A special overhead crane load test

After the bridge crane is produced, there will be equipment performance testing before it is officially shipped to the customer. After the bridge crane is installed, various safety tests need to be performed, including load tests. When conducting load testing, the process needs to be arranged according to the customer's preparation. Today we share a more interesting testing process. In order to test this bridge crane, the customer prepared 100 tons of water.

Bridge crane specifications and testing procedures

The new has crane has a safe working load of 75t and an 18m span with a 12m height of lift, reeved on six falls of wire with a 50m longitudinal travel distance.

Prior to testing the crane, the customer prepared a calibrated test weight in the form of a 100 ton water bag, as well as a precision calibrated 100 ton load cell, a laser deflection measurement unit and all associated rigging equipment required to conduct and perform such tests. Four water bags are assembled via a load cell and crane hook assembly, the so-called "swarm effect".

Prior to the actual testing, the crane installation engineer participated in multiple on-site meetings with the customer and crane manufacturer. He needs to review drawings, customer procedures and initiate installation plans.

Logistical factors and intricate planning was involved to work out how to get nearly 100t of water to the client’s location.

This meant a convoy of 8 water trucks having to be mobilised to the site and the water being vacuumed through pumps into the suspended water bags.

The crane manufacturer also flew in from Sweden to see their crane undergo its testing, which would have been the first time they had seen the crane since it went through its FAT (Factory Acceptance Testing) and FAMAT (Failure and Mode Analysis Testing).

Since the crane has a lifting capacity of 75 tonnes, an overload of 25% more than the SWL has to be applied, meaning 93.75 tonnes has to be applied incrementally, this is called the 'proof load'.

Once the load is applied, the crane installation engineer needs to conduct several tests such as functional tests, electrical inspections, structural inspections, deflection readings, static and dynamic tests.

All these tests are carried out under the close supervision of engineers and comply with DIN EN 13001/15001 standards. The crane and structure were successfully installed within three days.

What we learned from this case

After we complete the production of the crane, we will conduct a factory inspection according to the customer's requirements, so we have some experience in load testing of bridge cranes. After studying load testing cases from other companies, we found some learning materials from the Internet to improve ourselves. We extracted some content from what we learned, including when performing load testing on bridge cranes, commonly used methods include but are not limited to the following:

• Theodolite detection technology: Use theodolite to detect the main beam of the crane, and measure the deflection value of the main beam by observing the change of the scale ruler.
• Total station detection technology: The total station is a powerful and widely used optical instrument and can be used for the detection of bridge cranes.
• Radiographic inspection technology: used to detect the quality of welds in the upper and lower cover plates and webs of the bridge crane's main beam.
• Acoustic emission testing technology: This is a non-destructive testing technology that can be used to detect some key parts of bridge cranes.

During load testing, you need to pay attention to the following issues:

• Preparation: Before starting the test, you need to turn off the power, check the tightness of all connected parts, check the winding of the wire rope, check the insulation resistance of the circuit system and electrical equipment with a megohmmeter, lubricate all lubrication points, and ensure that all reducers , brakes and hydraulic oil tanks have been oiled as required. At the same time, any loads that may interfere with the test need to be removed.
• Designated personnel: Ensure that all personnel not related to the test have left the test site, such as driving inspectors, ground command personnel, hook lifting personnel, etc.
• Test steps: Carry out no-load test, dynamic load test and static load test according to the test requirements, observe and record the test results.
• Security measures: When conducting load testing, necessary security measures need to be taken, such as setting security warning signs, restricting access, etc., to ensure the safety of the testing process.
• Data analysis: Organize and analyze test data, identify possible problems, and make necessary adjustments and improvements based on test results.

In short, when performing load testing of bridge cranes, it is necessary to pay attention to safety issues and adopt appropriate testing methods and steps to ensure the accuracy and reliability of test results. At the same time, necessary adjustments and improvements need to be made according to the actual situation to adapt to different testing needs and conditions.

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