How to Calculate Blind Flange Thickness With Opening 1

[mechyp]

Dear All

any clause for Calculating Blind Flange Thickness with opening grater than 1/half of flange OD(flat head

this Bolting joint as per UG-34(j)

Blind flange 20" (As Per B16.5)
Nozzle OD 438
Thickness 37 Thk min

as per UG-39(C)(1) i have to go Appendix 14 but scope of Appendix-14 is
The shell-to-flat head
Joint shall be either integral, as shown in Fig. UG-34
sketches (a), (b-1), (b-2), (d), and (g), or a butt weld, or a
full penetration corner weld .
.
my joint configuration as per UG-34(J)

 

[SnTMan]

yp3135, calculate as a loose ring flange per Appendix 2, see for example Fig 2-4 (1).

Regards,

Mike

 

[mechyp]

thanks mike

also I have to do calculation for compensation of opening as per UG-37 ?

yogesh

 

[EngAddict]

"also I have to do calculation for compensation of opening as per UG-37 ?"

No, if you designed it as a flat end then you would also have to do the reinforcing checks but the reducing flange already includes the reduced area in the calculation.

 

[SnTMan]

Agreed, no reinforcement calcs needed.

Regards,

Mike

 

[mechyp]

thanks

it clear to me

yogesh

 

[jtseng123]

yp3135,
It does not sound right to me. You say the flange is B16.5, now you will change the thickness, that means the bolt length will change too. Is it still qualified as B16.5 ? Many times, B16.5 flange will fail App 2, but that does not mean the flange is no good. I have seen reinforcing calc for studed nozzel on blind in the past.

 

[EngAddict]

"Is it still qualified as B16.5 ?"

No, it is custom to App2 (even if the thickness does not change).

 

[mechyp]

yes if std flange is not qualify as per Appdix-2
then we have to increase thickness also stud length


Can i design it as per flat head (UG-39)?
opening will be grater then 1/half OD flange(large opening)
or it comes under U-2(g)
just for information

yogesh

 

[jtseng123]

yp3135,

To make it clear the one I have seen reinforceing calc is for small nozzles (2"-6") not greater than 1/2 of the flange size.

Flange needs additional rigidity check to prevent leak. Head or shell just needs simple reinforcement.
You nozzle OD is no greater than 20". that means you are cutting less area than a regular flange. What's missing is the hub area. If you can build a hub to simulate the standard flange, you will be fine without calc.

Other way: weld a weldolet, that will give you a big chunk of steel and the blind will be very rigid.
Or, use 20" standard flange (not blind), and weld to a reducer, then weld to nozzle, so you don't need to run any calc.

To check any B16.5 standard flange or blind by App. 2 has no meaning at all in the first place, because most of them will fail. Insisting doing that will yield you a special design flange if you are happy with that.

 

[SnTMan]

yp3135, you are outside the scope of UG-39, also note the diameter your opening is referenced to is the mean gasket diameter, not the OD, see Fig UG-34 (j). So it's worse than you thought

Calculate per Appendix 2, disregarding any contribution by the nozzle. If a standard blind is not thick enough, make one from plate. No big deal.


Regards,

Mike

 

[EngAddict]

I would start with a standard 'off-the-shelf' B16.5 blind, partial pen weld it to the pipe and design as an integral slip-on to App2. Then you might find you may not need to increase the thickness. If you do need to increase the thickness then fabricate with the rest of your forgings or machine out of plate as Mike suggested.

Mike, why are you suggesting design it as loose?

 

[SnTMan]

With the right weld detail, it could most likely be considered an integral flange, as EngAddict suggests. It seems your pipe dimension does not permit the use of a B16.5 standard slip-on or weld neck flange, correct?

Don't forget to take a look at "optional" type flanges in Apx 2 as well. This may permit the flange to be considered as integral with a simpler weld detail.

EngAddict, I suggested loose because a) it is simple, and b) I didn't read the OP carefully enough at first to realize it had an attached nozzle

Regards,

Mike

 

[mechyp]

Mike

joint configuration is like this

dish to 20" std neck (B36.10) to 20" Wnrf Flange (B 16.5 #150) to 20" Blind flange to self reinforcing Nozzle neck OD 438 mm thickness 37mm( neck height more then 200mm)

blind to neck joint is like UW16.1(e)


yogesh

 

[SnTMan]

yp3135, this would appear equivalent to Apx 2 Fig 2.4 (7) (full welded thru the flange), and assuming your fillet meets the figure (7) requirements, I don't see why you could not treat this as an integral flange.

Regards,

Mike

 

[mechyp]

Mike

its not In Apx 2 Fig 2.4 (7)

see self reinforcing neck is not welded to Vessels

vessels to 20" nozzle neck to 20" wnrf flange

20" Blind flange with self reinforcing nozzle opening is bolted to wnrf flange

so Blind flange is bolted Cover

it clear to u

regards
yogesh

 

[SnTMan]

yp3135, I guess its' not clear to me. You said "20" Blind flange to self reinforcing Nozzle neck OD 438 mm thickness 37mm( neck height more then 200mm)" and "blind to neck joint is like UW16.1(e)", leading me to believe that the construction was equivalent to Fig 2.4 (7).

Then you said "20" Blind flange with self reinforcing nozzle opening" and "so Blind flange is bolted Cover", leading me to the same conclusion.

How about a sketch?

Regards,

Mike

 

[mechyp]

but mike blind cover is bolting to 20" WNRF flange which is connected to vessels.

u r right blind to reinforcing neck joint construction was equivalent to Fig 2.4 (7).

what about bolted joint between blind flange and weld neck flange.


Regards
yogesh

 

[SnTMan]

yp3135, does not Apx 2 consider bolt areas required, available, gasket dimensions and properties etc and so forth? I don't understand the reason for yout latest question.

Regards,

Mike

 

[Spoonful]

I would just use as jsteng123 suggested, bolt to your 20inch WN flange with another 20inch WN flange, which is welded to a 20inch to 16inch reducer, as your nozzle OD 438, greater than standard 16inch pipe OD, you could chop back some length of the small end of the reducer until it matches your pipe. then problem solved, provided you have no space limitation.

Regards

Spoonful