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3. Controlled leak tightness
3.1 Smooth annular clearance
For a component to move through a wall, there must be a clearance between them. The greater the clearance, the greater the leakage. However, with certain liquids, especially if the viscosity is high enough, leakage will be low and perfectly acceptable if the liquid remains inside the system, as in a hydraulic directional valve spool, for example. This simple type of sealing is also common in transmission hydraulics.
Flow through an annular leak in laminar regime gives a leak volume flow rate Q v equal to :
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Controlled leak tightness
Bibliography
Standards
- Hydraulic and pneumatic transmissions – O-rings – Part 1: internal diameters, cross-sections, tolerances and dimensional identification code. - ISO 3601-1 - 2012
- Hydraulic transmissions – Cylinders – Dimensions and tolerances of seal housings for single-acting pistons and piston rods in reciprocating applications. - ISO 5597 - 2018
- Hydraulic cylinders – Dimensions and tolerances of housings for plastic-reinforced...
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