Modified Flanges as Listed Components 1

[AndyChE]

Can modified B16.5 flanges be used as Listed Components within a B31.3 piping system?

In particular I have a 2" blind flange that I want to bore through and slide a 1" tube through and fillet weld on both sides. Also I have several 1", 1½", and 2" lap joint flanges that need to be bored out to fit over a lap joint stub end. Thicknesses of the flanges remains the same and sealing surfaces are not impacted.

Any input is appreciated. Thanks in advance.

 

[JLSeagull]

Could a reducing flange work in your application instead of drilling a blind flange?

 

[AndyChE]

I would have to use a 2" to 1" reducing flange and then get a fitting for connecting 1" pipe to 1" tube. I suspect the parts are out there, but that ends up with at least one extra weld and an extra fitting. That is an option.

I would still have an issue with my lap joint flanges, however. The heart of my question is whether I can modify B16.5 flanges and still use them as B16.5 flanges as long as I don't affect the thickness or the sealing surface. I have done it before, but not in a piping system that was subject to B31.3.

 

[jte]

Andy-

Regarding your 1" connection in a 2" blind flange: Take a close look at Table F6 on page 162 of the 2003 edition of B16.5. You're basically fabricating a reducing flange from a blind flange. If you had a 3/4" connection in the 2" blind, you would be fine with no further design changes in accordance with Note 1.

On the other hand, a 1" connection requires a hub. But the hub on a slip on 1" flange is roughly 1/8" high so that your fillet weld probably creates the hub which is required anyway. But now you're effectively doing a weld buildup to create this flange and I'm not sure that that's explicitly ok...

jt

 

[doct9960]

AndyChE,

What I don't understand is why wouldn't your stub ends fit into their corresponding ASME B16.5 lap joint flanges. What standard or specification are your stub ends designed to? Are they in accordance to ASME B16.9 or are they fabricated in accordance to ASME B31.3?

 

[AndyChE]

The stub ends are not fabricated in accordance with B16.9 or B31.3. They are unique to the manufacturer and are part of a manufactured piping system (see link):

http://www.resistoflex.com/rotateflange.asp

 

[doct9960]

AndyChE,

I am quite positive that the rotatable flange assembly by Crane Resistoflex meets ASME B31.3 requirements. Why don't you ask them if their components are manufactured in accordance to one of the standards in Table A326.1?

 

[unclesyd]

Why not get a reducing flange with the bore 1 size samller and bore it out to the 1" tube size. If you have enough demand you can get a reducing flange bored to size.

We routinely modified flanges for Resistoflex Piping Systems and If I recall the amount of metal removed to accommodate the stub end was quite small. Again if I recall correctly the final ID was just outside the tolerance of the flange as per code.

 

[MMCrash]

I would use a 2" x 3/4" Reducing Flange. The bore for 3/4" is 1.09" for slip-on and 1.11" for lap joint flanges. If you can weld with the a gap. If you want a tight fit use 2" x 1/2" and bore out. The hub for the 2" x 1/2" is1-3/16"

 

[AndyChE]

Thanks for the replies, but my conundrum is not necessarily what will work technically, it is what will "meet code."

If I modify a standard 16.5 flange can I still use its temperature-pressure ratings as a listed component or does it then become an unlisted component that I have to verify using section 304.7.2?

 

[eliebl]

Check ASME B16.5 table 6 (or F6 for imperial) to determine the size of opeing which can be bored in a blind flange before you have to change to a hubbed reducing flange. These openings would then be considered part of the B16.5 blind flange design and standard components.

EJL

 

[JohnBreen]

........also, read ASME B31.3, paragraphs 304.4 (including its sub-paragraphs) and 304.5. This will take you to ASME B&PV Code, UG-34.. You should really consider using a B16.9 reducer.

Regards, John.

 

[AndyChE]

Table F6 of B16.5 gives the smallest size requiring a hub as 1" NPS (1.315" OD) so a 1" OD tube would be smaller than this and even though it is not threaded I would think it is covered. Thank you very much eliebl.

JohnBreen - Thanks. I would have used a reducer, but it was going form tubing to piping so they were harder to find and this could be made easily. It has since been built so I have to figure out a way to qualify it now.