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
Where:
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.

Where:
p = Pressure differential (Pa)
r_o = Unsupported disc radius (mm). For plates substitute r_o with width

S_max = 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

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