megging questions again

[puckman]

Maintence team i know do pm on 3 phase motors of all sizes which include vibration and temp.
testing with a point and shoot basic tool. There is another test they call megging and all they are doing is taking a ohm reading with a digital muilti meter. Can they possibly be tracking or testing anything of use ? Is this helpful? I like to know what pm some of you electricians do that work on electrical systems . Thanks for all the help..

 

[Pierre C Belarge]

Maintence team i know do pm on 3 phase motors of all sizes which include vibration and temp.
testing with a point and shoot basic tool. There is another test they call megging and all they are doing is taking a ohm reading with a digital muilti meter. Can they possibly be tracking or testing anything of use ? Is this helpful? I like to know what pm some of you electricians do that work on electrical systems . Thanks for all the help..

If they are meggering the motors, they are not using a multimeter. If they are usings multimeter, they are not meggering.

If they are actually meggering as part of a maintenance program, yes, they may be tracking information about the condition of the motor over time... looking for telltail signs of the trend the motor is going in. Such as the windings are status quo - the windings are showing a pattern of degradation and will need an orderly shutdown for PM.

 

[76nemo]

What they are doing is applying a higher than normal voltage and stressing the insulation looking for leakage. I have all kinds of links on the topic if you would like a few. Insulation testing is a premium ethic in preventive maintenance. I'd say the only better thing in preventive maintenance for motor work is IR scanning.

They are not simply looking at resistance to ground with a DMM, they are stressing certain voltage levels across the winding/s and then looking at that reference. Insulation breaks down over time due to very many different elements. Trending these recordings over time can save you from a possible emergency shutdown by servicing/replacing equipment before it comes to that point.

Megohmeters have many, many uses. I'd take the time to get familiar with their applications.

 

[iwire]

Is it possible they could be using one of these DMMs?

The Fluke 1587 and 1577 Insulation Multimeters combine a digital insulation tester with a full-featured, true RMS digital multimeter

http://us.fluke.com/usen/products/Fluke+1587+1577.htm

 

[76nemo]

Is it possible they could be using one of these DMMs?




http://us.fluke.com/usen/products/Fluke+1587+1577.htm

Speaking of which, how do like your 1587 so far? Are you using it full time?

 

[iwire]

Speaking of which, how do like your 1587 so far? Are you using it full time?

Sadly no, the job that I needed it for went away with the start of the banking crisis.

I have only played with the 1587 a couple of times. I still use my normal 87 as my first choice. I thought I had some site lighting to troubleshoot with it but I found the problem quickly above ground. I was kind of disappointed, I wanted to try out the 1587.

 

[puckman]

Maintenace men were using dmm to take ohm reading. I asked what was he looking for and he said 500 ohms. They have a megger in dept. but don,t know how to use it and either do I.
I was just wondering besides seeing an open or short inthe motor what good would the dmm be for pm?
The motor being "meggered" as they said was a motor appearing to run ok, being pm ed.
The reason for the post was to pickup some tips on pm with motors. I only use a dmm when troublshooting a problem with a motor and i don,t have much of a understanding of the megger, yet. Thanks

 

[76nemo]

Maintenace men were using dmm to take ohm reading. I asked what was he looking for and he said 500 ohms. They have a megger in dept. but don,t know how to use it and either do I.
I was just wondering besides seeing an open or short inthe motor what good would the dmm be for pm?
The motor being "meggered" as they said was a motor appearing to run ok, being pm ed.
The reason for the post was to pickup some tips on pm with motors. I only use a dmm when troublshooting a problem with a motor and i don,t have much of a understanding of the megger, yet. Thanks

Understand that a DMM really has no functionality in testing motor applications. The insulation must be stressed in order to tell what level of degradation the motor has undergone.

 

[zog]

Understand that a DMM really has no functionality in testing motor applications. The insulation must be stressed in order to tell what level of degradation the motor has undergone.

And that a PI test is much more valuable than a spot test for motors.

 

[brian john]

They are performing vibration anaylsis and understand what they are doing but can't bother to read the literature for a megger?

 

[satcom]

Understand that a DMM really has no functionality in testing motor applications. The insulation must be stressed in order to tell what level of degradation the motor has undergone.

