As one of the important assembly processes, welding plays a decisive role in product quality.
With the increase of welding work, the impact of welding occupational hazards on welders has attracted more and more attention.
Due to different processes, metal welding may produce hot splash particles, strong visible light, ultraviolet, infrared, electromagnetic and other radiation hazards.
Hot splashing particles will burn the welder;
The strong visible light produced by welding may cause temporary blindness, while the long-term effect will cause visual impairment, photophobia and other reactions;
The thermal effect produced by infrared radiation will cause eye heat of welders, long-term contact will lead to cataract, and infrared radiation may also burn the skin;
Ultraviolet rays can harm the cornea and lens of the eye, cause electro-optic ophthalmia, and may lead to blindness and cataract.
Welding eye protectors equipped with qualified welding filters are important welding protectors to help welding operators and auxiliary personnel protect against occupational hazards from welding.
1. Type of welding filter
According to the working principle, the welding filter is divided into two types.
One is the automatic dimming welding filter. The filter assembly consists of a reflector reflecting ultraviolet and infrared rays, a polarizer, a liquid crystal assembly and a control circuit.
The automatic dimming filter has two light-shielding number states: bright state (usually the shading number is 3 or 4) and dark state.
It is bright during welding preparation, which is convenient for the welder to observe; It can be switched to dark state within 0.1ms after arcing.
The barrier of automatic dimming filter to infrared and ultraviolet rays is completed by independent infrared and ultraviolet reflectors, while the transmittance of visible light is realized by changing the size of shading number.
Automatic dimming filters usually have multiple shading numbers to choose from to adapt to different welding operations.
The other is the commonly known black glass welding filter.
The black glass undertakes the function of blocking ultraviolet, infrared and visible light at the same time.
The larger the shading number of the filter, the greater the blocking rate of ultraviolet, infrared and visible light.
Black glass welding filters usually have only a single shading number.
With the change of welding parameters, welding filters with different shading numbers need to be replaced.
In welding operations with high heat production, it is recommended to use welding filters equipped with independent infrared and ultraviolet reflectors, or welding filters with high infrared reflectance.
Infrared radiation is greatly reflected rather than absorbed. The advantage is that the heat energy transmitted to the welder’s eyes through the filter will be reduced, which will increase the comfort of wearing, especially for long-time operation.
2. Selection of shading number of welding filter for welder
The selection of shading number of welding filter is related to many factors such as welding method and process.
For gas welding, gas cutting, brazing and other related operations, the flow of gas or oxygen is the main reference factor for selecting the shading number of the filter (see Table 1 and table 2).
Table 1 shading number of filter for gas welding or brazing operation
|Combustible gas flow||q≤70||70＜
|Recommended value of shading number||4||5||6||7|
g unit: L / hour;
Based on the different conditions around the grave, the actually selected Wenguang number can be increased or decreased on the basis of the above-recommended value.
Table 2 shading number of filter for oxygen fast flame cutting
|Recommended value of shading number||5||6||7|
g unit: L / hour;
Based on the different conditions around the grave, the actually selected Wenguang number can be increased or decreased on the basis of the above recommended value.
With the increase of gas flow, the shading number of the filter shall be appropriately increased;
For arc welding, arc gouging, plasma welding and cutting, the welding current is the main reference factor (see Table 3).
Table 3 recommended shading number of filter for arc welding
① Heavy metals: steel, alloy steel, copper and copper alloy.
② Arc cutting is a cutting method that uses carbon electrode and compressed air to blow away molten metal.
For the same welding method, the greater the welding current, the corresponding increase of the shading number of the filter is required.
Arc type, welding material and shielding gas are also factors that need to be carefully considered.
Other factors also have important effects on the selection of the shading number of the welding filter, although it is difficult to evaluate these effects in a specific way.
These factors include the daylighting conditions of the welding operation environment, and the relative positions of the welder and the welding torch or arc are different due to the length of the welder’s arm, the welder’s operation habits or the limitation of space, and the individual difference factors of welder’s sensitivity to light.
For welding filters with different shading numbers, the transmittance of ultraviolet, infrared and visible light can be from en169, en379 and ANSI Z87 1 and GB / t3609 1 and other relevant standards.
In fact, the shading number selected by referring to table 1, table 2 and table 3, which is consistent with the welder’s current operation, shall have sufficient barrier rate to visible light, ultraviolet and infrared, which is safe for the welder.
On the basis of the above-recommended values, welders should consider their own feelings and appropriately increase or reduce the shading number.
Attention should be paid to the filter with too high shading number, whose visible light transmittance is relatively low.
The welder needs to be closer to the welding torch or arc to clearly observe the welding part, which is extremely unfavorable to the welder’s occupational health;
First of all, welders are prone to fatigue;
Secondly, welders may also inhale more harmful welding smoke and harmful gases, and are easy to be burned by splashing droplets;
Third, the welder will be closer to the welding torch or arc, and the amount of ultraviolet radiation and infrared radiation will be greater.
