In the SW6 external pressure calculation, how is the calculated thickness of the external pressure cylinder calculated?
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This post was last edited by WallaceLee on 2021-3-22 22:25. When SW6 performs external pressure calibration, the calculation book derived from the external pressure cylinder calibration contains a "calculated thickness δ". This external pressure "calculated thickness δ" should be the reference thickness obtained during the external pressure calculation - corrosion allowance C2 - negative deviation C1: That is, the calculated thickness δ = reference thickness - corrosion allowance C2 - negative deviation C1, and it seems that the calculated thickness is related to the input calculated length L. But I don’t seem to find the calculation formula or derivation process for calculating thickness δ in GB150? I want to ask now: 1. How to obtain the calculated thickness δ for external pressure cylinder calibration? 2. Is there a detailed formula calculation or derivation process? 3. What parameters are related to the calculation of thickness δ? My little brother is very talented! Ask God for answers!
There seems to be no detailed calculation formula for 150
This thickness should be iteratively calculated by computer according to the pressure cylinder calibration formula in Chapter 4 of GB/T150.3. According to the external pressure cylinder calibration formula, this thickness should be related to the diameter of the container, the length of the external pressure cylinder, and the cylinder material. It is also related to the shape. The ratios of cylinder length and thickness, diameter and thickness are in different ranges, and the calculation methods are also different. Just follow Chapter 4 of GB/T150.3.
This post was last edited by wanlirn on 2021-3-23 11:32 150 Part 3 Section 4 External pressure calculation does not have a formula but some empirical curve charts, so what do you want to ask. Also, what does thickness mean, a term you invented?
GB150, the design part includes calculation of wall thickness
The reference thickness is included in the calculation results exported in SW6, not my imagination. Thank you.
That’s it, thank you very much for your reply
Try other formulas: Brace-Bryan formula: External pressure critical pressure for long cylinder buckling Pcr=2* E * (t/D)^3/(1-u^2)=2 * E * (t/D)^3/(1-u^2)=2.2 * E * (t/D)^3, Mpa, t and D mm Critical stress of long cylinder under external pressure σcr=Pcr * D/(2 * t)=E * (t/D)^2/(1-u^2)=1.1 * E * (t/D)^2 The short cylinder uses the US Navy test water tank formula: Pcr'=2.59 * E * (t/D)^2.5/(L/D-0.45 * (t/D)^0.5) Critical length of external pressure long cylinder and short cylinder Lcr=1.17D * (D/t)^0.5=1.17 * (D^3/t)^0.5 Critical length of external pressure rigid cylinder and short cylinder Lcr=1.3 * E * t/(t * (D/t)^0.5) After filling in the diameter and thickness 20.9, we can see that 7m is a short cylinder, and the critical pressure is 0.38Mpa ； After filling in the diameter and thickness of 23.8, we can see that 6.66m is a short cylinder, and the critical pressure is 0.55Mpa. ； After filling in the diameter and thickness 30, we can see that 12.73m is a short cylinder, and the critical pressure is 0.51Mpa. ；
This post was last written by wx_Catherine_Mi edited my humble opinion on 2021-3-24 10:58: The external pressure calculation, according to GB150, does not have a direct formula like the internal pressure calculation. It is a reverse process. If you look at the GB150 external pressure, the parameters that appear are L, Do, δe, and E. You can also look at the standard interpretation of GB150. The reference thickness you mentioned should be the nominal thickness recommended by SW6, which is rounded. After subtracting C1 and C2, the effective thickness is obtained.
There is no word "reference thickness" in 150. You may not understand the difference between direct calculation and verification calculation.