Gesang Technical Manual – Hose and Joint Foundation
1. **Hose Construction**
A typical rubber hose consists of three main layers: an inner layer made of synthetic rubber that contains the fluid being transported, a reinforcement layer made of steel wire or fiber to withstand internal pressure, and an outer protective layer of synthetic rubber to shield the inner components from environmental damage. These layers are essential for ensuring the durability and performance of the hose under various operating conditions.
2. **Working Pressure**
When selecting a hose and its fittings, it is crucial to ensure that the maximum recommended working pressure of the assembly is equal to or greater than the system's maximum operating pressure. Additionally, any pulse or peak pressures in the system must not exceed the hose’s rated working pressure to prevent failure.
3. **Test Pressure**
The test pressure is typically conducted at room temperature using water or another suitable medium. The hose assembly should be subjected to twice its working pressure for 30 to 60 seconds without any leakage or pressure drop. This test follows the ISO 1402 standard to verify the integrity of the assembly.
4. **Burst Pressure**
Burst pressure refers to the pressure at which the hose will rupture. It should be at least four times the rated working pressure. However, this value is not used as a basis for selection during normal operation, as it represents the ultimate failure point rather than a safe operating limit.
5. **Fluid Compatibility**
The hose must be chemically compatible with the fluid it carries. Incompatible fluids can cause degradation, leading to premature failure or improper system function. Always check the manufacturer’s recommendations for fluid compatibility.
6. **Temperature Range**
To maintain the hose’s performance, both the fluid temperature and the surrounding environment should remain within the hose’s specified temperature range. Exceeding these limits can cause the hose to age prematurely and lead to leaks or failures.
7. **Minimum Bend Radius**
The minimum bend radius is the smallest radius the hose can safely bend while operating at its rated pressure. Bending beyond this radius can significantly reduce the hose’s strength and lead to failure. Also, the straight section between the hose and the fitting should be at least 1.5 times the hose’s outer diameter.
8. **Storage of Hoses and Fittings**
Proper storage is essential to ensure the hose remains functional within its shelf life. In Germany, storage must follow DIN 20066:2002-10 standards. According to this, hoses used in assemblies must be less than 4 years old, and the entire assembly should not exceed 6 years from production, with no more than 2 years of storage time.
ISO/TR 17165-2 provides slightly different guidelines, stating that hoses and assemblies should not be used more than 10 years after manufacturing.
Shanghai Gesang Electromechanical Technology Co., Ltd. provides this information as a reference.
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