1. What are the basic knowledge of safety helmets
Knowledge about safety helmets: A safety helmet is a shallow dome hat made of steel or similar materials worn to protect the top of the head. , protective equipment to prevent impact objects from damaging the head.
It consists of a hat shell, a hat lining, a lower cheek strap and a rear hoop. The cap shell is hemispherical, solid, smooth and has a certain elasticity. The impact and puncture kinetic energy of the striking object are mainly borne by the cap shell.
There is a certain space between the cap shell and the cap lining, which can buffer and disperse the instantaneous impact force, thereby avoiding or reducing direct damage to the head. Impact absorbency, puncture resistance, lateral rigidity, electrical insulation, and flame retardancy are the basic technical performance requirements for safety helmets.
Brief introduction: A safety helmet is a head protection device that prevents head collisions from being hit by objects and falling. English name: safety helmet is a shallow dome hat made of steel or similar materials worn by miners and underground engineering personnel to protect the top of their heads.
A lightweight protective helmet usually made of metal or reinforced plastic worn by workers in industrial production environments. A hat worn by workers during construction or mining.
Used to protect the head from falling objects. Generally made of wicker, rattan core or plastic.
Main features: A lightweight, low-risk safety helmet with good air permeability; It is well ventilated and lightweight, providing comprehensive comfort to the wearer; The protective function of the safety helmet: When the operator's head is hit by a falling object During an impact, the helmet shell and lining are used to instantly decompose the impact force to the entire area of ??the skull, and then the elastic deformation, plastic deformation and allowable structural damage of the buffer structure of each part of the helmet are used to absorb most of the impact force. , so that the final impact force on the personnel's head is reduced to less than 4900N, thereby protecting the workers' heads. The shell material of the helmet plays an important role in the overall resistance performance of the helmet.
Structural parts: Cap shell: withstands blows and isolates falling objects from the human body. Hat band: Keep the helmet in a certain position on the head.
Top strap: Disperses the impact force and keeps the cap shell floating to disperse the impact force. Rear hoop: The locking device of the headband.
Chinstrap: Assists in maintaining the status and position of the helmet. Sweatband: Absorbs sweat.
Cushion pad: Reduces the impact force when an impact occurs. Wearing height: reflects the height difference from the forehead to the top of the head, which may interfere with eyes, ears and other items worn.
The helmet band is too small and separates from the forehead. The fastening part is not closed and cannot guarantee a certain state and position on the head.
Vertical spacing: reflects the gap between the inside of the hat shell and the top of the head. If it is too small, ventilation will be poor; if it is too large, the center of gravity of the helmet shell will rise, causing the helmet to be unstable on the head.
Horizontal spacing: Provides buffer space when there is lateral force in impact. It is also a heat dissipation channel.
Structural form: 1 The top of the cap shell should be strengthened. Can be made into a bare top or ribbed structure.
The hat shell is made without rim, with rim or rolled edge. 2. The plastic cap lining should be made into a structure with a back hoop, so that the size of the cap hoop can be freely adjusted (pulled adjustment, button adjustment, knob adjustment, etc.).
3. The chin strap without a back hoop and hood lining can be made into a "Y" shape. If there is a back hoop, it is allowed to be made into a single piece. 4. The hatband that touches the forehead should be breathable and sweat-absorbent.
5 The padding around the hat hoop can be made into strips or blocks, leaving space for air circulation. 6 Safety helmet manufacturers must strictly comply with the national standards of GB2811-2007 for production.
7 Type Y helmets do not allow side pressure, because type Y helmets only protect injuries caused by linear impacts from top to bottom, but cannot protect against pressure from the side.
Main brands: 1. MSA 2. Sporian (Baku) 3. Haitang 4. North 5. Deltaplus 6. Lakeland 7. Jieshi Ratio (JSP) 8. Ruizhong Safety Helmet (RZ) Pressure-bearing principle: The safety helmet can withstand pressure mainly based on three principles: 1. Buffering and shock absorption: There is a gap of 25~50mm between the hat shell and the hat lining. , when an object hits the helmet, the hat shell will not directly affect the top of the head due to force deformation.
2. Dispersed stress effect: the cap shell is oval or hemispherical, with a smooth surface. When an object falls on the cap shell, the object cannot stop and slide off immediately; and the force at the impact point of the cap shell is Transmitted to the surroundings, the force reduced by the cap lining buffer can reach more than 2/3, and the remaining force is transmitted to the human skull through the entire area of ??the cap lining, thus turning the focus point into a force surface, thereby avoiding the impact force on the human skull. The stress is concentrated at a certain point on the cap shell, which reduces the force per unit area. 3. Biomechanics: The national standard stipulates that safety helmets must be able to absorb 4900N.
This is because of biological tests, which show that the human cervical spine has a maximum limit when it is stressed. If it exceeds this limit, the cervical spine will be injured. In mild cases, it will cause paralysis, and in severe cases, it will be life-threatening. Procurement supervision: 1 Procurement of safety helmets: Enterprises must purchase products with product certificates and safety marks. The purchased products can only be used after they have been inspected and accepted.
2 Safety helmets should not be stored in places such as acid, alkali, high temperature, sunlight, moisture, etc., and should not be placed together with hard objects. 3 The service life of the helmet: calculated from the date the product is manufactured.
Knitted hats made from plant branches shall not be older than two years. Plastic caps and paper and plastic caps shall not be older than two and a half years.
Fiberglass (vinylon steel) rubber caps are no more than three and a half years old. 4. Enterprises should conduct random inspections and tests on expired safety helmets in accordance with the "Regulations on the Supervision and Administration of Labor Protection Equipment" (Order No. 1 of the State Administration of Work Safety). They can continue to use them only after they pass the test. In the future, they will be randomly tested once a year. If the safety helmets fail to pass the random test, The batch of safety helmets will be scrapped.
5 Production safety supervision and management departments at all levels must supervise expired safety helmets and urge the enterprise's safety technology department to inspect them, and they can only be used after they pass the inspection. Marking packaging: 1 Each safety helmet should have the following four permanent marks: A. Manufacturer's name, trademark, model; B. Year and month of manufacture; C. Production certificate and verification; D. Production license number.
2 Safety helmets are packaged at the factory. Each hat should be wrapped with paper or plastic film as a liner and then placed in the carton. Safety helmets packed into boxes must be finished products.
3. The product name, quantity, weight, volume and other precautions should be marked on the box. 4 Each box of safety helmets must be accompanied by instructions.
5 If the helmet is marked with a "D" mark, it means that the helmet is insulating. Classification: Safety helmet products are divided into two categories according to their uses: general operation (Y category) helmets and special operation (T category) helmets. The T category is further divided into five categories: T1 category.
2. What are the common sense about the use of safety helmets
Before use, check whether the safety helmet is expired and whether it is damaged, especially the joints of the lining and the lining. Damage, because when a heavy object hits the head, what really works is the cushioning between the lining and the helmet to disperse the pressure.
In addition, the headband should be tightened when wearing it to prevent it from falling off.
Many safety helmets now have chin straps. One theory is that the chin strap should be fastened very tightly to prevent the hat from falling off, but another theory is that it should not be tightened. In addition, the connection between the chin strap and the hat does not need to be very strong, it just needs to be fixed tightly so that it cannot fall off. Some helmets have a very strong connection between the chin strap and the hat, making it impossible to break free at all.
There have been cases abroad in the construction and high-altitude industries where people were strangled to death after falling from heights, so you may notice that there are no chin straps in the promotional pictures of foreign safety helmets.
3. What are the basic properties of safety helmets?
Functions of safety helmets 1. Impact resistance.
2. Penetration resistance.
3. Low temperature resistance.
4. Combustion resistance.
5. Electrical insulation properties.
6. Lateral rigidity.
Main structure of safety helmet
Hat shell: withstands blows and separates falling objects from the human body.
Hat band: Keep the helmet in a certain position on the head.
Top strap: Disperses the impact force and keeps the cap shell floating to disperse the impact force.
Rear hoop: the locking device of the headband.
Chinstrap: Assists in maintaining the status and position of the helmet.
Sweat-absorbent band: Absorbs sweat.
Cushion pad: Reduces the impact force when an impact occurs.
Wearing height: reflects the height difference from the forehead to the top of the head, which may interfere with eyes, ears and other items worn. The helmet band was too small and separated from the forehead. The fastening part is not closed and cannot guarantee a certain state and position on the head. Vertical Spacing: Reflects the gap between the inside of the shell and the top of the head. If it is too small, ventilation will be poor; if it is too large, the center of gravity of the helmet shell will rise, causing the helmet to be unstable on the head. Horizontal spacing: Provides buffer space when there is lateral force in the impact. It is also a heat dissipation channel. [1
4. What materials are general safety helmets made of?
Commonly used materials for safety helmets and their advantages and disadvantages
1. High-density polyethylene (HDPE) :
A lightweight material with good rigidity, high mechanical strength, high temperature resistance of 127℃, low temperature -70℃, good electrical insulation and corrosion resistance
Poor toughness and soft surface , avoid contact with gasoline, otherwise the performance will deteriorate
2.ABS acrylonitrile (A), butadiene (B) and propylene (S):
Good rigidity and not easy to deform , impact resistance, corrosion resistance, good electrical insulation and corrosion resistance, high temperature resistance 100 ℃
Not resistant to combustion, low temperature resistance, poor aging resistance
3. Fiberglass Vinyl Polyester fiber:
Low thermal conductivity, good high temperature resistance, low temperature resistance, corrosion resistance, combustion resistance, and better electrical insulation properties
5. The basic technical performance requirements of safety helmets are: Which
(1) Impact absorption performance refers to the helmet's ability to absorb impact energy when it is impacted by falling objects. A better helmet can absorb 80-90% of the impact it bears during the impact absorption process, minimizing the impact force acting on the renti to achieve the best protection effect. The formulation of the impact absorption energy index is based on the maximum impact force that the renti cervical vertebrae can withstand. According to the method specified in GB/T 2812-2006, after high temperature, low temperature, water immersion, and ultraviolet irradiation pretreatment, the impact test is carried out. The force transmitted to the head mold shall not exceed 4900N, and the cap shell shall not have any fragments falling off.
(2) Puncture resistance is the ability of the helmet to withstand the impact of a falling object with sharp corners. This is a test of the strength of the helmet shell.
6. What properties are required for a safety helmet?
Performance requirements for safety helmets Safety helmets are mainly used for safety protection to prevent personal safety from falling objects from high altitudes. They must have the following properties:
(1) Impact absorption performance;
(2) Penetration resistance;
(3) Low temperature resistance;
(4) Combustion resistance;
(5) Electrical insulation performance;
(6) Lateral rigidity.
Introduction to safety helmet knowledge
Safety helmets can withstand pressure mainly based on three principles:
1. Buffering and shock absorption: hat shell and hat lining There is a gap of 25~50mm between them. When an object hits the helmet, the helmet shell will not be deformed due to force and directly affect the top of the head.
2. Dispersed stress effect: the cap shell is oval or hemispherical, with a smooth surface. When an object falls on the cap shell, the object cannot stop and slide off immediately; and the force at the impact point of the cap shell is Transmitted to the surroundings, the force reduced by the cap lining buffer can reach more than 2/3, and the remaining force is transmitted to the human skull through the entire area of ??the cap lining, thus turning the focus point into a force surface, thereby avoiding the impact force on the human skull. The stress is concentrated at a certain point on the cap shell, which reduces the force per unit area.
3. Biomechanics: The national standard stipulates that the helmet must be able to absorb 4900N.
7. How to use a helmet correctly
First of all, you must choose a helmet that suits your head shape.
Before wearing, you must carefully check the certificate, instructions for use, period of use, and adjust the size of the cap lining. There must be a 20-50 mm space between the top and the inner top of the cap shell, so as to form a The energy absorption system distributes the impact force over the entire area of ??the skull, reducing damage to the head. Secondly, you cannot disassemble or add accessories to the helmet at will, so as not to affect its original protective performance.
The safety helmet must be worn correctly and fastened, and cannot be loose or loose to prevent it from accidentally falling off during work. During use, the helmet will gradually become damaged, so check it frequently.
Once abnormal damage or cracks are found on the cap shell and cap lining, or if the horizontal and vertical spacing between the cap lining and the inner top of the cap shell does not meet the standard requirements, it cannot continue to be used and must be replaced. In addition, when the helmet is not in use, it must be placed in a dry and ventilated place, away from heat sources, and away from direct sunlight. This will ensure that the protective function is not affected during the effective period of use.
Finally, pay attention to the use period. Expired helmets must be inspected and only those that meet safety requirements can continue to be used, otherwise they must be replaced.
8. Cycling: How much do you know about helmets?
The helmet is the big mushroom worn on the head when riding.
Because it can provide protection for the fragile head, it is a must-have equipment for cyclists. It is used to prevent collisions, prevent branches and leaves from being hit, prevent flying stones from being hit, divert rainwater, be breathable, and increase speed.
A helmet with a visor can protect you from the sun, and a reflective logo on the helmet can also prevent accidental collisions when riding at night. The criteria for judging the quality of a helmet include texture, weight, lining, wearing comfort, breathability, and wind resistance effect: Texture helmets are generally made of foam materials (which break when impacted to absorb vibration and achieve the effect of protecting the head). And it has a smooth shell surface; the lining is the part of the inside of the helmet that contacts the head. It can improve wearing comfort at ordinary times and provide a buffering effect when the head is hit.
A well-made helmet has a larger lining coverage, better texture, and is more firmly bonded to the inside of the helmet; wearing comfort is mainly due to weight, lining, straps, and whether the head circumference is appropriate. My personal feeling is that wearing a comfortable helmet can greatly reduce the pressure on the rider's head and neck and maximize the protection effect when suffering an impact; a breathable head that is not breathable for a long time will have adverse effects on the scalp. It can also make cyclists feel uncomfortable. Therefore, a good helmet either has a larger number of holes or a larger hole area, all of which are to improve breathability; wind resistance effect The helmet collects human hair inside the helmet, which itself reduces the wind resistance of the head. For those who are keen on improving speed, the impact of helmet shape on wind resistance is also worthy of attention.
Types of cycling helmets: Half-face cycling helmets are divided into road-specific (no brim), road and mountain dual-use (with removable brim), etc. Some friends also use helmets similar to those used for baseball or roller skating.
Full-face cycling helmets are similar in shape to motorcycle helmets and are generally used by downhill or climbing enthusiasts. Since the invention of the bicycle, it has gradually become a better means of transportation and leisure for people. Especially after cycling became a competitive sport, people became even more fond of it.
But as a sport that relies on speed, safety has become an important issue.
So, people thought of helmets.
The emergence of bicycle helmets not only ensures the safety of cyclists, but also improves the performance of racing athletes. As early as the 1880s, people riding high-wheel bicycles in some clubs were the first to discover the benefits of using helmets. Later, with the increase in hard asphalt roads and stone roads, the number of head injuries while riding bicycles also increased, and pith helmets It came into being.
Pith was a cushioning material capable of absorbing impact, but this helmet soon gave way to a padded leather-based design that lasted until the 1970s. This helmet was originally called a "hairnet" because it had long, padded leather covers that went over the head like a net.
This helmet is very attractive, with foam padding wrapped in soft, high-quality leather. Although this kind of helmet can indeed protect the ears of a fallen cyclist from being rubbed or bruised by the ground.
But unfortunately, its impact resistance is poor. An important development was the soft helmet, which looked a bit like a bowl with vents. This helmet was made of polystyrene and covered with a synthetic stretch fiber material (LYCRA). Later, foam was added to the inside. pad.
The impact resistance standards for bicycle helmets and the firmness of the buckle were both proposed by the U.S. Consumer Product Safety Commission (CPSC) in the mid-1970s. Project parameters of one kind or another are proposed by various agencies, such as the SNELL Foundation, the American National Bureau of Standards, and the American Society for Testing and Materials.
At that time, there was only one lightweight motorcycle helmet that met this standard. However, cyclists refused to wear such helmets because they were heavy and not breathable.
To this end, BeLL Biker first developed a bicycle helmet that complies with CPSC standards. It is made of ABS plastic as the outer shell and wrapped in polystyrene foam. Later, the updated shell material PVC and the higher-priced material polycarbonate greatly reduced the weight of the helmet.
Generally speaking, a bicycle helmet must be able to withstand at least two collisions. The first time is when it collides with another cyclist or car, and the second time is when the cyclist falls down and is hit by himself. When the ground hits the ground, these materials have a good buffering effect on both impacts. There have been many changes in the shape of bicycle helmets since their inception.
Round helmets have long been outdated. Today’s helmets have become smaller along the edges, and the ventilation holes have also been greatly changed, which truly has a cooling and breathable effect and is also in line with aerodynamic principles. For example, the Limar F111 bicycle helmet exhibited at an international bicycle products exhibition this year had as many as 37 holes, while last year's helmet had only 23 holes.
In addition to road bicycle helmets, with the emergence of mountain biking, its helmets also appeared. For example, BELL X-RAY is larger and less aerodynamic than road helmets. The main function of these helmets is to allow sweat to evaporate at a low speed in hot climate conditions.
Like today's COOLMAX LINERS helmets, these helmets are almost multi-functional because they also help absorb moisture. Generally speaking, most helmets do little good if an athlete falls backwards.
This has attracted the attention of helmet manufacturers. For this reason, GIRO has developed a positioning system to ensure that the back of the head is tightly buckled in the helmet. For example, the toothed buckle used in the ROCLOC helmet is a pioneering work of the company. The company also uses 10 positions to adjust the helmet to ensure the fit of the helmet.
The SPORTSCOPE helmet changes the common system style and introduces six pieces of strong and flexible nylon mesh materials. The integrated material blocks can be changed according to the user's requirements. . This helmet eliminates the need for padding and reduces the distance between the helmet and the skull.
The function of bicycle helmets in protecting the lives of cyclists is unquestionable.
According to a report from the Insurance Institute for Highway Safety, 98% of the number of cyclists who died in the United States in 1999 were not wearing helmets. People who wore helmets in collisions reduced their risk of serious head injuries by 85%. In addition, wearing a helmet not only It feels cool, and it really does.
At the same time, the vents on the helmet allow the head to pass freely.
9. What are the common safety helmet products
(1) Fiberglass safety helmet.
This kind of safety helmet is made of glass fiber or vinylon fiber and unsaturated polyester resin, which is hand-pasted and then heated and solidified or molded. It has good high and low temperature resistance, electrical insulation, corrosion resistance and flame retardant properties. It is mainly used in metallurgical high-temperature places, oil field drilling, forest logging, power supply lines, high-rise building construction and construction in cold areas.
(2) Plastic safety helmet. The plastics used in this kind of helmet include polycarbonate, ABS, ultra-high molecular polyethylene, modified polypropylene, etc. These materials are all thermoplastic engineering plastics and have good impact resistance, high temperature resistance, electrical insulation and other properties.
Changing the formula can also improve its flame retardant, anti-aging, low temperature resistance, antistatic and other properties. Compared with fiberglass safety helmets, plastic safety helmets are cheaper and therefore are widely used in various industries.
(3) Tape miner hat. The cap shell of this product is made of rubber and canvas, which are then molded and vulcanized.
Its biggest feature is its good antistatic performance and durability. Mainly used in coal mines, underground mines, tunnels, culverts, etc.
(4) Cold-proof helmet. This is a helmet that keeps the head warm and prevents damage from objects in the cold season. It consists of a hat surface, a hat lining, a lining shell and other cold-proof components (hat ear fans, hat ears, etc.).
The surface of the hat is made of leather, artificial leather or other fabrics, and the inside of the hat is filled with cotton, acrylic cotton and other cold-proof materials. The lining shell is a hemispherical hard shell made of engineering plastics or other materials, and the cold-proof components are Made of plush or shearling. Cold-proof safety helmets are suitable for use by workers working outdoors and outdoors in cold areas in winter.
(5) Paper glue safety helmet. The cap shell is molded from papermaking wood pulp with strong additives. It is resistant to high and low temperatures and has strong aging resistance. It is suitable for construction, mining, oil fields, chemical industry, transportation, transportation and other industries.
When used for outdoor operations, it can also protect against solar radiation, sand and rain. (6) Safety helmet woven from plant strips.
Safety helmets woven with plant strips should be glued with steel paper, plastic plates or coated with a layer of fiberglass on the top of the hat shell to increase their strength. This type of product has good air permeability and light weight, and is suitable for use in hot areas in the south and in workplaces without open flames.