Mining flame-retardant steel wire wound hose, pressure 42MPa
In high-pressure, flammable, and explosive special working conditions such as mining and tunnel construction, flame-retardant steel wire spiral hoses are core components for transporting high-pressure fluids (such as hydraulic oil and emulsions), and their performance directly affects production safety and efficiency. This article, written by LETONE Hydraulic Hose Division, will focus on three core indicators: a 4-layer steel wire spiral structure, a pressure resistance of over 42MPa, and flame-retardant properties, providing an in-depth analysis of the technical points and application scenarios of this type of hose.
I. Structural Design and Pressure Resistance
The 4-layer steel wire spiral hose is formed using a staggered winding process with high-strength steel wire. Each layer of steel wire is spirally wound at a balance angle of 54°~56°, forming a mesh reinforcement layer. This structure can evenly distribute fluid pressure and avoid local stress concentration. According to GB/T 3683-2011 standard, 42MPa belongs to the ultra-high pressure level (Type 4SN), requiring passing pulse tests (≥200,000 times without leakage) and burst pressure tests (≥4 times the working pressure). In practical applications, the 4-layer structure offers over 60% improved fatigue resistance compared to the traditional 2-layer steel wire braided hose, making it particularly suitable for the frequent high-pressure impact conditions of equipment such as tunnel boring machines and coal mining machines.
II. Technical Implementation of Flame Retardant Properties
The flame retardancy of mining hoses must meet the requirements of MT/T 98-2006 "Safety Specifications for High-Pressure Mine Hose". The outer layer typically contains flame retardants such as aluminum hydroxide and antimony trioxide, with an oxygen index ≥28%. Some high-end products use chloroprene rubber (CR) or flame-retardant polyurethane (PU) as the covering layer, which forms a carbonized layer to isolate oxygen in an open flame environment. It is worth noting that flame retardant performance must be designed in conjunction with antistatic properties; the surface resistivity must be controlled within the range of 10^6~10^8 Ω to prevent gas explosions caused by electrostatic sparks.
III. Key Application Scenarios and Selection Recommendations
1. Hydraulic supports for fully mechanized mining faces: 4SH grade rubber hoses with an inner diameter of 19-25mm are required to withstand frequent working pressures of 31.5MPa. The bending radius should be ≤8 times the hose diameter to accommodate confined spaces.
2. Mining drilling equipment: Wear-resistant models with a polyamide (PA) lining are recommended to withstand the scouring of fluids containing rock cuttings.
3. Tunnel grouting systems: Compatibility between the hose and chemical grouting materials is crucial; nitrile rubber (NBR) inner lining is preferred.
For maintenance, it is recommended to check the exposed steel wires of the hose every 500 hours. If cracks are found in the outer rubber layer or more than three steel wires are exposed, the hose must be replaced immediately. During storage, avoid direct sunlight; the ambient temperature should be maintained between -15℃ and 40℃.
IV. Comparison of Mainstream Products in the Market
Taking the LETONE brand 4SN-25-42MPa model as an example, it uses imported German steel wire (tensile strength ≥2150MPa) and a burst pressure of 168MPa, far exceeding national standards. Some low-priced products, in order to reduce costs, may use recycled rubber or reduce the number of steel wire layers, resulting in an actual pressure resistance of only around 30MPa, posing a serious safety hazard. It is recommended to request third-party testing reports when purchasing, and to focus on verifying the number of steel wire layers (X-ray film) and flame retardant test certificates.
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