What is the outer diameter of a DN500 seamless steel pipe?
Thread Content
What is the outer diameter of a DN500, PN2.0 seamless steel pipe? Could it be that the standards are different as well? I used to use 530, but now the national standard is 508. Could this difference cause inconsistencies in the flanges and gaskets? Or do they have their own standard systems? I’m currently facing the problem of mismatched sizes in graphite composite gaskets. Is there anyone who can explain how to choose the appropriate standards in practice?
HG 20553-93: Dimensions of seamless and welded steel pipes for chemical piping. I checked this, and the outer diameter is indeed 508
Firstly, the PN2.0 notation is not used for pipes; when selecting a pipe, the wall thickness is determined based on the design pressure. For DN500 pipes, an outer diameter of 530 is generally chosen, and the same applies to pipe fittings and flanges. If a pipe with a diameter of 508 is selected, it is necessary to specify this clearly when purchasing pipe fittings and flanges to avoid mismatches
Both of these numbers are correct; the key is to determine which series of pipes you will use, that is, which standard to follow. Series A is the internationally standard series, that is, imperial pipes; the outer diameter for DN500 is 508. Series B is the series still in use in China, that is, metric pipes; the outer diameter for DN500 is 530. This post was last edited by 30dman on 2009-4-8 at 14:22.]
No, it’s only the walls that are thicker under high pressure; the outer diameter remains the same. If the outer diameter were larger, how could it fit with the flange? The outer diameter is 508
You are absolutely right; to add, choose the appropriate flange corresponding to series A and B.
Seamless pipes come in two nominal diameters. The outer diameter series of steel pipes are listed in the table, and the corresponding flanges also come in two types, which are also listed. European Series American Series Series 1 Series 2 Series 1 400 406.4 426 406.4 450 457 480 457 500 508 530 508 600 610 630 610
SH3405 (Series A) is φ508； φ530 is also commonly used in national standards
Careful attention must be paid to the pipe diameter and pressure; otherwise, it will cause a lot of trouble. It must be paired.
When selecting flanges, it is necessary to first determine which series of pipes will be used, so as to avoid matching issues. If it has already been purchased, it can be quite troublesome, especially with large-diameter pipes; unlike smaller pipes, it’s not possible to use short sections to replace the flanges (and that’s not even a viable solution).
There’s a slight issue with what you said: when the pressure is high, the wall thickness needs to be greater. Since DN500 already specifies an inner diameter of 500, a greater wall thickness will naturally result in a larger outer diameter. Therefore, the choice between 508 and 530 depends on the calculated wall thickness; if the calculated value is less than 4, then a steel pipe with an outer diameter of 508 should be chosen, along with appropriate flange gaskets. If the wall thickness is greater than 4, then a steel pipe with an outer diameter of 530 should be selected.
To be honest, I don’t agree with your view. DN500 does not necessarily mean that the inner diameter is 500; for pipes with the same standard and nominal diameter, a greater wall thickness does not result in a larger outer diameter. DN500 is merely the nominal diameter of this pipe. The nominal diameter is a standard size used for various pipes and piping fittings; it is not the actual outer or inner diameter of the pipe, although its value is often close to or equal to the pipe’s inner diameter. For a given standard and each nominal diameter, there is a corresponding outer diameter, while the inner diameter value varies depending on the thickness. The selection of the pipe wall thickness is determined through calculations, taking into account the properties of the medium. It is not as the original poster suggested: that if the calculated wall thickness is less than 4, then a steel pipe with an outer diameter of 508 should be chosen, and if the wall thickness is greater than 4, then a steel pipe with an outer diameter of 530 should be selected. ”However, the selection of the flange gasket in conjunction with it is correct
DN500 is not the actual inner diameter of the pipe
Pipes in imperial units are certainly different from those in metric units
In accordance with the standard HG20592-97, steel pipe flanges, gaskets, and fasteners are specified; the outer diameters of the steel pipes covered by this standard fall into two series: A and B. Series A is the internationally standard series, corresponding to imperial pipes, with an outer diameter of 508 for DN500, while Series B is the series used in China, corresponding to metric pipes, with an outer diameter of 530 for DN500. DN500 is used for pipes; since it needs to fit with flanges, its outer diameter is restricted ； But for equipment, those with a diameter greater than 426 need to be coiled; the inner diameter of a DN500 device is 500, while the outer diameter is determined by the wall thickness.
The most common option is 530. If a inner diameter of 500 is required, the wall thickness of 508 would be too thin; for other options, the outer diameter can be chosen based on the desired wall thickness.