Protection of labor and occupational health in the production process aims to isolate the human body from potential hazards and toxic substances, creating a safe, hygienic, and comfortable work environment to ensure safe production.
Safety in production includes two aspects: prevention of work-related accidents, such as electric shocks, fires, explosions, metal splashes, and mechanical injuries; and prevention of occupational hazards, such as dust, toxins, radiation, and noise.
This article will discuss the protective measures against harmful factors.
1. Ventilation protection measures
By implementing comprehensive protective measures during electrical welding processes, it is possible to ensure that electrical welders only inhale trace amounts of smoke and toxic gases. Through the detoxification and excretion functions of the human body, the toxicity can be minimized to prevent welding fume and toxic gas poisoning.
Ventilation technology is a powerful measure to eliminate welding dust and toxic gases and improve working conditions.
2. Types and scope of ventilation measures
Ventilation measures can be divided into general ventilation and local ventilation based on the scope of ventilation.
Due to the high cost of general ventilation, its ability to immediately reduce smoke concentration in specific areas is limited, and its smoke exhaust effect is not ideal. Therefore, except for large welding workshops, local ventilation measures are generally adopted.
3. Mechanical ventilation measures
Mechanical ventilation refers to the use of ventilation equipment to supply and exhaust air for ventilation and detoxification.
Among the mechanical exhaust ventilation measures used in welding, local mechanical exhaust ventilation is the most widely applied, as it is effective, convenient, and cost-effective.
There are three types of local mechanical exhaust devices: fixed, movable, and random.
(1) Fixed ventilation devices
General ventilation: In specialized welding workshops or workplaces with a high welding volume and concentrated welding machines, comprehensive mechanical ventilation should be considered. Multiple axial flow fans can be centrally installed to exhaust air from the workshop, ensuring a constant supply of fresh air.
Local ventilation: This can be divided into supply ventilation and exhaust ventilation. Local supply ventilation temporarily blows away harmful substances near the welding area, which dilutes the air in the working area to some extent.
However, it may still pollute the entire workshop and does not effectively remove dust and toxic gases. Local exhaust ventilation is currently the most effective and convenient measure with lower equipment costs.
Fixed exhaust hoods are suitable for welding locations that are fixed and have small workpieces.
When installing such ventilation devices, the following requirements should be met: the exhaust path should be reasonable, ensuring that toxic gases, dust, etc. do not pass through the breathing zone of the operator; the exhaust outlet velocity should be around 1m/s; the air volume should be adjustable, and the outlet of the exhaust pipe should be 1-2m above the top of the workshop.
(2) Mobile exhaust hoods
They can be easily moved according to the operation and location of the welding site. They are particularly effective for welding in enclosed cabins, chemical containers, and pipelines or in large workshops where fixed welding is not possible.
When using this device, place the suction head near the arc and turn on the fan to effectively remove smoke and toxic gases. The mobile exhaust hood system consists of a small centrifugal fan, ventilation hose, filter, and exhaust hood.
Currently, the most commonly used and effective forms are the purifier-fixed suction head mobile type, fan and suction head mobile type, and axial flow fan exhaust hood.
(3) Random exhaust hoods
These hoods are fixed on or near automatic welding heads and have a significant exhaust effect. Generally, micro-mesh fans or pneumatic jet injectors are used as air sources, and they come in two forms: near-arc and hidden-arc exhaust hoods.
Compressed air injectors can also be used for welding boilers and containers to achieve good results. The principle of smoke extraction is to use compressed air to create negative pressure in the injection chamber, effectively sucking out the toxic fumes and dust.
4. Personal protective measures
Even in a good working environment, there are still risks to the human body if personal protective measures are neglected, and the risks are even greater when working in enclosed containers.
Therefore, strengthening personal protective measures is crucial. In addition to wearing appropriate work clothes, shoes, hats, gloves, goggles, masks, and face shields, if necessary, a supplied air helmet can be used.
(1) Prevention of smoke and toxic gas
When welding in containers, especially when using argon arc welding, CO2 gas shielded welding, or welding non-ferrous metals, in addition to enhancing ventilation, a ventilation cap should be worn. Compressed air treated with filters should be used for ventilation, and oxygen should not be used to prevent combustion accidents.
(2) Prevention of arc radiation
It is known that arc radiation contains infrared, ultraviolet, and intense visible light, which have varying degrees of impact on human health.
Therefore, the following protective measures must be taken during welding operations: wearing proper work clothing (preferably white), helmets, gloves, foot covers, and face shields.
