The influence of dry-wet alternating environment on the strength of hand chain hoists: principles, consequences and countermeasures

The influence of dry-wet alternating environment on the strength of hand Chain Hoists: principles, consequences and countermeasures

In the field of industrial lifting, hand chain hoists, as a common manual lifting tool, are widely used in factories, mines, construction sites, docks, warehouses and other places. Its main components include wire ropes, wheel sets, transmission systems, hooks, lifting chains, etc. The materials and structural designs of these components are affected by the use environment. For international wholesale buyers, it is crucial to understand the impact of different environments on the strength of hand chain hoists, because it is directly related to the quality and safety of the product. This article will deeply explore the specific impact of dry-wet alternating environment on the strength of hand chain hoists, analyze from multiple aspects such as corrosion, material performance changes, and mechanical structure damage, and provide corresponding protection and maintenance measures to help buyers better select and use hand chain hoists.

1. Characteristics of dry-wet alternating environment and factors affecting hand chain hoists
Dry-wet alternating environment refers to the situation where the environmental humidity changes repeatedly between dry and wet within a certain period of time. This environment is more common in coastal areas, outdoor construction sites, and some industrial sites that require frequent cleaning. In this environment, the metal parts of the chain hoist will be subject to varying degrees of corrosion and wear, thus affecting its overall strength and service life.
(I) Corrosion problems caused by humidity changes
When the ambient humidity is high, water molecules in the air will condense into a water film on the metal surface of the chain hoist, providing conditions for corrosion reactions. At this time, the microscopic defects on the metal surface are prone to form galvanic cells, accelerating the electrochemical corrosion of the metal. For example, in a steel chain hoist in a humid environment, the iron atoms as the anode lose electrons, undergo an oxidation reaction, and generate iron ions; while the carbon atoms as the cathode, oxygen obtains electrons at this location and undergoes a reduction reaction. Under the combined action of the two, loose iron oxide, i.e. rust, gradually forms on the steel surface, resulting in a thinning of the metal thickness and a decrease in strength. With the cycle of alternating dry and wet conditions, the corrosion process will continue to repeat and intensify, further weakening the bearing capacity of metal parts.
For stainless steel chain hoists, although they have good corrosion resistance, they may still be corroded in an environment of alternating dry and wet conditions, especially in humid air containing salt, acidic or alkaline substances. Because the corrosion resistance of stainless steel mainly depends on a dense chromium oxide film formed on its surface, and this film may be destroyed in harsh environments, causing local corrosion, such as pitting and crevice corrosion. These forms of corrosion will form small holes or cracks on the metal surface, reduce the strength and toughness of the material, and affect the performance of key components of the hand chain hoist, such as hooks and lifting chains.
(II) The impact of temperature fluctuations on material properties
Dry-wet alternating environments are often accompanied by temperature changes. The increase in temperature will accelerate the chemical reaction rate of metal materials, including corrosion reactions and changes in the internal structure of the material. In a hot and humid environment, the metal parts of the hand chain hoist are more susceptible to corrosion, and the structure of the corrosion products may become looser, further reducing the strength of the metal. At the same time, repeated changes in temperature will cause thermal fatigue in metal materials and cause microscopic cracks in the material. These cracks will gradually expand under stress and may eventually lead to the breakage of the parts.
In addition, temperature changes will also affect the non-metallic parts of the hand chain hoist, such as seals and grease. For example, high temperature will make the grease thinner, causing it to flow out of the lubrication area, thereby increasing the friction between metal parts and accelerating wear. Low temperature may make the seal hard and brittle, lose its sealing performance, and make it easier for external moisture, dust and other impurities to enter the interior of the hand chain hoist, affecting its normal operation and indirectly affecting the strength and life of metal parts.
(III) Damage to the mechanical structure caused by alternating dry and wet conditions
The alternating dry and wet environment will cause the mechanical structure of the hand chain hoist to suffer multiple damages. When the environment is humid, moisture may enter the interior of the hand chain hoist and contact with transmission parts such as gears and bearings, resulting in poor lubrication and increased friction between parts. If it is in this state for a long time, the gear tooth surface will be aggravated, and problems such as tooth deformation and tooth surface pitting will occur, reducing the transmission accuracy and load-bearing capacity of the gear. At the same time, the rolling elements and raceways of the bearings are also susceptible to corrosion and wear, which will reduce the rotation accuracy of the bearings, generate vibration and noise, increase energy loss, and affect the overall performance and strength of the hand chain hoist.
During the drying stage, although the moisture evaporates, the corrosion products produced by the previous corrosion reaction may remain in the gaps between the metal surface and the parts. These corrosion products usually have high hardness and brittleness. During the use of the hand chain hoist, they will aggravate the wear between the parts and cause further damage to the mechanical structure. In addition, the alternating dry and wet conditions will also cause uneven thermal expansion and contraction of metal parts, resulting in increased matching clearances between parts or stress concentration, affecting the stability and strength of the mechanical structure of the hand chain hoist.

