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Starting a PdM program that includes Oil analysis for our refrigeration compressors & chillers.
Looking at an Acid test kit for a quick go/no for oil quality.
After that, will a traditional sampling program of oil quality, wear metals, Acid levels, etc.. be sufficient.
Also, is there a predictive method to reduce ***** leaks?
Thanks in advance,
Kurt
Hi Kurt
I'm afraid I don't know of an acid test kit for oil, but I would take this sort of thing with a pinch of salt, I've seen some rather knackered oil samples with no acidity problems. On the reverse side, new oil with some additives can have an acid number (TAN) up to 0.3ppm which doesn't mean there's anything wrong with it. A visual examination can tell you a lot really, or if you want a single test then perhaps a crackle test or some sort of viscosity check would be more useful.
If you're looking at oil analysis then you should also be looking at refrigerant analysis, this is often forgotten about but will give you useful information, and can give you indicators of where you could be losing efficiency.
Whoever you go with, it is important that you get interpretation with your results, otherwise you'll get a load of numbers back that don't mean a lot. A bit like putting your gauges onto a chiller when you don't know which gas is in it.
I'm afraid there isn't a way of analysis to tell you if the system is undercharged, until ESP becomes available as a detector. Aside from looking at levels in the chiller (obviously), or doing a full system analysis on a computer, you could look at running hours - if the running hours are going up and up and the load isn't changing much then it could be the system charge is disappearing. It could also mean a load of other things too though.
The acid test kit you are referring to is similar to the Sporlan acid test kit I assume? I have used these in the past for checking oil quality after a burnout on hermetic or semi-hermetic compressors.
My feeling is they simple provide an idea of when you can quit changing the filter-driers after a burnout. They do not provide sufficient information other than a Go, No go feedback. This in itself may not provide the correct answers you would expect.
I have not used these on systems where open-driven compressors are used, since the electrical motor is outside of the refrigeration system. I guess I felt the test kit offered no value, since the potential for electrical burnout was very remote.
As Johnny Rod pointed out, analysis and the results are only one part of the equation. The test results only tell you where you are, a baseline (based on new oil or refrigerant) should be established to provide a range.
Once this is established, you can develop methods or procedures to bring the oil or refrigerant quality back to acceptable levels.
The test and the methods then become part of your program.
Other items you might consider for your program are:
Thermography (motor & starter connections, bus bars, etc.)
Water quality & treatment (chilled water & condenser water)
Recording of operating data (power, ambient conditions, etc.) The more data you have, the better you are able to correlate operating characteristics with performance and costs.
For example, if you can measure chilled water flow rates, you could compare the cost of operating the chiller versus the amount of water flowing during the same time. This is benchmarking the operation.
If the chiller spends long periods of time to produce chilled water at part load, the cost per GPM of chilled water will increase.
With this kind of information you can then investigate improved methods of operation to reduce the cost per GPM.
Chillers normally use kW/Ton as an efficiency measurement, but I feel a method similar to the above is more meaningful when evaluating changes to the chiller, or chilled water system.
Some ideas to consider.
Regards,
US Iceman
Thanks to Both Johnny & Ice for the feedback.
I presently do chart the water treatment & quality & we perform the IR on the compressors. (for the first time ever!!)
The Sporlan test kit is correct. I really wanted to know if it had any real value. I know quite a bit about machine oil analysis & result interpretations, but very little about refrigerants.
Interesting about checking the refrigerant & comparing it against a base line sample. How is that performed & what kind of results does it yield?
If you have any links about that, I will certainly research it.
Thanks again
Kurt
The same general techniques apply in terms of wear elements no matter what the machine, but with refrigerants water content, oil viscosity, acid numbers and others come in. With viscosity, it is important to ensure that all refrigerant is removed from the oil before testing to get consistent viscosity results.Quote:
Originally Posted by KurtMc
For base line measured results, you would normally take a sample after an hour or so run time and get that sample tested. Subsequent samples are measured as a trend against your baseline sample taken soon after the oil change. If you send samples away to a lab, they normally do that for you.
Steve
Thanks Steve.
We recently had some oil changes performed in our chillers. I'll have a sample of that sent for testing to start.
