Hope College Department of Physics and Engineering
Research Experiences for Undergraduates
Summer 2001
Project Summary

Project Title:Determination of Response Time for Frangible Pressure Vents
Student Name: Jennifer Folkert
Student’s home institution: Hope College
Research Advisor(s): Dr. Roger Veldman
Source of Support (NSF-REU, or other): Sherman-Fairchild Foundation

Pressure vessels are used in many different areas of industry. Main concerns with these vessels are accidental overpressurization causing vessel rupture, and/or damage to equipment and personnel. Passive vents, known as burst or rupture disks, help combat these concerns. In the event of overpressures, especially those arising from an internal explosion, it is important that the frangible vent members break quickly and cleanly to create an unobstructed vent opening.

This study examined the response time of frangible vent panels under static pressurization. The effects of panel thickness and pre-pressurization were considered.

We used tempered glass pieces as the frangible vent members. Tempered glass is a type of glass that shatters into many small fragments when broken. This makes it an ideal choice for our experiments because with one initial fracture, a tempered glass substrate shatters and can be blown out by the pressure in the tank. Our experiment evaluated the time it took for the glass to create an unobstructed vent opening after fracture initiation.

First, using a simple equation for one-dimensional motion under constant acceleration, the theoretical position of the panel can be found.

Where:

x = Position of the glass panel in the direction normal to the glass face
a = Initial panel acceleration (assumed to be constant for small displacements)
t = time (panel is released at t=0) Substituting the appropriate values for various levels of pre-pressurization provides equations of motion to describe the position of the glass fragments after fracture initiation. We conducted experiments to verify these equations using both varied pressures with a constant thickness of glass and varied glass thickness with a constant pressure.

Using photos similar to those in Figure 1, I measured the distance the glass had traveled from the tank. As is evident from the photos, it is difficult to define precisely where the leading edge of the glass particles is for any given instant. However, we did get reasonable correlation between predicted and experimental data.

Figure 2 shows data for a constant thickness of glass, 4.8 mm, under varying pressures. Figure 3 shows data for a constant pressure of 41,379 Pascals, with varying glass thicknesses. For both cases, the experimental data points generally follow the predicted curve. Because of this correlation, the simple equation of motion can be used in future research. The research this summer gave the results we had hoped to find, and we look forward to continuing to study frangible pressure vents. A special thanks goes out to Dr. Roger Veldman, Brad Mulder, and the Sherman-Fairchild Foundation for all their help and support.
 
 


 


 
 
 


Figure 3

Slide show of Jennifer Folkert's work