2. The specific impact of the alternating dry and wet environment on the strength of key components of the hand chain hoist
(I) Impact on the hook
The hook is one of the key load-bearing components of the hand chain hoist, and its strength is directly related to the safe use of the hand chain hoist. In the alternating dry and wet environment, the metal surface of the hook will be corroded, forming pits and cracks. These defects will reduce the effective bearing area of ​​the hook, causing uneven stress distribution when bearing loads, and it is easy to break at the stress concentration point. At the same time, corrosion will also make the material of the hook brittle, reduce its tensile strength and toughness, increase the risk of the hook breaking during use, and may cause serious safety accidents.
For example, a hook originally designed to carry 3 tons may have its actual effective carrying capacity reduced to 2 tons or even lower after a long period of dry-wet alternating corrosion. If it is still used according to the original rated load, the hook is likely to deform or break, which will bring great danger to the operator and equipment.
(II) Impact on the lifting chain
The lifting chain is the main component of the hand chain hoist to transmit tension and is composed of multiple chain links. In an environment of dry-wet alternation, the relative movement between the chain links and between the chain links and the sprockets intensifies the wear. At the same time, moisture and corrosive substances can easily penetrate into the interior of the chain, causing the metal surface of the chain links to rust and corrode, reducing the diameter of the chain links and reducing the strength.
When the chain is subjected to tension, the weak links after corrosion and wear are prone to breakage, causing the entire lifting chain to fail. In addition, the toughness of the chain will also decrease due to corrosion, and it is more likely to suffer brittle fracture when subjected to impact loads or frequent stretching. According to statistics, the breaking strength of the lifting chain after being used in a dry-wet alternating environment may be reduced by 30% - 50% compared with the normal use environment, which seriously affects the lifting capacity and safety of the hand chain hoist.
(III) Impact on hand chain sprockets and gears
Hand chain sprockets and gears are important components of the hand chain hoist transmission system. Their meshing accuracy and strength directly affect the operating performance and efficiency of the hand chain hoist. In a dry-wet alternating environment, the tooth surfaces of the sprockets and gears are susceptible to corrosion and wear, forming pits, pits and grooves. These damages will increase the roughness of the tooth surface, reduce the meshing efficiency of the gears, and cause more vibration and noise during the transmission process.
With the increase in the use time, the gear teeth may break and the tooth surface may peel off, resulting in the failure of the transmission system. At the same time, the wear of the sprocket will make the fit between the chain and the sprocket loose, affecting the lifting and lowering control accuracy of the hand chain hoist, and increasing the difficulty and risk of operation. For example, when lifting heavy objects, due to the poor coordination between the sprocket and the chain, the heavy objects may shake or slide down, which not only reduces work efficiency, but may also cause accidents due to the loss of control of the heavy objects.
(IV) Impact on the brake
The brake of the hand chain hoist usually adopts a ratchet friction plate one-way brake, which can brake automatically under load to ensure that the heavy objects stop at any position. In an alternating dry and wet environment, the friction plate and ratchet of the brake are easily affected by moisture and impurities. When the environment is humid, moisture will enter the brake, reduce the friction coefficient between the friction plate and the ratchet, resulting in a weakened braking effect, and the heavy objects may slide down.
In the dry stage, the corrosion products and impurities such as dust on the surface of the friction plate and ratchet will increase the wear between the components, further reducing the braking performance of the brake. In such a harsh environment for a long time, the key components of the brake, such as springs and friction plates, will age and deform, lose their normal braking function, and bring great hidden dangers to the safe use of the hand chain hoist.

