Electric hoist dynamic load test: a key step to ensure lifting safety

Electric Hoist dynamic load test: a key step to ensure lifting safety
In the industrial field, electric hoists are a common lifting equipment, and their safety and reliability are directly related to the safety of personnel and the integrity of property. As an important means to test the performance of electric hoists, dynamic load test plays an irreplaceable role in the normal operation and long-term use of electric hoists. This article will explore the relevant contents of the dynamic load test of electric hoists, including the purpose, standards, methods, precautions and judgment of test results, etc., aiming to help international wholesale buyers better understand the quality and safety of electric hoists and provide a reference for purchasing reliable electric hoists.

1. Purpose of dynamic load test
The main purpose of dynamic load test is to verify whether the various mechanisms and components of the electric hoist can operate normally under actual working conditions, and whether the overall performance of the equipment meets the design requirements. By simulating the force conditions of the electric hoist during normal use, potential problems can be discovered in time, such as the reliability of the brake, the stability of the mechanical transmission, the wear of components, etc., so as to ensure the safety of the electric hoist in actual use, reduce the risk of accidents, extend the service life of the equipment, reduce maintenance costs and downtime, and improve production efficiency.

2. Standards for dynamic load test
(I) Wire rope electric hoist
According to the provisions of standard JB/T 9008.1, the dynamic load test of wire rope electric hoist requires that the lifting mechanism operates at 1.1 times the rated load for 30 minutes under the conditions of rated voltage and rated frequency, and the trolley runs back and forth for 10 minutes.
(II) Chain electric hoist
According to the provisions of JB/T 5317, the lifting mechanism of chain electric hoist and pneumatic hoist operates at 1.25 times the rated load for 1 hour.

3. Methods of dynamic load test
(I) Preparation before test
Comprehensive inspection
Carry out a comprehensive appearance inspection of the electric hoist to ensure that there are no obvious damage, deformation, cracks and other defects on the surface of the equipment, and the quality of the welds meets the standard requirements.
Check whether the bolts and nuts at each connection are tightened to ensure that the connection is firm and reliable.
Check the appearance quality of the wire rope or chain, including whether there are broken wires, wear, deformation and other problems, and check whether its fixing condition meets the requirements.
Check the quality of the hook, such as opening degree, torsional deformation, dangerous section wear, etc., to ensure the hook is safe and reliable.
Check whether the parts of the brake are complete and intact, whether the wear degree of the brake friction pad is within the allowable range, whether the contact between the brake wheel and the brake shoe is good, etc.
Check whether the oil level of the reducer is normal and whether there is oil leakage. At the same time, check the meshing of the gears to ensure smooth transmission.
Check whether the insulation resistance of the electrical system meets the requirements, whether the connection of each electrical component is firm, whether the operation button is flexible and reliable, whether the limit switch and other safety protection devices are sensitive and accurate, etc.
Preparation of test load
According to the rated lifting capacity of the electric hoist, prepare a test load of corresponding weight, such as standard weights, heavy objects, etc. For tests of 1.1 times or 1.25 times the rated load, it is necessary to accurately calculate and balance the weight to ensure the accuracy of the load.
Selection of test site
Select a spacious, flat, and obstacle-free site as the test site to ensure that the electric hoist has enough operating space during the test and ensure the safe operating distance of the test personnel.
(II) Test operation steps
No-load operation test
Before loading the test load, first perform the no-load operation test of the electric hoist. After power on, operate the electric hoist to lift, lower, walk left and right, etc., check whether the operation of each mechanism is smooth and flexible, whether there is any abnormal sound or jamming, and observe whether the safety protection devices such as limit switches are working properly to ensure that the electric hoist operates normally under no-load conditions.
Loading test load
Gradually load the test load onto the hook of the electric hoist. Note that the loading process should be smooth and slow to avoid excessive impact on the equipment. During the loading process, closely observe the stress conditions of various parts of the electric hoist, such as whether there are obvious deformation, shaking, abnormal noise and other abnormal phenomena.
Dynamic load test operation
According to the corresponding standard requirements, operate the electric hoist to lift, lower and travel the trolley. For the wire rope electric hoist, the lifting mechanism operates for 30 minutes at 1.1 times the rated load under the conditions of rated voltage and rated frequency, and the trolley runs back and forth for 10 minutes; the chain electric hoist and pneumatic hoist operate for 1 hour at 1.25 times the rated load. During the test, the prescribed operating procedures must be strictly followed to ensure that the electric hoist moves smoothly and accurately, and various operating parameters such as lifting speed, running speed, current, voltage, etc. are recorded.
Observation and Recording
During the entire dynamic load test, a special person is arranged to carefully observe each part of the electric hoist, including the action of the brake, the winding of the wire rope or chain, the deformation of the hook, the operation of the reducer, the operation of the electrical system, etc., and the observation results are recorded in time. At the same time, professional measuring instruments are used to measure and record relevant parameters, such as measuring the lifting height, running distance, brake slippage, etc., so as to analyze and judge the test results later.
(III) Inspection after the test
Unloading and cooling
After the test, first slowly unload the test load to ensure that the electric hoist is in an unloaded state. Then cut off the power supply and let the electric hoist cool naturally for a period of time to return to normal temperature.
Comprehensive inspection
Carry out a comprehensive inspection of the electric hoist, focusing on the parts that are subjected to greater force during the test, such as the main beam, end beam, hook, wire rope, brake, reducer, etc., to check whether there are abnormal phenomena such as deformation, cracks, wear, looseness, etc. At the same time, check whether the electrical system is damaged or short-circuited to ensure the integrity and safety of the equipment.
Data collation and analysis
Collate and analyze the various data recorded during the test, compare the data changes before and after the test, and judge whether the performance of the electric hoist under dynamic load meets the design requirements and relevant standards. For example, whether the braking slippage of the lifting mechanism is within the allowable range, whether the synchronization of the operating mechanism is good, and whether the insulation resistance of the electrical system meets the standard.

