Reducing threaded flanges - ASME B16.5 table 6 vs EN 1092-1 ???

[XL83NL]

Does anyone happen to know if/how the equivalent of ASME B16.5 table 6 is addressed in EN 1092-1? Or another way to check conformity w/ EN 1092-1 for reducing threaded flanges, apart from doing calcs acc. EN 1591-1?
Background is the application of small threaded (e.g. NPT) holes in blind flanges for instrument/tubing connections. PS; Im not referring to type 13 flanges, since they dont reduce in size.

From what I understand, the standard is pretty silent on this matter - afaik it refers to EN 1591-1 for calculation basis of flanges. It doesn't provide as to how big a hole in a type 05 flange may be.

 

[europipe]

Don't know whether they exist.
Can't You screw a bushing in it?

 

[XL83NL]

The idea behind the NPT hole (or even any hole) is an opening that allows for tubing or instrument connections, e.g. using Swagelok male threaded connectors.
Table 6 of B16.5 dictates the max size a hole in a blind flange may be (without affecting the MAWP of the flange) before you need to 'step up' to reducing flanges with hubs.
These hubs compensate for the area loss you get when the opening is too much and affects the pressure bearing area too much.

So yes, a bushing can be screwed in, but that closes the hole and is opposite of what I need.

One way I could think of to bypass this problem is by using EN 13445-3 para 10.6 (pierced circular flat ends, bolted to the shell), however this approach is not as straightforward as B16.5 table 6.

 

[europipe]

I'm nearly shure they is no standard in DIN/EN.
Specify them to a vendor with a drawing.

 

[XL83NL]

Any supplier/vendor we buy flanges from will drill you any hole in any flange, if you want, and still mark it the same rating. They only care for sales

 

[crcenteno]

Do you have to comply with a client spec, CE marking or anything like that in your piping system?

If not, I think it is ok to think that if you drill a smaller hole than the equivalent type13 flange, you should be fine.

I have used type 13 flanges adding a reducer coupling to match my instrument and sometimes I drilled a blind flange.

 

[crcenteno]

If you have to fully comply with an international standard, openings in pressure parts are covered in chapter 7 of EN 13480-3, the EN piping design code, parallel to 13445-3 that you mentioned (EN pressure vessel design code).

Best,

 

[XL83NL]

CE-marking; yes.
For our scope of work, client specs usually dont apply. We however had a recent job w/ piping to EN 13480

The thing with type 13 flanges is they already have a NPT hole, int he size of the flange.
Buying it without a hole and tapping the whole is what we do right now, but based on our experience that more expensive than tapping an NPT hole in a type 05 (i.e. blind) flange.
I think para 10.6 of EN 13445 is the same as para 7.2.5 of EN 13480.

To which EN-standard conformed those reducer coupling you mentioned? I have a hard time finding any equivalent EN spec to e.g. B16.11 (half couplings) and MSS SP-79 (reducer inserts).

 

[crcenteno]

Hi,

I believe reducing couplings are covered by EN 10253 std.

Anyway I do think that type13 flanges are G threaded and not NPT threaded, check that.

 

[crcenteno]

Threaded fittings are also covered by EN 10241.

Best,

 

[XL83NL]

Hi crcenteno, you're correct, type 13 flanges have either Rc or Rp thread (tapered or parallel), not NPT.
EN 10253 does, AFAIK, not cover threaded couplings. Ill look into EN 10241, thanks!

 

[XL83NL]

EN 10241 covers steel. Any suggestions for a stainless variant of threaded fittings acc EN standards?