What is the safety factor of electric hoists usually?

What is the safety factor of electric hoists usually?

1. Overview of electric hoists

Electric hoists are a kind of light and small lifting equipment with the advantages of small size, light weight and easy operation. They are widely used in material handling, installation and maintenance in industries, construction, logistics and other fields. It is usually composed of an electric motor, a transmission mechanism and a drum or sprocket. According to the form of lifting chain or wire rope, it can be divided into wire rope electric hoists and chain electric hoists.

2. Safety factor requirements of electric hoists
Wire rope electric hoists: According to JB/T 9009-1999 "Wire Rope Electric Hoist Safety Rules", the safety factor of the wire rope should not be less than the requirements in the following table.
Mechanism working level | Safety factor
---|---
M3 | 5
M4 | 5.5
M5 | 5.5
M6 | 6
M7 | 6
Chain electric hoists: Generally, the safety factor of the chain should not be less than 5 times.

3. Factors affecting the safety factor of electric hoists
Lifting capacity and working level: The lifting capacity and working level of electric hoists are important bases for determining their safety factors. The larger the lifting capacity and the higher the working level, the greater the required safety factor to ensure that the equipment can operate safely and reliably under long-term, frequent and heavy-load working conditions.
Quality and performance of parts: The quality and performance of various parts of electric hoists such as hooks, wire ropes, drums, brakes, etc. directly affect the overall safety factor. For example, the hook should be made of standard materials with sufficient strength and toughness, and an anti-unhooking device should be installed; the material, structure and tensile strength of the wire rope should meet the corresponding requirements to ensure that it can withstand large tension without being broken when lifting heavy objects.
Use environment and working conditions: Different use environments and working conditions will also affect the safety factor of electric hoists. Using electric hoists in harsh environments such as high temperature, humidity, and corrosiveness will accelerate the wear and aging of parts, reduce their service life and safety, so it is necessary to appropriately increase the safety factor or take corresponding protective measures. In addition, if the electric hoist is used to lift special items such as molten metal and dangerous goods, the nature of the items and the possible risks should be considered to further ensure that the safety factor meets the requirements.

4. The embodiment of safety factor in the design and manufacture of electric hoists
Design and manufacture of hooks: The hook is one of the key load-bearing components of the electric hoist, and its design and manufacture must meet strict safety standards. The shape, size and material of the hook must be accurately calculated and selected to ensure that it has sufficient safety factor when bearing the rated load. For example, the stress at the dangerous section of the hook should be less than the allowable stress of the material, and a certain safety margin should be considered. At the same time, the hook should also be surface treated and tested to prevent cracks and defects that affect its safety.
Selection and configuration of wire rope: When designing an electric hoist, it is necessary to select a wire rope of appropriate specifications and models according to the lifting weight, working level and use requirements, and ensure that its safety factor meets the standard requirements. The selection of wire rope should not only consider its breaking tension, but also comprehensively consider factors such as its flexibility and wear resistance. In addition, the winding method and fixing method of the wire rope on the drum should also be reasonably designed to ensure that the wire rope is evenly stressed during the lifting process, reduce wear and deformation, thereby extending its service life and improving safety.
Design of drum and pulley: The size, strength and surface quality of the drum and pulley will affect the stress and wear of the wire rope, and thus affect the safety factor of the electric hoist. The diameter of the drum should be large enough to reduce the bending stress generated by the wire rope during winding; the wheel groove shape and surface roughness of the pulley should match the diameter and structure of the wire rope to ensure that the wire rope runs smoothly on the pulley and reduce the risk of wear and wire breakage.

5. The importance of safety factor in the use of electric hoists
Ensure operational safety: The safety factor is an important guarantee for the safe operation of electric hoists during use. In actual operation, overload, sudden impact load, component failure, etc. may occur. A sufficient safety factor can enable the equipment to withstand these unexpected situations to a certain extent, avoid accidents such as heavy objects falling due to component breakage or failure, and protect the safety of personnel and equipment.
Extend the service life of equipment: Reasonable design and use of safety factors can make the various components of the electric hoist operate under safe working stress, reduce fatigue damage and wear, and thus extend the service life of the equipment. If the safety factor is insufficient, the components will be in an overstressed state for a long time, and fatigue cracks, deformation and other problems are prone to occur, resulting in premature scrapping of the equipment.
Meet the requirements of regulations and standards: Complying with the safety factor standards of electric hoists is the legal responsibility of enterprises and users. All countries and regions have formulated corresponding safety regulations and standards for lifting equipment, and have made clear provisions for technical indicators such as the safety factor of electric hoists. Ensuring that the safety factor of electric hoists meets the requirements is not only a need to ensure production safety, but also an important measure for enterprises to operate legally and avoid legal risks.

