Category: Q & A

Will Limit Switches Work Properly if the Motor is Reverse Phased?

Will Limit Switches Work Properly if the Motor is Reverse Phased?

limit switchesJoe, an outside sales and service representative for a Columbus McKinnon distributor and recent safety webinar attendee, asks the following question about limit switches:

“Will limit switches work properly if the motor is reverse phased?”

Perry Bishop, Columbus McKinnon trainer and safety webinar presenter, answers:

When the up or down buttons are actuated, they pull in the proper contact for motor control, hence the up contactor or the down contactor. If the up or down buttons are actuated on a reverse-phased motor, the proper contact pulls in BUT the motor turns in the opposite direction.

If the up contact is in and the motor is headed in the down direction, it is going toward the lower limit switch. When the lower limit switch is activated the motor doesn’t stop because the lower contact is not controlling the motor – the upper contact is. This can lead to two problems:

1) Two-blocking, or running the chain completely out of the hoist, depending on the direction the motor is going
2) Tearing up the limit switch and possibly stripping the shaft

The UP button on the pendant should always be pushed first.

When discussing reverse phasing, it is critical that all customers (and installers) know that when activating the hoist for the first time, the UP button on the pendant should always be pushed first. By doing this, if the hoist is reverse phased, the hook will lower revealing that the motor leads are wired incorrectly. If the motor is phased properly, the hook will raise and the limits will function properly. Either way the potential for “two-blocking” is avoided.

In conclusion, limit switches will not work properly if a motor is reverse phased.

Want to learn more? View our Safety Webinar on “Understanding Hoist Control Circuits.”

This blog post was updated on 10/22/2015 with additional content.

Perry Bishop
Perry Bishop is a Technical Trainer for Columbus McKinnon Corporation.
Reading RFID Chips on Rigging Equipment

Reading RFID Chips on Rigging Equipment

RFID chip

Mike, a Lead Rigging Technician for an equipment rental company in the entertainment industry and recent safety webinar attendee, asks:

“How far away should you be to read a RFID chip for rigging equipment tracking and inspection?”

Troy Raines, Columbus McKinnon Chain & Rigging Product Engineering Manager and safety webinar presenter, answers the RFID chip question:

This is an excellent and frequently asked question.  The simple answer is that it depends on the type of RFID chip being used in the product. For CM Smart ID, we chose a chip that would require the user to touch the reader to the chip. While this might seem inconvenient, the benefits far outweigh the disadvantages for the following two reasons:

  1. To properly inspect any piece of rigging hardware, the qualified person must actually handle it. It wouldn’t be safe or effective to “inspect” rigging hardware from any distance. There is too much risk that a minor issue could be overlooked until it became a more serious safety hazard.
  2. To effectively track inventory, it wouldn’t be accurate to accidently scan the wrong shackle because multiple shackles in the area could be read at the same time. The count would frequently be wrong because you wouldn’t know which shackles were and were not scanned.

Want to learn more? View our Safety Webinar on RFID: Simplifying Rigging Hardware Inspection and Tracking.

Gisela Clark
Gisela Clark is an eMarketing Specialist for Columbus McKinnon Corporation.
Understanding Chain Slings: Why Do Only 3 of 4 Chain Legs Take the Load?

Understanding Chain Slings: Why Do Only 3 of 4 Chain Legs Take the Load?

Randy, an Instrument Technician in the energy industry and recent safety webinar attendee, asks:

“Why do only 3 of 4 chain sling legs take the load?”

Peter Cooke, Columbus McKinnon Training Manager and Safety Webinar Presenter, answers:

understanding chain slings
When using a chain to build a sling, tolerances for chain can make the legs slightly longer or shorter than one another. Because of this, the National Association of Chain Manufacturers (NACM) agreed to only count 3 of the 4 legs of a quad sling to be rated the same. When you first lift the load off the ground the legs that are under tension will stay under tension, so it is important for the rigger to visually see how many legs are loaded before lifting the load off the ground.

To do this, tension up the legs, but do not let the load leave the ground. Safely approach the sling being sure to stay out of the path of tension. You can then quickly check the legs by shacking them slightly. Although you may find all four legs are taking the load, only three are used for calculating the max working load limit of the sling.

It is important to always check the manufacturer’s load charts and safety information prior to making any lift. You must be qualified to lift the load you are rigging.

Want to learn more?

View our Safety Webinar on How to Size Your Chain Slings.
View our blogs on chain sling inspection.

Peter Cooke
Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.
Customer Questions Acceleration Time on Variable Frequency Drives

Customer Questions Acceleration Time on Variable Frequency Drives

3-VFDTom, a salesperson for a CMCO distributor and recent safety webinar attendee, asked the following question on variable frequency drives:

3-step infinitely variable control is 1st detent slow speed, 2nd detent HOLD, 3rd detent acceleration. If the application absolutely requires less than 2.0 second acceleration (Lodestar) can anything be done to accommodate?

