The significance of pipeline size classes
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This post was last edited by Aarontong on 2015-12-21 at 22:32. Recent projects use American standard pipes, with the lowest pressure rating being 150lb, which corresponds roughly to PN20. However, for pipes, parameters such as wall thickness are calculated based on the design pressure; even pipes of class 150 can have different wall thicknesses. So what is the meaning of the pound rating? I was confused when I first started working on designs
It’s not roughly equivalent to PN20; it is exactly equivalent to PN20. It’s just a matter of different systems. It’s just like how some people prefer to use kilograms, while others prefer to use MPa
I mean, since things like wall thickness are all calculated, then what’s the use of the pressure rating? What can it be used to determine? The flange?
I eagerly opened the “Discussion Thread,” only to find that it indeed contained questions directed at others. I was puzzled; hey, isn’t this supposed to be under “Help Requests”: lol? ;P The wall thickness can be calculated, as can the pressure rating and the diameter. Under normal circumstances, the calculation results rely on existing standards, which facilitates production. You see, even a 150-pound pipe can be connected to a 300-pound flange, as long as the materials can be welded together.
First of all, it should be clear that the pressure class applies not to the pipes but to the flanges. The pressure class acts like a series of products; for the same material, flanges with different pressure classes have different pressure-temperature curves. The pound rating itself has no practical meaning. The original poster can take a look at ASME B16.5
It seems I should go to the help section, where there might be more people;P
When encountering pipes for the first time, it’s difficult to sort out all the details. The value is determined as 1.5 times the design pressure of the pipe, which is approximately 5.8 Mpa. According to HGT 20519-2009, the pipe material grade specified for this type of pipe is 400 lb, with the code C. However, the client claimed to have never seen pipes of 400 lb grade; yet 400 lb is indeed mentioned as a grade for flanges in B16.5. This led to confusion. By reviewing some documents from previous projects carried out by the company, it was found that usually, grades above 300 lb go straight to 600 lb, and flanges of grade C, or 400 lb, are quite rare. Is it possible that flanges of this grade simply don’t exist very often? The same is true for pipes of DN65 size
Yes, 400 pounds and 65mm – these are things that aren’t typically seen in ordinary projects, unless there is a very special reason for it~
The concept of pound rating applies to flanges or valves that contain flanges, but similar designations such as 300# and 600# can also be seen on the pipes connected to them
It’s normal for a pipeline to have two valves of different grades. 300LB ； 150LB