Rubber hose pipes are hose pipes made from rubber formulations and are widely used in industries such as agriculture, military, medical and civilian applications. Rubber hose pipes are divided into non-reinforced hose pipes and reinforced hose pipes.
Reinforced rubber hose pipes are hose pipes with one or more layers of reinforcing material between the inner and outer layers of rubber or on the outside of the inner layer (without an outer layer). The reinforcing layer is structurally diverse, and there are two main types of reinforcing materials: fibers and metals (the metal reinforcing material is generally steel wire). Steel wire is an important structural component of rubber hose pipes, especially high-pressure hose pipes, and is in significant demand in the rubber hose industry.
To better understand the role of steel wire in rubber hose pipes and the requirements for steel wire in rubber hose pipes, the following sections describe the application of steel wire in rubber hose pipes in three parts.
According to the SAE J 517 standard, the working pressure of reinforced rubber hose pipes is roughly divided into 5 levels: low pressure, medium pressure, high pressure, very high pressure, and ultra high pressure. The pressure level depends on the inner diameter of the hose, with smaller inner diameters being able to withstand higher pressures under the same structure, and larger inner diameters being able to withstand lower pressures.
Low-pressure hose pipes use fiber-reinforced materials, medium-pressure rubber hose pipes can use fiber-reinforced or steel-wire-reinforced materials, while high-pressure, very high-pressure and ultra-high-pressure hose pipes are generally reinforced with steel wire. Hoses for special applications may use aramid fiber-reinforced materials with a lower specific gravity and higher tensile strength than steel wire. The reinforcing layer of steel wire-reinforced rubber hose pipes has a braided structure and a winding structure, and sometimes a mixture of both.
Under the same conditions, hose pipes with a winding structure have higher resistance to pulse pressure performance than those with a braided structure, because there are no interweaving points between the winding steel wires, and there is no local friction between the wires.
Reinforced rubber hose pipes are flexible conduits used for conveying liquids, gases, and particulate or powdered solid materials, as well as transmission of hydraulic and pneumatic power. Hoses must withstand varying degrees of internal and external pressure (positive or negative) whether conveying materials or transmitting power. Therefore, the main function of the steel wire reinforcing layer is to strengthen the rubber hose, and to enable it to withstand positive and negative pressure.
During use, particularly for hydraulic hose pipes, rubber hose pipes are subjected to pressure that is not constant. They must withstand pulsating pressures that range from 0 to 125% of the working pressure and sometimes even higher instantaneous impact pressures. In hose design, a safety factor is required to be added to the required working pressure, which is the ratio of the minimum burst pressure to the maximum working pressure, with safety factors ranging from 2 to 5, generally 4.
During the working period, the wire reinforced flexible hose must not only withstand cyclic changes in diameter enlargement, contraction, elongation, and shortening due to pressure, but also withstand cyclic bending deformation caused by installation. Furthermore, the conveyed material, transmission medium, weather and environment, high and low temperatures, and other factors may cause deterioration of the inner and outer layers of the hose, affecting not only the performance but also the service life of the hose.
In hose design, the consideration of steel wire primarily focuses on tensile strength, toughness (flexibility), and specifications. Suitable steel wire is selected according to the pressure level of the hose. In general, the lower the tensile strength of the steel wire, the better the flexibility, while the higher the tensile strength, especially at its upper limit, the worse the flexibility and the greater the brittleness.
However, it is more important to develop steel wire with high strength and good flexibility simultaneously, which will play an important role in improving the performance and service life of the wire reinforced flexible hose. The adhesion between steel wire and rubber is important for the flexibility and pulsation performance of rubber hose pipes, particularly hydraulic hose pipes.
After the rubber hose is formed and vulcanized, the various components of the hose body are well bonded, making the hose body an indivisible whole, which is one of the issues that must be considered in hose design. In addition to measures taken in rubber formulation and hose vulcanization methods, the surface treatment of steel wire and its coating is also crucial for bonding with rubber.
Steel wire is an important constituent material of reinforced rubber hose pipes, and plays a key role in hose pressure, pulsation, impact, and flexibility.
