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Yes oil samples do more but a in screw there is no need to look for metal wear like you need in a centrifugal. Also any acid is bad and needs to be fixed asap. A oil sample on a RTAC is a waste of time and money especially if you use a plastic bottle.
why wouldn't you need to look for wear metals in a screw? it is a mechanical piece of equipment just like a recip, scroll or centrifugal. as for the acid, 'any' is not a number that can be trended over time...sure, lower is better but what is lower? i have sampled many RTAC's (among others like it) using plastic bottles and found that the moisture pull through is not significant if you ship it within a day or two.Quote:
Originally Posted by FixItRight
Oil samples from high pressure chilers are pointless . The machine sits at a positive pressure , its not like a centravac where if it has leaks air gets in and moisture which create acids .The only reason for acids to develop in high pressure chillers is bad service practices and equipment failures (burnouts).
Also the oil charge (particularly on Tranes) is critical they are cut to the bone for unit efficiency .
So if you take half a dozen oil samples you have significantly reduced the oil charge .
Ok so add some more oil you say (you just diluted your readings and risked letting in moisture ) see my point ?
If you insist on taking them they should either be in glass bottles or shipped within 24hrs .
The only time I would take an oil sample from a high pressure machine would be . If the customer insisted it be taken, if the chiller suffered some kind of failure or if we took over another machine from another contractor where the chiller had had problems and refrigerant removal etc .
If you take an oil sample lets say for the sake of argument out of a 200ton screw machine . it comes back with elevated metals . Do you really and honestly believe the customer will say .Ok open it up and fix it , or sure I know its running well but slap a new 25K compressor on it anyway just to be safe ???? Lets get real here!!
Penny to a pinch of S%$# there going to say "when it croaks we'll fix it or buy a new one ".
Now I know your all going to say well we covered our ass and told the customer it was an issue so they cant come back at you . And to a point your right , but do you also think if you didnt take a sample and it croaked the story would be any different ?:.02::.02:JMHO
I'm with Healey and FixIt here. Oil analysis on a P.M. basis for air cooled screw compressors that are more or less disposable is a waste of time. The info you get from an oil analysis can be useful in the event that you suspect a problem. With POE oils, there's a high risk of moisture contamination before it even reaches the lab unless you use a glass sample bottle. We stopped doing regular oil samples on air cooled machines a while ago and opted to go with a simple acid test.Quote:
Originally Posted by Healey Nut
i recommend oil samples on everything except scrolls...they are vaulable on scrolls, but like graham said, after a few oil samples, you have to add oil and then start the trending over because it is diluted...they really hold only a little bit of oil although they are getting bigger and the bigger tandem units hold more than their screw counter parts...so I may change my stance on scrolls in the near future.
the oil analysis provides too much information for so little a cost to ingnore in my opinion.
Same recomendations from down here, reckon it is in the customers interest to be proactive not reactive with maintenance.Quote:
Originally Posted by jayguy
For Trane products we were air-freighting plastic bottle POE oil samples into Charlotte and had no major issues with moisture.
The only time we take an oil sample from a screw chiller is when we do an R'Newal. It is required by the factory. They also want a refrigerant sample.
True. But, as Healey Nut said, just what can (or will) be done with that information? If there is no backup chiller, AND it is a critical application, AND the customer says he would spend the money, based on oil sample results, then I can see taking oil samples. I have yet to come across a site, with RTAC's, that meets those conditions. I would be very surprised to see a customer actually spend that kind of money based on a test, while the chiller is still running.Quote:
Originally Posted by jayguy
Maybe start budgeting for a future failure.
any megger reading history on that chiller especially after a cycle
lots can be done with the information. why log a chiller? why meg a chiller? why lube a motor? should we wait until all parts break before we fix anything?Quote:
Originally Posted by Nuclrchiller
i prefer to view myself as the waiter in a restaraunt...i am not to decide how the customer spends his money, but i know they won't do anything if it isn't on the menu. perhaps you are leaving some money (and profitable work) on the table.
why lube a motor? That is funny if you think that an oil sample is as important as lubing a motor. If you don't lube a motor it will fail but a oil sample is just a test. Also there is a high chance of contamination from moisture with POE.Quote:
Originally Posted by jayguy
Jay, I'm just gonna presume you're being facetious asking those questions. ;) I just want to make sure this doesn't sink into some kind of argument. I think this is one of those things that are best left to a judgement call made on site on each individual piece of equipment, and application. Of course, keeping in mind such things as what has customer bought? What is customer expecting? etc... But I am curious - have you, or anyone, replaced a functioning compressor on a RTAC based on oil sample results? What about based on megger results?