Tips & Tricks

The collision of the creative and practical parts of the brain gives us the world's great inventions.

08/26/2008


The collision of the creative and practical parts of the brain gives us the world's great inventions. The basic tools man has invented %%MDASSML%% the lever, the wheel, the pulley %%MDASSML%% haven't been improved on centuries later, but the way those tools are adapted continue to evolve. Electricity is a force of nature and physics, but the taming of that force allows it to move mountains and still remain safe to use.

This is how Tips & Tricks was born more than 20 years ago %%MDASSML%% by facing the problems we see each day on the plant floor and crafting a creative solution. Hundreds of great ideas over more than two decades have helped Plant Engineering readers out of tight spots and helped get the job done safely and efficiently.

Even in today's high-tech world, the basics of tools and nature haven't changed. How we use them has changed dramatically. But there always will be room in a high-tech world for innovative ways to move motors, measure voltage or simply fill in a hole. Here are the 2008 contributions from PLANT ENGINEERING readers to the legacy of Tips & Tricks:



Identifying bad sensors

We have numerous automated machines on site and often cylinder piston position sensors go bad or out of adjustment. It is hard to tell which sensor is out of adjustment if several are daisy-chained to one PLC input. A trick I have found is to use a little pocket “pencil” magnet. When placed next to the sensor that is out of position, the string light's up to indicate the sensor that needs adjusting %%MDASSML%% great time saver.

Peter Palmer

Facility engineer

Endura Products

Greensboro, NC

Fixed tool head near flywheel

In our press shop we have a blanking line where we cut coils into blanks of the appropriate size. The press has a 1.8 meter diameter flywheel. A brake on the outer surface of the flywheel stops the machine. Because of the continuous braking operation, line marks are generated on the outer surface of the fly wheel, which result in poor braking action and affect the life of new brake lining. In the past the flywheel was sent out for machining of its outer surface to remove these marks. However, the total time to accomplish this was 26 hours. To reduce the machining time, we installed a cutting tool head near the flywheel in the press, which enables us to machine the flywheel in 45 minutes.

V.K.Arora

India

Turning items on the conveyor

Material handlers experience an ergonomic issue when cartons are in an undesirable orientation on a continuous motion conveyor. This causes them to bend their wrists every time they remove a carton from the conveyor.

Since the conveyor belt is continuously in motion, you can install a stationary object that contacts the corner of the carton, causing it to turn 90 degrees. If you want the carton to turn a full 180 degrees, install a second stationary object downstream from the first one, which will cause the carton to complete the turn.

Fred R. Hoefer

PM/Project Team Leader

CIBA Vision Corporation

Duluth, GA

Sand as an emergency ballast

In a recent wind event, we had a large portion of our fully adhered EPDM roof system de-laminate. Luckily it did not come completely off. It was held on by the various roof curbs and penetrations, but was billowing 3 to 6 feet in the air.

To reduce the chance of complete failure while negotiations were made with the manufacturer and insurance carrier, 40-pound bags of play sand were used as emergency ballasts. This worked for more than one year, and the roofing contractor removed them during installation.

Thomas Lawson

Facilities Project Engineer

Nissan North America Inc.

Decherd, TN

Run pumps at slower speed

Many companies have processes that require pumps to supply fluids. In many cases, these fluids are throttled back by a gate or ball valves to get the volume needed for their process. The motor is still running at full speed using more electrical power than necessary.

The best way to approach this problem is to install variable frequency drives to run the motors. The drives can be adjusted to the speed needed to pump the right amount of fluid leaving the valves wide open. In most cases, this approach will save you at least 30% in electricity.

Dave White

Maintenance Manager

Titan Wheel Corp. of IL

Quincy, IL

Rusted nuts, socket wrenches

What do you do when a nut has so much rust on it that you can't get a socket to fit on it? When using an adjustable wrench, often the bolt is so tight that the wrench will slip off the nut. Twelve-point sockets might fit on the nut with the assistance of a hammer, but many times the nut is rusted to the bolt so badly that the socket rounds off the corners before the nut starts to turn. Another method is to put a six-point metric socket on an SAE nut. In most cases, the metric equivalent is a few thousands of an inch larger, providing just enough room for the rust, but snug enough to provide a firm fit on the nut.

Frank Anderer, CPE

Facilities Engineer

Navistar Inc.

There's more than one way…

My favorite trick is used when trying to disassemble rust-siezed bolts. After heat-expanding the nut with a torch, lay a wax candle or crayon onto the threads of the bolt. At the elevated temperature, the wax melts and flows like penetrating oil, lubricating the threads. It is still necesssary to loosen the bolts while the nut is hot and expanded, but the odds of it coming apart without twisting off the bolt or galling the flats of the nut are greatly improved over using just the heat/expansion technique.

Ed Rauch

Melting and Recycling Technology Leader

Molten Metal Process Group

Oswego, New York

PLC troubleshootingby adding counters

When troubleshooting on a machine with a PLC, add counters to catch fast transitioning inputs or bits. A possible use would be if you have a fault condition that is triggering, but the fault has multiple possible causes, and the cause happens too fast to catch by watching on a PC or operator interface. Just add a temporary counter in the program for each of the possible causes. The next time it trips, just look to see which counter has incremented. Some PLC programming packages have built in “plotters” or graphs to do this sort of monitoring, but they will not always catch a transition that lasts only one or two PLC scans. A counter in the PLC program will count a transition that lasts just one scan.

Jeff Schindler

Senior Controls Engineer

Production Control Units Inc .

Dayton, OH

Fatigue failure in bolted joints

Fatigue failures can be particularly hazardous because they often occur with no visible warning signs and the failure is often sudden and total. While most maintenance technicians understand how to torque fasteners properly, very few understand the reason why it is so critical to torque properly in applications subject to fatigue. Some simple rules to help avoid fatigue failures include:

Always replace all fasteners in a joint set when one fastener has failed

Never re-use fasteners where the service manual specifies new fasteners when re-assembled

Never use fasteners with any evidence of damage such as nicks or bad threads

Learn to “read” any failed fastener and recognize the signs of a possible fatigue failure

Get engineering support to analyse the loads when a fatigue situation is suspected; especially where danger to people, environment, or property is a possibility

Don't substitute a different grade or type of fastener without review; you may set the stage for another, more serious failure

Don't substitute a standard grade washer where a hardened washer is specified, and never use lock washers in a joint subject to cycling loads

Don't substitute gasket material types (especially non-metallic for metallic types) without a design review.

If you suspect fatigue, a rule of thumb is to calculate the number of cycles a ferrous metal part has been exposed to before it failed. For failures at less than 10,000,000 cycles, suspect fatigue. With failures at more than 100,000,000 cycles, fatigue is not likely. It takes a 3,600 rpm motor only 46 hours to produce 10,000,000 cycles. A 75 rpm mixer shaft coupling bolt failing after 2

Sam McNair, CMRP

Life Cycle Engineering

Charleston, SC



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