Chris Zgoda, Corporate Trainer and webinar presenter, answers:

Thank you for your question. When the power is on and applied to the inverter, you can access the “U” parameters. The “U” parameters are the monitor parameters that allow the user to see what is happening. Too low of an acceleration time could present the following two issues:

  1. It could pull too much voltage off the DC Bus too quickly and cause a Uv (Under Voltage) fault.  Viewing the “U” parameter that monitors the DC Bus voltage you will see the DC Bus has approximately 340 Volts on it for a 230V hoist.  With an UP run button press you will note the voltage drops significantly at the first button press. With too quick of a ramp-up time, the voltage will drop even more causing an Under Voltage.
  2. Another potential fault is an Oc fault (Over Current) fault, meaning the inrush current that energizes the motor stator. Generally, the inrush current is about 150% of full load amps. The faster you take that motor from 0 RPM to 1725 RPM, the more current “energy” it will need.  So you could have a huge inrush current, especially if you have a heavy load on the hook, which may cause the drive to fault out, too.  You can also monitor the output current from the drive in the “U” parameter.

I might also note that the acceleration times are based on the full scale frequency of operation,  meaning an acceleration time of 5 seconds is from 0 to 60 Hz. If you press the pendant button for the 1st speed, it would not take 5 seconds to reach 6 Hz. It would be approx. 0.5 seconds.

Always follow factory service procedures when making adjustments to products.

For additional information, check out our Variable Frequency Drives Safety Webinar.

Gisela Clark
Gisela Clark is an eMarketing Specialist for Columbus McKinnon Corporation.
Do Chain Slings Need to Be Load Tested After a Repair Has Been Performed?

Do Chain Slings Need to Be Load Tested After a Repair Has Been Performed?

Chain SlingXavier, a salesperson for a CMCO distributor, asks the following question:
“I am doing some research on the guidelines and laws concerning repairs made to chain slings. I found some very conflicting information from OSHA and ASME. To summarize, ASME states that chain slings do not need to be load tested after a repair has been performed. OSHA says that new and repaired chain slings must be load tested before being returned to service. I was hoping to get your opinion and maybe Columbus McKinnon’s official stance on this issue.“

Peter Cooke, CMCO Training Manager, answers:
Thank you for reaching out to us with your concern. This is a great question. If the chain is a welded assembly (only certain companies are authorized to do this) and a welded link was repaired, then the sling needs to be load tested. If the sling is made up of mechanical components and those components have been individually load tested by the manufacturer, no load test needs to be done.

For example, I have a single-leg sling and I replace the top oblong link. The oblong link is connected with a mechanical coupler, such as a Hammerlok, and has been tested by the manufacturer. Under these conditions, I do not have to load test the sling, but I would recommend inspecting the sling, link by link, to be sure all components are safe to use per ASME B30.9 and OSHA 1910.184.

For additional information, check out our Chain Sling Inspection Safety Webinar or our new Rigging Catalog.

Gisela Clark
Gisela Clark is an eMarketing Specialist for Columbus McKinnon Corporation.
A Chain Sling Question from the Mining Industry

A Chain Sling Question from the Mining Industry

Chain Inspection photoHere is a question from Adam, a mobile crane operator working in the mining industry, who regards proper rigging equipment and practices as a major safety priority:

“We have a 1-inch GR80 chain sling, 30 feet in length that is around ten years old and in good condition, although there is inner link wear throughout the sling at its bearing points. The narrowest measurement in link diameter at any point was .945″, which is well away from removal criteria. No components in the sling show any evidence of a stretch condition, and the sling has not been subjected to overload to the best of our knowledge, though I cannot guarantee that.

“The reach of the sling is approximately four inches longer than its tag indicates. According to my calculations, this stretch is due to the contact wear in each link. The chain moves freely and there is no binding or restriction of movement. Is this legitimate? If so, does the tag need to be replaced or modified to indicate its current length? Our inspections have always been completed by a company assigned employee.”

Response from Peter Cooke, training manager:

Thank you for reaching out to us. For your reference, I have included a section on alloy rigging chain inspection from our Columbus McKinnon rigging catalog here. Be sure to do a link-by-link inspection and follow the rejection criteria from OSHA 1910.184 and ASME B30.9. Be sure there are no stretched links. Reference the “Allowable Chain Wear Allowance tables” from the manufacturer and ASME B30.9.

