Conditions for branch pipe connection
Thread Content
SH/T 3059-2012 Specification for the Selection of Materials for Petrochemical Piping – Clause 7.9.3: For branch connections under the following conditions, tees, 45° elbows, and crosses should be used: a) when the design pressure is equal to or greater than 2.0 MPa, the design temperature exceeds 250 ℃, and the ratio of the nominal diameter of the branch to that of the main pipe is greater than 0.8; b) for pipeline branches subject to mechanical vibrations, pressure fluctuations, and rapid temperature changes. Among them, for a) where the design pressure is equal to or greater than 2.0 MPa, the design temperature exceeds 250 ℃, and the ratio of the nominal diameter of the branch pipe to that of the main pipe is greater than 0.8, are all these conditions required to be met simultaneously, or is just one of them sufficient?
Both conditions must be met; since when the design pressure is ≥ 2.0 MPa, a tee cannot be used if the ratio of the nominal diameter of the branch pipe to that of the main pipe is too small, as tees come in specific standard sizes. Three conditions constitute a working condition, and a tee is used when all of them are met.
I think all three conditions need to be met simultaneously. If the temperature and pressure requirements are met, but the diameter of the branch pipe is much smaller than that of the main pipe, a branch pipe support is usually chosen; it’s not possible to use a standard tee in such cases. And if temperature and pressure are not taken into account, as long as the ratio of the nominal diameter of the branch pipe to that of the main pipe is greater than 0.8 (or fairly close to it), a tee is usually also chosen. Therefore, I think the meaning of this sentence is that if all three conditions are met simultaneously, then a tee should be chosen; but it doesn’t mean that a tee isn’t necessary when only one or two of the conditions are satisfied.
I looked at the material list from my colleagues in the company; it’s PN16kg, and basically all of them chose tees. I told them that welding through the holes was an option, but they spent half a day discussing option a) without reaching any conclusion. Science students, you’re not good at Chinese.