Detailed explanation of firefighters' extinguishing protective footwear performance coefficient and design principle

First, the protection function

In order to reduce all kinds of fire casualties caused by inadequate protective performance of protective equipment and improve the overall wearability of firefighters' protective footwear, relevant national agencies have formulated a series of standards to regulate the protective performance of protective footwear. Including GB / T 28409-2012 "Personal protective equipment, selection, use and maintenance of foot protection shoes ( boots ) ", GB 21147-2007 "Personal protective equipment protective shoes", AQ / T 6108-2008 "Safety shoes, protection The selection, use, and maintenance of shoes and professional shoes, GA 6-2004 { Firefighters fire protection boots, etc.) The standard describes the anti-mite performance, anti-puncture performance, heat insulation performance, and anti-skid performance of protective footwear. The specific content is as follows:

1. Flood prevention performance

Flood prevention performance usually refers to the flood prevention performance of Baotou. GB / T 28409-2012 , GB 21147-2007, and AQ / T 6108-2008 define the flood protection performance of ordinary individual protective footwear, that is, the protective cover can provide impact protection at least 100 J energy test and at least Pressure protection during 10 kN pressure test, and the minimum distance between the protective cuffs after testing is no more than 15 mm . In addition, GB 21147-2007 also stipulates that in the case of not damaging the protective footwear, the protective toe inside the footwear should not be able to move. Except for all-rubber and all-polymer shoes, there must be a protective footwear with protective toe inside. The front lining or part of the upper lining serves to protect the baotou with a layer of edge covering starting from the rear edge of the protective bolster, extending at least 5 mm below it and at least 10 mm in the opposite direction .

The above three criteria is mainly used for general personal protective footwear, and GA6 - Boots head 2004 is aimed at firefighters fire protective boots, protective boots are prescribed fire by 1O. After a 78 kN static pressure test and an impact test with a mass of 23 kg and a fall height of 30 mm , the gap height of the protective cap should not be less than 15 mm .

In order to achieve the above performance, in the design of fire extinguishing protective footwear, it is usually necessary to add a high-strength protective toe cap at the front tip. Currently, the material of the protective toe cap is mainly made of metal materials ( such as steel and aluminum alloy ) , and some researches also mention To high-strength composite materials.

2, puncture resistance

The GB 21147-2007 requirements for the puncture resistance of general protective footwear and the anti-piercing performance requirements of the fire extinguishing protective footwear in GA 6-2004 are the same, ie the force required to penetrate the sole during the puncture resistance test should not be less than 1 100 N.

In the design of protective footwear, in addition to selecting a sole material with excellent performance, a puncture-resisting mat is added at the middle bottom to improve the puncture resistance of the protective footwear. There are mainly three types of puncture-resistant mat materials used in the market. , They are metal and alloy materials, bottom leather materials and textile composite materials. GB 21147-2007 stipulates that the puncture-proof pad should be installed in the sole, and the pad cannot be moved without damaging the protective footwear. It should not be located above the edge of the protective cuff or contact with it. In the area of ​​the shoe seat, the maximum distance between the bottom edge and the pad should be 17 mm . The maximum distance between the bottom edge and the piercing pad edge should be 6 except for the shoe area . 5 mm . And the maximum diameter of the puncture-resisting pad fixed to the sole is 3 mm The openings should not exceed 3 , and no visible traces of cracking should occur after 1 × 10 flexion. It is particularly important to note that for protective footwear used in workplaces with magnetic and live working, anti-piercing pads should be made of non-metallic materials.

To sum up, we must design the structure and select materials according to the characteristics of the use environment. If the risk factor at the rescue site is high, in order to provide effective protection for the foot and calf, the general design of the boots is higher, but the boots used in magnetic and live applications, such as boots, anti-puncture pads and various Accessories should be careful not to use metal materials.

3, thermal insulation

The fire extinguishing boots specified in GA 6-2004 shall have a temperature rise of not more than 22 °C on the inner surface of the sole of the soles of the soles of the soles of the feet , in accordance with the test requirements for a continuous 30 min . GB 21147-2007 also pointed out that the protective shoes should not be deformed or embrittled after the test to reduce the function.

Insulation performance is generally achieved through the use of heat-insulating materials with excellent properties, such as non-woven fabrics made of permanently flame-retardant fibers, Kevlar® insulation materials, and the like. In addition, in the design of protective footwear uppers, it is possible to learn from the multi-layer structure design of fire fighting clothing. For example, the upper surface of the upper surface of the footwear is a comfortable layer, a heat insulation layer, and a waterproof breathable layer. The combined design of performance materials improves the overall performance of protective footwear.

