Exhibition, on the sealing design theory and calculation method of the interface rubber ring, obtained. The modulus of elasticity of the apron depends on the hardness of the rubber. The rough point is discussed by the compression test of the apron sample. It is used for the calculation of the interface density 2.2 section compression deformation rate. 0- and Y-shaped apron compression test The actual compression ratio of the cross-section of the apron (hereinafter referred to as compression 2 sealing parameter 2.1 minimum contact compressive stress, the apron is installed in the interface gap of the rigid body structure smaller than the cross-sectional diameter or height, The reaction force generated by the compression deformation of the section is the contact pressure of the apron (ie, when the sealing frictional resistance (ie, fp) generated at the interface sealing surface is greater than the pressure load of the pipeline conveying medium, the U can maintain its sealing. The distribution of c and fP of the circular section rubber seal (hereinafter referred to as the 0-shaped apron) and the lip-section rubber seal (hereinafter referred to as the Y-shaped apron) are as shown in the sum.
Minimum means the lowest CC value that the apron should have in order to maintain the seal of the interface. Add the safety factor (K value is set to the design value of the selection and the apron seal calculation. The ac value of the apron is the cross-section type and size of the apron, the maximum compressive deformation rate (Pmax) of the section, ie, the elastic modulus, etc. The complex function related to many factors. The value of the apron used to be the rubber hardness (MPa) of rubber hardness (MPa) of Table 1 is the compressive deformation of the apron section and its cross-sectional diameter or degree. The ratio of the compression ratio of the apron directly affects the sealing and flexible performance of the interface and its application period. Therefore, choosing a suitable apron compression ratio is also an important part of the interface seal design. The apron should be selected according to the pipe diameter, the type of pipe, the type of conveying medium and its working pressure. The interface of low pressure water supply and drainage pipeline should be 15% ~ 20%. The interface of medium pressure water supply pipeline should be 25% ~ 30% u high pressure water supply and low and medium pressure gas transmission and large diameter pipeline interface should choose 35% ~ 40%. 2.3 Seal The frictional resistance of the frictional apron has a complex function relationship with many factors such as ac, contact area and friction coefficient. It is the key sealing parameter for the U seal design.
2.4 Compressive Stress Relaxation Rate Ring The effective application period of the sealing and flexible joint interface depends on two properties of the viscoelastic material of the rubber: compression set and compressive stress relaxation rate. Both are also important design basis for the u seal design. The actual accurate value of the compression stress relaxation rate of the apron can be measured by the long-term compression test of the apron sample, expressed as a percentage of its initial stress. When the apron seal is calculated, the value of the seal friction resistance actually possessed by the apron should be corrected by this value.
3 Aperture seal design and calculation Generally, the pipe diameter, pipe type, type of conveying medium and working pressure are known. The rubber ring selected by the heuristic method is calculated and calculated (and fp. and the pipeline medium containing safety factor). The fp of the test pressure is compared to determine whether the selected apron meets the sealing design requirements of the interface. The calculation procedure is as follows: 3.1 Calculate the original cross-sectional diameter or maximum height before the apron is installed: 3.1.1 Calculate the 0 shape according to the following formula Cross-section diameter of the apron before installation: diameter, cm; ring diameter installation factor of a 0-shaped apron, 3.1.2 can calculate the maximum width of the cross-section of the Y-shaped apron before installation. hmaxo: KY-shaped apron Ring diameter installation factor: when installed on the pre- (self) stress reinforced concrete pipe socket sealing surface, take = 0.85~0.90; when installed in the groove of the cast iron pipe socket, take Kb 3.2 to calculate the ring length reduction after the installation of the limb ring Section diameter or ring shortening, increasing section maximum height: 3.2.1 Calculate the cross-sectional diameter of the ring extension after the 0-shaped apron is installed according to the following formula: small cross-sectional diameter, cm; diameter, cm; , take Kr upper style in China Learned from the 1962 annual meeting. Since the derivation base equation of this formula misuses the inner diameter of the ring of the 0-shaped apron as the middle diameter, the ds value calculated by the 3 -2 formula is more deduced than the formula derived from the ring diameter. The calculated ds value is too small. PanIW.Kao, the chief engineer of the St. Flora Pipe Factory in the United States, calculates the length of the straight line segment with the diameter of the apron ring before and after the stretching according to the geometric method of equal volume before and after the apron stretching. Simple method of equal volume, the simple and accurate ds value calculation formula is derived as follows: small cross-sectional diameter, cm; diameter, cm; Y-shaped apron is installed on the pre- (self) stress reinforced concrete pipe socket sealing surface, ring extension The length of the section with a reduced length hs: can still be calculated according to the formula 3-3, but should be replaced by hnm. d. 3.2.3 Calculate the Y-shaped apron installed in the groove of the cast iron pipe socket, the section of the ring shortened the maximum 篼Degree h; the ring diameter installation coefficient of the Y-shaped apron is 1.03~1.04. Due to the small increase of the cross-section, considering the safety and reliability of the seal of the interface, the calculation of the apron seal can still be calculated according to the maximum height of the original section. formula.
