Do PM Benifits Outweigh Harm???

[zog]

This is a broad statement. As far as I know OSHA hasn't adopted the NFPA 70E. yet.

They adopted part of it, just not the parts regarding PPE, ESWP's, etc.. But OSHA has adopted the part of 70E that discusses instalation and maintenence practices. The new law went into effect Aug 2007.



http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=19269&p_table=FEDERAL_REGISTER

 

[zog]

I read in a previous post that someone smoked all their lighting during a pm, my previous company powered up after a PM and all the AC load turned on at the same time and took out a HV fuse(down for another day). Just read an article ECM about an experienced electrician getting lit up because he didn't know HV switch was backfed. I haven't heard of anything good happening from a PM.

All 3 of those examples are from people doing PM's and not being qualified or better yet certified to do so. An "experienced electrician" better know how to tell a switch is back fed or keep thier paws out of the switchgear.

Do you think it is worthwhile doing a PM annually? To me it just seems like more harm then good, both equipment and people. Half the time at my previous company the people doing the PM didn't really know what they where looking for. I believe in infared testing, but I'm not sure about exercising breakers, retightening lugs, messing with the Medium Voltage Gear.

If you people have no idea what they are doing it is a complete waste of time, thats why there are professionals that specialize in this sort of thing.

(After bragging at lunch when we got back 800A ground fault and he didn't know how to reset the breaker.:smile

Well, maybe a good PM program would have prevented that ground fault. How did you reset the breaker?

 

[zog]

So have you had breakers not reset during a PM? What have you found that offset the effort/risk?

Better they don't reset after a PM then when your plant is dark and the production manager is screaming at you.

 

[zog]

I would perfer not stick my head in the sand and learn what the real benefits are to recommend this in the future. It would help if I had some concrete proof of what a PM discovered/prevented, but I have nothing. Sounds like you have nothing to offer either. I'll continue sitting in the dark.

You have not looked very hard, all sorts of studies to prove the economic advantages to a good PM program. Try google, it helps you find stuff.

At a recent Powertest conference a speaker had compiled data spanning 40 years and thousands of breakers and found that 70% of power breakers that have not been PM'ed in 24 months failed testing. IEEE has tons of data on this too. EPRI requires all thier plants to rebuild (Not just PM, but complete tear down and rebuild) all of thier breakers every 10 years.

 

[weressl]

This is a broad statement. As far as I know OSHA hasn't adopted the NFPA 70E. yet

Yes, they have. It's the "General Duty Clause". Lawyers will tell you that it has been adopted.. Better to use it!

read and weep:grin:

Appendix A​

​

​

​

?References for Further
Information​

The references contained in this appendix
provide nonmandatory information that can
be helpful in understanding and complying
with Subpart S of this Part. However,
compliance with these standards is not a
substitute for compliance with Subpart S of​

this Part.

.........

NFPA 70​

​

​

​

?2002 National Electrical Code.
(See also NFPA 70?2005.)​

NFPA 70E​

​

​

​

?2000 Standard for Electrical
Safety Requirements for Employee​

Workplaces. (See also NFPA 70E?2004.)

 

[zog]

. I think an infrared scan is be the most bang for the buck and the least disruption

On MV gear? Waste of time. Typical insulation failure in MV gear has a very short window, days, maybe weeks, where a peding failure will produce enough heat to show up on a IR scan, you would need to get very lucky. PD surveys are much better at detecting pending MV switchgear failures far in advance. And they are easier and less intrusive than IR scanning.

 

[StephenSDH]

You have not looked very hard

Could have just posted a link for me:smile:. I have looked. I would guess 75% of the companies I have done work for are reactive only.

* >55% Reactive
* 31% Preventative
* 12% Predictive
* 2% Other

http://www1.eere.energy.gov/femp/operations_maintenance/om_reactive_main.html

70% of power breakers that have not been PM'ed in 24 months failed testing

Can you post a link for this. Sounds like some Square D imitation breakers from China.

 

[zog]

Can you post a link for this. Sounds like some Square D imitation breakers from China.

There are no counterfeit power breakers on the market that UL, or any OEM is aware of. The small residential ones that are counterfeited all the time (All OEM's) are not large enough to warrant any testing.

Those stastics are for all power breakers, all real breakers from all the OEM's. Thats why every breaker maintence manual says clearly how often the breaker shoud be PM'ed, because they know they require PM's to reliably function.

