How to Define Quality of Flexible Coupling


High-quality flexible coupling can provide reliable sealing performance, preventing media leakage or infiltration and maintaining the integrity of the pipeline system. They also have a longer service life, can withstand repeated connections and disconnections, and are resistant to corrosion and wear, reducing maintenance and replacement costs. In addition, high-quality flexible couplings have good pressure resistance and stability, allowing them to operate safely under high pressure and load conditions, reducing the risk of accidents and damage. To ensure the sealing performance and pressure resistance of clamps, pay attention to the quality of flexible coupling rubber seal rings, clamp castings, and clamp joints, as well as the transportation and storage of clamps.

The Quality of Rubber Seal

Rubber seal rings play a crucial role in sealing performance, and their quality and surface condition are of utmost importance. Defects such as bubbles, impurities, cracks, and unevenness can disrupt the tight contact between the seal ring and the valve body, leading to leakage or penetration issues, which in turn affect the normal operation of the equipment. These defects can also reduce the strength and durability of the rubber material, resulting in wear, aging, cracks, or even failure during use. In the manufacturing process of clamps, we strictly control the quality of materials and processing techniques to ensure that the surface of rubber seal rings is smooth and uniform. We also conduct quality inspections and screenings to ensure that their quality and performance meet the requirements.

a qualified rubber seal of flexible coupling on white background.

Qualified rubber seal

A poor-quality rubber seal of flexible coupling on white background.

Defective rubber seal

Rubber Seals Quality standard
- Nominal Diameter DN/mm
Defects - 50–200 225–500 600–1000
Bubbles Length/Width <2 mm <2 mm <2 mm
Depth <0.5 mm <1 mm <1 mm
Quantity <2 <3 <4
Impurities Length <2 mm <2 mm <2 mm
Width <1 mm <2 mm <2 mm
Depth <1 mm <1 mm <1 mm
Quantity <3 <3 <4
Surface Defect Depth <1 mm <5 mm <1 mm
Height <1 mm <5 mm <1 mm
Length <4 mm <5 mm <10 mm
Quantity <3 <4 <5
Crack - not allowed not allowed not allowed
Four qualified coupling body with different view on white background.

Quality of Coupling Castings

Flexible coupling should not have casting defects such as porosity, sand holes, inclusion, cold shut, and cracks that affect mechanical properties. Porosity refers to the holes formed by the accumulation of gas during the casting process, which often exist inside the clamp castings; sand holes are pits on the surface of the castings; inclusion refers to the oxides and other impurities trapped in the metal during the casting process; cold shut refers to the incomplete connection area formed due to improper internal structure or pouring method during the solidification of the metal liquid in the casting process; cracks refer to cracks or cracking phenomena in the castings. If the clamp has these defects, it will significantly reduce its strength and sealing performance, and may cause sudden fracture of the clamp during use, posing serious safety hazards. We avoid casting defects such as porosity, sand holes, inclusion, cold shut, and cracks in the production process of clamps to ensure the mechanical performance, sealing performance, and reliability of the clamps are effectively guaranteed.

A detail of flexible coupling.

Quality of Coupling Castings

Coupling joints play a sealing role in pipeline systems, and the quality of their sealing performance directly affects the normal operation and safety of the pipeline system. Good sealing performance can effectively prevent media leakage or the infiltration of external media, ensuring the stability and efficiency of the pipeline system.

Transportation and Storage

During the transportation of clamps, it is strictly prohibited to come into contact with corrosive substances that are harmful to rubber. Avoid rainwater and store the clamps in a cool, dry, well-ventilated area away from heat sources and corrosive gases.