3. Comprehensive influence of dry-wet alternating environment on the overall strength and service life of hand chain hoists
The dry-wet alternating environment damages the key components of the hand chain hoist through the above-mentioned factors, thereby affecting its overall strength and service life. With the continuous intensification of corrosion and wear, the carrying capacity of the hand chain hoist gradually decreases, and the matching accuracy between the components also gradually decreases, resulting in poor operating efficiency and reliability of the entire system. During use, operators will feel abnormal conditions such as increased pulling force, slower lifting speed, and heavy objects sliding down of the hand chain hoist, which not only increases the difficulty and labor intensity of operation, but also greatly increases the risk of safety accidents.
From the perspective of service life, the life of a hand chain hoist in a dry-wet alternating environment may be shortened several times compared to a hand chain hoist used in a dry or stable environment. Frequent maintenance and replacement of parts not only increase the cost of use, but also affect the normal production progress. Therefore, for users who use hand chain hoists in a dry-wet alternating environment, it is particularly important to understand the law of strength change and influencing factors, and take effective protection and maintenance measures.

4. Protection and maintenance measures for hand chain hoists in dry-wet alternating environments
(I) Select appropriate materials and surface treatment processes
In order to improve the corrosion resistance of hand chain hoists in dry-wet alternating environments, key components should be manufactured with materials with strong corrosion resistance, such as stainless steel and galvanized steel. Stainless steel has good corrosion resistance and can effectively resist corrosion reactions in humid environments; galvanized steel forms a zinc protective layer on the surface of steel to isolate steel from contact with corrosive media, thereby extending the service life of components.
In addition, surface treatment processes such as electroplating, painting, and chemical plating can also be used to further enhance the corrosion resistance of metal parts. For example, electroplating the lifting chain of a hand chain hoist can not only improve its surface hardness and wear resistance, but also effectively prevent the chain from rusting and corrosion. At the same time, during the surface treatment process, the uniformity and adhesion of the coating should be ensured to avoid local corrosion caused by uneven or falling coating.
(II) Strengthen lubrication and sealing measures
Good lubrication can reduce friction between hand chain hoist components, reduce wear rate, and also play a certain anti-rust role. In an environment of alternating dry and wet conditions, grease with good waterproof and rust-proof properties should be selected, and the moving parts of the chain hoist should be lubricated regularly. For frequently used chain hoists, the lubrication cycle should be appropriately shortened to ensure the lubrication effect.
At the same time, in order to prevent moisture and impurities from entering the interior of the chain hoist, effective sealing measures should be taken. For example, sealing elements such as sealing rings and gaskets are installed between the shell and components of the chain hoist to ensure good sealing performance. During daily use and maintenance, pay attention to checking the aging and damage of the sealing elements, and replace the damaged seals in time to keep the internal environment of the chain hoist dry and clean.
(III) Regular inspection and maintenance
Regular inspection is an important means to ensure the safe use of the chain hoist in an environment of alternating dry and wet conditions. The inspector should conduct a comprehensive inspection of each key component of the chain hoist, including hooks, lifting chains, sprockets, gears, brakes, etc. Focus on checking the wear, corrosion, deformation, cracks, etc. of the components, as well as the lubrication and sealing conditions.
For any problems found, appropriate maintenance measures should be taken in a timely manner. For example, for slightly corroded parts, rust removal and painting can be carried out; for severely worn parts, they should be replaced in time. At the same time, the hand chain hoist should be regularly subjected to load tests to check whether its load-bearing capacity meets the requirements. Through regular inspection and maintenance, potential safety hazards can be discovered and eliminated in time, the service life of the hand chain hoist can be extended, and its normal operation in a dry and wet alternating environment can be ensured.
(IV) Reasonable storage and use
In a dry and wet alternating environment, the storage of the hand chain hoist also needs attention. The hand chain hoist should be stored in a dry, ventilated and clean warehouse as much as possible to avoid open-air storage. If it must be stored in the open air, rain and moisture-proof measures should be taken, such as covering with waterproof cloth. When using the hand chain hoist, it should be avoided to work for a long time in a humid environment as much as possible to reduce the erosion of moisture on the hand chain hoist.
During the operation, the hand chain hoist should be operated strictly in accordance with the operating procedures to avoid illegal operations such as overloading, oblique pulling and crooked hanging, so as to reduce excessive stress and wear on the parts of the hand chain hoist. After use, the dust, oil and moisture on the surface of the hand chain hoist should be cleaned in time to keep it clean and tidy for the next use.

