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Anonymous Poster #1

Joint Efficiency Of Pressure Vessel

09/11/2014 2:42 AM

What shall be joint efficency of joint between elliptical head and shell of pressure vessels?

Thickness of elliptical dish end is 12 mm and shell as 14 mm. The service of vessel is normal servcie.

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#1

Re: Joint efficiency of pressure vessel

09/11/2014 2:49 AM

100%, we don't do less!

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#6
In reply to #1

Re: Joint efficiency of pressure vessel

09/11/2014 5:21 AM

Off topic? And we havent even been told the country, standards to work to; I even think there is a Titanium jewel in the equation and Carbon Steel.

If we cant do 100% we should back off.

The post is too anonym and short headed to give a better response. If this is an engineering forum then this apparent engineer should make sure he formulates one combined question for the whole lot worth the engineer.

Rant off and out

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#7
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Re: Joint efficiency of pressure vessel

09/11/2014 5:40 AM

The circumstances for other joint efficiencies have been given. If you don't know how pressure vessels are done, don't give fictitious advice.

In particular, an assumption of 100% joint efficiency is not conservative, and may be unsafe.

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#9
In reply to #7

Re: Joint efficiency of pressure vessel

09/11/2014 6:17 AM

Aha!

https://au.answers.yahoo.com/question/index?qid=20070430094310AAuh2QZ

For me it reads like 100% makes 100% sure its fine.

Going less is not conservative but less documented.

https://www.google.com/#q=joint+efficiency+factor

The PDF that pops up there is of interest.

What do I miss?

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#11
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Re: Joint efficiency of pressure vessel

09/11/2014 6:32 AM

Q1. Gatorbait answered correctly, but you clearly did not understand it.

Q2. The first .pdf was about pipeline joints, and mentioned 80% efficiency. It does not support your 100% efficiency idea.

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#2

Re: Joint efficiency of pressure vessel

09/11/2014 2:56 AM

An inefficient joint. Is that an euphemism for "leak"?

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#8
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Re: Joint efficiency of pressure vessel

09/11/2014 5:46 AM

No. Although verified good welds are as strong as the parent material, welds without verification (e.g., radiography) cannot be assumed to have full strength. Hence the lesser efficiencies of 70% or 85% (and maybe other values in other Codes than ASME).

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#10
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Re: Joint efficiency of pressure vessel

09/11/2014 6:24 AM

Here is a link!

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#12
In reply to #10

Re: Joint efficiency of pressure vessel

09/11/2014 6:35 AM

That says pretty much what I said, but not what you said.

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#17
In reply to #12

Re: Joint efficiency of pressure vessel

09/11/2014 8:45 PM

Funny that! This was the intention. Not sure why you had to mark it OT when it supports what you say.

But loose with your OT gun, aren't you?

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#13
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Re: Joint efficiency of pressure vessel

09/11/2014 6:36 AM

"Strength" would be a better descriptor than "efficiency".

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#14
In reply to #13

Re: Joint efficiency of pressure vessel

09/11/2014 6:42 AM

Maybe, but "efficiency" is the ASME terminology, and it should be readily enough understandable. (I'm beginning to waver on this point, though, as in readily to whom?)

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#3

Re: Joint efficiency of pressure vessel

09/11/2014 2:58 AM

The joint efficiency you are allowed to claim (and use in calculations) depends on the level of radiography you use. If no radiography, 70%; partial radiography, 85%; full radiography 100%.

(At least that's the idea and how it used to be; I'm not sure it's up-to-date.)

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#4

Re: Joint efficiency of pressure vessel

09/11/2014 3:07 AM

The joint efficiency shall be inversely proportional to the grillage ratio.

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#5
In reply to #4

Re: Joint efficiency of pressure vessel

09/11/2014 3:18 AM

Sounds like the same AP as this guy

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#15

Re: Joint Efficiency Of Pressure Vessel

09/11/2014 8:34 AM

0.85

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#16
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Re: Joint Efficiency Of Pressure Vessel

09/11/2014 8:59 AM

Wrong. There are specific circumstances for other values.

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#18

Re: Joint Efficiency Of Pressure Vessel

09/13/2014 12:54 AM

Assuming you are designing vessel with code ASME BPV Section VIII Div-1,

As per figure UW-3: Weld joint between shell and head comes under "CATEGORY-A"

Then you refer to Table-UW12, for referring to this table you must get below listed information first,

1. What type of welding joint will be done between shell and head. It may be double butt, single butt with backing strip etc.

2. What is the limit of radiography which you want to specify. If you, as a "Pressure Vessel Design Engineer" specify "Full Radiography" you must take Joint Efficiency as 1 (one). If you specify "Spot Radiography" you must take joint efficiency as 0.85.

Lastly, this is what is given in ASME pressure vessel design course notes: The majority of pressure vessel welds use a Type 1 joint design. A Type 1 joint has an efficiency of either 0.85 or 1.00, corresponding with spot or full radiographic examination, respectively.

I hope this is clear. Correct me if I am wrong.

For your info, I never designed a vessel but I could gather this information from code and a handbook I have. Just read the code mate!!!!

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#19

Re: Joint Efficiency Of Pressure Vessel

09/14/2014 11:38 AM

Hello Anonymous Poster#1,

Calculating joint efficiency as per ASME BPVC Sec-VIII Div-1 is not rocket science.

I assume, vessel comes under ASME BPVC Sec-VIII Div-1.However; following information is required to calculate joint efficiency of circumferential seam,

1. Shell and head are seamless construction or shell and head are with seam construction (Circumferential seam's joint category can be assessed based on this information)

2. What is the cir. seam type of joint (ie, Type-1 or Type-2 etc.)?

3. What is the marking under the code symbol of this vessel (RT1, RT2,RT3 or RT4? {ie, extent of examination (radiography) of welded joints}

Based on that information joint efficiency can be easily calculated.

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