Thorough Inspection of Components: Before using a manual chain hoist, the operator must conduct a detailed inspection of each and every component and part, including each link of the chain. Only when everything is in good condition can it be put into use. This initial inspection is of crucial importance as any defect or damage in the components could potentially lead to serious accidents during the lifting process. For example, a worn-out or cracked link in the chain might not be able to bear the weight it is supposed to, resulting in a sudden breakage and the dropping of the lifted object. The inspection should cover not only the visible parts but also the internal mechanisms such as the gears and bearings to ensure they are functioning smoothly.
During the inspection, the operator should check for signs of wear and tear, corrosion, or any other form of damage on the chain links. Each link should be examined carefully to make sure it is intact and free from any cracks or deformities. The hooks at both ends of the chain also need to be inspected thoroughly. They should be free from bends, cracks, or any other damage that could affect their ability to securely hold the load. Additionally, the hand chain and the sprocket wheel should be checked for smooth operation. The teeth on the sprocket wheel should be in good condition, without any signs of chipping or excessive wear, to ensure that the hand chain can engage properly and transmit the pulling force effectively.
Prohibition of Overloading: Once the hoist is in use, it is strictly prohibited to overload it. Overloading can place excessive stress on the chain, the hooks, and other components, significantly increasing the risk of failure. The rated load capacity of the manual chain hoist is determined based on its design and manufacturing specifications, taking into account factors such as the strength of the materials used and the mechanical design of the hoist. Exceeding this rated load not only endangers the safety of the lifting operation but can also cause permanent damage to the hoist itself, reducing its service life and potentially rendering it unusable.
To ensure compliance with the load limitation, it is essential for the operator to accurately determine the weight of the object to be lifted before starting the operation. This may involve using weighing scales or referring to the object’s specifications if available. In some cases, when the exact weight is not known, a conservative estimate should be made, and if there is any doubt about whether the hoist can handle the load, it is advisable to use a hoist with a higher load capacity or seek additional assistance to ensure a safe lifting operation.
II. Correct Chain Usage and Handling
Vertical Hanging of Loads: The lifting chain of the manual chain hoist is required to hang the heavy object vertically. This is to ensure that the force exerted on the chain is evenly distributed along its length. When the chain is not vertical, the distribution of the load becomes uneven, causing some links to bear more stress than others. Over time, this uneven loading can lead to premature wear and even breakage of the chain.
To achieve vertical hanging, the operator needs to carefully position the hoist above the object to be lifted and ensure that the chain is directly aligned with the center of gravity of the object. This may require some adjustments in the positioning of the hoist and the attachment points of the chain to the object. In addition, during the lifting process, the operator should continuously monitor the position of the chain to make sure it remains vertical. If the object starts to sway or the chain deviates from the vertical position, appropriate measures should be taken to correct it, such as slowing down the lifting speed or adjusting the pulling force.
Proper Alignment of Chain Links: It is essential that there are no misaligned links between the individual links of the chain. Misaligned links can cause the chain to bind or jam during the lifting operation, resulting in difficulties in pulling the chain and potentially leading to chain breakage. To ensure proper alignment, the operator should visually inspect the chain before use and during the operation if possible. If any misaligned links are detected, the chain should be carefully adjusted to correct the alignment.
This may involve gently manipulating the links to get them back into their correct positions. In some cases, if the misalignment is due to a damaged link, the damaged link should be replaced immediately to avoid any further problems. Additionally, when storing the hoist and chain, they should be carefully coiled or stored in a way that prevents the links from getting misaligned. This can be achieved by using proper storage racks or containers designed to keep the chain in an orderly and protected state.
III. Correct Pulling Technique and Precautions
Alignment of Pulling Direction: When pulling the hand chain, the operator must ensure that the direction of the pull is in the same plane as the hand chain wheel. This alignment is crucial for the smooth operation of the hoist. If the pulling direction is not in the same plane as the hand chain wheel, it can cause the chain to rub against the sides of the wheel or other components, resulting in increased friction and wear. This can also lead to difficulties in pulling the chain smoothly, making the lifting operation less efficient and potentially causing the chain to jam or break.
To achieve the correct alignment, the operator should stand in a position where they can comfortably pull the hand chain in a straight line that is parallel to the axis of the hand chain wheel. They should also hold the hand chain firmly but not too tightly to allow for a smooth pulling motion. During the pulling process, the operator should be aware of the feel of the chain and make any necessary adjustments to the pulling direction if they notice any resistance or unusual movement.