5. Case analysis
During the construction process, a coastal construction site frequently used hand chain hoists for hoisting construction materials. Because the area is close to the sea, the air humidity is high and the temperature difference between day and night is large, forming a typical dry-wet alternating environment. In the early stage of use, the performance of the hand chain hoist was good and could meet the construction needs. However, as the use time went by, some problems gradually appeared in the hand chain hoist, such as rust on the surface of the hook, the lifting chain became stiff and aggravated, the operation was laborious when lifting heavy objects, and sometimes the heavy objects would slide down.
After inspection, it was found that the key components of the hand chain hoist, such as the hook, lifting chain, sprocket, etc., were corroded and worn to varying degrees, and the friction plate of the brake also deteriorated due to water ingress. In response to these problems, the construction site has taken a series of protection and maintenance measures: severely corroded hooks and excessively worn lifting chains have been replaced, and all parts of the hand chain hoist have been thoroughly cleaned, rusted and lubricated, and sealing measures have been strengthened. At the same time, in the subsequent use process, the operation is strictly carried out in accordance with the operating procedures, and regular inspections and maintenance are carried out. Through these measures, the performance of the hand chain hoist has been significantly improved, and the service life has been extended, ensuring the safe and smooth progress of the construction process.

6. Summary
The dry and wet alternating environment has a significant impact on the strength of the hand chain hoist, mainly reflected in corrosion, changes in material properties and damage to the mechanical structure. Under the combined effect of humidity changes and temperature fluctuations, the metal parts of the hand chain hoist are susceptible to corrosion, resulting in a decrease in strength; at the same time, problems such as thermal fatigue, poor lubrication and wear will also aggravate the damage of the mechanical structure. The combined effect of these factors reduces the overall strength and service life of the hand chain hoist and increases safety risks.
In order to ensure the safe use and stable performance of the hand chain hoist in the dry and wet alternating environment, it is essential to take effective protection and maintenance measures. By selecting appropriate materials and surface treatment processes, strengthening lubrication and sealing measures, regular inspection and maintenance, and reasonable storage and use, the corrosion resistance and service life of the hand chain hoist can be significantly improved, and the probability of equipment failure and safety accidents caused by environmental factors can be reduced. For international wholesale buyers, understanding this knowledge will help to accurately evaluate product quality during the procurement process, and provide users with good usage guidance and after-sales service, thereby enhancing market competitiveness and meeting the needs of different customers.
In actual applications, according to the specific use environment and requirements, users can choose the appropriate type and specification of hand chain hoists, and strictly follow the relevantAt the same time, manufacturers should also continuously improve product design and manufacturing processes, improve the environmental adaptability and reliability of hand chain hoists, and jointly promote the healthy development of the hand chain hoist industry.