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Industrial Electronic Repair

Are You Well Grounded? Don't Be "Shocked" if You're Not

National Circuit - Wednesday, November 24, 2010

“Shocking” Info Bites: 

  • Almost 500 people die each year from electrical accidents, mostly in the workplace, putting it among the top 10 causes of accidental death in the U.S.
  • Approximately 80% of all injuries and fatalities caused by electrical accidents are not caused by the electric shock itself, but by the intensive heat, light and pressure blast caused by electrical faults. 
  • The blast made by vaporizing metallic components can break bones and damage internal organs.

Scary?  Don’t be one of these statistics. One important factor in plant safety is proper grounding techniques.   There is no faking it here, so make sure you are working with a licensed master electrician.   Here are just a few important things to remember about grounding to protect both people and equipment:

  • The ground wire must be sized the same size as the supply wires or one size smaller as a minimum.  The three-phase power brought into a plant must also have a ground wire.
  • Do not mix wires of different voltages in conduit.
  • Never run any wires through an electronic control panel that do not relate to the function of the panel; electronic control panels should never be used as a junction box.
  • Never allow field wiring to come in close proximity with the controller boards.
  • Never add relays, starters, timers, transformers, etc. inside an electronic control panel without first contacting the manufacturer for specific instructions.
  • Never run refrigerant tubing inside an electronic control panel (ammonia will destroy your electronics).
  • If the electronic control panel has a starter built into the same panel, be sure to run the higher voltage wires as indicated by the manufacturer since EMI from the wires can interfere with the electronics if run too close to the circuitry.
  • Never daisy-chain or parallel-connect power or ground wires to electronic control panels.
  • Sensitive electronics require special grounding; ground impedance of one ohm or less may protect people from electric shock but may not be enough protection for electronic equipment.  IEEE recommends a ground impedance to be less than 0.25 ohms for proper protection.
  • Check all devices immediately after installation to verify proper wiring; receptacles should be checked to avoid common wiring errors such as reversed polarity or an open neutral.
  • Check the manufacturer’s requirements, codes, and always hire a licensed master electrician for electrical work.  It may save a life and it will almost certainly save your electronic equipment.

The bottom line is, we CAN protect ourselves from electrical accidents AND prevent costly equipment damage by using certified devices, testing equipment from reputable manufacturers, and keeping up to date on electrical codes. For specific code compliance information see http://www.neccodebooks.com or get the latest electrical codes from http://www.nfpa.org/catalog/.

If your electronic equipment does get fried, we will be delighted to provide power supply repairs, servo drive repairs, or virtually any other type of industrial electronic repairs you need.  National Circuit's tech team is here to help you.

What To Do About Loose Connections

National Circuit - Tuesday, November 09, 2010

Wow.  Loose connections…now that’s a “loose” term if ever there was one! 

Connection problems are indeed responsible for many problems with electronics of all sorts. 

Note the key words are connection problems because the problem may very well NOT be looseness at all.  So step away from the torque wrench or worse-yet the screwdriver. 

What seems like a “loose” connection could be just that, but electronic problems are more often the result of bad connections caused by:

  • Oxidation of contacts
  • Corrosion of contacts
  • Dirty contact surfaces
  • Cross threading
  • Wrong bolt or screw
  • Wrong connection sizes
  • Broken conductor stands away from the fitting

Tightening the connections in any of the above scenarios will not fix the problem and may make it worse.  Connections that are disassembled, cleaned, and reassembled have a higher repair success rate.

It should also be noted that tightening connections as part of regular maintenance can often be the cause of problems, not the cure. 

Truly loose connections result in higher resistances which creates excess heat, one of the biggest causes of electrical fires. 

Loose, under load terminals result in arcing which damages the threads and causes microscopic pitting.  Then, even if the terminal screw is retightened, it will not properly compress the conductor and will reseat  only to the point where the damage occurred.  You still end up with overheating and inoperative equipment, or maybe even a fire.

Remember this equation:  Clean contact surfaces and the proper exertion of force and pressure = good connections.

If you are sure that your connection(s) need tightening, always use a torque wrench with appropriate torque values as set by the manufacturer or codes to avoid over-tightening.

How often should you inspect connections?  If your shop is clean, climate-controlled and reasonably vibration free, once a year.  A dirty, high vibration shop should have more frequent inspections.

For most shops, getting printed circuit board repairdrive repair or otherindustrial electronic repairs, it's best to send them to an expert electronic repair provider.

At NCI, our techs do it all day every day.  After being inspected and repaired, your entire unit, not just the connections, will also be under warranty for one year.  Check out our website at www.industrialelectronicrepair.biz  or call our customer service team at 800-257-4021 for assistance.