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Pulling forces together (Load Testing)

  1. Jun 16, 2012 #1
    Hello,

    Here's my question:

    When load testing a lifting lug that is welded to the ceiling, placing it under 5 tonnes of pull, using a chain block to tension and a web sling that is attached to the floor directly below, are you:
    A) Pulling 5 tonne down from the lug and 5 tonne up from the floor
    B) 2.5 tonne down from the lug and 2.5 tone up from the floor
    C) Anything else?

    Diagram

    _____________________CEILING
    Lug ----> ρ
    |
    |
    |
    * 5 tonne pull *
    |
    |
    |
    __________ρ__________ FLOOR
     
  2. jcsd
  3. Jun 16, 2012 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    It depends on what moves. If nothing moves, all tensions are balanced so everything is being pulled in the opposite directions by equal forces. So the ceiling is pulling the floor up and the floor is pulling the ceiling down, each using 5,000 x 9.8 Newtons of force, and the building structure is pulling down on the floor and up on the ceiling to balance the tension between the floor and ceiling with the same force.

    AM
     
  4. Jun 17, 2012 #3
    Nothing moves, the tension is balanced with a chain block pulling 5tonne in the middle. So could you say that both lugs are certified to lift 5 tonne?
     
  5. Jun 17, 2012 #4
    The certified load is always less than the test load.

    That is you can work at the certified load indefinitely (until the next test) but the actual test is conducted at a higher load. This builds a safety factor into the certification process.

    The accuracy of load indicators for chain winches are less than the accuracy achievable by hanging weights from your lug and may not be accurate enough to allow certification.
     
  6. Jun 17, 2012 #5
    I see, so could you tell me, if i tensioned the chain block to 5 tonne on the load test indicator did i, in effect;

    Test both lugs to 5 tonnes
    or ,
    Test them each to 2.5 tonne?
     
  7. Jun 17, 2012 #6
    If the test held at 5 tonnes then both floor and ceiling connections were tested to 5 tonnes.
     
  8. Jun 17, 2012 #7
    Thank you very much!
     
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