Pressure Determination of Fused Quartz

For applications where fused quartz tubing is exposed to internal pressures, the following formula helps determine the maximum pressure which can be applied at room temperature. 


CFQ Rupture Formula For Tubing

S = pr/t
S = Hoop Stress (Pa)
p = Working pressure (Pa)
r = Inside Radius of Tube (mm)
t = Wall Thickness (mm)

This formula is not applicable when the internal pressure exceeds 7x105 Pa (100 psi).

CFQ Rupture Formula For Discs And Plates

Many applications of fused quartz discs, plates and sight glasses require calculating pressure differential. The following formulae can be used for room temperature applications of circular parts with either clamped or unclamped edges.


Window-Thickness-Clamped_1        Window-Thickness-Unclamped_2

equation-pressure determinationequation-pressure determination_2


p = Pressure differential (Pa)
ro = Unsupported disc diameter (mm). For plates substitute ro with width

Smax = Maximum stress (approx. 7 to 1 safety factor) 7.0 x 106 Pa
t = Disc thickness (mm)

However, the following factors will effect the strength of these parts and must be considered when using the formulae:

  • Surface should be highly polished and free of scratches
  • Means by which a sample is clamped into a pressure device
  • The clamping material used
  • The thermal gradients expected across the surface and between the surfaces
  • The rate of pressure increase that will be applied
  • Temperature of specimen


Pressure vs. Thickness 
Note: Test results. Actual results may vary.  

For more information regarding the use guidelines for fused quartz, click here.

*The marks followed by an asterisk (*) are trademarks of Momentive Performance Materials Inc.