Odd Oil Situation

[brian_chapin]

I'm having an oil situation here at a facility and wondered if anyone could throw some light on it.

In one of our facilities, we've seen viscosities between 85-91 for several years from our compressor oil. The oil is Clavus 68 from Shell. When I test it new, I get a viscosity in the 65 range. However, all six of our compressors regardless of duty have oil viscosities in the 90 range.

What could be causing this? I am not seeing this increase in viscosity in the other facilities although none of them:

1) Run anywhere near as hard
2) Run in a vacuum
3) Are using the Shell oil

We use an autopurger - we routinely test the oil and have found no contamination at all. Of course, we have also seen no sign of anti-wear additives in the oil either.

I understand that the recommendation is to replace oil when it varies 5% from the initial viscosity. That's a very expensive proposition when you are talking about 6-700 gallons of oil.

[US Iceman]

I think what you are finding is typical of mineral oils and believe this is due to what are called the "light-ends" of the oil. As the oil is used it tends to de-gas into various hydrocarbon vapors. This process causes the remaining oil to increase in viscosity.

On the fully synthetic oils this issue is not found (as best as I can remember). As a result, the viscosity index remains stable through temperature changes and longer life.

From conversations I have had and am trying to remember this is where the recommendations come from for more frequent oil changes, when mineral oils are used.

I prefer the synthetic oils myself because they seem to work better and last longer. And yes, they are more expensive but it is also important to look at long term effects also.

If I missed something.... I'm sure someone will correct me or add to the explanation.

[brian_chapin]

I am seriously considering trying Royal Purple Uni Temp synthetic. They are claiming a 10% electricity reduction and are willing to provide a logging meter to prove it over several months.

More info: http://www.royal-purple-industrial.c...dsi/utemp.html

Has anyone used this?

[US Iceman]

You need to talk to CPI in Midland, MI. They are the oil suppliers used by Howden, Frick, FES, & Vilter. That should speak volumes on who trusts who.

[Sergei]

I am seriously considering trying Royal Purple Uni Temp synthetic. They are claiming a 10% electricity reduction and are willing to provide a logging meter to prove it over several months.

More info: http://www.royal-purple-industrial.c...dsi/utemp.html

Has anyone used this?

Hi, Brian.
I'm very sceptical about 10% of energy savings. In energy savings 10% is a lot. This is my fist concern.
Second is logging power use for several months. This is fundamentally wrong, because a lot of variables have influence on these numbers. Certainly, we all interested in energy savings on long run. However, correct energy comparison should be done within short period of time to minimize fluctuation of refrigeration loads and ambient condition.
In your case, choose 2 identical compressors operating in parallel and run them at 100% load. If they have port sides, close them. Compare power use. It should be equal or close. Change oil for one of them and compare power use again. This is correct comparison. Don't pay for this oil if energy savings less than 10%. Why do they want to log energy use for several months?

[US Iceman]

When I worked for one of the large ammonia compressor manufacturers we were approached by this firm to recommend their oil and additives. Our answer was always NO.

As a manufacturer you become responsible for all claims (yours or others; valid or not). This results in the manufacturers having to spend a lot of time investigating why the product did not work and why they will not honor a warranty claim. In some cases the manufacturers may tell you the warranty is void if other oils are used, than those recommended.

Sergei touches on some of the aspects of energy savings. All too often energy analysis can be a liars game. Any assumptions made on why the energy increased or decreased are often not correlated to the actual operation. As a result, the head pressure could have decreased for 3 months, which could save a lot of energy. However, if the oil additive is added during this time someone can claim the savings as their own.

If you want to save energy; modify how the plant & system is being operated. That is where the energy costs are. And... you have more control over this aspect and absolutely none with any additives.

[brian_chapin]

If you want to save energy; modify how the plant & system is being operated. That is where the energy costs are. And... you have more control over this aspect and absolutely none with any additives.

We've already picked all the low-hanging fruit off the energy savings tree.

I have several years of data logs for my compressors and a very good idea of what they are costing us in electricity.

My concern with our current oil (and all of these compressors are way beyond warranty) is that its pour point is -30f and we are running our boosters at -45f. I imagine that the oil is a sludge at that temp and we do often have issues attempting to start idle ammonia pumps until we warm them up and drain a small amount of oil out of them.

[rupcic]

Hy,
in my country (Brazil) we are having problems to find an PAO oil. It's international problem? Does anyone reard it ? Regards!

[Iceehot]

Be careful changing oils, some are not compatible and the drop or two leftout in the system can turn into wax when new oil mixes with it. Then it will plug solenoids, strainers and cause headaches.

[GrantD]

Hi,

Check out CPI oil site on the web. Good synthetic oils, lists pros cons and compares to mineral oils. We use CPI 100-68 on our NH3 plants. Brilliant stuff.
Grant