ASME Below-the-Hook Lifting Devices - Lifted Load Questions

[starcasm]

Hello All!

A customer wants me to check an existing equipment skid for operating load cases and a hoisting and rigging load case. This post is about the hoisting and rigging load case only and the application of ASME BTH-1.

The equipment skid is comprised of various pumps, compressors, pipes, and electrical boxes supported by a steel frame 13'x36' in plan view. There are 4 lifting lugs that I used the ASME BTH-1 standard to check. I also checked the weld connection to the steel frame using this same standard.

Now, the equipment skid framing needs to be checked for the hoisting and rigging load case. Do I stop using ASME BTH-1 and just apply impact factors to the skid framing? Or do I stay consistent and consider the equipment skid framing as part of the lifting devices to be checked?

My engineering judgment tells me to be consistent and consider the skid frame as part of the BTH lifting device assembly. Otherwise I would apply impact factors that seem arbitrary. I am curious to see how others have applied ASME BTH-1 and where the "cut off point" is for applying the standard when the lifted load is part of the BTH lifting device.

Thank you in advance.

 

[dik]

I would normally just design the lifting lug...

There are some exceptions... some mining regulations require that the 'frame' be designed with a SF=5 against failure and if going down the shaft, a SF=10 may be required for both the lug and the frame and rigging.

Dik

 

[JStephen]

Assuming this is a typical skid with those devices permanently attached to it, I would say that your skid is the "load" itself and neither it nor the lugs attached to it are lifting devices per ASME BTH. As it happens, BTH is a handy reference for designing such items, so it's appropriate to use it as a reference. But it would be at your own judgment what design standards, if any, actually applied to the skid or lifting lugs welded to the skid. Note that if BTH/ASME B30.1 applies to the skid, then you're also obligated to label it for allowable load, load test it, etc.