4. Precautions for dynamic load test
(I) Safety first
Testers must have professional knowledge and skills, be familiar with the structure, performance and operation methods of electric hoists, and strictly abide by safety operating procedures.
Set up obvious safety warning signs at the test site, prohibit irrelevant personnel from entering the test area, and ensure the safety of personnel during the test.
When operating the electric hoist, it should be stable and slow, avoid sudden start and stop, and prevent the swing and impact of the test load from causing damage to equipment and personnel.
When loading and unloading the test load, use appropriate tools and equipment to ensure the stability and safety of the load and prevent the sudden drop of the load.
(II) Equipment inspection and maintenance
Before, during and after the test, the electric hoist must be fully inspected to promptly discover and deal with potential problems to ensure the safe operation of the equipment.
For equipment failures or abnormal conditions found during the test, the test must be stopped immediately for repair and treatment. It is strictly forbidden to operate the equipment with problems.
After the test, the electric hoist must be maintained and maintained as necessary, such as cleaning the equipment surface, lubricating parts, tightening connection parts, etc., to extend the service life of the equipment.
(III) Environmental factors
The temperature, humidity and other conditions of the test environment should meet the normal use requirements of the electric hoist. Avoid conducting tests in extremely harsh environments to avoid affecting the accuracy of the test results and the performance of the equipment.
During the test, attention should be paid to avoiding interference from external factors, such as wind and vibration, to ensure the stable operation of the electric hoist and the reliability of the test data.

