A closed-end steel cylindrical pressure vessel shown in the figure is to work under 15 bar gauge pressure. The end cover is planned to fix to the vessel with 10 bolts (8.8 Grade). The weight of the cover is 55 kg. Estimate the proper bolt size for the design. (Use design factor as 4).
Note: Ignore gasket stiffness and the force occurred due to compression of gasket.
Note 2: Assume that transverse forces on the bolts occur only due to weight of the cover.
Step 1 : Write down input parameters which are defined in sample example including material properties.
Step 2 : We need to calculate forces experinced on a single bolt. To be able to do the calculation, bar to MPa unit conversion shall be done. Go to "Unit Converter" page to convert bar to MPa. Convert 15 bar to Mpa.
Pressure inside the vessel is 1.52 Mpa.
Step 3 : Calculate the axial and transverse force per bolt.
Faxial = nd*pg*π*di2 / (4*n) = 4*1.52*π*2502/(4*10) =29830 N (Note that this force is eccentric to bolt axis. See figure.)
Ftransverse = nd*mc*g / n= 4*55*9.81/(10) =216 N
Step 4 : Calculate the required bolt size by using input parameters given in Step 1 and Step 3 .
Minimum friction coefficient between clamped parts is entered 0.1 which is minimum static dry friction value between steel -steel as suggested in VDI 2230 Part-1.
Since pressure is not dynamically changing, loading is static. Axial force introduction location is eccentric to bolt axis.
Bolts are assumed to be tightened with torque wrench.
According to calculation results, minimally 10 bolts of M20 with 8.8 strength grade is needed to meet design requirments. As mentioned in bolted joint calculator, this calculator is just to give an initial estimate for the bolt sizing. Further calculations are needed for detailed bolt sizing.
The problem is completely solved with calculators which are summarized as follows.