The Megger usually, finds the motor problems before it fails. so it is a valued tool for PM's

 

[76nemo]

The Megger usually, finds the motor problems before it fails. so it is a valued tool for PM's

For some reason, did you think I said insulation testing wasn't valuable??? That was my whole point. I think you are guilty of what I do all the time on these forums,.... I read too quickly.

Insulation testing and IR scanning is by far the best PM that can be performed. A DMM won't do squat in prediction, that's all I meant:smile:

 

[satcom]

For some reason, did you think I said insulation testing wasn't valuable??? That was my whole point. I think you are guilty of what I do all the time on these forums,.... I read too quickly.

Insulation testing and IR scanning is by far the best PM that can be performed. A DMM won't do squat in prediction, that's all I meant:smile:

no I read it just fine, the rest of my post is missing, where I noted the other options for maintance testing of motors.

 

[Luketrician]

Sadly no, the job that I needed it for went away with the start of the banking crisis.

I have only played with the 1587 a couple of times. I still use my normal 87 as my first choice. I thought I had some site lighting to troubleshoot with it but I found the problem quickly above ground. I was kind of disappointed, I wanted to try out the 1587.

Sorry a little off topic but wasn't there a recall on the Fluke 87? The 87s had a flaw in the auto-range mode function, that made it possible for the 87 to not show voltage on a circuit when there actually was voltage present.

 

[zog]

Sorry a little off topic but wasn't there a recall on the Fluke 87? The 87s had a flaw in the auto-range mode function, that made it possible for the 87 to not show voltage on a circuit when there actually was voltage present.

There were several recalls on the 87's, they are all on the Fluke website. The bad batch of test leads was the one that affected most people, I had 2 sets that were recalled.

 

[zog]

Insulation testing and IR scanning is by far the best PM that can be performed.

Cant agree with that, depends on the equipment you are talking about, Tan Delta, Power Factor, Partial Discharge, Corona, and Pdm are all superior for the right equipment. IR scanning is waaaaaay overrated for predicting failures.

 

[Fulthrotl]

Maintence team i know do pm on 3 phase motors of all sizes which include vibration and temp.
testing with a point and shoot basic tool. There is another test they call megging and all they are doing is taking a ohm reading with a digital muilti meter. Can they possibly be tracking or testing anything of use ? Is this helpful? I like to know what pm some of you electricians do that work on electrical systems . Thanks for all the help..

megging or meggering, is simply testing a component or conductor with
a megohmmeter.

there are a number of models that are combined with a DMM, particularly
the fluke series. results are expressed in megohms, or gigaohms.

the process usually consists of applying a dc voltage, and measuring the
insulation resistance *while the insulation is under stress*. the applied
voltage is typically 500 or 1000 volts, but can be as low as 50 volts or
as high as 5000 volts.

a DMM cannot perform this test.

meggering is also very useful for testing feeders before placing them into
service. and much safer. if you've ever had 500 mcm cables go to ground,
it's an unfortunate career experience.

a megohmmeter will find problems that a DMM cannot. motors, as they
age, will show reduced resistance. periodic testing can allow you to
change out the motor before it goes BANG!

hope this helps.

 

[480sparky]

Since no one else has posted it on this thread....

A Stitch in Time.

 

[ohm]

We had a Crane "canned pump" on the bottom of an experimental coal/oil/hydrogen thermal reactor running at 3000 PSI @ 800 deg F.

Once a week an ME would take vibration measurements using a portable analyzer. He saw real high readings at 10AM & recommended it be shut down.

The plant manager wanted to set a record, so kept running. At noon the pump caught fire and we were all manning fire hoses till 6PM.

The plant was down for six months & cost millions to fix.

 

[480sparky]

We had a Crane "canned pump" on the bottom of an experimental coal/oil/hydrogen thermal reactor running at 3000 PSI @ 800 deg F.

Once a week an ME would take vibration measurements using a portable analyzer. He saw real high readings at 10AM & recommended it be shut down.

The plant manager wanted to set a record, so kept running. At noon the pump caught fire and we were all manning fire hoses till 6PM.

The plant was down for six months & cost millions to fix.

But.... did a record get set?