5. Determination of dynamic load test results
(I) Qualification criteria
Reliable brake action
During the dynamic load test, the brake of the electric hoist can act quickly and accurately, and the brake is stable during the lifting and lowering process, without hook slippage, and the brake slippage meets the requirements of relevant standards, such as the brake slippage of the lifting mechanism is not more than 100mm, etc.
There is no looseness, damage or abnormality in the parts
During the test, the various parts of the electric hoist have no obvious looseness, wear, deformation, cracks or other damage. The mechanical transmission system runs smoothly, without abnormal sounds and jamming. The wire rope or chain is wound neatly, without kinks, broken wires exceeding the standard, etc. The hook has no excessive deformation and opening enlargement. The electrical system operates normally without short circuit, open circuit, overheating and other faults. The operation of each electrical component is accurate and reliable.
All performance indicators meet the requirements
The performance parameters of the electric hoist, such as lifting speed, running speed, lifting height, and running distance, meet the design requirements and relevant standards during the test, and their deviations are within the allowable range. For example, the deviation between the lifting speed and the running speed does not exceed ±5% of the rated speed.
(2) Unqualified situations and treatment methods
Brake failure
If the brake is found to be slow in action, ineffective in braking, or slipping hooks during the test, it will be judged as unqualified. At this time, the brake needs to be inspected and repaired in detail. It may be caused by serious wear of the brake friction pad, excessive gap between the brake wheel and the brake shoe, fatigue or damage of the brake spring, etc. Replace the worn brake friction pad, adjust the gap between the brake wheel and the brake shoe, or replace the brake spring and other parts, and retest until the brake works reliably.
Damage to parts
If the main beam, end beam, hook, wire rope, chain, reducer and other parts of the electric hoist are found to be severely damaged such as deformation, cracks, and fractures during the test, they will be judged as unqualified. Replace or repair the damaged parts according to the specific situation and degree of damage. For example, if the main beam has excessive deflection or cracks, it may be necessary to reinforce or replace the main beam; if the wire rope breaks excessively or the chain is severely worn, a new wire rope or chain must be replaced. After completing the replacement or repair of parts, re-inspect and test comprehensively to ensure the safety and reliability of the equipment.
Performance indicators do not meet the standards
When the performance indicators of the electric hoist, such as the lifting speed, running speed, and lifting height, do not meet the design requirements and relevant standards during the test, it is judged to be unqualified. It is necessary to check and adjust the mechanical transmission system and electrical control system of the electric hoist. It may be caused by insufficient power of the motor, incorrect transmission ratio of the reducer, improper parameter setting of the electrical control system, etc. After replacing a suitable motor, adjusting the transmission ratio of the reducer, or resetting the parameters of the electrical control system, the test is carried out again until all performance indicators meet the requirements.

6. The importance of dynamic load test in the quality control of electric hoists
(I) Ensure safe use
The dynamic load test simulates the actual working state of the electric hoist and conducts comprehensive inspection and testing of its various mechanisms and components. It can timely discover potential defects and problems in the design, manufacturing, assembly, etc. of the equipment, such as the reliability of the brake, the stability of the mechanical transmission, the strength and stiffness of the components, etc. If these problems are not discovered in actual use, they may lead to serious safety accidents, such as falling objects, equipment damage, casualties, etc. Therefore, dynamic load test is a key link to ensure the safety of electric hoists. Only electric hoists that have passed strict dynamic load tests and are qualified can be safely used in industrial production and other practical work, providing strong protection for the safety of personnel and equipment.
(II) Improving product quality
Dynamic load test is an important means for electric hoist manufacturers to improve product quality and market competitiveness. By conducting dynamic load tests, manufacturers can gain an in-depth understanding of the performance of products under actual working conditions, discover the shortcomings of products, and make improvements and optimizations to these problems. For example, according to the test results, adjust the structural design of the product, improve the manufacturing process, select more suitable materials, etc., so as to continuously improve the quality and performance of the product, so that it can better meet market demand and customer expectations. At the same time, strict quality control and testing procedures can also help establish a good brand image, enhance customer trust and satisfaction with the product, and promote product sales and sustainable development of the enterprise.
(III) Comply with industry standards and regulatory requirements
In the lifting machinery industry, countries and regions have formulated a series of strict standards and regulations to ensure the safe operation and quality reliability of lifting equipment. As one of the important contents of electric hoist quality inspection, dynamic load test is a basic requirement that manufacturers and users must comply with. Only by conducting dynamic load tests and complying with relevant standards and regulations can electric hoists legally enter the market and be put into use. This not only helps to regulate market order and protect the legitimate rights and interests of consumers, but also promotes the healthy development of the entire lifting machinery industry and improves the overall quality and safety level of the industry.

7. Summary
The dynamic load test of electric hoists is an important link to ensure its safety and reliability. It is of vital importance to ensure the safety of personnel, reduce property losses, and improve product quality and market competitiveness. By conducting a comprehensive dynamic load test on the electric hoist, problems with the equipment can be discovered and solved in a timely manner, so that it can operate stably and efficiently in actual use.