This picture serves as a reminder of why no one should ever stand under a hanging load!

We can prevent accidents like the one pictured above by performing frequent and periodic inspections on cranes and below- the-hook lifting equipment. Frequent and periodic inspections are defined in ASME B30.20 Below-the-Hook Lifting Devices, while crane inspections are defined by other industry standards. Lifting beams come in many different configurations, but inspections are very similar. The Frequent Inspection starts with a global review of the beam which looks for obvious material deformation, bent hooks, missing retaining pins, keeper bars, safety signs and manufacturer's labels. Then inspect the hooks or attachment

points of the load to the beam:

       Are the pins that connect the "J" hooks or other lifting points to the beam in good condition? If there is more than 2-5% obvious indentations, consult the manufacturer about replacements. Are the hooks bent?  If so they need to be replaced.

       For beams with adjustable lifting points or bails, we carefully inspect the mechanism that holds the assembly position.

       Is there sufficient wear or degradation that would allow the assembly to inadvertently slip out of position during a pick?

       Are the pins or clips that hold the position in good condition? Are the shackles/links/hooks/slings in good condition?

       Are the pins or other retaining devices in place to prevent the load from being released?

       Are they sized properly if they have been substituted from the original design?

The next step is to visually inspect the beam for obvious weld cracks or other signs of deformation. Cracks in structural members would warrant the beam being tagged out of service until repairs can be made. Cracks in spacers or other non-load bearing members need to be evaluated to determine if they would be detrimental to the operation of the beam. The bail or bail pin between the crane and the beam should be inspected for obvious wear and excessive indentations. If the beam is made of channel, I-beam or other structural members, checking the straightness of the beam can determine if the beam has been subjected to excessive forces or loads. A simple piece of string pulled taught along the edge of the structural member will quickly determine the difference in the camber and sweep of the lifter. Anything in excess of 3° out of alignment should be investigated.

       During Periodic Inspections, the same inspections as above are performed and recorded for trending data. In addition, the following items are inspected:

    Dye-penetrant checks should be performed at the critical loading areas on all hooks or other members that connect the load to the beam. After removing paint, oil, and other debris, this non-destructive test should indicate no cracks in the base metal.

    Dye-penetrant checks should be performed at all structural welds in the bail assembly and the beam. After removing paint, oil, and other debris, this non-destructive test should indicate no cracks in the welds (or in the base metal of the pin.)

The mill duty equipment found in industry is usually designed for severe duty cycles and minimal maintenance. The inspection criteria and maintenance procedures mentioned are what we at Bushman Equipment have found to be useful in maximizing the longevity of lifting equipment. This is not intended to usurp the original manufacturer's recommendations or other regulatory authority. While required by ASME standards, inspection of all lifting equipment is also a prudent maintenance procedure because it improves the overall productivity and safety of the manufacturing line. Maintaining a regular inspection and maintenance program on lifters will help ensure a long useful life of the lifter and a better return on your investment.

For more information refer to ASME B30.20 standards.

Crane safety requires careful attention to detail.

Bushman Equipment, Inc. recently designed and manufactured a modified version of the model M2038 motorized, rotating axis grab that increased the efficiency of an assembly process at The Falk Corporation plant in Milwaukee, WI. Falk is a manufacturer of industrial-mechanical power transmission components.
Marty Kuklinski, Senior Tool Engineer at Falk, needed a system with the capability to lift and simultaneously rotate a family of machined gear housings safely and efficiently. This would allow assemblers to access the top and bottom of the housing while it is suspended from the grab.

Local Bushman representatives from John Maye Associates LLC assisted the Falk engineering team with this special application. They determined how the operational characteristics of a model M2038 could be adapted into a grab that would provide an effective solution. Such special application requirements are a routine request for Bushman, and their custom design team easily refined this model into an innovative lift, clamp, and rotate device for Falk.

The grab is designed to grip the outside of the gear case and rotate its horizontal axis 90 degrees. A self-locking acme screw shaft, actuated by a motor, provides the gripping strength. In addition, a set of specially designed sliding incline planes automatically increases the gripping force based on the weight of the load being lifted. A reducer, with an adjustable torque limiter, protects the motor. The bail is adjusted using an acme screw assembly to accommodate a variety of different gear case models and differing centers of gravity. Two self-locking worm gear reducers, driven by electric motors, enable the rotation process. This special design allows the customer to properly position the gear cases, thereby eliminating product damage and improving the assembly process.

