Saturday, May 8, 2010

Fires of an Industrial Nature

Industrial Machine Fires
A look at what a troubleshooter finds.
When he repairs them and what he finds that causes them

By Nick Markowitz Jr.
Qualified Electrical Contractor

When I'm not involved with fire investigation and research work, I work as a master-level electrical and electronic troubleshooter. I do this for different companies as well as contractors. When they have a problem that their normal maintenance people or electricians can not find, I'm the guy they call.

In the 34+ years of doing this work I've enough stories to fill several books over. However, there are several recurring issues I see on an almost daily basis that causes the vast majority of machinery and equipment related fires. Many of these come back to:

1. the wrong fuse or circuit breaker for over-current protection
2. and the wrong application of parts being used and for the voltages used

Take the machine shop which called me couple weeks back. They had an Italian-made auto-feed radial drill which kept blowing fuses. When they could no longer get the special 25 Amp beer-bottle-shaped German fuses, someone got the bright idea of replacing the fuse with a standard 25-Amp, Class-R American fuse.

So the machine operator fiddled around and got one to fit in the socket, started the machine up and it ran fine, until the end of the shift when there was a noise in the gear head. He immediately shut down the machine and looked everything over. Then when he went to restart the machine, there was a loud buzz then a pop and lots of smoke. There had been a single phasing power condition in the plant and one phase was out, which he did not realize. When he went to start the machine, instead of the fuse blowing like it should, the fuse held and a $3,500.00 gear motor was toast from the single phasing condition.

So what went wrong... a 25-Amp fuse is a 25-Amp fuse, right? Answer: wrong!

The German-made fuses where a class J fuse, which blows very quickly compared to the Class R fuse that the machinist used. The problem is equipment made in the USA follows the NEMA (National Electric manufacturers Association) Standard for Electrical Equipment, which allows for a small amount of damage before a fuse blows. Compare this to overseas' equipment which is made to the IEC (International Electrical Commission) Standard, which allows no damage at all, and that is accomplished by fast-acting fuses. This is why when you compare a motor starter relay for a USA machine to a IEC machine, the USA fuses are three times the size of the IEC built machines.

This is also where many problems get started. When you go into a Industrial supply house and order a Type 00 NEMA starter USA made, they're in the $400-900 range while a comparable Type 00 in IEC is in the $200-300 range. So you know what happens, you get a mix of NEMA and IEC components and wiring and you have a disaster in the making.

Not only are components manufactured to different standards, so is the wiring in the machine. IEC involves wire sizes using metric measurement. USA machines use the AWG or American Wire Gauge standard. So the question is, can IEC and NEMA exist in the same machine? The answer to this is "yes they can, if proper design is followed, which means proper sized and type fuses and wiring as well as withstand ratings, which brings us to another problem, wrong components on wrong voltages.

I received a call from a large institutional facility with an Olympic-sized pool which used several of the same motors. They kept having problems with motors 3 and 4 always burning out. And this last time it caught the pump room on fire, which was put out with a hand extinguisher. I saw the problem on first view--the wrong motors where being installed.

The pump house has a 120/208 VAC, 3-phase, 4-wire service and 2 of the 4 motors where rated for 230 volts only . They where not dual rated 208/230 volts like the other 2 motors. These 230 volt motors will run on 208 but on hot summer days when the voltage can dip they will overheat and stall.

So you have 2 options, buy a proper 208/230 volt-rated motor or install what are known as Buck/Boost transformers in line with the motor. This allows a 230-only motor to operate on 208 Boost mode or a 208 only motor on a 230 volt line or Buck mode. They put the proper dual-rated motors in and have not had a problem since. **

I ran into a similar but different problem in a Fabricating shop where they kept blowing Relay's and motor starters out in a large metal shear.
This is a big boy it can handle a 18' foot piece of high carbon steel up to ¾ " thick and they where running it on 480 Volts 3 phase but when I opened the lid to the controls it was marked 230 volts ac only? What was this machine doing on 480 volts? Well it seems the electrician who came and installed the machine convinced the owner that the machine would run much more efficient on 480vs 230 which is usually the case but not this time.

He should have installed a step down transformer from 480 to 230 but what he did was just change the motor leads which let them run on 480 volts. Which you can do the motors are rated 230/480 volt but the problem was the relays and other components were all rated to handle 300 volts maximum and while the machine would run on 480 it was overwhelming and burning up parts. This also presented a danger to the operators because at least once the lid on the control box blew open from the violent reaction from parts shorting out.

In this case because the transformer was going to run over $2500.00 it was cheaper to just replace all the 300 volt undersized parts with parts rated to 600 volts. Which is what the previous electrician should have done but did not.

He then showed me a machine called a Iron Piranha it nibbles and punches steel plates and was always blowing out and burning up the control relay here the proper voltage relay was installed but not the proper amperage withstand rated one. The relay was designed to handle 600 volts at 15 amps but the machine draws 25 amps and while the relay could handle an occasional cycle of 25 amps thru it when the machine was being constantly used it could not and the relay would catch fire so a 30 amp rated relay was installed which handled the load plus gave the machine a safety factor when it was in constant use .While working at this facility one of his customers who was picking up an order, asked me to come over to his oil blending facility seems the lights always blinked in back work area of the plant and electronic items were getting damaged from surges. Now this was a long run but the wiring seemed sized right and terminated right but when I put my meter at main service it was 120/230 but when I got to the shop side it was 20 volts low on one side and 30 volts high on the other phase. I suspected a loose Neutral wire which can cause this condition but they seemed tight it was when I started following the neutral wire out thru the shop I was horrified to find the neutral wire
was not going back to the main service but to a steel beam which was being used as ground and was causing the voltage imbalance. They arranged to have a proper sized neutral line run from the shop to main service and all the problems disappeared.

This could have been disastrous if the neutral wire had fallen off the steel beam all the items in the shop would have produced 230 volts at there receptacles causing a fire due to the imbalance. This is why electrical services have a ground rod and ground to metal water pipe should the neutral be lost coming in off the pole, besides the other safety issues they handle.

As you can see there is a lot more to know about machines than the typical text book or training class provides. The other problem with machines and equipment is that until the 2007 NEC code there was no set standard to be followed with the designing of machines

Only a couple paragraphs and good common sense. But wait are not all machines suppose to be UL or other 3rd party rated what about OSHA .Well the answer comes down to who was enforcing what code in what area and when it comes to industrial machines it is anything goes. Yes you will find UL listed components but the whole control most likely is not unless it is for special applications like Elevators or hazardous locations like Petro Chemical plants.

NEC now has guide lines which are supposed to be followed but go into any maintenance
Shop or for that matter many electrical contractors' shops and see if you can find a NEC or any other code book. Unfortunately there are many electrical contractors who never get there work inspected or permitted and maintenance people only know what the other guy taught them. And since Heavy Commercial and Industrial sites rarely get inspected for anything other than OSHA coming by if a complaint has been filed there is several generations of wiring and machinery which has been installed any way any one cares to.

This is why these types of fires are difficult to investigate and determine a cause unless an investigator has strong engineering skills in this particular area.
Because when it comes time to pointing fingers, who do you point them at?
And unless it is a considerable loss to an insurer or there's death or serious injury most claims are just paid or never even turned in they just have some one come and fix it, and hopefully they know what there doing.

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