Allowable vertical offset between two adjacent saddles in a horizontal vessel supported by three saddles
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Recently, a horizontal vessel was designed, and the user requested that it be supported by three saddle supports. According to Appendix D.4.6 of NB/T 47042-2014, the allowable vertical displacement between two adjacent saddles was calculated; the resulting value was very small, less than 0.1 mm. Should this requirement be specified on the general layout diagram of the pressure vessel design? If such a request is made, it seems truly difficult to control things. Additionally, which thickness does δ in the formula refer to? In the formula, a is denoted as A? in the definitions and examples provided in the NB/T 47042-2014 standard on horizontal vessels. I’m not sure how others handle this...
According to the standard definition, it seems to be the nominal thickness, but I’m not sure as there is no symbol indicated. The values calculated according to the definitions are not as small as yours; is there a problem with the calculations?
I just calculated the thickness based on the nominal value; please give me your data and I’ll do the calculations for you.
The inner diameter of the cylinder is 3200, the nominal thickness is 26; the distance between the two end saddles is 4890 from the middle saddle, and the distance from each end saddle to the tangent line of the head is 800.
There’s no need at all to use a three-seat saddle here; it’s too close.
I’ve done ones with a diameter of 3200 and a length of 13000 that also had two saddles. You’re so close to the cylinder; you definitely can’t withstand it. I can only persuade the owner. Three saddles cannot be installed.
After checking the standards and their definitions, δ is not explicitly defined in either of them. I believe that the nominal thickness can be used instead. As for the symbol a, it is not what the original poster mentioned; it is actually α, the azimuth angle of the cylindrical shear stress, as shown in Figure 5b.
a should be A, check the definition table
It’s not about the angle. You’ll understand it by looking at the standard definition