UG 45 minimum nozzle thickness

[francifo]

Can someone tell me if the following (my interpretation of UG45) is correct:
example:
UG 45 (b)(1) : 12.95 mm
UG 45 (b)(2) : 11.33 mm
UG 45 (b)(3) : 5.88 mm
UG 45 (b)(4) : 11.33 mm

My chosen nozzle thickness is 11.33 mm

 

[stanrick]

Is your vessel for internal pressure, external pressure, or both internal and external? I believe the answer to this question determines whether to use (b)(1), (2), or (3). You still need to compare this to the result from (a).

 

[jte]

UG 45 (b)(1) : 12.95 mm
UG 45 (b)(2) : 11.33 mm
UG 45 (b)(3) : 5.88 mm
UG 45 (b)(4) : 11.33 mm

My chosen nozzle thickness is 11.33 mm

How can (3) be smaller than (1) and (2)? In your case, it appears that (3) should be 12.95 mm.

What is your diameter and CA? It seems odd that the external pressure thickness of the head or shell happens to coincide with the standard wall nozzle thickness.

Look at it this way: ...the thickness of a nozzle neck... shall not be less than the smaller of (3) or (4). Perhaps the wording could be simplified to "No thinner than the required shell or head thickness for internal or external pressure (with CA included for both) but need not exceed Standard wall pipe with CA added."

In this case, it should be 11.33 mm as you surmise, but don't forget UG-45(a) and (c).

Take a look at Appendix L, L-7.2.3 (page 562 of the 2007 ed) for a good example.

As an example of (b) only, if a 12" nozzle is inserted into a shell which has a minimum (corroded) thickness for of 0.20" for internal pressure, 0.15" for external pressure, with a CA of 0.10":

(b)(1) is 0.30"
(b)(2) is 0.25"

so (b)(3) is 0.30" (SHELL thickness, not nozzle)

Your minimum nozzle thickness is (b)(3) but need not exceed Standard wall (0.375)(7/8)+0.1 = 0.43" so your minimum nozzle thickness based on UG-45(b) only is 0.30" Keep in mind that you will check the nozzle thickness for internal pressure and other loadings in UG-45(a) and (c).

Now, if we increase the internal pressure so that the shell requires 0.70" for internal pressure and keep everything else the same:

(b)(1) is 0.80"
(b)(2) is 0.25"

so (b)(3) is 0.80"

(b)(4) is still 0.43", so your so your minimum nozzle thickness based on UG-45(b) only is 0.43"

jt

 

[djws]

Hi,

Just a clarification for jte.

I am not sure if I agree with your statement "Look at it this way: ...the thickness of a nozzle neck... shall not be less than the smaller of (3) or (4). Perhaps the wording could be simplified to "No thinner than the required shell or head thickness for internal or external pressure (with CA included for both) but need not exceed Standard wall pipe with CA added."

ASME Section VIII, Div. 1 - 2007.

UG-45(b) states that

"Additionally, the minimum thickness of a nozzle neck or other connection (except for access openings and openings for inspection only) shall not be less than the smaller of the nozzle wall thickness as determined by the applicable rule in (b)(1), (b)(2) or (b)(3) below, and the wall thickness as determined by (b)(4) below:"

Meaning that if the vessel minimum required wall thickness with corrosion allowance is less than the thickness of of standard schedule pipe with corrosion allowance, then the nozzle minimum required wall thickness is set to that vessel minimum required wall thickness with corrosion allowance. However, if the code calculated nozzle minimum required wall thickness is greater than the thickness of standard schedule pipe with corrosion allowance, then the code calculated nozzle minimum required wall thickness is used which will be greater than the thickness of standard schedule as indicated above.

 

[jte]

djws-

I think you are mixing UG-45(b) and UG-45(a). My writeup above has "based on UG-45(b) only" in bold twice since I'm focused on that paragraph only.Of course, if I calculate the required wall thickness of the nozzle and it is thicker than Sch 40, I will use the thicker value. That is the job of the (a) paragraph. Having checked the (a) paragraph, I then proceed to the (b) paragraph. Having checked the (b) paragraph I will also check the (c) paragraph.

Let's say that the (a) paragraph wall thickness of a 12" nozzle calc's out to a required pipe wall of 0.25" (I am using a magical pipe with zero mill tolerance and zero corrosion allowance). No shearing load exists on the nozzle neck (i.e. UG-45(c) is irrelevant to this example). This nozzle neck is inserted into a shell which has a calculated thickness of 0.20" (substantially weaker nozzle material than shell material). My chosen nozzle wall will be 0.25" which is governed by UG-45(a) since the result of UG-45(b) is 0.20".

On the other hand, now I'm taking the same nozzle but the shell is 1" thick. Now the (b) paragraph governs. I shall take the smaller of 1" or Standard wall (0.375" thk). So I will call out the nozzle neck as 0.375" wall even though the (a) paragraph minimum is 0.25".

I am not sure if I agree...

I'm always open to discussion. When you are sure that you agree or disagree, let me know. But please provide numerical examples backing your position. Also, please read and ponder Interpretation Vlll-1-83-199.

jt