Pipe joint chamfering sealing rubber O-ring is a junction of seal, the O-ring will be fitted to a produced groove by chamfering and then squeeze through the shell to create a seal. What should concern when design rubber O-ring product is that must be slightly stretched, appropriate to reduce the amount of compression, appropriate to increase the fill rate. Chamfering is generally 15 ° ~ 30 °, according to the working pressure selected, under pressure, to an angle close to a small value. On the contrary, whichever is greater. Its chamfered is easy to use, operate, manufacture and process characteristics seal between the fitting and the hydraulic valve, so it’s widely use on sealing pipe joints. This article focuses on the design and selection of sealing the chamfered O-ring.

Rubber O ring is static seal, without considering the rubber O ring is mounted to the O type ring groove deformation and other assembly effect, simple calculation of joint diameter (d ') unilateral interference of 10~20 wires can be 0.1~0.2mm. Of course, taking into account the part size tolerance (O type ring diameter, inner diameter of rubber O ring the sealing surface, inner diameter, rubber ring type O slot size and land size), eccentric coaxial degree and location of equipment, can further calculate the limit when the assembly of unilateral move, to ensure that this time the loose side interference is not negative. In order to further determine the sealing surface, O type ring groove, and size tolerance. Then calculate the land value D' (O type sealing ring groove diameter) D '=d2 2H where: d2=d1/1.03-1.07

One important reason for the destruction of the rubber O-ring is pushed in the inner pressure in the working gap, the gap allowed values of operating pressure, the rubber hardness of the rubber O-ring diameter and cross-sectional size of d0, O-ring compression the size can directly affect the sealing performance and service life. The amount of compression is too small, the sealing effect is not good, the amount of compression is too large for O-ring assembly adverse, which increasing frictional resistance movement, life will be shortened. Therefore, seal design process, to control the amount of compression reasonable O-ring, generally 7% to 30% compression rate prevail. Sectional diameter of the compression of the rubber O-ring installation is 5% to 3.5% for the fixed seal made too large value for the active seal taking small value.

To ensure a reasonable sealing performance, dynamic sealing and static sealing should have a suitable surface roughness. Usually static sealing Ra6.3μm ~ Ra3.2μm, dynamic seal Ra3.2μm ~ Ra1.6μm. But not the roughness is higher ,and will be better, if the surface roughness of installation is too high, so flatness is poor, there will be some ribs. After one hand, the O-ring is compressed, and some surface due to the seal is not solid ,lead to oil spills. With the other hand, the O-ring will be high pressure to low pressure in the direction of the direction of the slide in the groove, causing the O-ring damage and leakage.

Tensile elongation the rubber O-ring is too large, it will cause stress relaxation, resulting in an increase in the inner diameter of the O-ring. Resulting in the formation of the contact gap and the shaft surface, the installation process will make it fall off because of vibrations. Meanwhile, the rubber O-ring due to the intensity of the uneven squeeze, affecting the life of the O-ring.

Design requirements for mounting parts

(1) the O type ring installation groove parts must ensure adequate surface roughness, smooth appearance, no damage.

(2) chamfer parts should have positioning table to prevent binding of uneven surface, and influence between the hole and shaft coaxial degree, resulting in O-ring excessive wear.

Installation requirements of rubber O ring

(1) to check whether the introduction angle meets the requirements of the drawing, 15 degrees ~30 degrees, as well as the 2K D size.

(2) seals and parts should be coated with grease or lubricating liquid, but not containing solid additives in grease, such as molybdenum disulfide and zinc sulfide.

(3) before the installation of the axis of the installation of the appearance of the inspection, the surface must not fly edge burr, impurities, dust and other defects and scratches.

(4) installation process prevent O-ring bumps, should first file repair flat burr, in the parts of the threads and a keyway surface coated with adhesive tape to be installed, play a role in protecting the O-ring.