Also known as buckling pin devices or rupture pin devices, these are nonreclosing pressure relief devices in which a pressure-containing member is held closed against the system pressure by a load-bearing pin that has been engineered to fail when the system pressure reaches some specified pressure. When the pin fails, the pressure containing member is moved by the system pressure, allowing relief flow through the now-open device. Breaking pin devices have many of the same advantages as upture disks – rapid-opening performance, high capacity per unit nominal pipe size, simplicity of design, and ease of maintenance. These devices also have the additional advantage that the load-bearing component is external to the process fluid. This means that the load-bearing part is not subject to corrosion, fouling, etc. due to the process fluid, and that the equipment need not be opened to atmosphere to reset the device after it has operated.
Like rupture disks, breaking pin devices have the distinct disadvantage of nonreclosing operation. They also have the unique disadvantage of being easily rendered inoperable by the insertion of a rigid object in the space normally occupied by the breaking pin.
Breaking pin devices have not yet achieved significantly wide application in the process industries.
Limitations on Use
Section VIII of the ASME Boiler and Pressure Vessel Code currently restricts the use of breaking pin devices to the inlet of a pressure relief valve. In such installations, these devices are subject to the same requirements as are rupture disks.