Prohibition of Oblique Pulling: It is strictly prohibited to pull the chain obliquely as this can easily cause the chain to get stuck or jam, which is known as “carding the chain”. Oblique pulling changes the angle at which the force is applied to the chain, causing it to rub against the wrong surfaces or get caught in the gaps between components. When the chain gets stuck, it becomes extremely difficult to continue the lifting operation, and attempting to force the chain to move by pulling harder can lead to severe damage to the chain, such as breaking links or bending the chain itself.
To avoid oblique pulling, the operator should always keep the pulling direction straight and in line with the intended path of the chain. This requires careful attention to the positioning of the hoist and the object being lifted, as well as the operator’s own stance and pulling motion. If for some reason the chain starts to deviate from the correct path during the pulling process, the operator should immediately stop pulling and correct the situation by repositioning the hoist or adjusting the attachment points of the chain to the object.
Smooth and Steady Pulling: When pulling the hand chain, it is necessary to apply the pulling force smoothly and steadily. Sudden jerks or uneven pulling can cause the chain to jump or get stuck. Jumping of the chain occurs when the pulling force is not applied evenly, causing the chain to momentarily lose contact with the sprocket wheel and then slam back into place. This can cause damage to the chain and the sprocket wheel over time. Stuck chains, on the other hand, can halt the lifting operation completely and require time-consuming troubleshooting to resolve.
To ensure smooth and steady pulling, the operator should use a slow and consistent pulling motion. They should start pulling gently and gradually increase the force as needed, but always maintaining a smooth transition. If the operator notices any resistance or difficulty in pulling the chain, they should stop immediately and investigate the cause. It is not advisable to force the chain to move by pulling harder, as this can lead to more serious problems such as chain breakage or damage to other components. Instead, the cause of the resistance should be identified and addressed properly, which may involve checking for misaligned links, obstructions in the chain path, or problems with the hoist’s internal mechanisms.
IV. Use of Tripods and Safety Precautions
Proper Spacing and Connection of Tripod Legs: When using a tripod with the manual chain hoist, the three legs of the tripod must maintain a relative spacing. The legs should be evenly spaced to provide stable support for the hoist and the lifted object. Uneven spacing can cause the tripod to tip over during the lifting operation, endangering the safety of the operator and anyone in the vicinity.
In addition to maintaining proper spacing, the legs of the tripod should be connected with ropes. The ropes serve multiple purposes. Firstly, they help to keep the legs in their relative positions, preventing them from spreading too far apart or coming too close together. Secondly, they provide an additional level of safety in case one of the legs fails or gets knocked out of position. The connection ropes should be of sufficient strength to withstand the forces that may be exerted on them during the lifting operation.
When placing the connection ropes on the ground, the operator must be careful to prevent them from tripping the workers. The ropes should be laid out in a way that does not create any obstacles or trip hazards. This may involve coiling or tucking the ropes neatly out of the way of the workers’ paths. If possible, using brightly colored ropes can also make them more visible and easier to avoid.
Limit on Lifting Height: The lifting height of the manual chain hoist should not exceed the standard value. Exceeding the standard lifting height can put excessive strain on the chain and the pins that hold the chain links together. This excessive strain can cause the chain to break or the pins to snap, resulting in the dropped object and potentially causing serious accidents.
The standard lifting height is determined based on the design and strength characteristics of the hoist and the chain. It takes into account factors such as the maximum load capacity, the material strength of the chain, and the mechanical design of the hoist. The operator should be aware of the standard lifting height specified for the particular hoist they are using and ensure that they do not exceed this limit during the lifting operation. If the need arises to lift an object to a height higher than the standard value, alternative lifting equipment with a higher lifting capacity and suitable for the required height should be considered.
In conclusion, the safe operation of manual chain hoists in lifting operations requires strict adherence to the above safety technologies. Each aspect, from pre-operation inspection to correct handling and pulling techniques, and the proper use of associated equipment like tripods, is crucial for ensuring the safety of the operator, the integrity of the equipment, and the success of the lifting operation. By following these guidelines, the risks associated with using manual chain hoists can be significantly reduced, creating a safer working environment for all involved in the lifting process.
