LWN inside standard diameter in NPS higher than 12 INCH
LWN inside standard diameter in NPS higher than 12 INCH
(OP)
In LWN (Long Weldig Neck) NPS higher than 12" most of the datasheets propose the inside diameter as the outside diameter of the Pipes acc. ASME 36.1
Which is the reason? Is it to be used as Slip ON Flanges?? If so, why is not allow or recommended directly a SO Flange?
I will appreciate your collaboration to solve this doubt.
Which is the reason? Is it to be used as Slip ON Flanges?? If so, why is not allow or recommended directly a SO Flange?
I will appreciate your collaboration to solve this doubt.





RE: LWN inside standard diameter in NPS higher than 12 INCH
Slip on flanges will not work on long weld neck flanges. Slip on flanges are only meant to be used with pipe. LWN flanges have their own flanges integral with the neck that has the same bolt circle as all of the other ANSI flanges.
RE: LWN inside standard diameter in NPS higher than 12 INCH
http://www.friulanaflange.it/eng/pdf/B16.5/B16.5-L...
I would like to know why sometimes PIPE STD ID is used and why in other cases the OD of NPS is uses as bore diameter.
As far as I know, LWN are also used in pressure vessels. In this case, you should use WT=0 Flange to match the LWN with the same bore and it has not any sense.
RE: LWN inside standard diameter in NPS higher than 12 INCH
LWN
8" NPS
OD = 9.75 (per ANSI standards)
ID = NPS = 8"
Pipe
8" NPS
OD = 8.625
Sch-80 = 0.5" thk
ID = 8.625 - (0.5 * 2) = 7.625
This is how ID is calculated for both options. Any resemblence in ID is purely coincidence.
RE: LWN inside standard diameter in NPS higher than 12 INCH
The last question. Which WN do you select to match a 14" LWN?
I think, the best one for LWN 8" (ID: 8") would be: WN 8" WT:0.312" (equal ID of the LWN)
But with a 14" LWN?¿ a WN with WT: 0?¿¿?
Thank you for your support,
RE: LWN inside standard diameter in NPS higher than 12 INCH
RE: LWN inside standard diameter in NPS higher than 12 INCH
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: LWN inside standard diameter in NPS higher than 12 INCH
In this case just in the union of the LWN & Flange there should be a mismatch due to the different IDs
I can not understand this matter.
RE: LWN inside standard diameter in NPS higher than 12 INCH
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: LWN inside standard diameter in NPS higher than 12 INCH
RE: LWN inside standard diameter in NPS higher than 12 INCH
Afox88 provides another viable alternative which is to use a nozzle configuration which is far more frequently used than LWN's.
LWN's are very good from a vessel perspective, primarily as they are much more robust than your typical pipe nozzle neck to WN flange construction.
RE: LWN inside standard diameter in NPS higher than 12 INCH
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: LWN inside standard diameter in NPS higher than 12 INCH
2.8: Straight Hub Welding Flanges (LWN)
2.8.3 BORE. The bore diameter shall be equal to B (Inside Diameter) of the welding neck flange. Other bores may be furnished by agreement between the end user and manufacturer. In no case shall the bore diameter exceed the bore of the same size and class lapped flang
RE: LWN inside standard diameter in NPS higher than 12 INCH
You're asking questions we can't answer as the datasheets and purpose is unclear.
your earlier attachment from a supplier makes it clear (in small writing at the top) that dimension B (Bore) ad Y are "specified by client".
Hence if you want a slip on flange, then your B is the OD of the connecting pipe. If it isn't then you calculate and specify "B" to match your connecting pipes and be strong enough for the pressure.
LWN flanges are mostly seen when you have a small distance from flange to next weld and hence can save a weld and don't have this small spool piece.
Often seen on vessels to allow stand off from the vessel. What B is is up to the designer.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: LWN inside standard diameter in NPS higher than 12 INCH
RE: LWN inside standard diameter in NPS higher than 12 INCH
RE: LWN inside standard diameter in NPS higher than 12 INCH
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: LWN inside standard diameter in NPS higher than 12 INCH
RE: LWN inside standard diameter in NPS higher than 12 INCH
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: LWN inside standard diameter in NPS higher than 12 INCH
Looks like a LWH, sounds like a LWN...
RE: LWN inside standard diameter in NPS higher than 12 INCH
They still call them straight hub welding flanges , but 2013 edition it's now figure 4.
Length is quoted as 229m for NPS4 and lower and 305mm for NPS>4" (though can be amended by agreement). Otherwise dimensions as per Weld Neck Flanges for each size and class rating. Bore is equal to dimension B of welding neck flanges unless by agreement and should not be bigger than the lapped flange bore.
So quite a flexible design....
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.