Load Test of Overhead Cranes (Multiple)

[SEOH]

I am working on a project where we have two overhead cranes running on the same runway. The cranes need load tested per OSHA requirements. My question is: OSHA nor ASME B30.20 make it clear if the load test needs to be performed with both crane bridges under load at the same time?

Any thoughts?

 

[TehMightyEngineer]

We have similar setups in our precast shops and I've interpreted it as; no, you do not need to load test both cranes at the same time. It's definitely loosely worded though so I could see arguments both ways. In our case using both overhead cranes to team lift is very rare and when utilized is practically never going to be at the rated limits for both cranes. Likewise we almost never have both cranes doing heavy lifts simultaneously adjacent to each other. Given the intent of the load test to establish whether there were any major design, fabrication, or installation errors it seems that the vast majority of issues would be discovered by load testing each crane individually and thus the complexity of load testing both simultaneously is not warranted. However, if you had a shop where regularly both cranes were utilized at max load simultaneously then, while not specifically required, it would seem prudent to test the cranes in that configuration.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[MotorCity]

Recently had a similar situation. We did not load test both cranes simultaneously. The cranes are to be tested to 125% of rated capacity. That extra 25% is similar to an impact load in terms of magnitude.

Since you do not design the structure for two cranes w/ simultaneous impact load, you would not load test both cranes simultaneously which would produce the same effect. I would not argue against testing one crane at the prescribed 125% while the other crane is simultaneously loaded at 100%.

 

[dhengr]

SEOH:
The intentions of the OSHA and ASME tests you are talking about are to test the immediate structural member cap’y. and mech. component strengths of the O.H. crane. The tests are not intended as a means of testing the, worst case, strength and adequacy of the bldg. structure, that would be a whole different testing regimen. However, in the process of testing the crane, you will want to consider load and trolley locations which cause the max. loads, forces and stresses in the various components. That is, with the trolley almost anyplace, (1.25)(rated crane cap’y.) pretty well tests the trolley and its mech. parts, but it may not test the trucks, or induce the max. bending or shear on the spanning bridge structure.

 

[TehMightyEngineer]

dhengr: To expand on that, my usual process for testing an overhead crane is to pick up the load about a foot of the ground with the trolley at center span of the bridge, run the trolley to one end of the bridge, travel the crane down the runway the length of least one runway span with the load at one end of the bridge, move the trolley back to center span of the bridge, and finally raise the load up more to ensure the crane hoist isn't having any issues as the hook gets closer to the hoist, and then set the load down. This should efficiently load tests most of the components in their worst conditions including the end trucks and the supporting runway framing.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[FLCraneBuilder]

We very often do two crane pics full loaded (what we refer to as tandem picks)
and is common for us to set up radio controllers such that they operate two cranes simultaneously - to support this scenario. Bridge Building shops often do 3 & 4 crane pics

As said by others, OSHA is not clear on this

so it comes down to:
1) what is the actual operational application of your cranes? Does it merit this form of testing?
2) What is management comfortable with? - In this litigious society we live in
3) What is the building, columns & runway beams designed for? Two cranes bumper to bumper or X feet apart? All this may be moot if not bumper to bumper. Be reminded that the runway structure, hence facility, will see double the longitudinal force no matter how far apart the cranes are (at least that's how we design for longitudinal restraint)

Best regards