Why is there such a large difference between using mm and using SCH for calculating pipe wall thickness?
Thread Content
This post was last edited by shiworkstation on 2023-2-7 at 15:20. The wall thickness calculation formula is based on the \"Code for Design of Industrial Metal Piping\"; the pipe has a diameter of DN20, an outer diameter of 26.9 mm, and a design pressure of 15 MPaG. The pipe material is 304, and the calculation does not take into account factors such as corrosion allowance or thickness reductions due to slotted threads. The final calculated wall thickness is around 2 mm, but for SCH calculations, SCH120 is required. No corresponding wall thickness can be found in the tables, so SCH160 has to be used, resulting in a wall thickness of 5 mm. The difference is quite large; I’m not sure if there’s an error in the calculations or what else might be causing this. Is there anyone who knows about this?
66666666666666666
15MPa, DN25 pipe, wall thickness 2mm? This is a bit too thin, isn’t it? Even without considering other factors, the design wall thickness for pipes with a pressure of 4 MPa and a DN25 size is generally chosen to be 3 mm or more.
The pipe is DN20 (a mistake was made earlier); its outer diameter is 26.9 mm. Without taking into account factors such as corrosion allowance or the thickness reduction caused by slotted threads, the wall thickness chosen for calculation is 2 mm. Similarly, to calculate sch, the wall thickness chosen is 5 mm. Some people agree with my 2mm result, but I still have doubts, so I’m asking.
I suspect you’re using 2MM to make shrapnel bombs
Your two values are not on the same channel: DN20 – no thinning is taken into account, so 2mm is used; it’s simply a result of formula calculation, without considering manufacturing processes such as thinning or welding； However, for SCH calculations, SCH120 needs to be used; since no corresponding wall thickness is available in the tables, SCH160 has to be chosen, which results in a wall thickness of 5 mm. According to the poster’s comparison, this corresponds to the calculation values for GB pipe wall thicknesses, expressed in millimeters, as opposed to the SCH code, which has no unit. How is this comparable?
Thinning was not considered because the pipes are connected using clamps, without welding, and there is no need to thread the pipes.
The small-diameter stainless steel pipes used for ferrule connections have a different size series from the welded or seamless stainless steel pipes used for general fluid transport.
Can it be connected using a ferrule at 16Mpa? It definitely has to be a flange connection. For sizes larger than DN50, SCH40 is generally chosen, while for smaller sizes SCH80 is used. Even at pressures that aren’t that high, welding can still cause penetration issues; therefore, it is recommended to use a slightly thicker wall thickness for smaller pipes.
Those with bayonet connections belong to tubing； Pipes whose wall thickness is calculated using formulas generally fall under the category of piping ； It is recommended to use clamping sleeves, as this allows for checking the gap and prevents it from being either too tight or too loose ； Precision tube ； Ask the owner whether bright annealing is required.