Rotating axis grab built by Bushman Equipment for the Falk Corporation

A unique, rotating axis grab solved a challenging problem faced by a manufacturer of special refractory products. The application required a unique grab that could safely pick up and gently rotate 2,500 lb refractory blocks.

These refractory blocks are very brittle and slippery to hold, similar to chalk. The dilemma for Bushman was to apply the right combination of gripping pad material and gripping force. If the block were to slip, the dust would fill in the pad crevices and the grab would lose its grip. If the block was gripped too tightly it would crumble and fall to the floor. Additionally, the sides of the blocks were not parallel, and had low spots making the application even more complex.

Bushman developed a special five surface gripping pad to be able to apply the right amount of pressure. The rectangular center pad is surrounded by four round satellite pads, each of which are in a “ball and socket” pivot joint attached to a spring backed movable arm. The satellite pads compensate for the uneven surface of the blocks, and maintain enough gripping area to adequately distribute the required gripping force. The pad material was made from special conveyor belting and glued to the plate. The block is rotated about its axis by the grab rotation drive system. Bushman selected an AC adjustable frequency drive to achieve smooth starting and stopping, thus preventing the block from slipping out of the grab’s grip.

This design effectively provided a solution to handle heavy, yet delicate loads with uneven, slippery surfaces, and simplified a difficult and time consuming process for the customer.  

Downtime for maintenance is a standard part of production.  It helps to ensure reliable equipment performance.  However, it still means that for some period of time, you are not making product, but instead are generating cost.  Thus, reducing downtime provides a favorable payback, because it allows quick resumption of production.  When the same solution that reduces downtime also enhances operator safety, the decision to implement is easy!

Custom 70,000 lb capacity grab has four legs that open and close on a circular-plate electrode simultaneously, ensuring that equal pressure is applied to the entire outside diameter.

Nucor Steel was trying to reduce maintenance downtime on its electric steel furnaces. The maintenance involved removal of the bottom electrode, a 120 inch diameter circular steel plate.  Through the course of furnace operation, the plate sustains a significant amount of wear during the melting process, and must be replaced every eight weeks.  The plate is part of a complex assembly that enables current to flow through the scrap metal charge, causing it to melt. 

The old method for retrieving the bottom electrode plate was to hydraulically push it up in the air, then retrieve it with a mechanically activated clamp device.  This work was very complicated and time consuming, depending on the thickness and wear pattern of the electrode. It usually took up to an hour of operator time just to hook up to the electrode.  Nucor also had some bad experiences in removing the plate with the original lifting device that further extended downtime by 6 to 8 hours.

Lifting grab is designed to withstand high temperatures inside electric steel furnace.  Its legs are operated remotely as the grab secures and lifts bottom electrode in furnace without human intervention.

Bushman Equipment, a Milwaukee-based custom manufacturer of handling and positioning equipment, accepted this unique challenge.  It helped Nucor Steel design a motorized grab that can be lowered into the hot furnace to securely grab the plate for lifting, regardless of the furnace temperature and electrode characteristics.  The electrode can now be changed in about an hour, without human intervention.  

Bushman Equipment’s 70,000-lb capacity grab has four legs that open and close on the circular plate simultaneously, ensuring that equal pressure is applied to the entire outside diameter.  The grab is lowered into the furnace by an overhead crane, and the legs are operated remotely.  Special wear bars that can withstand the high temperatures are attached to the top and bottom of each of four sliders; these wear surfaces allow the four legs to extend and retract easily. 

A drive system that includes a brake motor and double reduction gearboxes eliminates the potential for back drive in case the plate or grab contacts obstacles during lifting.  A low-speed, high-torque clutch is used to prevent the drive system from being damaged during the clamping process.  

The first time this lifter was put into service, Nucor Steel saved up to 8 hours in removing the electrode plate and performing needed maintenance, while providing for a safer operation.  And, from a bottom-line standpoint, the company was able to start generating cash more quickly!