecting the o-rings. I will conduct some immersion tests soon and get back on here with the results.

josef
28-10-2014, 07:54 AM
Hi,
Grasso used in Europe only HNBR, CR for applications R22.
The difference in size which are known (2.62, 3.53, 5.33, 6.99, ....) using 3, 4, 4.5, 5, 5.33, 5.7, ...mm.
I think that Parker is not.
Josef.

RANGER1
28-10-2014, 08:40 AM
Thanks Ranger1. We modify the OEM seals to use a pinned stationary on the Grasso's but its up to the client to fit a pin to the housing. We also machine the o-ring grooves in the rotary to take an imperial BS size o-ring. We did use use Kalrez on one problematic compressor in the past. The boss doesn't want to use Kalrez because of the cost factor. There is nothing more frustrating than having a seal let go because of o-rings that cost under $10 each. If it was up to me I would certainly go the Kalrez way.
Our next step is to use Parker grade N1195 or N1173 HNBR and see if it gives longer life.
As for oil temp. I am told that the seal is only seeing 50 C. Where they are measuring that I'm not sure.
I suspect its the oil that is affecting the o-rings. I will conduct some immersion tests soon and get back on here with the results.

Suniso mineral oil nitrile or neoprene Ok normally.
Is it only the "0" rings showing deterioration which one/s
The ones where you used "Kalrez", are they Ok?
Ask them what is oil pressure if they are using oil pump for lubrication.
Has coupling alignment been checked recently, suggest laser with a print out of readings.
Have thrust bearings been checked, is compressor due for service?

cricri
30-10-2014, 07:58 AM
Hi DHP,
the Orings damaged are they "square" and hardened?
2 failures in 24 hours cannot be a wrong material selection.