Regarding the roughness of the flange sealing surface?
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HG/T20592~20635-2009, pages P15 and P248: The notes below the tables showing the surface roughness values for flange sealing surfaces state that raised surfaces, recessed/raised surfaces, and fully flat sealing surfaces are characterized by serrated concentric circles or spiral grooves that form naturally during machining with cutting tools. The radius of curvature of the cutting tool should be no less than 1.5 mm; the depth of the resulting serrated concentric circles or spiral grooves is approximately 0.05 mm, with a pitch of around 0.45–0.55 mm. Does this mean that for the 09 version standard, watertight lines need to be machined on all types of sealing surfaces—convex, concave/convex, and flat? Is it the same for machining the sealing surface when gaskets are spiral wound gaskets or metal toothed gaskets? What was the intention behind the 1997 standard separating the roughness of the sealing surface from the type of gasket?
Additionally, for the flange sealing surface machining process: 1. Adjust the spindle speed and feed rate on the lathe to reach 3 directly. 2~6.3 microns. 2. After the entire sealing surface is machined to 3.2~6.3 microns, concentric circular grooves 0.05 mm deep are processed again. Which of these two processes is better? Additionally, if concentric circles are required, the roughness of the flange sealing surface should be the roughness after the lines have been machined, as this is the surface that comes into contact with the gasket. Thank you for your expert answer
No, it is not necessary to have a waterline on the sealing surface; this can be determined through communication between the customer and the manufacturer
This understanding is correct, right! Current flange standards generally no longer require a waterline specification, but they do specify requirements regarding the roughness of the flange surface. For example, in the case of welded high-neck flanges, the roughness of the flange surface is required to be between 3.2μm and 6.3μm, and spiral or concentric grooves must also be present on the surface. But please be careful to make the distinction: this pattern is not a water line. The pattern is fine lines that appear naturally during machining, whereas a water line consists of 2 or 3 deeper grooves that are created separately. Do not get them mixed up.
Does this mean that for the 09 version standard, watertight lines need to be machined on all types of sealing surfaces—convex, concave/convex, and flat? Is it the same for machining the sealing surface when gaskets are spiral wound gaskets or metal toothed gaskets? What was the intention behind separating the roughness requirements for the sealing surface from those for the type of gasket in version 97? Yes, the aim of version 97 was likely to use non-metallic gaskets with RF(A) fine-threaded sealing surfaces; when metal gaskets were used, no spiral grooves were created on the RF surface, and the metal gasket surface had contact surfaces similar to spiral grooves. Separating these two aspects was necessary because some cryogenic gases require better control over surface roughness. The prototype for the chemical industry standards in Europe is EN1092, and whenever EU standards are revised, the chemical industry standards are also revised accordingly. Version 09 was based on revisions to EN1092-07. Additionally, regarding the machining process for flange sealing surfaces: 1. Adjust the spindle speed and feed rate on the lathe, so as to directly reach level 3. 2~6.3 microns. 2. After the entire sealing surface is machined to 3.2~6.3 microns, concentric circular grooves 0.05 mm deep are processed again; which of these two processes is better? Additionally, if concentric circles are required, the roughness of the flange sealing surface should be the roughness after the lines have been machined, as this is the surface that comes into contact with the gasket. It’s easier to machine spiral grooves; concentric circles are more complicated to handle. Generally, after rough machining, precision machining is carried out directly. The roughness of the sealing surface refers to the roughness after completion of machining, while the line depth and spacing are recommended dimensions – meeting the specified roughness level is sufficient to consider it acceptable. For more details, refer to ASME B16.5, clause explanation number 4.4
The waterline on the sealing surface is not necessarily required to be present; it should not be included.
Sealing surface water line: It is not the three inverted triangular sealing lines as commonly understood, but rather the threaded grooves that are formed naturally by the cutting tool. These are what are commonly referred to as fine threads of the American standard; all sealing surfaces no longer have those three water lines machined on them.
I just came to take a look at the posts below – a flange manufacturer
No water line needed? I was wondering which standard has been established so far? :o