KTM Solutions Professional Engineering Provides New Life to an Old Tool

Background

Recently, a local manufacturer contacted KTM about investigating a set of lifting fixtures that had been in use for over 30 years. As a part of our client’s safety program, they had decided to evaluate all of their lifting devices to ensure that they were safe and in compliance with industry standards. They specifically asked us to examine a set of spreader beam lifts that were used to pick up large enclosures and were rated at 10 ton capacity.

The Problem

Upon initial inspection, it was clear that the lifts had a structural problem. The round fastening holes had become ellipse-shaped, a definite sign of yield failure. Our engineers determined that the beam itself was adequate to support the rated load (as calculated per the ASME standards); however, it was clear that the way the beam fastened to the enclosure could result in loading only a small number of the attachment fasteners that were necessary to carry the rated load. The holes had been designed to be slightly oversized to ensure ease of assembly. This oversizing was not, in itself, a problem, as ASME’s Below-the-Hook design standard does not require fasteners to be tightened to a specific torque if the fastener acts as a pin, as opposed to a friction clamp. In this instance, our client wished to avoid bolt torquing as this could damage the enclosure being picked up and slow down the assembly processes. Not torquing the bolts, however, meant that the system would need to be analyzed as a pin connection since there was a very real potential for only one bolt to carry the load. In fact, the elongation in the existing bolt holes suggested that single bolt loading was indeed the case. While this is permissible under certain requirements of ASME-BTH standard, the load applied to these holes was too great for repeated use.

The Solution

Through additional research at the client facility, we determined that, while a past usage of the device required a much higher load capacity, our client’s current usage required only a fraction of the original load rating. By making some minor hardware changes and down-grading the lift rating, our client was able to safely continue using the lifting beam. The end result was a very happy client with peace of mind that their lifts are now adequate for the job.

About

KTM is a team of professional engineers that partners with manufacturing companies to overcome challenges and deliver the custom design solution and the expertise you need for your project.