Do I Need to Pull Test

Pull Testing Lifting Equipment:

I get asked all the time about pull testing lifting equipment. Is it required? How do you do it? Who does it? I have written the answer out via email so many times I thought it was probably time to make a post about it. Lets start with exploring exactly what the code says:

As a note – I highly recommend you purchase ASME B30.20 before working inside this code. I am grabbing snipits from the code so that we can discuss from starting point but you should read and understand the whole code before acting on any of this.

  • “New and reinstalled lifting devices shall be tested by a qualified person, or a designated person under the direction of a qualified person, prior to initial use to verify compliance with applicable provisions this volume…”

So we are required to do testing and inspection. It goes on to say:

20-1.3.8.2 Load Test

  • “prior to intial use, all new, altered, modified, or repaired lifting devices should be tested and inspected. If performed, tests shall be done under the direction of a qualified person and a written report furnished by such a person…”
  • “The load test, if made, shall consist of the following operation as a minimum requirements
  • Hoist the test load a sufficient distance to ensure the load is supported by the lifter, or apply the required load if the test is made using a testing machine.
  • After the test load is released, visually inspect the lifter for deformation, cracks, or other defects.

The first thing I would look at is just how the words are chosen. There are lots of ifs and should but no musts or shalls.  When I read this I feel like it is saying you need to do some sort of testing and inspection and a lift test is recommended but not necessary.

I have seen people interpret this code one of three ways:

  • Load test every device produced.
  • Do testing but not necessarily load testing.
  • Load test each new design as pat of the design validation.

The main issue I have with testing every beam is that in many cases it can be cost prohibitive. For smaller bars, say a 10ft long 5ton there really isn’t a problem as any overhead could pull test it. But take for instance a 100ton lifting beam. To load test this you need a crane, but you don’t want to take that crane to 100% capacity so you end up needing around a 125ton crane. Then you need counter weights – if you are like many companies out there that don’t want 150tons of weights sitting around you end up needing the counter weights off a second large crane. Then you get into the paradox of load testing as there are the same risks for testing the new device as there are for using it. If the equipment breaks there is a chance you could tip the crane over. This process could cost upwards of $10,000 per device.

People often respond to this explanation with why don’t you build a test bed? I don’t think there is much of a savings if you think of the equipment required to test a lifting beam that could be 100ft long and over 100tons capacity. The equipment ends up being heavy and slow to use. The one company around here that has built one it worked really well with lifting beams but it was really awkward to deal with the sling angles on spreader bars. It also had a huge foot print.

But the fact it is hard isn’t a good reason to not be safe.

 

How Do I Do It?

In Canada we defer to engineers to make decision more often then other places in the world. Here we have a two part process that uses engineering to offset the risk of failure. The first part of the process is to have an engineer design the lifting device. This includes everything in the BTH-1 design code and they certify the drawing. This happens once per design.

The second part of the process is for each individual piece of equipment produced we perform a non-destructive test such as magnetic particle inspection and have an engineer review the equipment and the inspection and issue a certification. This happens when a new piece of equipment gets put into service put also on an annual basis. We generally only do pull testing when the customer or engineer requests it.

This process satisfies our health and safety people and honestly I think there are very few failures.

 

My thoughts:

I have produced many spreader bars but have only pull tested a few of them. As mentioned above you are testing to either validate the design or to check the manufacturing (or both). I feel a competent engineer following BTH-1 in most cases shouldn’t need to validate the design through pull testing (although they should reserve the right to request it). When I ask for pull testing to validate the design when there are additional unknown parameters, material strength or loading scenario that makes the calculation difficult to estimate. In a straight forward scenario I have found that BTH-1 design code is well written and sufficiently conservative for use with out requiring additional design confirmation. In addition if you are designing to a 3:1 safety factor but only testing 1.25:1 something would have to be drastically off in order for failure to occur.

There are three fundamental things that can go wrong during the manufacturing process of building most lifting equipment: material selection issues, error in the construction procedure (welding problem) or error following the drawings.  Load testing addresses most of these issues but does so in a reactive way.

You can also hedge against these problems with a post construction weld inspection to make sure construction matches the drawings and the welding was performed to standard. Material selection can be verified by conducting a review of the MTRS.

So what is the answer? You must inspect and test, you should load test and who ever is doing the engineering should specify the rest of the process. These are the notes we put on our drawings:

 

 

So those are my thoughts on load testing lifting equipment. If any one from the load testing camp wants to let us know how they do it I would love to hear it.

Until next time thanks for reading.