Consideration of limit values and calculation of extrusion gap Piston seal
X f max
X 2 max
X2 max
∅ d2 min
∅ dmin guide
∅ d1max
∅ dguide groove min
S min
∅ Dmax
∅ d2max
X3 min
X3 min
Designation of specified dimensions: d2max d2min d guide groove min Dmax Smin d1max
= = = = = =
minimum piston diameter after seal maximum piston diameter after seal minimum inside groove diameter of guide strip groove maximum bore diameter minimum guide strip thickness (see guide elements) d1max > d2min
Designation of calculated dimensions: d min guide x f max x2 max x3 min
= minimum guide diameter = maximum guide play = maximum gap on non-pressurised side of sealing component = minimum difference between guide and piston
Calculation 1. 2. 3. 4. 5.
dmin guide x f max x2 max x3 min d2min
= = = = =
Dguide groove min – (2 · Smin) Dmax guide – dmin guide (Dmax – d2min)/2 + x f max/2 (dmin guide – d2max)/2 Dmax + x f max – 2 x2 max
Comments regarding consideration of limit values The permissible gap dimension x 2 max on the non-pressurised side of the sealing component is specified in the model descriptions of our sealing components. To prevent seizure between the metal of the piston and cylinder, or rod and gland assembly, a minimum difference X3min between the guide and rod/ piston is necessary. The values specified in the table given below apply with maximum exploitation of the max. permissible specific surface pressure of the guide element used. If the maximum permissible specific surface pressure of the guide element used is not exploited to the full, the reduced deflection of the guide element provides for smaller x 3 min dimensions. Merkel Guide Ring Guivex SBK, KBK
X 3 min
0.10 mm
Temperature
–30 °C bis +100 °C
Tolerance (S)
–0.01 bis –0.06
We however recommend using the specified values for your calculations as in practice the lateral forces occurring vary widely and the guide play is increased by wear. For calculation of the limit values a calculation program is available; it can be requested by sending an e-mail to info@simrit.de.
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