Maintenance and Repairs — Back to Basics

With all the automation in today’s manufacturing plants, the typical maintenance technician with a few years or more of experience has an array of high-tech skills. The acquisition of these skills is often not easy, and the challenge of becoming proficient is part of what makes this work interesting and rewarding. In many cases, the person who just brought a particularly complex machine back online could look in all directions for as far as he can see and not see one other person capable of doing that (his buddy Frank could, but Frank is on the next shift).

It’s not just complex equipment you have to know, it’s also complex and capable test equipment. It’s not the 1970s, where being able to use a Simpson 260 analog meter was good enough for most electrical work. A Rip Van Winkle from that era, waking up today, would be astounded at what you can do with even a mid-level DMM. Trot out half a dozen other diagnostic tools, and you quickly can compare to a deer in the headlights.

But if he’s got a solid grounding in the basics and you do not, he will run circles around you. Having a solid grounding in the basics means that you not only understand them, but your thought process begins with them when performing work and especially when troubleshooting.

If a motor in a PLC control loop fails to run when the process variable says it should run, for example the mixer needs to run once the vat is full of material, what should you do? Being a bit of a PLC wizard, it would make sense to start by simulating the inputs and checking the lights on the output module. Hmm. Ok, maybe the module is bad so replace it. And so on. But Rip won’t start there, he’ll walk out to the motor and notice the disconnect is open. Problem solved.

What Rip did was start with the basics. Checking for power is the first thing you do when something doesn’t work. But why the motor power? In any PLC-controlled system, you always start with the final control element and checking the PLC itself comes last. There weren’t PLCs in Rip’s day, but there were electronic control systems (the predecessors of PLCs). When Rip’s father started out, plants used mostly pneumatic controllers. The basic rule was always the same, start with the power supply.

How many power quality problems have defied “expert” analysis and not been solved despite buying the latest harmonic analyzer? You can bet a large portion of those, if not all of them, were ultimately solved by doing something very basic, such as eliminating neutral-ground bonds or in some other way bringing the system into compliance with Art. 250.

How often to you revisit this list of basics?

• Ohm’s Law. This is the key concept to correctly applying Art. 250, part V. It’s key to many other things, as well.
• Equipment hygiene. Properly securing cables, putting covers back on, removing scrap, ensuring markings are legible, and generally keeping things clean and tidy will eliminate an assortment of failure risks.
• Troubleshooting basics. The first step is to correctly define the problem. If you get this wrong, you’ll chase your tail for a while until you come up with a different definition. Which still might not be the right one.
• Documentation basics. You always record the “as found” condition before changing anything. If it doesn’t match the “as left” condition that was previously recorded, you gain valuable information. If you make changes and don’t know where you started, you lose valuable information. Always record how you left it. If the form permits, record why you changed it.
• Lubrication basics. If motors are failing at a high rate and the failure mode is related to the bearings, you probably have someone mixing incompatible greases.
• Job planning basics. This boils down into these main areas: procedures, test equipment, spare parts, lubricants, special tools, and PPE. Arriving at the work area only to trek back to the shop for an insulation resistance tester shows you didn’t read the procedure and thus did not address the basic planning for test equipment.
• Safe condition basics. You know this particular machine runs just about all the time. So one of the first things you want to do is coordinate with Production on when you can shut it down. Hauling all of your stuff out there and then asking could mean they tell you that you can’t do it today because of an order deadline. In an operating plant, it’s a basic fact of life that you need permission to perform lockout/tagout and if they can’t spare the equipment at the moment you won’t get that permission.