The Answer to this Week’s Application Challenge: Below the Hook Lifters

The Answer to this Week’s Application Challenge: Below the Hook Lifters


A customer has a below the hook device for lifting a specific part that weighs 100 lbs. The tag has fallen off and you are requested to do a load test, re-attach a tag and return it to him. The lifter was made “in-house” and does not meet the BTH-1 Standards. There is documentation from previous inspections and it appears that the device has been in service for 6-7 years. Is load testing the device and marking the lifter with a WLL and serial number for traceability to the load test certification acceptable? 


No –  a load test does not verify the working load limit (WLL).  Engineering calculations have to be done on each below the hook lifting device in accordance with BTH-1 before this lifter can become compliant with ASME B30.20 and BTH-1.

The engineering calculations have to take into account the application of the rated load along with the weight of the lifter. For Design Category B, the most common classification, the lifter must be designed to have a minimum of a 3:1 safety factor for limit states of yielding.

With the introduction of the new BTH-1 specification all lifters must be rated for Service Class. The Service Class or Fatigue Life takes into account the number of load cycles that a lifter sees and the service life desired. For instance a lifter that is rated at Service Class 2 can be used for up to 500,000 cycles.

Since most below the hook lifters are welded assemblies, the other design feature that must be considered is the design of the weld joints.  ASME B30.20 states that all welds must be in accordance with ANSI/AWS D14.1 

The above is general information.  For complete design specification you should refer to the latest ASME B30.20 specification.

Mike is a Mechanical Engineer for our Cady Lifters product line at Columbus McKinnon Corporation.

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One Reply to “The Answer to this Week’s Application Challenge: Below the Hook Lifters”

  1. Hi, Are there any websites or books, documents, where you can find examples of application of the BTH 1? I’ve read part of it, but I still have doubts about the checking procedure.


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