O-ring are the most commonly used seals in seals. But because of the selection, groove design, processing and assembly of improper, often caused by oil spills fault, is a small bad event.
The standard of O-ring in our national standard has gb1235-76, GB3452.1-88 and GB3452.1-92, of which gb1235-76 specified o-ring cross-section diameter (also known as line diameter) 1.9, 2.4, 3.1, 3.5, 5.7, ETC., O-ring using "outside diameter X-Ray Diameter "marking method, generally known as the old GB; GB3452.1-82 and GB3452.1-92 basically the same, generally known as the new GB, it provides the O-ring section diameter of 1.8, 2.65, 3.55, 5.3, etc., the new national standard adopted international practice, O-Ring using" diameter X-ray diameter " Method of labeling.
Choose O-Ring, first should try to choose the new GB, line diameter 2.65 and 3.55 of the most common use, in the outer diameter of more than 30, the size of the structure allows the case, as far as possible to choose the diameter of 3.55 O-ring, to achieve greater compression and contact area.
O-ring materials are mainly butyl cyanide rubber NBR and fluorine rubber fkm, fluorine rubbers are more suitable for high-temperature operating conditions.
In addition to the material, O-ring is an important indicator of its hardness, generally using the shore hardness to indicate that from 60 to 90 or so, the larger the value of the higher the hardness. Under the same pressure, the higher the hardness, the stronger the ability to prevent extrusion (deformation and even tearing). Therefore, should choose the high hardness O-ring.
However, the common O-ring in the market are made of butyl cyanide rubber, the shore hardness is generally around 70, difficult to meet the requirements of a considerable number of working conditions.
O-Ring Groove Design has relevant national standards, the main dynamic seals, axial static seals and radial static seals three kinds. The O-Ring of flange, box lid and so on are more convenient to assemble and ensure sealing performance. In addition, China's national standards of the groove size standards have been significantly behind, such as national standards under pressure O-ring groove diameter is equal to O-ring outside diameter, and Parker Flange connector O-ring groove outside diameter is less than O-ring diameter. Design should be appropriate reference to foreign standards.
The sealing surface with O-ring shall not use a planar sealant, and a small amount of butter can be applied to the O-ring to keep it from falling off. In the maintenance, according to the Groove size to determine the O-ring specifications, not the diameter of the thicker the better.
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