4, anti-skid performance

According to GA 6-2004 , the starting slip angle must not be less than 15 when carrying out anti-skid performance tests on fire extinguishing boots . . GB 21147-2007 has regulations on the distribution area of ​​non-slip sole patterns, the thickness of non-slip soles, and the pattern depth, as shown in Figure 1 . The non-slip sole should have a pattern that opens to the sides (see Note: L is the length of the sole ) .

Figure 1 bottom pattern distribution position

According to the sole material and molding method, the thickness of the outer sole and the height of the bottom pattern also include 3 kinds of situations.

For direct injection, vulcanization or adhesive outsole, as shown in Figure 2 , the thickness should not be less than 4 mm , the bottom pattern height should not be less than 2 . 5 mm .

Figure 2 Direct injection, vulcanization or adhesive outsole

For multi-layer outsoles, as shown in Figure 3 . The thickness should not be less than 4 mm , and the height of the bottom pattern should not be less than 2 . 5 mm .

Figure 3 Multilayer Outsole

For all-rubber and all-polymer shoes, as shown in Figure 4 . The thickness should not be less than 3 mm , the thickness should not be less than 6 mm , and the height of the bottom pattern should not be less than 4 mm .

There are three main reasons that affect the slip resistance of soles: the sole material type, the bottom pattern type, and the surface media. At present, rubber materials are often used for extinguishing protective footwear outsoles for their good abrasion resistance, slip resistance and water resistance. The influence of the bottom pattern type and surface media on the anti-skid property of footwear has been studied by scholars at home and abroad. Mark G. Blanchette et al., The width (3, 6, 9 mm 3 levels), the depth (2, 4, 6 mlTl 3 levels) and direction (parallel, inclined, vertical) starting three levels, 27 pairs of selected different types of The groove combination of soles was used to study the effect of groove parameters on the effective friction at the bottom of the shoe. The results show that the most non-slip groove combination is a tilted direction, with a width of 3 mm and a depth of 2 mm ; the combination of the minimum anti-sliding groove is a parallel direction, with a 6 mm Width and 6 mm The depth, the direction of the groove is an important factor affecting the friction performance of the sole; Chen Yu studied the effect of temperature, groove width of the tread pattern and the medium of the road on the anti-slip performance of the sole. The results show that temperature, sole material, and interaction between temperature and material have significant effects on the anti-slip performance of the sole; the groove widths of the sole material, the road surface, the contaminants and the sole pattern, and the interactions between the four factors, It has a significant effect on the anti-slip performance of the sole; the coefficient of friction (CoF) of the sole increases with the width of the groove; when the pollutants are on the road surface, the COF of the sole decreases sharply.

Figure 4 All-rubber and all-polymer shoes

In addition, according to different rescue environments, considering the distribution of bottom pattern area, shape, direction, and depth, etc., the corresponding bottom pattern combinations are designed.

Second, comfort

1, breathability

The Hexus "Fire Eagle" ultralight new fire boots and the Italian superior 9005 fire boots have all introduced the concept of breathable systems in their design. The use of waterproof and breathable materials is one of the main channels for improving the breathability of protective boots. At present, the materials used for the protection of boot uppers are mainly high-quality full-grained waterproof leather, waterproof and flame-retardant leather and other leather materials.

2, the overall quality

Sharon S. Chiou et al . measured the amount of oxygen consumed by 13 female firefighters and 14 male firefighters walking 5 minutes in a full suit and randomly assigned boots , and crossing the obstacles. The results showed that after walking for a period of time wearing heavy boots, the firefighters were more likely to fall over the obstacles. The quality of the boots affected the metabolic rate ( each mass increase of 1 kg and the metabolic variable increased by 5 % to 11 % ) . GA 6-2004 also stipulates that the mass of each pair of fire extinguishing boots should not exceed 3 kg .

The lightweight design of the sole structure and the use of double-density injection techniques are the primary means of reducing the overall quality of protective footwear. The combination of a rubber outsole and a foamed midsole can be used to reduce the overall quality of the sole and also improve the cushioning performance of the sole.

3, the hardness of the sole

The GA 6 - 2004 specified, the sole hardness generally between 55 ° to 70 ° (Shore A).

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.