Vibration condition monitoring why?

[RANGER1]

Vibration analysis or condition monitoring is recommended?

If you have a number of compressors on a number of sites & over the years have never given any problems, is there any justification for condition monitoring?

Do you use it to prolong overhaul or major maintenance intervals?

Is it best used for critical machinery in process plant, so if it goes down the whole show stops! I would say yes

In my experience compressors don't fail unless something is basically wrong with system, for example
liquid floodback
poor oil filtration & maintenance
high oil tempratures
diluted oil.

Generally speaking from my experience

9 times out of 10 slide valve is worn allowing rotors to contact , causing rotor tip wear.
This can be caused by general wear & tear.
5 times out of ten rotor journals are worn due to poor oil filter maintenance, blown out oil filters etc.

I'm not sure vibration analysis can prevent this happening even if oil analysis is carried out at regular intervals as well (more money).

I think laser alignment has generally improved compressor life as it simplify's alignment for people with basic knowledge & near enough attitude.

Interested in any comments & experience

[Brian_UK]

I believe that vibration analysis would show that your bearings etc are beginning to suffer 'damage' long before you would have a mechanical failure.

You say that the journals are worn due to poor maintenance etc and this is no doubt true but, do you find out about the journal damage when it is too late?

[Magoo]

Hi Ranger 1
most of my clients that have critical plant installations do vibration analysis checks every 3 months, particually compressors mainly screws on my advise. The vibration service provider can develop trending profiles, which will generally co-incide with compressor manufacturers recommend strip and inspect periods, which in turn supports my advise to strip and inspect. I can usually here the noise change in a compressor on monthly checks, which corresponds to trend changes from vib., checks.
Lazer alignment is the best thing since sliced bread in my mind. Man I hate spending a day doing an alignment with two DTI's.
My thoughts anyway.

[RANGER1]

I believe that vibration analysis would show that your bearings etc are beginning to suffer 'damage' long before you would have a mechanical failure.

You say that the journals are worn due to poor maintenance etc and this is no doubt true but, do you find out about the journal damage when it is too late?

I don't think vibration analysis can tell if whitemetal bearing/journals have wear, open for correction though.
This has never caused a failure to my memory, maybe you don't know until you pull it apart on 30-40 000 hr service. The only indicator may be low oil pressure due to excessive clearance.

Roller bearigs I think you can hear before failure, if you know the plant well enough.

I know i am negative about it , unless someone can convince me otherwise!

[RANGER1]

Hi Ranger 1
most of my clients that have critical plant installations do vibration analysis checks every 3 months, particually compressors mainly screws on my advise. The vibration service provider can develop trending profiles, which will generally co-incide with compressor manufacturers recommend strip and inspect periods, which in turn supports my advise to strip and inspect. I can usually here the noise change in a compressor on monthly checks, which corresponds to trend changes from vib., checks.
Lazer alignment is the best thing since sliced bread in my mind. Man I hate spending a day doing an alignment with two DTI's.
My thoughts anyway.

So Magoo would you use it as a tool for plants in general, or only critical installations?

Most failures are because someone did something wrong, or didn't do something they should have (in my opinion).

I also have found that the clients (not many of them) who are padantic & overservice usually are the ones who have more damage than the average client. Why who knows, just there luck .

Granny drives her car to church on Sundays has constant problems with car .
Someone else flogs the guts out of their car, doesn't change oil etc & goes forever.

[HVACRsaurus]

Hi Ranger,

I'm with you on this one. I know lots of people (and companies) that bang on about the benefits of VA. Some sites where I work have VA monitoring connected 24/365, but im most instances by the time that the VA is showing signs of trouble the compressor has already suffered excessive wear & damage, generally more wear & damage than would otherwise be the case if the compressor had been periodically overhauled (according to hours run) in a more traditional manner. To clarify, I am familiar with instances where people have run compressors with VA and destroyed (beyond economical repair) machines. In other cases, I've been involved with sites who engage in periodic servicing/overhaul, without any VA whatsoever, and have enjoyed many years of trouble free operation, some machines in the order of 190K total hours run. This said, I am a huge advocate of Lazer Aligment, I generally do my own with company equipment, and I've seen many package issues resolved by performing a good line-up.

[RANGER1]

Hi Ranger,

I'm with you on this one. I know lots of people (and companies) that bang on about the benefits of VA. Some sites where I work have VA monitoring connected 24/365, but im most instances by the time that the VA is showing signs of trouble the compressor has already suffered excessive wear & damage, generally more wear & damage than would otherwise be the case if the compressor had been periodically overhauled (according to hours run) in a more traditional manner. To clarify, I am familiar with instances where people have run compressors with VA and destroyed (beyond economical repair) machines. In other cases, I've been involved with sites who engage in periodic servicing/overhaul, without any VA whatsoever, and have enjoyed many years of trouble free operation, some machines in the order of 190K total hours run. This said, I am a huge advocate of Lazer Aligment, I generally do my own with company equipment, and I've seen many package issues resolved by performing a good line-up.