If I leave the sample bottle open for sometime, will any refrigerant trapped in the oil boil out?
Thanks in advance,
Kurt
Yes, that will happen to some degree. You need to do that to stop the sample bottles exploding in transit!Quote:
Originally Posted by KurtMc
But further to that, the lab needs to further "boil out" the remaining refrigerant. I am not totally sure of the process but I think is a matter of heat and vacuum.
I used labs that had refrigeration experience, or via manufacturers' service departments who selected suitably equiped labs.
Steve
Hi Kurt,Quote:
Originally Posted by KurtMc
The refrigerant should de-gas out of the oil sample, but you may have to be careful with the venting process.
If the sample is exposed to atmospheric pressure too quickly the refrigerant will boil off, but the mixture will probably turn into a foam (like shaving cream). You might loose the majority of your oil sample.
For the refrigerant testing I'll defer to Johnny Rod. I think he may have a better perspective on this topic.
Regards,
US Iceman
A quick note on oil sampling, it's best to take a sample from the system after it's been run for a while as Steve says, otherwise you might only see nice clean oil and all the crud has separated out on standing. It can be a bit frothy alright but leaving the lid of the sample container loose for a while to degasshold be fine. The sample containers we use are pretty tough so put up with a little bit of residual pressure.
For refrigerant analysis there are a smaller range of tests (for more info see www.hudsontech.com until our own site is revamped), which are composition (for blends), moisture, acidity and chlorides (degradation products), solids and involatile residue, and non-condensable gases. Involtile residue (oil) and non-condensables will reduce the system's capacity/efficiency so monitoring these is a good for your electricity bill. There are also knock-on effects e.g. high non-condensables means high discharge temperatures which leads to to more acidity. The other contaminants need to be controlled so you don't compromise reliability.
All of these contaminants can build up over time, particularly where systems are opened up for maintenance. As with oil, you should get interpreted results back so they mean something to you. Ideally you should take refrigerant and oil samples together and periodically so you have more pieces of the jigsaw of how your system's running.
That's the short version! Does it help?
the question u should b asking is why have u had a burn out it usually is system failure ie moisture
thats one reason why ur oil turns acidic
Moisture can lead to acidity before the burnout happens, as oil and refrigerant (some worse than others) are broken down in the hot compressor discharge to give traces of acidity which can then attack hermetic motor winding insulation etc. If the moisture isn't brought under control the acids accumulate in the system. After a burnout there will be a lot more acid for sure, but if you have a programme in place of monitoring these things then you have a good chance of heading off your problems before they turn into failures. The first step is knowing what you have, which means looking at the oil to tell you about the compressor and looking at the gas to tell you about the refrigerant circuit. Add these to your other pieces of info like vibrational analysis etc. and you soon have a good picture of what is happening behind the copper tubes.
Hi JohnnyQuote:
Add these to your other pieces of info like vibrational analysis etc.
This sounds interesting, could you expand a little on the method?
Hi Frank
I don't have a lot of info on vibration analysis, it's an engineering thing really and I'm a chemist, but basically you attach an accelerometer to the right place on your equipment and take a reading which is a waveform (sound is a vibration). This is broken down using Fourier transform maths to split out the frequencies that make it up, and if you know what to do with the info it can tell you about the state of the equipment. Crudely, knackered things vibrate more, but the trick being that as bearings etc. deteriorate over time you get an early warning that something is amiss and can plan in some service work before you get an unexpected failure. You can do this yourself or get people in to take the readings, I think if you do it yourself you can send the sound files to your chosen specialists who can then do the clever bit and give you the output. I did a quick search for some info, this is a fairly good overview but you might be less interested in the really geeky bits:
http://www.cage.curtin.edu.au/mechan...ions/intro.htm
It's something a lot of people do to look for bearing wear, shaft misalignment, etc. Taking readings over time most likely gives you a better picture as you build up a norm of how the machine runs. A familiar-sounding approach perhaps?
Thanks Johnny
Some interesting maths. I've had a quick look and will study it later. Nice link.
As you are a chemist I've got a question - is it OK to post here? it's concerning the dilution strength of the absorbent in one of my chillers. (lithium bromide).
Fire away - best start a new thread though.