 

[jim dungar]

I think the OP has a valid question.

He asked for specific examples to try to make an informed decision, and there have been precious few examples posted where the benefits saved by PM outweighed the cost. I think an infrared scan is be the most bang for the buck and the least disruption.

I also think there are some things that definately should be done.... operating large switches, breakers etc.

It is certainly not on a par with changing the oil in a vehicle's engine, and I doubt seriously there are too many large frame breakers laying around on the occassion of PM, that wouldn't be laying around anyway.

Sure, there are those who make a living doing this stuff, and sure there are hacks, and one more sure... you'll find stuff, you'll find a whole lotta nothin too. How many of you would be so willing if you were paying the bill?



Dollars spent doing PM << Dollars saved doing PM... I wouldn't bet the rent on it.

Company decided that their 34.5 kV tap changer was too old to maintain, but they left it in service and simply stopped PMing it. They woke up one day to a large boom as their unmaintained switch took out the transformer feeding their facility. The facility was down for 4 weeks while a temporary transformer was found and installed. I wonder how much they saved (down time, alone, was figured at >$40K/hr)?

 

[quogueelectric]

I think the OP has a valid question.

He asked for specific examples to try to make an informed decision, and there have been precious few examples posted where the benefits saved by PM outweighed the cost. I think an infrared scan is be the most bang for the buck and the least disruption.

I also think there are some things that definately should be done.... operating large switches, breakers etc.

It is certainly not on a par with changing the oil in a vehicle's engine, and I doubt seriously there are too many large frame breakers laying around on the occassion of PM, that wouldn't be laying around anyway.

Sure, there are those who make a living doing this stuff, and sure there are hacks, and one more sure... you'll find stuff, you'll find a whole lotta nothin too. How many of you would be so willing if you were paying the bill?



Dollars spent doing PM << Dollars saved doing PM... I wouldn't bet the rent on it.

I would bet the mortgage on it every day of the week. It is most definitely on par with changing oil in a vehicles engine. When you buy equipment it must be maintained and if you cannot afford to maintain the equipment you should not buy it. There is a mentality for some types of managers to run everything into the ground and say how smart they are because they cut unnecessary costs then gives the nightmare they created hanging the rubber on the next manager when everything falls apart due to lack of maintenance.

 

[quogueelectric]

read and weep:grin:

Appendix A​

​

​

​

?References for Further
Information​

The references contained in this appendix
provide nonmandatory information that can
be helpful in understanding and complying
with Subpart S of this Part. However,
compliance with these standards is not a
substitute for compliance with Subpart S of​

this Part.

.........

NFPA 70​

​

​

​

?2002 National Electrical Code.
(See also NFPA 70?2005.)​

NFPA 70E​

​

​

​

?2000 Standard for Electrical
Safety Requirements for Employee​

Workplaces. (See also NFPA 70E?2004.)

You would make a great politition because I still have no Idea what this means yet I walked away happy with the answer. BTW what did that really mean (break it down a little simpler for the good old cow if you would.) ??

 

[iMuse97]

couldn't wait to get my two cents in: on a job I've done, PM on XFRMRs always pays off at this housing complex that owns their own system. When they didn't do it, they would call after the gophers got in the things and they blew--that was always expensive. Now we clean them out 1x/yr and it's expensive, but not nearly as much as a blowup, and the power is only out a short time.

 

[weressl]

You would make a great politition because I still have no Idea what this means yet I walked away happy with the answer. BTW what did that really mean (break it down a little simpler for the good old cow if you would.) ??

You also wrote:

<<Yes, they have. It's the "General Duty Clause". Lawyers will tell you that it has been adopted.. Better to use it! >>

Why don't you ask the same lawyer to explain. (They usually have difficulty speaking humanese.)

In broad terms, OSHA is saying that while their law is PARTLY based on the listed documents and can be used as REFERENCE, they are NOT the law itself and should not be used as such.

One example would be a conflict between the two documents, where the OSHA document would be the winner in ALL cases.
Another example would be a requirement that is imposed by the Code and the litigant would maintain it that it is a Federal requirement. Unless the corresponding requirement can be found in 1910, Subpart S OSHA would stay silent on the matter thus the claim of Federal requirement would be invalidated. The vast majority of the Code requirements have no corresponding part in OSHA.

It is really important to understand what the role of the Federal Government is intended to have to understand why it is necessary to limit themselves. Along the same line lies the understanding why each State may or may not adopt the Code with or without exceptions and additions. It may seem inefficient and cumbersome but it is intended to retain self-governance.

