How a Tension Loaded Disk Works
As the pressure increases on the tension-loaded disk, the seating design allows the dome to thin out until it can no longer withstand the pressure. The disk ruptures. Metal segments fold back against the walls of the fitting in an irregular pattern to provide a full opening. The ultimate tensile strength of the metal determines its failure point when loaded in tension.
Standard Manufacturing Ranges
When you order a rupture disk (bursting disc), a manufacturing range is automatically assigned to the burst pressure you specify. The following table gives the standard manufacturing ranges. A manufacturing range eliminates the necessity for the manufacturer to stock all possible thicknesses of all materials, nearly 100,000 thicknesses in all, to make all burst pressures.
For example, if you order a B Disk to burst at 80 psig, BS&B will enter the order to the shop with the standard manufacturing range (+9,-5), or 75 to 89 psig. BS&B will try for your requested pressure of 80 psig, but will ship the lot of disks if the marked pressure falls between 75 to 89 psig. Once the disk is rated and marked 78 psig, the burst tolerance of ±5% now applies to this stamped pressure.
The standard manufacturing ranges shown in the following table can be reduced by 1/2 or 1/4 for an additional cost. Hastelloy C-276 / Alloy C-276 is available only with standard manufacturing range and 1/2 range.