Not knowing your exact configuration, I will use a standard DOS 1-inch grade 80 x 30’ reach sling as an example. If we just isolated the chain (taking out the master link, coupling links and hooks) you have approximately 106 links of chain. If you determined the minimum thickness to be 0.945” at the bearing points, that is approx. 0.055” of wear from the nominal dimension. 1” grade 80 chain has a pitch length of approx. 3.07” (dimension from the top inner link radius to the lower inner link radius) Let’s assume that wear occurred at both ends of the chain link. The pitch length would increase by 0.11”. Over the entire chain length you could see an increase in reach of approx. 11.66” (0.11” x 106 = 11.66”)

As long as there are no stretched links or deformation this would be acceptable. There is no rejection criteria for reach other than stretch. Wear is not stretch.

There is also no statement in 1910.184 and ASME B30.9 to replace the tag in this event with the correct reach.

A good practice would be to retag the sling with the current reach. The new tag would be considered a repair so your company’s name or initials would have to be on the tag. A load test would not be required. Lastly, lubricating the chain is an excellent way to minimize wear.

Peter Cooke
Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.
Ask Questions, Share Stories, Get Engaged on Social Media

Ask Questions, Share Stories, Get Engaged on Social Media

We decided to shift gears this week and show you a little of what we’ve been up to on social media lately. We have many exciting conversations and interactions happening there every day with our Channel Partners, end users and material handling professionals around the world. All of you reach out to us for different reasons. Here are just a few examples:

  • Some of you have a question you want answered. We received a tweet from a distributor in Mexico who requested special paperwork for border clearance. We got it to him within hours. This was one happy distributor!
  • Others have a cool picture from an exciting concert or event they attended, so we started a collection on Facebook. We love seeing photos from your kid’s sports game or stage performance or while on vacation. If you are lucky enough to get an application story that you can share, we could feature it right here on our blog. Just send it my way!
  • Some of you need expert advice on specific topics. We have addressed many of your questions here. Below are are few of our most popular posts:

Missing Chain Sling ID Tags and who is to Blame
What is the Working Load Limit of a 2 Legged Chain Sling?
The 3 Most Asked Questions from our CM-ET Motor Hoist Schools
Does your Overhead Crane meet OSHA regulations?
Can Lever Tools be Used to Adjust Slings?

  • We also enjoy your tradeshow engagement on Twitter & Facebook and sharing in your fun. Check out these cool beanies from USITT!

IMG_0654 Beanie Cap #3

Beanie Cap #1
Please feel free to reach out to us 24/7 on our social media channels. We are here to promote safety on the job and help you get the answers you need for any of your material handling questions. The first person to engage with us on each of our social media channels below and tell us your favorite CM product and why will receive a CMCO shirt!

(This means 6 winners in total.) We look forward to connecting with you!

Facebook
Twitter (Industrial Products)
Twitter (Entertainment)
LinkedIn
YouTube
Instagram
Google+

Gisela Clark
Gisela Clark is an eMarketing Specialist for Columbus McKinnon Corporation.
Can Lever Tools be Used to Adjust Slings?

Can Lever Tools be Used to Adjust Slings?

Q & A chat Richard, a salesperson for a CMCO distributor and recent safety webinar attendee, asks: 

“Is it acceptable to use lever tools to shorten or lengthen slings? Are there any concerns of locking up the lever tool brake?”

 

Peter Cooke, CMCO Training Manager and Safety Webinar presenter, answers:
Your first step is to go to the manufacturer to make sure the lever tool is designed for hoisting.  If the lever tool can be used for hoisting, then you need to pre-plan the lift. To do this, you need to know the share of load and go through the calculations to determine the center of gravity. From there you will be able to size your tensions and choose the right lever tool for the application.

To learn more about rigging using lever tools, we suggest you watch our safety webinar on this topic here.

Locking Up a Lever Tool Brake
In general, lever tools are defined by the type of brake they use:

  • Weston-Type, that utilizes friction discs and a ratchet and pawl
  • Ratchet & Pawl, that is a more archaic design similar to an old car jack.

To avoid locking up the hoist, we recommend a lever tool with a Weston-type brake for hoisting applications. These tools rely on friction and provide a smoother operation. To use the Weston-type brake tool you will need to release the load on the brake before removing the load. When the load is a few inches from the ground, switch the hoist to unload and release the tension by operating the handle. This will prevent the hoist from locking. If this is not an option, then you will need to use a ratchet-and-pawl-type lever tool to prevent the hoist from locking when the tension is removed.

Want to learn more about properly rigging and lifting a load? Watch our August Safety Webinar entitled “Determining the Center of Gravity.”

Peter Cooke
Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.
Does your Overhead Crane Meet OSHA Regulations?

Does your Overhead Crane Meet OSHA Regulations?

