When choosing the O-ring specification, the first thing to do is to determine the material of O-ring. At present, in industrial parts, the materials of O-ring in life include NBR nitrile rubber, NR natural rubber, Cr chloroprene rubber, EPDM EPDM EPDM EPDM, HNBR hydrogenated nitrile rubber, silicome silica gel, FKM, Viton, fluororubber, FLS silicone fluororubber, PU polyurethane, SBR styrene butadiene rubber, Buna butadiene rubber, acrylate rubber ACM, PTFE, polytetrafluoroethylene, etc. Each of the above materials has its own destination and use, including oil-resistant, chemical resistant, high and low temperature resistant, wear-resistant and so on. So when choosing the O-ring specification, you must know where the product is used, what it needs to bear, what role it plays, and its service life, so that you can choose the O-ring material you need purposefully.
O-ring specification size has outer diameter, inner diameter, line diameter to express. As long as we indicate the size of inner diameter and wire diameter on our engineering drawing, the outer diameter is equal to the inner diameter + 2 * wire diameter. Or only dimension the outer diameter and wire diameter. The two optional O-ring specification tolerance mainly includes the tolerance of inner diameter and the tolerance of line diameter. The size tolerance of O-ring mainly depends on the size. The larger the size, the larger the tolerance. For example, the tolerance standard of O-ring with inner diameter of 0.05 to 1.79mm is + / -0.10mm, and the tolerance standard of O-ring with wire diameter of 0.05 to 1.79mm is + / -0.07mm.
It is very important to choose the compression amount when selecting the O-ring specification, because the selection is not correct, otherwise it will not be sealed when assembling the product, or it will be too tight when assembling, so it will not play the role required by the product. Then how can we choose the compression amount of O-ring specification correctly? Here's a reference for you: the compression amount of O-ring generally depends on the hardness and material of O-ring. If the hardness of O-ring is 70 degrees, the compression amount of O-ring is equal to 20%. Of course, the lower the hardness of the O-ring, the greater the compression of the O-ring, which is mainly used in places with low pressure. So the higher the hardness of O-ring, the smaller the compression of O-ring. It is mainly used in the environment with high pressure, pressure resistance and small resistance. And so on, you can get the compression of any hardness O-ring you need.
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