What value should be adopted for the welding weakening factor of thin tubes subjected to internal pressure?
Thread Content
For thin tubes such as water wall tubes subjected to internal pressure and economizer tubes, when using 16508 (page 60) for calculations, the welding weakening factor is not assessed via UT or RT, nor is magnetic particle or penetrant testing employed. The selection of the welding weakening factor is specified as follows (16508, page 16): 1 for fully penetrative and completely non-destructive testing, and 0.85 for partially non-destructive testing； 100% non-destructive testing for single-sided welding: 0.9; partial non-destructive testing: 0.8. How should I choose this? What is the reason for choosing 1 in some calculation sheets? The boiler regulations do not specify which testing methods to use.
GB/T16508，P145，,146
I wasn’t clear enough; it’s not the joint connector, but rather the T-shaped fillet welds between the wall tubes and the boiler drum. It is not a Class A pot standard
For T-joint welds in pressure vessels, there is no concept of a weld joint coefficient; if anything needs to be taken into account, it is the need to increase inspection requirements, such as PT testing and structural rounding
Strictly in accordance with formula 16508, the maximum allowable operating pressure for straight pipes is equal to 2ψ/(Kd-δ), where ψ is the welding joint coefficient
①First, when the boiler structure is designed as a combination of a boiler shell and water tubes, the design and calculation of the tubular elements are carried out in accordance with standard 16507； ②Secondly, the strength calculation of the water wall tubes themselves does not need to take into account the fillet welds between the tubes and the drum; in actual production, water wall tubes are usually made using whole tubes, so the coefficient should naturally be set to 1 ；
At the very least, when you choose the joint coefficient, it has to be for a butt joint, right...
The welding joint coefficient applies only to butt joints; there is no such concept for T-joints.
This post was last edited by wanlirn on 2019-4-20 09:45. According to what was said on floor 6, that’s correct; for welding pipes using the YB4102 type of pipe, it’s sufficient to use grade 1, and its quality is ensured by the standards applicable to such pipes. As for the welding joint factor considered when verifying the maximum operating pressure under standard conditions, I believe it is there merely to ensure the completeness of the standards. Welded tubes can also be used for the heat exchange tubes in heat exchangers, and no non-destructive testing is required. There are even no specialized formulas for calculation and verification – only checks related to external pressure
Great master, I admire you utterly.
Savings boiler: The joining of the exposed parts of the elbows and straight pipes – this is a type of joint, and it’s necessary to determine the appropriate value for it.