Jason, an Assistant Manager with one of our Channel Partners, asks:

“I received a call from a customer for whom I had conducted an inspection. The customer stated they received an OSHA reprimand for not having monthly inspections on their cranes. They have 2 top-running bridge underhung trolley-type cranes. OSHA referenced 1910.179 J2IV and 1910.179 B1 as the violations.

In the book I have, 1910.179 B1 states that ‘this section applies to overhead and gantry cranes, including semi gantry, cantilever gantry, wall cranes, storage bridge cranes, and the others having the same fundamental characteristics. These cranes are grouped together because they all have trolleys and similar travel characteristics.’

Are the references for the reprimand accurate?”

Tom answers:

Some confusion exists among crane and hoist owners, users and service providers regarding crane configurations and the application of Federal OSHA 1910.179 regulations. Some of this confusion may be caused by the first definition in 1910.179 – (a)(1):A “crane” is a machine for lifting and lowering a load and moving it horizontally…”  Because all overhead crane configurations fit this definition to one degree or another, we tend to lump them together and assume that all are subject to these regulations.  This is not the case. I wrote an article on the subject entitled “Does OSHA 1910.179 apply?” To read the full article, go here.

A second resource I want to share with you consists of two OSHA interpretations:

Interpretation #1: Click here
Interpretation #2: Click here

Each interpretation makes it quite clear that OSHA 1910.179 does not apply to the crane types you describe. For OSHA to prevail on a General Duty Clause, which they have not cited, they would have to prove or establish risk of serious injury or death. If the operators are doing proper daily pre-operational inspections, or even inspections once per month, they are covered. These “Frequent Inspections” do not have to be documented. (ASME B30.17 & B30.16.)

ASME B30.16 covers the underhung hoist and the “hoist chains” cited in 1910.179(j)(iv). In short, OSHA doesn’t apply.

Below are some additional resources related to this topic:

Disclaimer:
This blog post is Tom Reardon’s opinion of the interpretation of the relevant sections of OSHA. The reader should seek a legal opinion.

Tom Reardon
Tom Reardon is a Technical Instructor specializing in Hoists & Overhead Cranes for Columbus McKinnon Corporation.
Forging vs. Casting: Which is better?

Forging vs. Casting: Which is better?

forging

This question, “Forging vs. Casting: Which is better?” is one that I have been asked many times. To properly explore the answer, let’s first consider the process of each.

Forging and casting are two very different manufacturing methods. When something is cast the material is heated above its melting temperature and poured into a mold where it solidifies. When something is forged it is physically forced into shape while remaining in a solid state – although it is frequently heated.

As an engineer, I have always known that forgings normally have less surface porosity, finer grain structure, higher tensile strength, better fatigue life/strength, and greater ductility than castings. In other words, forgings are generally better for shackles. The basics of why are pretty simple. When you melt metal to cast it, the grain size is free to expand. When it cools back to a solid, the grain structure is courser and more random, decreasing its strength.

But just how much better is a forging than a casting?

I  did some research on the internet and found an excellent research paper* written by members of the Industrial & Manufacturing Engineering Department at the University of Toledo, shared by the Forging Industry Association. This paper compares a single type of product made both ways. Read it here.

How’s this for hard numbers? No pun intended.

Based on this paper:

  • Forged parts had a 26% higher tensile strength than the cast parts. This means you can have stronger shackles at a lower part weight.
  • Forged parts have a 37% higher fatigue strength resulting in a factor of six longer fatigue life. This means that a forged shackle is going to last longer.
  • Cast iron only has 66% of the yield strength of forged steel. Yield strength is an indicator of what load a shackle will hold before starting to deform.
  • The forged parts had a 58% reduction in area when pulled to failure. The cast parts only had a 6% reduction in area. That means there would be much greater deformation before failure in a forged part.

To further illustrate the point, look at these photos from our in-house testing:

forging

These forged CM shackles show significant deformities before failure.

If you were hanging a load overhead from a shackle, wouldn’t you want that shackle to warn you before it failed? Or do you like surprises?

Fortunately, all of our CM shackles are forged;  and they’re forged right here in America at our Chattanooga, Tennessee Operations. Safer and made in America? I think that I will stick to forgings.  What will you do?

* The title of the research paper is “Fatigue Performance Comparison and Life Predictions of Forged Steel & Ductile Cast Iron Crankshafts” written by Jonathan Williams, Farzin Montazersadgh, and Ali Fatemi, Graduate Assistants and Professor, respectively, Mechanical, Industrial & Manufacturing Engineering Department, The University Of Toledo – Toledo, Ohio.

Troy Raines
Troy Raines is the Chain & Rigging Product Engineering Manager at our CMCO Chattanooga Forge Operations.