In many facilities, the breaker maintenance program consists of "replace when nuisance tripping becomes intolerable." Yet, nuisance tripping isn't the worst failure mode. It's far worse when the breaker just doesn't trip. This failure mode means you have no circuit protection.
Breakers fail in this "no trip" mode for a variety of reasons, all of which can be addressed in a way that nearly guarantees this mode will not occur. Among the causes:
If you look at that list, you can see these are essentially "time in service" issues. You can't prevent them, but you can correct them via "fix or replace." That is generally preferable to the spectacular fireworks method of determining a breaker went bad.
- Dust accumulation.
- Grease absent, hardened, or contaminated.
- Fatigue of metal parts.
- Trip linkage is broken or out of adjustment.
- Dashpot leaked.
||Get a grip on accuracy.
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Your company recently changed electrical testing firms. The new firm, which is NETA-certified, came highly recommended. However, the plant manager is puzzled by the firm's report. They identified nearly 30 breakers that need repair of some sort. "Yet," the plant manager says, gesturing around the room, "the lights stay on just fine."
The testing firm also submitted a list of recommended tests that haven't previously been done at your plant. These include transformer oil analysis, testing of the power factor correction capacitors, and a recommended program of cable testing.
The plant manager wants you to confirm or deny the firm's findings. Where do you start?
Visit EC&M's website to see the answer.
A cable pull isn't something you want to repeat in the near future, but certain mistakes can ensure that's exactly what you'll be doing. When you replace cables in a repair situation, there's often pressure due to a limited downtime window and managers hovering around. You'll save time by not hurrying, because you'll have to do the cable pull once.
Here's a list of some key tips to keep in mind when doing this type of work:
- Inspect the raceway before installing new cabling. Look for sharp edges at each access point of the pull (e.g., pullboxes). Ensure the raceway is securely supported.
- Inspect the cable. Ensure you have the right cabling and enough length of each type for a given pull.
- Test the cable. For critical cables, perform insulation resistance tests before and after the pull.
- Warm it. In an emergency repair situation, you don't have time to let cables warm up to an optimum pulling temperature. However, cold cables are typically brittle, and even minimal pulling force can be enough to damage the insulation. To avoid damage, aim a forced air heater at the spool(s) and pull slowly. The air blowing across the cable should feel warm, not overly hot, to humans. This process will also help dry the cable.
- Waste lube. Cable lube is cheap. Cables are not.
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Section 110.12 contains arguably the least understood and most commonly violated requirements in the NEC. For example, consider 110.12(A), which requires closing unused openings in equipment. If your facility already has this problem nailed, the odds are good you can find dozens of such violations in a tour of any facility picked at random.
You can't close these openings with duct tape or other flimsy material. The closure must provide protection substantially equivalent to that provided by the enclosure. Though the NEC doesn't explicitly state what kind of protection, it means protection from shock and arc flash. So use the standard enclosure plugs to close these openings.
To read more on this story, visit EC&M's website.
Follow these tips and you'll be more safe around flammable materials.
- Use the smallest work containers possible. It's much safer to accidentally knock over a small container of flammable liquid than a big one. Fume output from a small container is also less.
- Cover containers when not immediately using them. This reduces the fume emissions, chance of contamination, and likelihood of spills.
- Empty work containers into disposal containers, not the main storage container for the material. Exception: Your work procedure may instruct you to do this. The reason for this rule is to prevent contamination of the main storage container with unknown materials that end up reacting or causing other problems.
- If there's a spill, stop and clean up immediately if it's small. By doing this, you will limit the vapor concentrations, slipping hazards, and collateral exposure.
- Don't try to clean up a large spill. Instead, leave the area and warn others on your way out. Alert first responders and then your supervisor.