3.3 Calculate the original cutting length of the ring before the installation of the limb ring: 3.3.1 Calculate the original cutting length of the 0-shaped apron according to the following formula: the original cutting length, cm; the Y-shaped apron is installed in the pre- (self) stress reinforced concrete pipe Calculation of socket sealing surface L: Type 3-4 can still be applied. It is only necessary to replace ds with hmaxs. 3.3.3 Calculate the original cutting length of the ring when the Y-shaped apron is installed in the groove of the cast iron pipe according to the following formula: the original cutting length, cm; 3.4 Contact pressure: ton; 3.5 Calculate the contact pressure of the limb ring according to the following formula: : ac - the actual contact pressure of the apron, Nc - the actual contact pressure of the apron, Dc - the diameter of the ring of the apron, Cm; be - aperture section compression deformation of the contact width 0 and Y-shaped apron bc = 2.4C. 3.6 according to the formula to calculate the actual number of seal friction of the limbs; sliding friction take P = 0.4 ~ 0.6; rolling The friction takes P=02~0.3. The calculated fP value should be corrected according to the compressive stress relaxation value tested.
3.7 Calculate the safety factor and the test medium pressure required by the following formula: The frictional resistance of the limb should be: the pressure of the acupuncture should be the sealing friction of the rubber ring, the amount of steel; Dc.,) (,, M, the same PT ―Pipeline medium test pressure, K-total safety factor, take K=1.5~The total safety factor is considered as follows: (1) Compression stress of compressive permanent deformation and compressive stress relaxation during the long-term conveying operation of the rubber ring The difference between the loss value and the test value of the apron compression sample; (2) the fluctuation of the working pressure of the pipeline transportation medium (such as the pressure rise of the water hammer and the pipe bend); (3) the tolerance of the pipe interface gap; (4) the apron Section size and rubber hardness tolerance, etc. 3.8 Interface seal design and calculation Conclusion: The above calculation results, such as fp>fr, indicate that the selected apron meets the U seal design requirements. If fP 0 inch, the selected apron cannot meet the interface. Sealing requirements. The rubber ring should be re-selected. If the Pmax of the selected rubber ring is not the upper limit value, the apron that selects a larger cross section can be used to increase its Pmax and increase Ac and its fp value, meet the sealing requirements of the interface. If the Pmax of the selected apron has reached its upper limit, it is advisable to select a high-grade hardness apron to increase its E value and thus increase the apron. And its fp value can also meet the sealing design requirements of the interface.
3.9 Calculation of ac, fp and Pmax of too large or too small n gap: due to the unfavorable combination of the inner diameter of the sealing surface of the joint and the elliptical tolerance of the outer diameter of the socket sealing surface, the composition is too large or too small The interface gap will produce smaller or larger cc and fp and Pmax. This should also be calculated. If the apron of fp<6 or Pmax is too large, an effective remedy should be proposed to meet the requirements of the interface seal design.
4 Discussion 4.1 Through the comparison of the results of the example calculation, the ds value calculated by the formula 3-1 is smaller than the ck value calculated by the 3 3 formula, but the difference is still within the cross-sectional dimension tolerance of ±5.m. Within the allowable range. Therefore, the 3-2 type can still be calculated by the sealing of F and n. However, the ds value calculated by the 3-1 formula is less accurate.
4.2 Equation 3-6 is derived from the curve and the relevant foreign calculation formula. Therefore, the value calculated by the formula 3-6 is equal to or slightly smaller than the value of the curve. Therefore, the ac value and the fp value calculated by this formula are safe and reliable for the sealing design of the interface.
4.3 Technological innovation is the fundamental way to achieve sustainable development of enterprises. If the apron production plant can cooperate with the relevant scientific research departments to make some tests and long-term observations on the sealing parameters such as contact pressure stress and compressive stress relaxation rate of the rubber ring produced, it is to develop the knowledge economy of the enterprise and improve the technological content of the product. And a productive approach to market competitiveness. It also provides a reliable basis for the design and calculation of the seal of the interface.
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