A Case Study in Electrical Failure due to Corrosion Topic: Our Mission Statement

Posted on August 11th, 2016 in Uncategorized | No Comments »

Bus Plugs

Bus Plugs

Safety Disconnect Switch

Safety Disconnect Switch

This is the first in a series of blogs that outlines a detailed analysis of the corrosion problems found in a piece of equipment needing refurbishing.

At MIDWEST, a portion of our business is refurbishing electrical switchgear.  Refurbishing old equipment includes electrical, mechanical and cosmetic reconditioning of used switchgear.  For example, this includes reconditioning.

Most importantly, our shop wizards fully dissemble the functional electrical and mechanical innards and recondition and / or replace them as necessary, in order to bring the equipment back to full functionality, just as it was brand new from the factory.  This often includes plating electrical parts with a thick coat of pure silver.

And of course, each and every item is tested to our stringent standards before it is shipped out to a customer.

As far as just the cosmetics of the metal enclosure goes, for years I have watched our shop perform miracles.  They can take an old, corroded enclosure, sand it down to bare metal, prime it, and respray it in one of our paint booths, and have it come out looking just as good as if it were new. Their technical knowhow never ceases to amaze me.

Fusible Panelboard Switch

Fusible Panelboard Switch

 

 

Ounce of Prevention is Worth a Pound of Cure

Posted on June 16th, 2016 in Electrical Preventive Maintenance Services | No Comments »

MIDWEST Field Services was at a manufacturing facility in South Central Wisconsin performing inspections and testing of 15KV load break switches along with 480V indoor substations.  The services were being performed as part of scheduled electrical maintenance services.  During our inspection of the outdoor 15KV load break switches it was discovered that one of the fuse holder assemblies was not installed correctly resulting in excessive heat being generated and the fuse holder overheating to the point that it melted down and nearly fell out of the fuse assembly.  Had that occurred the 15KV fuse would have likely fell out of the holder resulting in a single phase condition and the potential for damage to the downstream equipment.  After a hard-focused inspection of the damaged fuse holder assembly it was determined that the threaded assembly was either cross-threaded or the threads in the cast part were defective leading to the assembly being hard to turn which one may have mistaken for it being tightened properly.  Catastrophic failure would have occurred if this deficiency hadn’t been corrected and was certain to occur if the regularly scheduled electrical maintenance services had not been performed.  In conclusion, we believe the old adage an ounce of prevention is worth a pound of cure holds true here because the cost of performing regularly scheduled electrical maintenance services was far less than the cost of damaged equipment as a result of the catastrophic failure to this fuse holder assembly, fuse(s), switches and associated switchgear.  Add those costs with the cost due to the loss of production resulting from the unscheduled outage would result in what is known in today’s production world as unacceptable.  The photo below shows the damaged part along with a complete part to show how much damage occurred.

Damaged Part Versus Complete Part

Damaged Part Versus Complete Part

Holding on by a Thread

Posted on May 5th, 2016 in Power Transformers | No Comments »

MIDWEST Field Services was at an educational facility in the Western United States performing inspections and testing of 15KV load break switches and indoor dry type transformers.  The services were being performed as part of an insurance claim.  The electrical distribution system had experienced a failure of some components within the system and the customer was having issues after replacing the damaged components and re-energizing the system.  Our services included but were not limited to performing hard-focused inspections, making minor adjustments to mechanisms, performing insulation resistance testing, contact resistance testing, and winding resistance testing.  No deficiencies were found with any of the equipment so all of the cover panels were installed and the equipment was energized.  It was at this time that the transformers secondary phase-to-phase and phase-to-ground voltages were measured and found to be fluctuating by as much as 50% below the expected voltage.  The equipment was shut down and the 15KV fuses for each of the load break switches were removed and the internal resistance was measured.  The manufacturer has a range for this fuse between 24.871 mΩ and 33.6 mΩ.  The fuses that were in service had resistance values that were nearly twice the manufacturer’s maximum tolerance.  These fuses were replaced with fuses that were within the manufacturer’s resistance tolerance and the equipment was again energized.  The secondary voltages for all of the transformers were again measured and found to be constant and within 1% of the nominal voltage.  One of the original 15KV fuses was opened up and found that the fusible link inside was connected by a small fragment of its original configuration.  The fuses were literally holding on by a thread inside which caused the increased internal resistance and translated into the erratic voltages seen on the secondary of the transformers.  Long story short, the entire electrical distribution system was exposed to the short circuit and while other components ultimately failed this event reinforced that the electrical stresses were experienced by the entire distribution system and caused other components (fuses in this instance) to be compromised to the point they were unacceptable for continued service.

