According to the usage environment and requirements of the fire hose, the fire hose must be resistant to high pressure, aging, corrosion, wear, high and low temperatures, and bending, while also being flexible and lightweight.
The lining is generally required to have a smooth inner wall without wrinkles, uniform thickness, certain elasticity and strength, as well as waterproof, mold-proof, low-temperature and aging-resistant properties.
The lining of certain water pipes used in special occasions must also have properties such as resistance to chemical corrosion, high temperature, and oil.
The physical properties required for hose lining are as follows: the tensile strength of rubber fire hose lining is not less than 8.30MPa, and the elongation at break is not less than 400%; the tensile strength of latex lining is not less than 12.41MPa, and the elongation at break is not less than 700%.
The requirements for common hose linings are as follows:
The lining made of TPU has high mechanical strength, excellent wear resistance, elasticity, corrosion resistance, low-temperature and aging resistance, and oil resistance. Its physical properties generally require a tensile strength of not less than 13.80MPa and an elongation at break of not less than 400%.
According to the different chemical structures, TPU can be divided into polyether type, polyester type, and polycarbonate type. Currently, polyether TPU is generally used in China to produce high-quality rubber fire hose lining.
Compared with TPU lining, PVC lining hoses are cheaper, lighter, and have simpler production processes, excellent oil and weather resistance, and are suitable for mass production and use.
Its physical properties generally require a tensile strength of not less than 8.30MPa and an elongation at break of not less than 400%. In addition, because PVC material itself has excellent flame retardancy, hoses with flame retardancy requirements must use PVC material.
The machine's caliber. The machine caliber refers to the diameter of the fixed ring on the circular loom, which determines the inner diameter of the hose, which is the fabric layer caliber.
Burst pressure. The national standard has clear requirements for the burst pressure of hoses. The number of longitude and latitude strands and the density must be determined based on theoretical calculations and experimental designs that achieve the highest burst pressure required by the double-jacket fire hose.
Pattern. The fabric layer generally has two appearance patterns: oblique and flat. Oblique refers to forming an inclined pattern on the surface of the fabric layer. Generally, hoses use the oblique pattern of two ups and one down. Flat refers to the interweaving of warp and weft yarns in an upward and downward manner.
Length of the loom. The length of the fabric layer cut off from the circular loom determines the length of the hose, which is generally determined by the hot vulcanization process and weaving process of the hose.
Shaping ability. Rubber fire hoses must have a certain shaping ability, which can ensure that the hose is not easily bent during use, so that the fire extinguishing agent can be smoothly sprayed.
The main factors affecting the burst pressure of hoses are production processes and design factors.
Production process. Adding twist during weaving can effectively improve the tensile strength, but excessive twist will reduce the tensile strength and hose softness. Therefore, the twist is generally controlled at around 30-200 T · m during actual production. In addition, uneven tension of single-strand filaments during weaving will cause the tensile strength after weaving to be smaller than the combined force of each single strand.
The shuttle wheel, hole plate, jump pole spring, tension spring, and other parts on the circular loom not being smooth will also cause the tensile strength to decrease.
Design factors. It is generally believed that the main factors affecting the burst pressure of rubber fire hoses are the tensile strength, elongation at break of longitude and latitude, and initial density of the hose.
Therefore, high tensile strength and low elongation at break materials should be selected when preparing the longitude and latitude threads. The latitude density can be appropriately increased without affecting the quality and softness of the hose.
Double-sided adhesive hoses contain a covering layer, usually made of the same material as the lining, with a slightly smaller thickness. The covering layer is generally designed with a structure similar to a "reinforcement rib" along the length direction, which can improve the wear resistance of the hose and increase the grip of firefighters on the hose.
The outer surface of the hose uses a coating made of high molecular polymer flexible coatings such as polyacrylate ester and PU.
The adhesive layer is the substance that bonds the lining, covering layer, and fabric layer together. Different adhesives need to be selected according to the materials of the lining, covering layer, and fabric layer.
