Should the blind plate of a raised-face flange not have its raised surface machined?
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Processing the protruding surface, in my opinion, reduces the strength of the blind plate. If the flange has a raised surface, it shouldn’t prevent the use of gaskets, right? There are also protrusions on the ring-shaped connection surfaces; when manufacturing corresponding blind plates, should these protrusions not be machined? Would that reduce the strength of the blind plates and lead to waste of material? Additionally, what is an appropriate value for the safety factor when calculating blind plates? The blind plates calculated by our factory’s designers using SW6 are not much thinner than the standard ones; is this an overkill in terms of safety?
I don’t think it will help either, but after all it’s not professional design, and I’m worried there might be some unknown effects of those protrusions.
The blind flange for convex flanges should not have its convex surface machined, in order to maintain the strength of the blind flange.
I just came across this recently – it’s an 8-character blind plate that was used in one of our new installations in 2009; the blind plate itself has raised and recessed surfaces.
Do you mean that, with a constant thickness of the blind plate, even if a bulged surface is created, its strength is not reduced? The sealing surfaces are connected in a ring shape; the height of the protrusions is equal to the depth of the grooves. Didn’t removing all that material have any impact? I have no experience in design and haven’t mastered mechanics either; I’m seeking advice……
Is this blind plate the same as a blind flange? If so, there still need to be protrusions.
There are two purposes for machining convex surfaces: 1) to reduce the contact area, increase the pressure on the sealing surface, and thereby enhance the sealing performance; flanges with a pressure rating of over 16 bar usually have convex or combined convex-concave surfaces, while flat flanges can handle a maximum pressure of 16 bar. 2) The roughness of the convex surface should be at least 12.5, while the roughness of other surfaces can be as high as 25; this difference helps to reduce manufacturing costs. In general, if you use a standard blind plate for a flat flange to fabricate a blind plate for a convex flange, the strength and stiffness will decrease. Under normal circumstances, if standard sizes are used, the strength of convex blind plates is higher than that of flat blind plates.
By blind plate, I mean a flange cover – it’s just temporary for pressure testing purposes.
A fully flat flange cover, or a flange with a blind raised surface or a convex surface, should yield the same results in terms of pressure testing as a flange cover with a raised or recessed surface. As you said, having a raised or convex surface reduces strength and stiffness; to achieve the same mechanical properties, it would be necessary to increase the thickness. Can it be understood in this way that for flange covers (blind plates) used for pressure testing, there is absolutely no need to machine protruding surfaces, recessed surfaces, or bosses on the ring connection sealing surfaces?
Temporary? You can take a steel plate, drill a few holes in it, and screw in bolts – that will also work. . .