 

[rcwilson]

I worked for a NETA company specializing in PM, and have also been a customer for many years. Problems we found:

100% of 600A frame and larger circuit breakers (40 breakers) at a large aerospace facility would not trip on overload or short circuit due to improperly adjusted trip bar. They had been that way for 7 years. Any 480V fault would have to be cleared by the 13.8 kV fuses.

About 40% of the breakers we tested in dirty industrial or commercial facilities had a problem: not tripping per the curve, broken insulators, inoperative ground fault, poor meggar readings, etc. Twice I recall the main breakers at major hospitals started tripping after a PM. The PM freed up the tripping mechanism so it responded to the overload which was occurring daily.

Loose connections with the resultant heating damaging cables.

Excessive conductive dust and dirt in medium voltage switchgear.

Dead control batteries in switchgear so no trips could occur. An hour after we got temporary DC power on, the breaker tripped when a car ran into a 13.8 kV pole and the line dropped on the car. We may have prevented a fatality.

1200 Amp Bolted Pressure Switches in hospitals that would not trip open on ground fault. We had to use a hydraulic Enerpac to force the switches open.

Inoperative transfer switches at hospitals. They worked during normal test but not during a power outage which was simulated during PM. Emergency generaotrs with no starting batteries.

Switching for a PM outage discovered the one lines were not correct. Loads and subs were fed from different breakers than indicated.

A few times the investigation of a major fault that cost millions in down time led to a program of preventive maintenance.

For one facility, our annual charges for maintenance were less than the savings on their insurance premiums. If the main transformer and switchgear were not inspected and PM'd every year, the insurance company jumped their rates.

But should you maintain every year? Depends on the enviroment and the cost of long outages. Spend money on infrared testing first to detect hot spots. Look at PD testing or other new methods. Operate breakers using the trip function. Excercise transfer switches. Test transformer oil, etc, etc, etc. Do something or you will be in trouble when that failure does occur.

 

[weressl]

They adopted part of it, just not the parts regarding PPE, ESWP's, etc.. But OSHA has adopted the part of 70E that discusses instalation and maintenence practices. The new law went into effect Aug 2007.



http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=19269&p_table=FEDERAL_REGISTER

Zog,,
In case you missed it, taken directly from the document referenced above:

Appendix A
—References for Further Information​

The references contained in this appendix provide nonmandatory information that can be helpful in understanding and complying with Subpart S of this Part. However, compliance with these standards is not a substitute for compliance with Subpart S of​

this Part.
.........

NFPA 70
–2002 National Electrical Code. (See also NFPA 70–2005.)​

NFPA 70E

​

​

–2000 Standard for Electrical Safety Requirements for Employee Workplaces. (See also NFPA 70E–2004.)​

The 'nonmandatoty' and 'helpful' would hardly qualify as adopted. Matter of fact it clarifies OSHA's nonbinding relationship to those standards and asserting their superiority over those.​

 

[wawireguy]

Is PM worth it? How much money is lost if there is a outage and power can't be rapidly restored? That's the question. I worked in a sawmill one time and I can't remember the dollar figure per minute that the company lost when the mill went down but it was substantial. If you don't lose much money and can have your equipment down for a while then I suppose PM might not be worth it.

 

[Howard Burger]

where'd you get the cent sign?

where'd you get the cent sign?

My 2?

So, how'd you get the cent sign for your contrib? I was grousing the other day that it had been removed from the keyboard. Thanks!

Howard Burger

 

[Howard Burger]

Oops

Oops

Sorry all, that was supposed to be a PM. Still getting used to this forum.

 

[Doug S.]

So, how'd you get the cent sign for your contrib? I was grousing the other day that it had been removed from the keyboard. Thanks!

Howard Burger

Howard,

I opted to reply publicly as others may find the answer useful.
(Moderator, I understand this is WAY OT, do as you please.)

The short answer I hold down the <ALT> key then sequentially press 155

Windows users can see a list of characters in "Character Map" <START> "RUN" type in charmap the press <ENTER> The internet is another great source of ALT characters.

NOT ALL CHARACTERS WORK IN ALL PLACES / SYSTEMS.

Other useful chars. on this site...

Ω <ALT> 234
? <ALT> 0176
? <ALT> 0216

?Helpful?

Regards,
█??g S

 

[mayanees]

?Helpful?

yup
thanks