Hole in a Blind B16.5 2

[ElCidCampeador]

Hi all,

I've this std blind 5 NPS acc. to B16.5. Now I want to drill a 2 NPS hole not in the center of the flange so that after I could weld a 2" LWN std acc. to ASME B 16.5. First of all, do I have to check the calcs? Is it permitted to drill a hole of this dimension? I check in B16.5 - Table 6, but I don't understand the point: do I need to reinforce the LWN? Would it be different if the hole is centered? Help! Thanks.

 

[racookpe1978]

And why the bloody hades would you NOT check the calc's?

Actually, with that tight a group of mis-matched, off-centered, non-Code-standard drilled and welded fittings all crammed into a short pressure fitting, you really DO need an accurate full 3D finite element analysis. Done by somebody who knows FEA and its limits.

What is your operating pressure, what temperature, and what fluid?
What materials do you think you are going to use?
How will you weld them, and with what filler?

 

[prex]

I assume that the LWN is to be welded on the same 2 NPS hole, so there's a single opening in the blind.
Under ASME VIII Div.1 this would require a reinforcement check per UG-39, as the opening exceeds one fourth the head diameter.

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[ElCidCampeador]

racookpe1978, if you are right (As I suppose), I don't understand what case refers to table 6 of ASME B16.5. Is it not similar to this one?

yes prex, the LWN has to be welded on the same hole, but I would ask: is there a size for the hole under that you might not check the calc's? A size that you can say "Ok, there's a hole, but the blind is according to B16.5, so it's ok"? Thank you all!

 

[XL83NL]

If you review table 6, youll find that the smallest size (i.e. eveyrhting bigger than that) requiring a hub flange (i.e. not allowing the drill a hole in the centre, but instead us a high hub flange or do the VIII-1 div2 calcs) for an NPS 5" blind flange, is NPS 1.1/2". So if you would have a 1" outlet on your 5" blind, you didnt need to do additional calcs. For 1.1/2", you do.
Another example; if you'd have a 4" blind, you would not need to do calcs for 1" holes and smaller. Ona 4" blind with a 1.1/2" hole, you however would need to do the calcs.

Slightly off topic, but B16.5 table 6 is often looked at as being related to holes in the centre. Off-centre holes are not allowed. You may want to review this informative thread too. There seems to be nothing in B16.5 explicitly saying this though.

 

[racookpe1978]

OK, now think again about the details of this odd-ball pressure fitting you want to jury-rig together.

5 inch NPS "pipe" of some unknown schedule made of some unknown material withstanding an unknown pressure at an unknown temperature of an unknown liquid (gas maybe?) of unknown properties. This "pipe" is mounted (somehow) to a 5 inch NPS flange (of some unknown class and material) that will be covered by a 5 inch blind flange (of unknown material and class), but it will be drilled out with a hole (maybe on-center or off-center) to weld on a 2 inch NPS Long Weld Neck flange.

The 2 inch NPS LWN is 2.375 OD, so your hole must be at least 2.4375 diameter for the new pipe to slide into to permit a outside fillet weld. That 2.4375 hole is more than half of the ID of the original 5 inch "pipe" that you are connecting the blind flange to. The fillet welds around the OD of the 2.375 will be at least 1/4 radius, thus the OD of the weld - without considering access margin outside of the wled - is 2.375 + .5 or 2.875 diameter across that original 5 inch blank flange.

And you ask if you need to analyze this?

Use a Code-rated reducer and full penetration butt welds. If you need to drain the 5 inch "pipe" use a Code-rated eccentric reducer,, flat side down. IF this entire jury-rig must be bolted-on, bolted-off assembly, put a 5 inch flange upstream of the reducer, and a 2 inch flange downstream of the reducer.

 

[ElCidCampeador]

I think to have found a way to avoid calc's, but I don't know if it's correct.

UG-36 (c) allows openings max 60mm in flat heads with required min thickness over 10 mm (this is my case). Under this condition I can consider the blind flange as a flat head which is according to B16.5 and drill a hole <=2". Is it ok? thanks

P.S: racookpe1978 lol! yeah, I'm the "Unknown" man

 

[ElCidCampeador]

Another thing: UG-34 (1) allows to use blind flange B16.5 as flat head (as sketch j-k figure UG-34). But my question is: for drilling a hole in this cover flange, what standard do I have to follow? ASME B 16.5, with the limits of the off-center hole&co of table 6, or UG-36 (c)?

 

[prex]

You can't just look at UG-36(c), go read UG-39.
As you are asking advice here, why don't you listen to the advice you receive?

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[marty007]

B16.5 Table 6 provides an allowance for centrally drilled holes. If you exceed this value, all of the pressure/temperature ratings of B16.5 are no longer valid.

In your case, you are exceeding the values provided in Table 6, so you must do calculations to determine the pressure/temperature rating of the blind flange.

Cheers,
Marty

 

[52104438]

as I know, if the opening hole on standard blind flange, the ASME VIII-1 UG39 shall be uesed to check blind flange strength without considering LWN hub reinforce, it's our AI required in a past project.

 

[bpv66]

Marty is correct. Once you cut an opening greater than what is permitted in Table 6 of B16.5 you can no longer use the pressure/temperature ratings. You must calculate the flange as a flat head.