Weld neck flange and pipeline wall thickness 2

[JohnWeal]

We have 4 pipeline sizes (700, 800, 1400 and 1600mm) and I was wondering what is the exact inside diameter.
The pressure is no more than 5 bar so only need a Standard wall thickness of 9.53 (0.375")

According to EN 1092-1, the weld neck flange bore shall taper at 15 degrees. However, also to consider is that the 'SP' dimension (adjusted wall thickness of the weld neck) is still thicker than the 9.53 pipe wall.

There are some other criterion but in a nutshell, what must the outside diameter of the pipeline be? I'm assuming it is the same as the weld neck flange and it is the bore of the WN flange that changes. Just a little confusing as the reduced wall thickness of the weld neck is 14.2 but the pipe wall is 9.53.

Appreciate any help.

Regards

John

 

[pennpiper]

John,
Piping Basics:
1, We have 4 pipeline sizes (700, 800, 1400 and 1600mm) and I was wondering what is the exact inside diameter. In pipe sizes that you are talking about the Pipe nominal size (NPS) is the outside diameter. Example: 700 metric = 28" imperial and may be called Sch 20 or "Std", both have a .375" wall

2, If you are buying Class 150 Flanges then you simply specify the Bore (ID) of the Flange to match the Bore (ID) of the Pipe, very simple (ie: Std Bore). The weld Bevel of the Flange will (or should) fit the weld Bevel of the Pipe.

3, According to EN 1092-1, the weld neck flange bore shall taper at 15 degrees. The 15 degree taper issue does not come into play with what you appear to be doing.

4. There are some other criterion but in a nutshell, what must the outside diameter of the pipeline be? The outside diameter of the pipe is the nominal pipe size.

Sometimes its possible to do all the right things and still get bad results

 

[racookpe1978]

Please look up the standard pipe diameter tables. They will have the standard pipe ID's.

What is your background in pipe design, and how long have you been working in this position please?

 

[LittleInch]

John,

You probably really need to get a copy of ASME B 36.10M and read the introduction and look at the tables.

Be aware that STD wall thickness is not really standard and depending on the pipe size sometimes is the same wall thickness ~(12" and upwards) , sometimes the same as schedule 80 and sometimes not(!).

Pennpiper has the answers, but a small correction - at 28" Sch 20 is actually 0.5" wt and is the same as XS, not STD.

The only time you want / need to machine the inner bore is if the flange design has a minimum wall thickness but this only works if you have the same strength material between flange and pipe.

The "preferred" value of neck thickness in EN 1092-1 varies with different pressure ratings. you don't say what pressure flanges you're using and the word "preferred" implies that you can have less if you specify it.

I don't know what you mean by "the reduced wall thickness of the weld neck is 14.2 but the pipe wall is 9.53." Can you explain please.

However it should be noted that a 9.5mmm wall thickness at 1600mm diam is a D/t ratio of 167. That looks very very thin to me. Anything much past 100 and you run into lots of difficulties with ovality, welding, buckling, dents etc.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JohnWeal]

Hello Littinch,
I am progressing through calculations in AWWA M11.

Will speak to piping fabricator today also.