Calculation of heat exchange tube rupture

In the post titled “Design and Selection of Safety Valves for Shell-and-Tube Heat Exchangers” at http://bbs.hcbbs.com/thread-1567510-1-1.html, there is a statement saying that if the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, then this accident scenario should be taken into consideration, and it is required that the fluid on the high-pressure side flow through the tube side. When calculating the overpressure caused by the rupture of a heat exchanger tube, API521 makes the following assumptions: 1) Only one tube in the heat exchanger is broken ； 　　2) The tube broke at the tube sheet ； 　　3) Part of the fluid on the high-pressure side enters the low-pressure side through the fracture at the tube sheet, while another part flows into the low-pressure side via a longer pipe. The flow rates in these two sections are simplified as twice the flow rate through the break at the tube sheet. It seems that it should be multiplied by 2.

HG/T20570.2-95 Safety Valves – Installation and Selection also requires taking the minimum value between the calculated value and the normal flow rate on the high-pressure side.

The HG/T20570.2-95 standard is quite old; it is recommended to use the methods specified in API 521-2014. When the pressure on the low-pressure side is less than 10/13 times that on the high-pressure side, it is necessary to consider the scenario of tube rupture. Aspenplus V8.8 has integrated PSVPlus, which can calculate the leakage rates under various operating conditions. For manual calculation, an orifice plate can be used; the flow rate doubles when a single pipe fails.