The filter with too small shading number will make the transmittance of visible light high, and the welder’s eyes are easy to fatigue, which may affect the quality of welding.
Long term use of filters with too high or too low shading number may cause the decline of welder’s vision.
3. Shading number of eye protector for welding auxiliary personnel
Auxiliary personnel entering the welding operation environment and personnel entering the welding operation environment shall wear welding eye protectors equipped with appropriate filters to prevent possible damage to their eyes caused by ultraviolet radiation and strong light of welding.
For welding auxiliary personnel and personnel entering the welding operation environment, the shading number of welding eye protectors can be determined according to their distance from the welding torch or arc, personal feelings and other factors.
Generally, welding eye protectors with shading number of 1.2 ~ 4 can be selected;
As the distance gets closer, the shading number of the eye protector of the welding auxiliary personnel needs to be further increased with the reduction of the distance, and the use of the welder’s protective mask, not just the eye protector, also needs to be considered;
If the distance between is the same as the distance between the welding operator and the welding torch or arc, the welder’s protective mask with the same shading number as the welder shall be selected.
On this basis, one shading number can be increased or reduced according to personal feelings.
4. Type and selection of welding eye protector
To protect the welder’s eyes from the occupational hazards from welding, selecting the filter with appropriate shading number according to the welding process conditions is an important step in the whole work.
On this basis, it is further determined whether to use the welding goggles (see Fig. 1) or the welder’s protective mask (see Fig. 2).
Fig. 1 welding goggles
Fig. 2 head-mounted welder protective mask
The choice of welding goggles or welder’s protective mask is related to the amount of ultraviolet radiation and hot particle splash generated by the welding operation.
UV radiation exceeds gbz2 2-2007 occupational exposure limits for hazardous factors in the Workplace Part 2: physical factors stipulates that the occupational exposure limit for 8h is 0.24uw/cm2, so the welder’s protective mask must be selected instead of welding goggles;
Even if the UV radiation does not exceed the occupational hazard limit, if there is splashing of hot particles or overhead welding, the welder’s protective mask rather than welding goggles should be selected.
According to the structural form, welding protective masks can be divided into hand-held, head worn and combined.
The biggest feature of the hand-held welder protective mask is that it is cheap, but its disadvantages are also very obvious, that is, it is unable to carry out accurate welding operations with both hands, and it is not suitable for welding operations in a compact space.
For welding operations with high welding quality or special stations, the head worn welder protective mask has obvious advantages.
The combined welder’s protective mask connected with the safety helmet is applied to the occasions with head protection requirements.
According to the type of welding filter, the welder’s protective mask is divided into black glass welder’s protective mask and automatic dimming welder’s protective mask;
Depending on whether the air supply device can be connected, it can be divided into air supply type (which can also be divided into electric air supply type and long pipe air supply type) and non air supply welder protective mask.
The air supply welder protective mask can not only protect the welding arc, but also provide excellent respiratory protection, reduce the welder’s heat load and provide better operation comfort (see Fig. 3).
Fig. 3 electric air supply welder protective mask
Welding goggles or welder’s protective mask without protective sheet will damage the welding filter due to hot splashing particles or other mechanical factors.
If the welding filter is found damaged, cracked or affecting the welder’s line of sight, it must be replaced with a new welding filter.
Such filters are consumer parts. Before each welding operation, the welding filter must be carefully checked to ensure that the welding filter meets the requirements.
The welder’s protective mask equipped with inner and outer protective sheets of the window (see Fig. 2).
Since the welding filter is protected by inner and outer protective sheets, it is usually only necessary to replace the inner and outer protective sheets, especially the outer protective sheet. If the protective sheet is damaged, deformed, cracked or affects the welder’s vision, it must be replaced with a new protective sheet. The protective sheet is a consumable part.
If the automatic dimming welder protective mask is used, before each welding operation, in addition to the above routine inspection, it must also confirm that the shading number and sensitivity setting of the welding filter meet the current operation requirements, the photosensitive hole is not blocked, and the response of the welding filter assembly is normal.
As a personal eye and face protective device, the welding protective mask should also consider the personal hygiene requirements.
After each use, it should be wiped with a wet cloth or a wet cloth stained with neutral detergent, and dried in a cool place for next use.
Ultraviolet, infrared and strong visible light produced by welding operation will endanger the health of welders.
The correct use and maintenance of welding eye protectors and wearing them all the time in the whole welding process are the basis of welders’ occupational safety protection.
Auxiliary welding personnel or personnel entering the welding area temporarily must also wear eye protectors that meet the protection requirements and meet personal needs all the time.