Overhead Crane: No-Load,Static Load & Dynamic Load Test

Overhead crane load testing

Overhead crane load testing is mandated by OSHA legislation to ensure electric hoist and overhead crane equipment is in good operating order prior to use, for the safety of your employees and facilities. In order to ensure that the overhead crane is assembled correctly in accordance with the designing parameters, load testing of overhead cranes is typically required by safety regulations and standards.

HD type single girder overhead crane load testing 

What is a Crane Load Test?

We will purposefully overload the overhead cranes during load tests to assess their condition. The burden must be manageable for you to lift and move in regular motions. To confirm that the hoisting crane equipment complies with OSHA guidelines, the lifting crane equipment is often tested with loads up to 125 percent. Wire ropes, hoist chains, and hooks must all be tested everyday, but large or extreme load tests should only be evaluated every six to twelve months.

• Prior to initial use all new and altered cranes shall be tested to insure compliance with this section including the following functions:
• Hoisting and lowering.
• Trolley travel.
• Bridge travel.
• Limit switches, locking and safety devices.
• The trip setting of hoist limit switches shall be determined by tests with an empty hook traveling in increasing speeds up to the maximum speed. The actuating mechanism of the limit switch shall be located so that it will trip the switch, under all conditions, in sufficient time to prevent contact of the hook or hook block with any part of the trolley.

Test loads shall not be more than 125% of the rated load unless otherwise recommended by the manufacturer. These test reports shall be on file where readily available to appointed personnel.

Types of Crane test

 Preparation before test

• Shut down all the power supply, check the connection of each drive mechanism according to the design data, check the deformation of the structure, the winding of the wire rope on the pulley and drum, check whether there are obstacles on the track and hinder the operation of the crane, and clean up the surrounding environment.
• Comprehensively check the correct position of all equipment, wiring and components in the electrical system, especially pay attention to the brake line and correctness, flexibility and reliability of various switches, and the correctness of wiring of each drive motor

  No-load test

•  Does not lift the load, switch on the power supply, start each mechanism to make it run, check the lifting limit, the correctness and flexibility of the running limit of the crane and trolley;Check whether the limit positions meet the design requirements
• Starts each mechanism to run repeatedly for three times, and observes the running condition of the mechanism. Pay attention to the small car cable conductive device, large car conductive device, etc..

Static load test

 The load of lifting rated load should be gradually added to rated load from small to large.Running three times in the full length of the bridge frame, no abnormality will occur. The unloading load will stop the trolley in the span and set the measurement benchmark. Lift 1.25 times the rated load, 100 mm above the ground, stop suspension 10 minutes, unload the load, check for permanent deformation, and then measure the actual arch value of the bridge frame.If there is permanent deformation, the actual arch value can be measured when the permanent deformation is no longer caused by lifting three times continuously.When the trolley is driven to the span end, the actual arch value is measured at no less than 0.7/1000s. At last, the trolley is parked in the middle of the bridge frame, lifting the rated load, and the arch value of the main beam is measured at no more than 1/800s.

Dynamic load test

The rated load is 1.1 times higher than the rated load, and the two mechanisms run in a positive and reverse direction at the same time. The duration of power connection should be intermittent according to the working level of the machine and controlled according to the operating rules.According to the working cycle sequence, the test time should last at least one hour.Each mechanism should operate sensitively, operate stably and reliably, and check the reliability of limit switches and protective interlock devices, the temperature rise of motors and electrical components should not exceed the specified standard, and observe the abnormal sound and vibration of the main engine.

Overhead crane load testing procedures

When testing the capability of overhead cranes, it is important to keep in mind that the test loads cannot exceed 125 percent of the rated lifting capacity. Additionally, all load testing reports must be filed so that the persons in charge may access them.

