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Re: Design of Crane-Supporting Structure Including Testing Load[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: Re: Design of Crane-Supporting Structure Including Testing Load
- From: "Gary L. Hodgson and Assoc." <design(--nospam--at)hodgsoneng.ca>
- Date: Thu, 10 Jan 2013 08:31:53 -0500
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Behnam,I am referring to Canadian standard CSA B 167 Section 6 for load testing. Prior to initial use, the following items and components shall be tested:
a, motions; b, limit switches at full speed; c, limiting and indicating devices (where provided); d, circuits, controls, interlocks, and sequences of operations; e, crane motions, holding brakes, and travel brakes with the hook carrying1) the rated load capacity. The specified speeds at rated capacity shall be attained, provided that the power supply to the crane is as specified; and 2) 125% of the rated capacity. The specified speeds need not be attained, but the crane shall be able to deal with the load without difficulty. Prior to initial use, the vertical deflection of all new, re- installed, modified or re-built equipment shall be measured. The vertical deflection of the girders produced by the weight of the trolley and the rated load shall not exceed the maximum allowed by the applicable design specification. The tests performed in accordance with item (e) shall be performed with the crane or hoist installed on its supporting members (runway of monorail). The test report shall be prepared that includes the results and readings from the test specified in this clause. The test report shall be retained in the log book.
The purpose of the testing is to prove the crane is satisfactory to lift the rated load plus 25% to confirm the structure of the crane and all its various mechanisms are satisfactory. Hence, the test to 125% of capacity should be conducted with the load in the centre of the span, with motions to the sides restricted to the centre half to two thirds of the span. Move the load down aisle with load centred and then move the trolley to each side within the limits mentioned above.
As far as I know, the 125% test load may be to allow for impact but I was not on this committee which prepared the standard. I was on a predecessor committee and I believe the purpose of the added 25% was to test components to ensure they could withstand accidental overloads. Cranes are designed for the rated load plus an impact factor. As the structure is designed for the rated capacity plus an impact factor of either 10% or 25% depending on the type of crane control, it should be Ok but I never allow the trolley in a test to reach its closest hook approach unless I check the structure design parameters.
I hope this helps. Gary On 2013/01/10 5:27 AM, Behnam Heydari wrote:
I have industrial concrete structure with 200 ton crane. My question is with regards to loads due to load-testing and rating of cranes. WorkersComp standards such as WorkSafeBC OHS Regulation 14 requires that cranes be tested at 125% of their rated capacity. How is this requirement addressed in the design of the crane-supporting structure? Is it assumed that the maximum wheel loads provided by the crane supplier already include this 125%, or does the designer of the crane-supporting structure need to apply 125% to the wheel loads on top of the 1.5x1.25 load factors? Alternatively, is it common practice to consider the 125% load test value in combination with 1.25 impact and a live load factor of less than 1.5 considering that the load is carefully controlled during the load test? Behnam Heydari
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