Proof load tests on board – test weights, water bags and dynamometers

Before the test

• Notice to the master. If stability could be endangered, the competent person tells the master the date and time, the test load and the maximum outreach over the side. They should not start until the master confirms in writing that stability will not be endangered and that the deck and hatch covers can support the test load.
• Rigging. Temporary guys and stays for masts or samson posts and any slewing guys are rigged. For gantry cranes on rails, movement along the track with the load suspended must be controllable.
• Conditions. Daylight, or adequate lighting; wind and gusting within the crane’s design limits; precautions for everyone near the test area.

The test load

• Weights must be suitable and of verified weight. Cast weights, and other weights where practicable, are weighed on a machine of certified accuracy. If weighing is not practicable, the weight is calculated and the calculation is kept and attached to the certificate.
• The test load includes its lifting gear (spreader, slings, shackles). It should be not less than the table value and not more than 2.5% above it.
• For cranes, the ILO code says test weights only should be used. For derricks after repair or renewal of a part, a spring or hydraulic weighing machine may be used, accurate to within plus or minus 2.5%, with the reading held steady for at least five minutes.
• The ILO model certificate (Form No. 2) is stricter: balances may be considered only for retests after repair or periodic retests of appliances with an SWL not over 15 t, accurate to within 2%, held for five minutes, and never for initial tests. Where weights are not used, the certificate must say so.

Water bags

Water-filled proof-load bags are widely used by service firms for cranes, davits and gangways. The international texts in this lesson do not mention them by name, so treat them as a method that needs acceptance:

• agree the method with the competent person, and with the RO when it acts for the flag, before the test;
• the mass of water and bag must be established, typically by a calibrated load cell in the rigging or a calibrated flow meter, with the calibration certificate available;
• bags fill gradually, which is useful for building up to the test load, but the test must still reach the full test load, with the same lifts, slewing and braking as a test with solid weights;
• an open-sea crane test may call for different loads; that is for the RO.

Running the test: derricks

The ILO code, appendix A.4:

• Test with the boom at its maximum outreach, at the lowest angle to the horizontal marked on it (ILO Form No. 2 says generally 15 degrees), in the two extreme slewing positions and midships.
• Raise the boom and load with the derrick’s own winches as high as possible so many rope layers reel onto the drum.
• In each position, lower the load about 3 m at normal speed and brake sharply; show the load can be held with the winch drive switched off.
• Union purchase: test as rigged per the rigging plan, through the working range, with the angle between the hoist ropes as near 120 degrees as possible, and on both sides.

Running the test: cranes

The ILO code, appendix A.5:

• Check from the maker’s data that the crane can take the test load, structurally and for stability.
• Raise the test load far enough to load every tooth in the gear wheels.
• Test variable-radius cranes at maximum, minimum and intermediate radii (ILO Form No. 2).
• Hydraulic cranes that cannot lift 25% over SWL: the greatest possible load, in general not less than 10% over SWL.
• After the overload test, put the crane through all motions at maximum rated speed with the SWL suspended (slewing limited to two complete turns if it slews freely), test all brakes, reconnect and test the safe load indicator by adding load progressively, and test all limit switches.
• Finally, the competent person thoroughly examines the crane.

Loose gear testing

Loose gear is usually tested in a test bed. The ILO code asks that the recording test equipment has been checked for accuracy by a competent person within the 12 months before the test, that machine errors are taken into account, and that pulley blocks are tested with their sheaves reeved where possible. Each item is thoroughly examined after the test.

The certificate

The certificate (ILO Form No. 2 or MSC.1/Circ.1663 appendix 1) states, for each appliance, its description and mark, the angle or radius at which the test load was applied, the test load, and the SWL at that angle or radius, with the competent person’s signature, date and place.