Pre-test procedures of overhead crane load testing

•  Look up the dos and don'ts, as well as the operational restrictions, in the overhead crane operator's manual.
• Verify  the lifting gear to be used with the overhead crane in normal duties.
•  Ensure that all lifting attachments are sold with load ratings that can be seen.
• 4. Verify that all necessary corrections and repairs have been completed by reviewing the notes from prior and ongoing test and inspections, as well as deficiency reports.
• Confirm that the overhead crane's entire safe operating load is prominently indicated on the crane or on a tag attached to it.
• .Confirm that all allowed operating configurations can support the cranes and loads on the crane runway and runway structure.
• The testing should use the appropriate loads. The proof load must be between but not greater than 125 percent of the rated load, with the rated load testing using a minimum partial load of 25 percent.
•  Review the load testing guidelines and restrictions provided by the overhead crane manufacturer. Remember to keep the reeving arrangement in mind.
• In order to ensure safe lifting practices, proper rigging should be employed for the load testing.
• Safety precautions should be taken to stop people or vehicles from entering the area where an overhead crane is operating.
• All parties involved in the overhead crane load testing, such as the operator, the riggers, and the hand signal man, must be aware of the load testing processes and how they are carried out.
• Thoroughly examine the overhead crane, paying special attention to its structural components since these will be put under stress during overhead crane load testing.
• Prior to the load testing, a visual inspection of the crane runway, track, powder conductors, collectors, and switch gear is recommended.

Overhead crane Load testing

• To measure the deflection of the crane's main girders and the runway girders at center span, the overhead crane should be set up on a stanchion or column of the runway with the trolley or electric hoist put next to the end of the truck at the start of the load testing.
• Lift the rated load high enough to ensure that the rated load is applied to each and every lifting gear train tooth.
• Reduce the load's height to between 4 and 8 inches from the ground.
• Take a deflection measurement. Measure the deflection by moving across the bridge to the runway girder's middle span. Measure the deflection by moving the trolley at its rated load to the middle of the bridge. comparing the results with the information provided by the manufacturer of the overhead crane.
• Start the load down gradually with the holding brake disengaged, and as the test load lowers, switch the controller back to the off position. The load control mechanism must stop the load from increasing.
• Visually check that proper operation ensures control of the rated load for overhead cranes equipped with primary and secondary holding brakes, eddy current or hoist eddy current or hoist dynamic load brakes, etc.
• To guarantee proper brake operation on overhead cranes equipped with a hoist dynamic brake, eddy current brake, or regenerative brake, compare lowering speeds to manufacturer's recommendations.
• Lift the rated load to a convenient height above the ground to ensure the safety of the electric hoist unit in the event of a power outage during material handling operations with the overhead crane and electric hoist. When the primary power source is cut off when the controller is in the lowering position, the load tested should stop descending. Lower the load quickly.
• To accomplish the proof load, test the overhead crane at 125% of its rated load. Repeat steps 2-1 through 2-7 to confirm that the crane functions all work properly throughout these activities.
• To maintain the safety and control of the load while handling the proof load, the overhead crane should be used at the proper speeds.
• Overhead cranes with two or more trolleys, hoists, or other attachments should be subjected to separate testing.
• Utilize the trolley's or electric hoist's full working range while the proof load is suspended from the hook. If necessary, make sure the trolley brakes are working correctly and permit load swing and coasting.
• To check for any binding of the bridge trucks and appropriate brake operation, etc., operate the bridge with the proof load suspended from the hook as close as feasible to the runway rail on each side throughout the full operational range of the runway system.
• When moving at maximum speed with the full rated load, test the brakes on the bridge and the trolley individually to ensure they can stop safely at a distance equal to 10% of full load speed in feet per minute.
• The overhead crane runway should be evaluated with two or more cranes present and loaded to capacity simultaneously. With the weights suspended as close to the runway as possible and the overhead cranes moving over the span between runway supports, the crane runway deflection should be measured. The data should then be compared to the relevant requirements.

Post overhead crane load testing 

• To ensure that the overhead crane passed the tests satisfactorily, a thorough inspection is required.
• Park the crane where it will be most convenient to use it and relax all rigging and reeving to make it possible to inspect the wire rope and reeving components.
• Before mounting the overhead crane, turn off the power and install a safety lock-out device.
• Inspect the runway of the overhead crane for structural flaws, loose or damaged fasteners, track alignment, and a secure connection to the structural support.
• Inspect the overhead crane runway's electrical parts for damage and appropriate functioning. Make that the electrical codes, connections, cables, and enclosures are tidy and secure.
• Verify that all of the wire rope, sheaves, and drums are free of damage or excessive wear. Keep an eye out for any potential damage to the anchor points and end fittings.
• Confirm that all required guards and crane safety precautions are installed. Ascertain that all shafts, couplings, and open gears that people could come into contact with are properly guarded.
• Ensure that all defects, damages, or fixes are marked appropriately.
• Lift the load blocks above any people or anything in the way. Make that the hoist drums have the wire rope wound appropriately. If there is a pendant, remove it from its assigned spot and open the main disconnect.
• Fill out the report form and, if necessary, hold a departure briefing.