Design of floating head flanges for floating head heat exchangers
Thread Content
When performing design calculations using SW6, does the input thickness for the floating head flange include a corrosion allowance? It seems that the calculation reports generated by SW6 do not take this into account. How should the distance over which the floating head cover extends into the flange be determined? That is the l value in the calculation of SW6 floating heads; it has been found that in the design, this value has a significant impact on the thickness of the flanges.
In the calculation software, the thickness of the floating head flange should be given without including a corrosion allowance; the nominal thickness specified on the final drawings must then take these factors into account as well. Regarding the I value, we generally use the thickness of the arch cover plus 2.
The flange thickness must be greater than the I value; this is the influence of the I value on the flange thickness. Therefore, the I value cannot be chosen arbitrarily – it is generally set to the head wall thickness plus 2 mm, and it must remain less than the flange thickness.
When using SW6 for calculations, it is not necessary to enter the I value immediately; the program will generate one automatically, which can then be adjusted manually. Note that the I value indicated in GB151 differs from that in SW6 – the value in SW6 is the correct one.
The question is, what was used as the basis for initially determining the L value for SW6? Then, if we make adjustments, what will we use as the basis for those adjustments?
I think when calculating floating head flanges, the I-value is relatively easy to determine; as the people above mentioned, once the thickness of the arch cover is known, an adjustment of 2 or more units can be made to that thickness until the required standard is met. However, it’s not so easy to determine the diameter of the bolt holes in floating head flanges, nor the size and quantity of the bolts. I’m curious to know how other professionals in this field determine these values
This post was last edited by tianchx on 2009-6-3 at 10:46. Under external pressure conditions, the flange penetration depth l of the spherical crown head has a significant impact on the calculated thickness of the flange; increasing l can result in a reduced flange thickness. However, under internal pressure, the effect is opposite. Therefore, the value of l should be chosen carefully. Generally, it is taken as the nominal thickness of the floating head head plus 2 mm (refer to the calculation examples in the GB151 standard)