For operations with intense radiation, such as argon arc welding, acid-resistant work clothing and ventilation caps should be worn.
Asbestos clothing should be worn in high-temperature conditions. Shielding panels should be placed around the work area to prevent arc flashes from harming others.
(3) Protection against noise
Personnel working for prolonged periods in a noisy environment should wear ear protectors to reduce the harm caused by noise. Ear protectors can be earmuffs or earplugs.
Although earmuffs provide better sound insulation, they are larger in size and less convenient to wear.
There are many types of earplugs, with the rubber earplugs being commonly used as they are convenient to carry, cost-effective, and provide good sound insulation.
The sound insulation values of these earplugs are 10-15dB for low frequency, 20-30dB for medium frequency, and 30-40dB for high frequency.
(4) Protection against arc flash
(1) When welding, the arc discharge between the two poles of the welding machine produces intense arc flashes, which can harm the welder’s eyes and cause arc flash keratitis.
To prevent arc flash keratitis, welders should use face shields that meet labor protection requirements. The welding lens on the face shield should be selected based on the intensity of the welding current, using shading lenses suitable for the working conditions.
(2) To protect the eyes of other personnel at the welding site, non-transparent protective screens should be installed in fixed welding locations and in welding sites where conditions allow, leaving a gap of no more than 300mm between the bottom of the screen and the ground.
(3) Proper organization of work and layout to avoid overcrowded work areas.
(4) Take breaks for the eyes as necessary. For long welding times and large-scale use, intermediate breaks should be taken. If arc flash keratitis occurs, medical treatment should be sought.
(5) Protection against arc burns
(1) Welders must wear appropriate work clothing, welding gloves, and foot covers while welding. Rolling up sleeves, wearing short-sleeved shirts, or keeping the clothing open during welding work is strictly prohibited to prevent burns from welding splatters.
(2) When changing welding rods during welding, it is strictly forbidden to casually throw away the rod ends to prevent burns to others and the occurrence of fire accidents.
(3) To prevent arc burns when operating switches and circuit breakers, welding pliers should be hung or placed on insulating boards when closing the circuit, and welding work must be stopped before opening the circuit.
(4) When preheating welded parts, the preheated area should be covered with asbestos boards, leaving only the welding area exposed for operation.
(5) Extra protection should be taken during overhead welding to prevent accidents caused by splatters.
(6) Protection against high-temperature thermal radiation
(1) The welding arc is a high-temperature and intense radiation source. Welding arcs can generate temperatures of over 3000°C. Approximately 20% of the total heat generated by the welding arc is radiated into the surrounding space.
The intense light and infrared radiation generated by the arc also cause strong heat radiation to the welder. Although infrared radiation does not directly heat the air, it can be converted into heat energy after being absorbed by objects, turning them into secondary heat sources.
Therefore, the welding arc is a high-temperature and intense radiation source.
(2) Ventilation and cooling measures: Strengthening ventilation facilities (mechanical or natural ventilation) in welding workplaces is an important technical measure for heatstroke prevention and cooling, especially when welding and cutting inside boilers, containers, or confined spaces.
Air supply and exhaust should be provided to the containers or confined spaces, enhancing ventilation.
During hot summer seasons, providing welders with salt-containing cool beverages to replenish body fluids is also a heatstroke prevention measure.
(7) Protection against harmful gases:
(1) During welding, in order to protect the molten metal in the weld pool from oxidation, welding rods contain substances that produce protective gases. Some of these protective gases are harmful to humans.
To minimize the production of harmful gases, high-quality welding rods should be selected, and the welding surfaces should be cleaned of oil before welding. If possible, automated welding processes should be used to keep welders away from the arc and avoid harming them with harmful gases.
(2) Utilize effective ventilation facilities to eliminate harmful gases. Mechanical ventilation facilities should be available in the workshop for ventilation and air exchange. When welding inside containers, fresh air must be supplied to the working area of the welder to reduce the concentration of harmful gases.
(3) Strengthen personal protective measures for welders, wearing protective masks; undergo regular physical examinations to prevent occupational diseases.
(8) Protection against mechanical injuries:
(1) Weldments must be placed stably, and special-shaped weldments should be supported or clamped to maintain stability.
(2) Welding circular workpieces with circumferential welds should not be lifted and rotated by cranes for welding, and operators should not stand on rotating workpieces to prevent falling and injuries.
(3) Protective covers should be installed for mechanical transmission parts of welding turntables.
(4) When cleaning and scraping welding, protective goggles should be worn.