6. How to ensure the safety factor of electric hoists
Strictly abide by standards and specifications: In the design, manufacture, installation, use and maintenance of electric hoists, relevant national standards, industry standards and enterprise standards must be strictly observed. These standards have detailed provisions for the safety factor of electric hoists and various aspects related to them. Enterprises and users should implement them conscientiously to ensure that the safety performance of the equipment meets the requirements.
Strengthen quality inspection and testing: Strict quality inspection and testing of raw materials, parts and finished products of electric hoists to ensure that their quality and performance meet the design requirements. During use, electric hoists should be regularly inspected and tested, including flaw detection and performance testing of key components such as hooks, wire ropes, brakes, etc., to promptly discover and deal with potential safety hazards and ensure that the equipment is always in good operating condition.
Correct operation and use: Operators must undergo professional training, be familiar with the performance, operation methods and safety precautions of electric hoists, and operate in strict accordance with operating procedures. During use, avoid illegal operations such as overloading, oblique lifting, rapid lifting or lowering, and reasonably control the lifting speed and height to prevent unnecessary impact and damage to the equipment.
Do a good job of maintenance: Regularly maintain the electric hoist, including lubrication, cleaning, and adjustment of each moving part, to keep the equipment in good lubrication and reduce friction and wear. At the same time, wearing parts should be replaced in time to ensure the normal operation of the equipment. Maintenance work should be planned and recorded in detail to track the operating status and maintenance history of the equipment.

7. FAQ
Q: Is the safety factor of electric hoist as high as possible? A: Generally speaking, a higher safety factor can provide greater safety protection, but this does not mean that the higher the safety factor, the better. Too high a safety factor may lead to problems such as excessive structural size, increased weight, and rising costs of the equipment, and may reduce the working efficiency of the equipment. Therefore, when designing and selecting electric hoists, the safety factor should be reasonably determined according to the actual use requirements and standard regulations, so as to achieve the economy and practicality of the equipment under the premise of ensuring safety.
Q: If the wire rope of the electric hoist is broken, can it still be used? A: Broken wires in the wire rope are a common problem. Whether it can continue to be used depends on the number, location and distribution of the broken wires. If the number of broken wires is within the range allowed by the standard and the broken wire parts are scattered, appropriate repair measures can be taken to continue to use it, but the use of the wire rope should be closely monitored. If the number of broken wires exceeds the standard requirements or the entire strand is broken, the wire rope must be replaced immediately to ensure safety.

8. Case Analysis
When a factory was using an electric hoist with a lifting capacity of 5 tons, due to the operator's misoperation, it overloaded and lifted a cargo weighing 6 tons. At this time, the actual tension of the wire rope of the electric hoist exceeded the safety factor range corresponding to its rated load. Fortunately, when the electric hoist was designed and manufactured, a sufficient safety factor was selected in accordance with the standard requirements. The wire rope was still able to temporarily withstand the tension under overload conditions, and no breakage accident occurred. This incident also reminded the factory to strengthen the training and management of operators to avoid similar situations from happening again. It also reflects the important role of a reasonably designed safety factor in ensuring the safety of personnel and equipment in unexpected situations.

9. Conclusion
The safety factor of an electric hoist is an important indicator to measure its safety. It involves all aspects of the equipment's design, manufacturing, use and maintenance. Enterprises and users should pay full attention to the safety factor of electric hoists, strictly abide by relevant standards and specifications, strengthen quality control and safety management, ensure that the equipment operates under safe and reliable conditions, effectively prevent and reduce accidents, ensure the safety of personnel and property, and improve production efficiency and economic benefits.