EOT Crane Deflection

What is the plumb bob for? A superfluous distraction in a test question?

Is there any other practical way to measure?

Strain gages.

Couldn't you suspend the plumb bob from the roof above using the piano wire? Use it as a point of reference to take measurements before and after applying the test load to arive at the deflection. I must be missing something here.

Part of my role in a previous life was to commission EOTC's and part of that job was to do deflection tests. What I say now is based on Australian Standard. Don't know where Tony gets 150% SWL it sounds a bit scary. The only time a crane lifts more than its rated capacity is when brake tests are done and not used for deflection test and is 120%SWL (I think). I used to suspend a tape measure off the crab (trolley) of the EOTC by means of vice grips with the bottom of the tape about 150mm above floor level. Maximum allowable deflection is 1mm in 500mm of span. So a 20 meter span is allowed 40mm of deflection at 100% SWL. Deflection must be measured with the bridge centred over building columns first. Measured at centre span and both extremes of the bridge. Once that is done crane must be moved so it is central between two columns and measured again. This will give an indication of building deflection as well. Measurement is simple. Put a straight edge from floor to tape, measure where the top of the edge is on the tape and record the number. Load the crane and then compare the straight edge and tape again. Difference between readings is the deflection of the crane. When releasing the load ensure that the unloaded measurement is the same to ensure that the bridge has returned to it normal state and n permanent distortion has occurred. Always do a couple of test lifts first to make sure it is safe to get under the crane. Hope this helps.

you don't!

I grew up in the local steel works in South Wales, working on cranes with a SWL of 400tonnes, and that was done by Lloyds of London Insurance Underwriters and a specialist team from a test company.

But why do you want to measure the deflection? Or is this homework?

Thinking about your question.... why do you what to know? So you can do it yourself?

Dangerous if that is the answer!

Second... for you to ask such a questions tells me your knowledge is very EXTREMELY limited and any answer given here could prove to be extremely dangerous to you and any crane you decide to "play" with.

I see you, taking any answer, and there are good ones here, and trying it yourself.

Don't do it! and furthermore I suggest that forum members don't give you any more ideas on how to do it either.

What happens when you don't know what you're doing!!

Dear Mr. Appanna,

Normally the EOT CRANE will be tested at Manufacturer's work place, as prescribed in the Standards/Agreement.

The Deflection Test can be done at Ground itself, before dispatch.

The Procedure followed is:

1. Keep the Trolley(s) at the centre.

2. Keep the Safe Working Load at the centre, by means of concrete block(s) or steel.

3. Before loading and keep the trolley at the centre provide a strain gauge or a vertical scale and pointer at the bottom of the Beam at the centre and note the scale reading.

4. Once the crane is loaded, the deflection will occur and note down the scale reading.

5. The Difference in the initial reading and final reading after loading is the deflection.

The Standard followed was Maximum Deflection SHALL NOT EXCEED L/900 where L is the Span of the Crane. Some Manufacturers follow L/800 as the Max. Deflection.

This measured deflection to be compared with Design Value and if it is more, the corrective action to be taken by the Designer/Manufacturer, to limit the Deflection to conform to the Standard or Design Value.

DHAYANANDHAN.S

Dear Texasron,bigg,Tony S, Philphy and dhayanandhan thank you all for your advice. Your inputs are helpful. As mr Dhayanandhan mentioned normally it is done at the manufacturers, but some principals insist on check up at erection.

Answering Brich"s apprehension, testing at rated load as well as at proof load which is higher than the SWL as specified in the statutory rules, is a standard practice and is required to be carried out periodically.

Dear Mr. Appanna,

The Deflection Test can be done at site after installation but before commissioning. The difficulty will be putting Safe Working Load and hook it up. Then measuring the deflection at the centre may pose some problem as the load should be at the centre and deflection also to be made at centre.

Alternate arrangement to be made for measuring the deflection at the centre if load is of bigger volume.

Dhayanandhan.S

Dear Mr. Dhayanandan,

This exactly was my initial apprehension . However I think the suggestion made by " bigg" to measure from the roof end or temporarily tack welding a pipe section at midspan to shift the plumb line position away from the load could solve the problem, I presume.

your details were quite informative and thanks again

"testing at rated load as well as at proof load which is higher than the SWL as specified in the statutory rules," Who's statutory rules?

"is a standard practice and is required to be carried out periodically." Who says so? To what standard, procedures or policies are you working to?

If these load tests are required for insurance purposes which is the usual case, then it should ONLY be carried out by a certified testing body like TUV or Lloyds, and NOT by you. What qualifications or certification do you have to allow you to conduct and certify a crane load test?