Worst of the 10 Worst Electric Poles

Posted on October 15th, 2015 in Uncategorized | No Comments »

Worst of the Worst 10 Electric Poles

The Worst Hollowed Out Electric Pole in 40 Years

When this electric pole (see image) was cut down, it exploded into a hundred pieces when it hit the ground. This was for a private overhead service along a roadway to remote buildings and was replaced with an underground service. It was obvious the pole was very old, but one would never guess it was so hollow, unless you tapped it with a hammer. And that could have been a mistake if the lines were still energized. The overhead lines may have been holding the pole up. This was the worst of the worst electric poles we have seen in 40 years. And no there were no 4 legged critters living in the pole. Just bugs, now homeless.

 

Circuit Breakers: We’ve got what you need.

Posted on February 23rd, 2015 in Circuit Breakers | No Comments »

MIDWEST sells reconditioned, used and new Circuit Breakers.  Call today at 800.803.9256! 

All manufacturer’s available – Cutler Hammer, General Electric, ITE, Siemens, Square D, Westinghouse, ABB, Airpax, Allen Bradley, American, ASEA Brown Boveri, Bryat, Bulldog, Challenger, Crouse Hinds, Federal Pacific, Fuji, Gould, Heineman, Kraus Naimer, Merlin Gerin, Milbank, Mitsubishi, Moeller, Murray, National, Sace, Sylvania, Telmand, Thomas and Betts, Trumbull, Tyco, Vois Worth, Wadsworth, Zinsco, etc.

Bus Plugs: We’ve got what you need.

Posted on February 23rd, 2015 in Bus Plugs | No Comments »

MIDWEST sells reconditioned, used and new Bus Plugs.   All manufacturer’s available – Square D, ITE, General Electric, Westinghouse, Cutler Hammer, Bull Dog, Continental, Federal Pacific, Gould, Siemens, etc.  Call today 800.803.9256!  http://www.swgr.com/store/Bus-Plug-Home.aspx

What is the lifespan of batteries for Arc Flash Hoods with cooling fans?

Posted on August 26th, 2014 in Uncategorized | No Comments »

The Arc Flash Department at MIDWEST is asked all the time about the life span of the batteries for the Arc Flash Hoods with cooling fans.  The cooling fans are powered by eight (8) AA batteries.  The batteries have a lifespan of 6 to 8 hours of continuous use.  Click on the link and you will find a list of all the Arc Flash Hoods that MIDWEST carries.  http://www.swgr.com/store/Protective-Clothing-And-Equipment/Hoods.aspx

 

AG65H-A - Arc Flash 65 Cal Hood with Cooling System

Hazard Risk Category 4 – ARC RATING 65 cal/cm² Style Hood with Cooling System

Infrared (Thermographic) Scanning Bus Plugs Finds Defective Connections

Posted on January 3rd, 2014 in Infrared Scanning | No Comments »

