Overload test in a traveling crane 1

[21121956]

Hello everybody:

In a hydroelectric power plant, the overhead traveling crane used for the assembly of turbines, generator and auxiliaries was not commissioned with overload, only was made the test with the nominal capacity. Today, two years later, there is a legal claim for that fact. The question is: apart from the purely legal, how technically necessary is it to do the overload test?

Thanks in advance for your comments.

El que no puede andar, se sienta.

 

[dhengr]

21121956:
Cranes are typically load testing to 1.25 times their rated cap’y. before they are fully commissioned. That’s pretty much an industry std. in the U.S. They are designed with factors of safety much greater than 1.25. What do your spec. and purchase order say for that crane, in this regard? Ask the manufacturer for this info. or for the certification info. from the time of delivery and installation. They may actually have done that final test in your plant. Does it need to be tested? Well…, I was always confident enough in my own designs (or our designs) that I didn’t think they had to be tested, but we had priced what the spec. and P.O. called for, so we did the testing to the customers satisfaction. And, afterword I could always say, ‘see, I told you so,’ with some degree of satisfaction. My calc’d. stresses, deflections, etc. were in pretty darn good agreement with the test results.

 

[Jboggs]

Another reason for overload testing is to prove factors that aren't related to design, such as assembly and welding techniques, actual material properties, even rigging methods. This also answers your other question - "how technically necessary is it to do the overload test". Absolutely necessary! Would you stand under a load supported by a crane that had not been overload tested? I would not. (I don't stand under any loaded crane. Period.)

Common practice is one thing, but where legal issues are concerned "common practice" has little to do with it. Different jurisdictions will have different standards. Even "common practice" varies from industry to industry, from country to country, even from company to company.

I think the issue here will be one of contracts. What test standard was ordered? What was accepted?

 

[dik]

Although 'standard practice', is the overload testing stipulated in a recognised code or standard? I'm not being difficult, I'd just like to know. Thanks.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[LittleInch]

Much depend son what the design code, the specification and the purchase order say.

If either of the first two call for such as test then "technically" it is required.

The thing with loads is that it is very rare for the 100% dead weigh value to be either exact or not involve some level of additional force from speed of lifting, lowering or moving.

These are difficult things to calculate therefore testing to 125% of the static load limit gives you technical cover for those additional loads.

where do you fit into this mess?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[robyengIT]

in Italy the overload test is done to check not only the load itself but the efficiency of the braking system in lifting and lowering

 

[21121956]

Hello everybody:

Thank you all for your contributions.

dik, regarding your question, I can comment on the following:

OSHA, Occupational Safety and Health Administration standard at 29 CFR 1910.179 (k) states:
(1) Operational tests.
(2) Rated load test. Test shall not be more than 125 percent of the rated load unless otherwise recommended by the manufacturer.

On the other hand, FEM, Federation Europeenne de la Manutention states that Dynamic Test is with 1,1 times the rated load and the Static Test is 1,25 times the rated load.

In some hydropower plants the Dynamic Test has been carried out with 1,25 times the rated load.

El que no puede andar, se sienta.

 

[dik]

[Major Edit] Thanks for the source... The FEM seems to put a value on it, but they may not be in effect in North America unless spec'd. It appears that OSHA stipulates 125% (implied, eg. 90% is less than 125%). Does OSHA stipulate that it must be 125% minimum?

I've always used 125% because it 'was the thing to do' without thinking about the merit of the load. It seemed reasonable and I had assumed it was a standard. (the 125% was just a standard load). I've loaded hundreds several dozen cranes to 125% increase and never had a failure. I didn't realise until now that it doesn't appear to have a basis. Thanks.

In response to the OP question, then there may be no merit to the 125% overload unless the crane manufacturer required it or OSHA stipulates a 125% min.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik