Composition structure
safety helmet is composed of cap shell, cap lining and chin strap and other three parts.
(1) cap shell: this is the main part of the helmet, generally using oval or hemispherical thin shell structure. This structure, under the impact pressure will produce a certain pressure deformation, due to the rigid properties of the material to absorb and disperse the force, coupled with a smooth surface and circular curve easy to make the impact of the object slide away, and reduce the impact of time. According to the need and strengthen the strength of the helmet shell, the shell can be made of light top, top rib, with and without the edge and other types.
(2) cap lining: cap lining is a general term for the contact parts within the cap shell directly with the top of the wearer's head, which is composed of cap band ring with, top band, guard band, bracket band, sweat absorption band, liner technology tether rope. Cap lining materials available cotton woven belt, synthetic fiber belt and plastic lining belt made, cap band for the ring-shaped belt, in wearing tightly around the human head, with the forehead part of the band lined with sweat-absorbing material, with a certain sweat-absorbing effect. Cap band ring-shaped band can be divided into fixed band and adjustable band two, cap band has added back neck band and no back neck band two. Top band is the top of the human head in contact with the lining band, top band and the cap shell can be riveted connection, or with the socket with the cap shell socket connection, top with cross-shaped, six stripes. Correspondingly set socket 4 ~ 6.
(3) chin strap: foot tied to the chin strap, play the role of fixed helmet, chin strap by the band and locking card composition. No back neck hoop cap liner, using the "y" shaped chin strap.
Protection mechanism
(1) buffer shock absorption role: cap shell and cap lining between 25 ~ 50 mm gap, when the object hit the helmet, cap shell is not due to the force deformation and directly affect the top of the head.
(2) disperse stress role: cap shell for oval or hemispherical, smooth surface, when the object falls on the cap shell, the object can not stay immediately slide down; and cap shell by the point of the blow to bear the force around the transfer. Through the cap liner buffer to reduce the force of up to 2/3 above, so that the force point into the force surface, thus avoiding the impact of the stress concentration in the cap shell on a certain point, reducing the force per unit area.
(3) biomechanics: the standard safety helmet must be able to absorb 4900N, one this is because the biological test, the human cervical spine in the force of the maximum limit, more than this limit cervical spine will be injured, the light cause paralysis, the heavy life threatening.
Classification
Safety helmet products according to the use of general operations class (Y class) helmet and special operations class (T class) helmet two categories, which T class and divided into five categories.
T1 class is applicable to the workplace with fire source.
T2 class is applicable to underground, tunnel, underground engineering, logging and other places of operation.
T3 category for flammable and explosive workplaces.
T4 (insulated) class for electrically charged workplaces.
T5 (low temperature) class for low-temperature workplaces.
Each kind of helmet has a certain technical performance indicators and applicable range, so choose to use the industry and operating environment according to the corresponding products, consumers can use the industry and operating environment according to the appropriate varieties. For example, the construction industry generally choose Y class helmet; in the power industry, because of contact with the power grid and electrical equipment, should choose to use T4 (insulation) class helmet; in the flammable and explosive environment operations, should choose T3 class helmet.
safety helmet color selection is relatively large, generally to light or eye-catching color is appropriate, such as white, light yellow, etc., can also be selected according to the requirements of the relevant regulations, follow the principles of security psychology selection, according to the sector distinction to choose, according to the workplace and the environment to choose.
Technical requirements
(A) General requirements
(1) The cap band is straight according to the applicable range for adjustment.
(2) The forehead area of the cap band should be sweat-absorbent or increase the sweat-absorbing band, whose width is greater than or equal to the width of the cap band.
(3) tether should be used soft textile, width of not less than 10mm band or diameter of not less than 5mm rope.
(4) shall not use toxic and harmful materials, contact with the human body part of the material shall not cause allergic irritation to the skin reaction injury.
(5) material aging resistance should be no less than the date expressed in the product identification, the normal use of helmets in the use of the period shall not be caused by material performance below standard, all materials used should have the same expected life.
(6) helmet accessories shall not damage the stability of the helmet when worn normally.
(7) weight (quality): ordinary helmet not more than 430g; cold helmet not more than 600g.
(B) basic performance
(1) impact absorption performance: according to the prescribed method, by high temperature, low temperature, water immersion, irradiation pretreatment to do impact testing, the force transferred to the head mold does not exceed 4900N; cap shell shall not have fragments off.
(2) puncture resistance: according to the prescribed method by high temperature, low temperature, immersion, irradiation pretreatment to do puncture test, steel cone does not touch the surface of the head mold; cap shell shall not have fragments off.
(3) the strength of the mandibular band: according to the prescribed method test, the mandibular band fracture force value should be in 150 ~ 250N.
(C) special performance
(1) electrical insulation performance: tested according to the prescribed method, the leakage current shall not exceed 1.2mA.
(2) flame retardant performance: test according to the prescribed method, the renewal of combustion time does not exceed 5s, the cap shell shall not burn through.
(3) lateral rigidity: test according to the prescribed method, the maximum deformation of not more than 40mm, residual deformation of not more than 15mm, the cap shell shall not have debris off.
(4) anti-static performance: test according to the prescribed method, the surface resistance value is not greater than 100 million ohms.
(5) low temperature resistance performance: according to the low temperature (-20 ℃) pretreatment for impact test, the force transmitted to the head mold does not exceed 4900N; cap shell shall not have pieces off; then use another sample by (-20 ℃) pretreatment to do puncture test, steel cone shall not touch the surface of the head mold, cap shell shall not have pieces off.
