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Sealing Systems Rotary Seal Application

Application description: Hydraulic Pump

  • Shaft diameter 0.750″ ±0.001
  • Bore diameter OD 0.753″ ±0.001
  • 150 psi Hydraulic oil
  • .103″ cross-section Quad-Ring® Brand seal
Ring SizeCross-SectionAxial Groove Width “D” +0.005/-0.000
Q4102 – Q41780.103 ±0.0030.110

1. Calculate groove dimensions

Groove Diameter = Minimum Shaft Diameter + (2 x Min Cross-Section) – 0.004″
Groove Diameter = 0.749 + (2 x 0.100) – 0.004
Groove Diameter = 0.945 in ±0.001

2. Groove width = 0.110″ -0.000/+0.005

3. Calculate Minimum Groove Volume

Minimum Groove Volume = ((Min Groove Dia. – Max. Bore Dia.)/2) x Groove Width
Minimum Groove Volume = ((0.944 – 0.754)/2) x 0.115
Minimum Groove Volume = 0.0109 in2

4. Calculate Maximum Quad-Ring® Brand Seal Volume

Maximum Quad-Ring® Brand Volume = (Maximum Cross-Section)2 x 0.8215
Maximum Quad-Ring® Brand Volume = 0.1062 x 0.8215
Maximum Quad-Ring® Brand Volume = 0.0092 in2

5. Compare Minimum Groove Volume to Maximum Ring Volume

In this application the Maximum Ring Volume is less than the Minimum Groove Volume; everything appears to be OK.

6. Calculate Minimum and Maximum Seal Squeeze

These calculations look at both ends of the worst-case stack up
tolerance, including rod shift, to determine the maximum and
minimum ring squeeze.


Maximum Seal Squeeze =
  • 1 – (Minimum Groove Depth / Maximum Ring Cross-Section)
  • Minimum Groove Depth = (Minimum Groove diameter – Maximum Bore)/2
  • Minimum Groove Depth = (0.944 – 0.754)/2
  • Minimum Groove Depth = 0.095
  • Maximum Seal Squeeze = 1 – (0.095 / 0.106)
  • Maximum Seal Squeeze = 10.3%
  • Minimum Seal Squeeze = 1 – (Maximum Groove Depth / Minimum Ring Cross-Section)
  • Maximum Groove Depth = ((Max. Groove Diameter. –
  • Max Bore)/2) + (Max Bore – Min. Rod)
  • Maximum Groove Depth = ((0.946 – 0.754)/2) + (0.754 – 0.749)
  • Maximum Groove Depth = 0.096 + 0.005
  • Maximum Groove Depth = 0.101
  • Minimum Seal Squeeze = 1 – (0.101 / 0.100)
  • Minimum Seal Squeeze = -1.0%

In this application, if every dimension went to the worst side of
the tolerance and the piston was side loaded, the seal would leak. To avoid these problems:
1. Reduce the clearance between the bore and piston.
2. Reduce the tolerances of the bore and piston.

3. Use a larger cross section Quad-Ring® Brand seal to absorb the extra tolerance.
4. Support the piston so that it can not move off center.

7. Calculate Maximum Clearance and Evaluate Possible Extrusion Issues

  • Maximum Clearance = Maximum Bore – Minimum Rod
  • Maximum Clearance = 0.754 – 0.749
  • Maximum Clearance = 0.005″ (0.0025″ Radial)

This application has a max clearance of 0.0025″ and must withstand 150 PSI without extruding the Quad-Ring® Brand seal. Refer to the clearance chart. A 70 Shore A material at 150 PSI can withstand a maximum clearance of 0.009, so a 70 Shore A material will work. Making improvements to the Minimum Seal Squeeze issues in Step 6 will also reduce any possible issues with seal extrusion.

8. Select seal size

For all rotary rod seal applications select a Quad-Ring® Brand seal that has an ID larger than the maximum shaft diameter.
Part ID >= 0.751″
Quad-Ring® Brand Seal Size = 4117

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