MIDWEST Infrared Scans miles of bus duct and thousands of bus plugs every year. By using our large real time Infrared (Thermographic) Scanners, this is a very practical and valuable service. Our Thermographers are frequently asked what the most common serious problem they find on bus plugs. The answer is heating at the disconnect fingers. The disconnect fingers are spring loaded contact clips located on the back side of the bus plug. Depending on the size of the bus plug, for example a Square D PQ3603 (30 amp bus plug), the disconnect fingers may be the size and appearance of small clothes pins or as big as your fist for a large bus plug, like a Square D PTQ36120 (1200 amp bus plug). If the mechanical connection of the disconnect fingers to the bus bar in the bus duct is deficient or outright defective, the heating at the connection can be enough for our experienced Thermographers to detect. The same for heat due to poor contact surfaces between the bus bar and contact tips of the disconnect fingers. Sometimes the disconnect fingers are not even clipped on to the bus bar, but are bent under or over the bus bar. These defects may be present for years and not manifest themselves until the circuit becomes more heavily loaded. MIDWEST’s Thermographers are trained and experienced in reconditioning and testing bus plugs in our Switchgear Service Shop. They may have even melted a few disconnect fingers on one of our high current test sets, just for fun of course, when no one was looking. Actually that is what we call ‘real world’ training.

Locating these problems on energized bus plugs is extremely important because of the damage that can occur to the bus duct itself. We can repair or recondition a 400 amp Cutler Hammer ITAP 365R bus plug, but the bus bar in bus duct is more costly and time consuming.  So finding this common problem with in-service bus plugs is also finding a more serious problem involving the bus duct. Both very important.

GE General Electric AC364RG Simple Fast Question with Pictures

Posted on November 15th, 2013 in Bus Plugs | No Comments »

General Electric AC364RG Bus Plug - Inside View

General Electric AC364RG Bus Plug – Inside View

MIDWEST’s Switchgear Engineers and Technicians receive calls for technical help with bus plugs every day, day after day. It’s a big part of the service MIDWEST provides to those purchasing electrical switchgear. Sometimes the questions are more about electrical power than equipment. Most of the questions deal with details about the equipment and problems associated with installation. But sometimes we get simple blunt non technical requests that surprise us and we have to think for a moment to realize why it’s important to the person requesting the information. An example is a purchasing agent that wanted the availability, cost, and pictures of a GE General Electric AC364RG bus plug. That was it. His name was Pat and that’s all he wanted and he wasn’t interested in any technical questions. After some conversation about many images available in GE catalogues and lots of images on the internet, Pat was getting a bit impatient. Polite but impatient. After a couple more quick questions, a number of things became suddenly clear. First, Pat was not Mr. Pat, but Ms. Pat, with a raspy voice. Pat’s job was simply to get a GE General Electric AC364RG fast. Availability, price, and images that was all she needed. Simply procurement and she seemed pretty good at it. But she was instructed to get pictures specifically of the inside of the bus plug and the back side of the bus plug. Could we get her the pictures or not? Our answer was yes. Her response was ‘Thank you.’ Done.  Purchasing agents frequently operate at hyper speed and have little time for conversation. She got the price, availability, and images she wanted. We got the order and a surprise by how fast it happened.

Transformer Calculator

Posted on May 29th, 2013 in Power Transformers | No Comments »

Transformer Calculator

Transformer Calculator to help customer decide what transformer they need for specific load.

MIDWEST’s web site has a “Transformer Calculator” to help customers decide what transformer they need for specific load. We are frequently asked by customers to help them determine what size transformer they need to replace an existing power transformer.  The Transformer Calculator uses voltage, current, and Kva.  If you have any two, it will calculate the third value.  This allows the user to quickly see what happens if they make some changes.  We had a customer ask about a Square D 50 Kva, 480 volt to 208/277 volt dry type transformer.  When we discussed their load needs and diversity, they decided they needed a 75 Kva transformer instead, based on their present and expected future load.  This is a common occurrence.  By having access to the power transformer calculator, you can play with the numbers yourself.  The usual variable is current, aka load, amps, juice.  The voltage is usually a known, fixed value.  So by calculating existing load and estimating future load, you can quickly estimate the size of the transformer you might need, in Kva, by using the Transformer Calculator.  We also suggest having at least 20% excess capacity.  Quick tools such as this should not be used for design purposes.  That needs to be left up to experts.