I'm glad that someone agrees, but lets face it you can have the fancy tools but you have to also know how to use them.
VA I'm sure can help if the right person is using it & regularily tests for a good trend, to determine possible
problem areas.
The problem is gaining trust in someone who hopefully hangs around for many years to come.
If it helped keep insurance premiums down I guess its a good thing, but probably not happening as far as I know.
If a machine farts you would want to be sure that there is something wrong though & thats my point.

Machines wear to some degree, that life, but it doesn't mean it will fail, like you say the time VA registers it might be to late regardless of what you do.

Agood tech can pick up oil compression issues, alignment,unusual noises, contaminated oil/filters etc
if given the chance.

[josef]

I am using Aligneo laser leveling pins-good machine, using the analysis of the vibration-good, a lot of money, not always says the real problem, my favorite instrument is a stethoscope-cheap and simple.
http://www.mapro.skf.com/products/ins_tmst3.htm


I think it is important to comply with a maintenance plan from the manufacturer.
Josef.

[PaulZ]

Hi All
I tend to agree with Ranger to some degree and with Magoo to some degree.
In my opinion and experience VA is good for motors and any compressor that has ball or roller bearings but probably not that useful for white metal bearings.
When recommending service and overhauls to clients we follow the manufacturers recommended maintenance and overhaul schedule.
I agree that laser alignments are important and we do these are done every 12 months.
Also another good practice to monitor wear in compressors is regular oil testing, every 6 months. The test kit are not expensive.
I my opinion you should not just rely on one form of testing or monitoring but use a combination depending on the type and age of the equipment being serviced.
I suppose it comes down to different stroke for different folks.
Regards
Paul

[Magoo]

Hi Ranger1,
no I would not concider VA as a general service tool on general plants. Only on single compressor [screws]critical plant. Those that I do have oil changes annually and filter changes 6 monthly, had an occassion that the VA reports picked up a trend on a screw which in turn was scheduled for a strip and inspect, the thrusts had started to loose tolerance the mains were still in spec' I could here a pitch change prior to VA test, another was a sudden shaft seal oil excessive leak and motor bearings pitch change, both shut down and changed out with no production losses. The next thing is thermal imaging, good for MCC's and distribution panels. Generally use an IR thermo myself.

[RANGER1]

Well aparently I'm not the lone Ranger, thanks for the feedback.

It will be interesting to hear from the new member who is VA expert.

[YBeck309]

I'm seeing more predictive diagnostics in the petro/chemical field on just about any type of rotating equipment. VA is a good tool, but only as good as the person reading the data. VA technology looks for trends & changes over a period of time & like a good pressure/temperature log reading, a person can identify potential problems creeping up. More Mechanical Engineers are better educated in this area & those of us who work in the large compressor field need training. I've seen Bently/Nevada systems on all kinds of equipment & the plant wouldn't perform the maintenance. So, in their case, it is a waste of money. However, thats a rare example & most plants swear by their PM readings & do all equipment on a monthly or bi-monthly basis. As for large commercial buildings, I don't see much use for predictive diagnostics as the chillers usually don't see the wear & tear of industrial compressors & chillers. If interested in vibration analysis, use the internet search & you'll find basic to complicated reading material online. SKF makes a good wall chart.

[brian_chapin]

Speaking as someone who works with hundreds of Process Safety Management covered Industrial Ammonia refrigeration systems, we use vibration analysis because:

1) The manufacturer recommends it
2) RAGAGEP (Recognized And Generally Accepted Good Engineering Practice) recommends it such as IIAR bulletins

When either of those two is true you pretty much have no choice to implement it in a PSM covered process.

[RANGER1]

Speaking as someone who works with hundreds of Process Safety Management covered Industrial Ammonia refrigeration systems, we use vibration analysis because:

1) The manufacturer recommends it
2) RAGAGEP (Recognized And Generally Accepted Good Engineering Practice) recommends it such as IIAR bulletins

When either of those two is true you pretty much have no choice to implement it in a PSM covered process.

Its an interesting subject with a lot of for & against.
I'm not sure all manufacturers would recommend it, from manuals I've seen its not in them.
Frick can supply it as an option with Quantum panel which is a good idea.

I just don't like the idea of lenthening full overhauls intervals because VA says its OK.

In our conditions in Australia from my experience with all brands, the slide valve is still a weak point
in most rebuilds. This to my knowledge does'nt show up on any VA trend.

Someone may be able to inform us if it can.

To analyse accurately all the correct information has to be also given as well eg

bearing type/number
rotor teeth 4/6,5/6 etc


With Mycom's own developed condition monitoring (coco) they can also establish oil compression
as well as other issues due to it being predominately developed for Mycom characteristics.

It true to say the guy doing the VA has to know how to interprit the unique characteristics of screw compressors.

[brian_chapin]

Frick can supply it as an option with Quantum panel which is a good idea.

That's more of a vibration condition monitoring than a stand-alone vibration analysis. They are quite different things. My comments were on stand-alone vibration analysis which is pretty much required in the US in a PSM plant for any major manufacturer's industrial NH3 compressors Frick/Mycom/FES/M&M/etc.