125% Crane Load Test 1

[StrP88]

Does anybody know where the 125% load coming from for the load rating/load test cranes?
What code? What standard this comes from?

Thank you

 

[jimstructures]

OSHA Requires the 125% load test. CFR 1910, I think, just Google Crane load test and the CFR number will come up.

Jim

 

[dhengr]

StrP88 :
Gosh...., one early morning some guy was sitting on the can, and thought 1.25 is a beautiful number, lets use that at the meeting today. That number has been around for some time now. I remember testing lifting equipment to 1.25 and 1.5 times to stenciled allowable load in the early 70's. You are being asked to prove that the system will carry a specific load, so you test it to something greater than that as proof, you pick a number and sell it to the client. In this process, we are thinking about all the components of the system, and the stability of the crane, etc., so obviously it should be grater than one, but we are not interested in having to rebuild any/all of the parts of the system because they have all failed.

 

[MotorCity]

It would be interesting to learn of how the 1.25 came about.....why not 1.3? why not 1.4? etc. Anyone who has been to an industrial or manufacturing plant would agree that things get abused and pushed to their limit every now and then. That includes equipment, parts, and even the building and its components. I have seen the results of building elements that have been used in a manner that the design engineer never could have imagined (for example, a come-along being wrapped around a column to move a heavy piece of equipment). Often in codes, the 1.25 is referred to an impact, collision, test, factor, etc......but in reality it is really the "stupid factor" to account for unintended consequences.

 

[JDengineer]

I would venture to guess it has more to do with the impact loading of the crane.
Most codes require a 1.25 load factor for the dynamic effects of initially moving or stopping the load.
Riggers should always know the weight of the item they are moving. They may of max out the claimed capacity without thinking about it. This 25% should still keep them safe.

 

[dhengr]

MotorCity:
Our design FoS’s are all greater than 1.25Fy whether you use ASD or LRFD, and by the time you figure in all of the .6Fy or .67Fy’s, etc. or the load factors, resistance factors, etc. etc. Many lifting components, particularly those subject to repeated reuse and abuse are designed with a FoS of 5:1: other components which get better care and inspection are designed with a FoS of 2 or 3. Most of these values are set by historical actions within an industry, by committee, a bunch of old guys/gals with considerable experience in that particular industry. They aren’t an absolute/perfect/exact number for all conditions. They are a reasonable number, based on long industry experience, to add some uniformity and consistency to a given process.

Over the years, and in a number of different code and industry environments, I’ve suggested that we give some of the code and std. writers a stipend as they leave that code committee, so they could write some history and chronology of the code parts that they were involved in, for all of our edification, addressing questions exactly like this one. Often, reading the commentaries of codes and stds. are as important, and more enlightening, than studying and applying the formulaic nature of the code or std. itself. And certainly, as our codes and stds. get more complex and convoluted we lose any feel for how things really work or perform, we just blindly apply the formulas and go on tho the next problem. Then, we also have many less experienced people, some completely unqualified, attempting to do this work, and it seems, with little or no guidance from a more experienced practitioner. The whole thrust of today’s code environment is that if you can read and digest the convoluted b.s. called a code, anyone can do that design, no questions asked or allowed, just follow the cookbook and shut-up, experience and basic knowledge of subject matter is not required, the code Gods will guide you.

For lack of real knowledge and real experience on the matter, we are inclined to want an exact number, or the perfect formula which solves all, to hang our hat on. We really don’t seem to be able to use basic engineering and mechanics of materials principles, along with basic code criteria to solve an engineering problem any longer, we want a code paragraph and an exact formula to solve the problem or we don’t know what to do. We design with FoS’s of 1.5-1.75 and test to 1.25 in this case, so we don’t bend things too badly, and other than setting some uniform number, who cares if it is 1.2, 1.25 or 1.3 or 1.4? Many times those numbers where spec’ed. by the client, but 1.25-1.5 has been the range as long as I’ve been doing this, 47 years or so.

 

[OldBldgGuy]

dhengr, I gotta say I loved that little rant. Too bad the ability to reason isn't included as a necessary part of getting a license. It really isn't difficult to figure out what you want to accomplish, and if you could get accurate information on materials and loads you could figure out your own what factors you should allow to get there and be safe for various end purposes, but that's really too much to ask, isn't it?

 

[FLCraneBuilder]

1) I respectfully disagree with Jim Structures - Paste from Osha below - states shall not be more than 125%

1910.179(k)(2)
Rated load test. Test loads shall not be more than 125 percent of the rated load unless otherwise recommended by the manufacturer. The test reports shall be placed on file where readily available to appointed personnel.

Note that in reading Osha Q & A's , it places a good bit of emphasis on the recommendation of the manufacturer

2) In my opinion, QC & legal folks make way to be of an issue on this topic.... the very large majority of accidents are human error, bad rigging, unknowns etc. A crane that works at 100% will work just fine @ 125% Assuming the motor controllers (or overload limit switches) are adjusted to allow higher current draw. Note that I don't believe the runway system designers consider this 125% load case... Nor should they... if the hoist is out in middle of the bridge, the runway doesn't see the greatest loads

3) Regarding Dhengr comment: - At CMAA, we are now incorporating commentary in to the specification, specifically where paragraphs are altered or added. It is our intent to capture the history of the decisions making process

Best Regards;

 

[jimstructures]

FLCraneBuilder In 25 years of designing buildings for cranes I have never seen a crane manufacturer recommend less than 125% for the testing load. OHSA says the load test should be done with up to 125% in the middle of the bridge, giving 62.5% of the max load on each crane beam. The ASCE standard requires the crane plus impact on the structural bracket or supporting assembly. I don't have the manual in front of me at the moment so I can't quote the exact wording.

OSHA CFR 1910.179(k)(2):
Rated load test. Test loads shall not be more than 125 percent of the rated load unless otherwise recommended by the manufacturer. The test reports shall be placed on file where readily available to appointed personnel.

So in practice, test loads in the middle of the bridge beam are 125% of the rated capacity, unless the manufacturer recommends more.

Jim

 

[IFRs]

Some states have their own more stringent rules. Be sure to check out yours.

 

[StrP88]

IFRs (Petroleum),

May I ask where can I find the State rules for cranes?
I am in the US and State of Indiana.
Is it in the State building code? Is there State of Indiana crane association?

Thanks for the direction.

 

[dhengr]

StrP88 :
Check out your local OSHA, your local Industrial Commission, etc., people who might govern this type of activity. Maybe ask your client who is requiring this test and what are their test criteria, so you can discuss these with them. And, don’t be embarrassed to ask that kind of question. We are not expected to know everything about everything under every condition, particularly about a new type of problem. We are expected to use good engineering judgement and use our experience and education/knowledge to make wise engineering decisions to safeguard workers and the public. ASME BTH-1 and their crane stds. are a good place to start, so we don’t look too dumb when we ask the question.

 

[IFRs]

I thought Michgan MIOSHA had more stringent requirements but I just checked and it seem to be 125%. It's been a while since I was involved in any BTH designs projects so I may be out of date and apologize.