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Recommendation of Gap Choice
In the piston seal and piston rod seal, there is some clearance between the moving surfaces. The size of gap directly affects the service life and processing cost. It is an important issue for designers to consider how to choose the correct maximum allowable gap.
Piston Seal
Piston Rod Seal
Note£ºmoving direction A=push B=pull
The size of maximum allowable gap is directly related to the diameter of dyn-amic side, the applied material of piston, the thickness of section, the pressure of system and the temperature of environment.
We have obtained a set of simple methods to choose the maximum allowable gap through many years of practice.
Through the chart, we can get the maximum allowable gap of the seal part app-lied under the corresponding condition. There is an example as follows.
Example 1 (chart 1)
d/D = diameter of dynamic side = 90mm
S = section =7.5mm
P = pressure =315bar
T = temperature =80¡æ
Example 2 (chart 2)
d/D = diameter of dynamic side =100mm
S = section =6mm
P = pressure =100bar
T = temperature =80¡æ
Note: The diameter of dynamic side is the diameter with sliding side.For the piston seal, it is the diameter of piston cylinder. While for the rod seal, it is the diameter of piston rod.
Connect d/D-S and P-T and extend them to respectively intersect with ¦Î1 and ¦Î2. Connect the two intersection points with straight line, and read the inters-ection value on the e-ruler, which is the allowable gap. (0.16mm in example 1, 0.18mm in example 2)
Condition£º
1. Process the surface according to the recommended value.
2. For lubricating fluid, if polyurethane of Shore hardness A85 and chemigum of Shore hardness A75 are replaced by polyurethane of Shore hardness A93 and che-migum of Shore hardness A85 respectively, the extrusion gap will increase 15%.
