PG-32 example

[xgiorg]

Mínimo diámetro para el cálculo de compensación:
P D
K= ------------ P = 49.5 Kg/cm2 S = 1800 Kg/cm2
1.82 S t D = 1300 mm t = 30 mm

K = 0.6547

D * t = 39000 mm2

(FIG PG-32) dmax = 8.08 (D t (1-K)) ? = 192.2 mm

d < 1/4 Di(shell) = 310 mm
< mayor of: 60 mm and the value obtain from FIG PG-32 = 192.2mm

Then no calculation need be made to determine the availability of compensation for a single opening under 192.2mm. Is it ok?

But if I change the pressure to 48.5 Kg/cm2:
K= 0.9786
dmax= 76.06 mm ---> it's a big difference!

--------------------------------------------------------
Also, with P = 49.5Kg/cm2 and a nozzle of 8" sch 120 ( 219.1 x 18.26 )

PG 32.3.2
D = 1300 < 1500
(d = 219.1) < (D/2= 650) --> 8” ? 20” ? OK

FIG PG-32: (219.1 – 18.26*2) = 182.58 < 192.2
Then it is no need to calculate the reinforcement.

But:
A = 5758 mm2
A1 = 464.5 mm2
A2 = 2071.5 mm2
A3 = 1095.6 mm2
A1+A2+A3 = 3631.6 mm2 < A = 5758 !! Then it need reinforcement!!

Is it correct? why it is no need of reinforcement calculation when it realy needs?

Any comments should be helpfull
Thanks.

 

[prex]

There's something unclear in what you state: please clarify.
The question is: how comes that you calculate K=0.65 with P=49.5 kg/cm² and K=0.98 with P=48.5 kg/cm² ?
Also consider that you can't change or determine independently the maximum allowable working pressure, as this will be the consequence of the other data: S, D and t.

prex

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[xgiorg]

I'm sorry, you are right, with 48.5Kg/cm2 K = 0.6415.
Now what I realy want to know is why a 8" nozzle is no need to calculate the reinforcement when it realy needs to be reinforced?

Thanks prex

 

[prex]

The maximum allowable working pressure for your shell is much higher than what you state (though it depends also on joint efficiency and corrosion allowance, that I don't know), so you are not comparing things correctly. As stated above MAWP must be determined based onto design data.

prex

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[GenB]

Sen~or como esta' Ud
something you are doing wrong,
less pressure smaller the k value if 49.5kg k =.6547
if pressure is less the k should be .55 or less

if within limits (on the table/chart)no calculations for compensation are required but do not confuse compensation with reinforcing. you will still need to calculate your welds strengths
genrlblr

 

[chicopee]

xgiorg, diatriba in ingles per farvor otherwise no comprende.

 

[xgiorg]

Oups, I have to write in english.... but I missed this comment... Wich is the difference between compensation and reinforcement, I mean, first I have to verify if there is need of compensation, and then I know if I have to reinforce the opening, isn't it?

 

[chicopee]

As far as I am concerned, the terms are synonymous but their use seems to be used dififferently as to which ASME code that you are using. ASME Power Code I uses the term compensation; with ASME Unfired Pressure Code VIII, the term reinforcement is used.

 

[gr2vessels]

When you cut a hole in the shell, you remove a part of that shell and you weakened the strength of the shell. That material has to be compensated around the opening in order to maintain the integrity and strength of the shell.
However, if you connect the opening with a nozzle, then additional factors have to be considered, including the stress due to welding, external nozzle loads, etc, which will adversely affect the strength of this joint. That's when you are evaluating the available strength and compare it with the minimum required strength of the joint. If needed, you can add more reinforcement to the joint, in various methods described in the Pressure Vessel code.
Cheers,
gr2vessels