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Valve-Stem Seals : Assembly Recommendation
No Flange - Type VA03


1. CONTACT POINT:

Valve-Stem Seal must be pushed on Valve Guide until bottom area of Valve-Stem Seal metal case contacts Valve Guide shoulder (see contact point in sketch). Due to the elastic characteristic of rubber, a spring back is allowed (0.5 mm max).

2. ASSEMBLY LOAD :

Assembly force must be applied to the upper surface of Valve-Stem Seal Metal Case. This area has been designed to support assembly load (std average range for assembly load is 200-500 N). Do not apply a. load on the top rubber surface of Valve-Stem Seal. Be sure that fitting device does not interfere with Valve-Stem Seal spring.

3. POSITION & FORCE CONTROL :

Final position of fitted Valve-Stem Seal can be checked with a position sensor on fitting cylinder that controls end of stroke of fitting cylinder. PLC program can include a timeout on position sensor signal: if position sensor is not energized within this timeout, this means that Valve-Stem Seal has not been completely fitted on Valve Guide. Maximum force can be controlled by a load limiting device calibrated to max load allowed.






Valve-Stem Seals : Assembly Recommendation
Flanged - Type VA09


1. FITTING OPERATIONS :

Fit the Valve-stem Seals, without lubrication in fitting Inside Diameter, pressing only on the metal-case (avoiding contact with the Valve-Stem Seal garter-spring). Use a slow assembly-speed (good = 200mm/min). Pick-up the Valve-Stem Seal and centre it in the Valve Guide using a centring pin, with correct chamfer and surface finishing in order avoid any damage to the sealing lip.

2. CONTACT POINT :

Valve-Stem Seal must be pushed on Valve Guide until flange of VA09 Metal Case contacts Cyl Head (see contact point in sketch). Due to the elastic characteristic of rubber, a spring back is allowed (0.5 mm max).


3. ASSEMBLY LOAD :

Assembly force must be applied to the upper surface of Valve-Stem Seal Metal Case. This area has been designed to support assembly load (std average range for assembly load is 100 - 300 N at 200 mm\min). Do not apply a load on the top rubber surface of Valve-Stem Seal. Be sure that fitting device does not interfere with Valve-Stem Seal spring.

4. POSITION & FORCE CONTROL :

Final position of fitted Valve-Stem Seal can be checked with a position sensor on fitting tooling, that controls end of stroke of fitting cylinder. PLC program can include a timeout on position sensor signal: if position sensor is not energized within timeout, probably Valve-Stem Seal has not been completely fitted on Valve Guide. Maximum force can be controlled by a load-limiting device calibrated to max load allowed.

5. VALVE FITTING OPERATIONS :

Fit the Valves using some drops of oil in the valve-guide and on Valve Stem in order to protect the Valve-Stem Seal Sealing-Lip from contact with the collets-grooves. Valve stem should be in clean conditions, grooves should have good surface finishing, without sharp edge, flashes or burrs that could damage the sealing lip.

6. EXTERNAL PARAMETERS AFFECTING ASSEMBLY LOAD :

Following parameters affect assembly load:

  1. Valve Guide O.D. Roughness
  2. Interference between Valve Guide O.D. and Valve Stem Seal fitting I.D.
  3. Valve Guide Chamfer
  4. Valve Guide Surface condition (oiled, dry, degreased)
  5. Assembly speed
  6. Correct position of the Valve Stem Seal (coaxiality, concentricity)