Blind to withstand Corrosion Allowance

No - B16.5 and B16.47 do not include a corrosion allowance. You must calculate as per B31.3 (refers to Sec VIII Div 1) or B31.3 (refers to Sec VI)

Hi. its me.. "last time Guest"..

I still not clear . Now i will be more worry. Never heard from other designer before whichever carbon steel vessel that have C.A. > 3mm required to use non-standard Blind "(150# / 300#) nor to recalculated the blind.

Even R.P.E or A.I never bring up this kind of issue.

It just my own thought.

So far i'm using PVelite never shown analysis for this.

I don't fully understand your question but I will offer this -

The ASME B16.5/B16.47 standards do not address corrosion allowance on "standard" flanges. These flanges are rated based on assumed gasket properties without consideration of corrosion allowance. Consequently, the ASME Code accepts these standard flanges based on the published pressure-temperature ratings without regard to corrosion allowance.

If flange corrosion must be considered, the flange should be analyzed per ASME Section VIII Division 1, Appendix 2. It is important to note that there is no assurance that B16.5/B16.47 flanges will meet their published pressure-temperature ratings when analyzed per Appendix 2. In such cases, it may be preferable to select the flange class so as to provide sufficient material and pressure rating for the intended service.

It is not often that flanges are used right at the maximum T-P rating so there is some leeway. I don't understand your PVelite statement/question.

Thanks so much coz u give such quick response..

I will give one of simple example for we analyse.

One vessel equipt with manways/handhole/spare that sure come with blind.

Material : carbon steel "Sa 516 Gr. 70N"

C.A. : 3mm

Flange rating : 150# with std raise face 1.52mm

Design Code : ASME VIII Div.1, Edition 2007

Please advise wether we still can use standard ASME B16.5 blind.

Or still we need to calculate with appendix 2 for each nozzles/manway/handhole provided with blind.?

Opinion are welcome..

Again thanks for all the support..

What are your temperatures and pressures?

......... or rather I should say that you won't know until you run the calculations.

............. in addition - PVElite does allow corrosion allowance in flange calculations

Taken from user manual:

Corrosion Allowance

Enter the corrosion allowance for this flange. The value entered here will be subtracted from the flange and hub thicknesses to obtain the thicknesses actually used in the computations.

Include Corrosion in Flange Thickness Calculations

The flange thickness is used in several places throughout Appendix 2. The Code states that every dimension used should be corroded. In the flange stress calculations the flange thickness is used. However, some feel that the corrosion should not be taken off of the thickness for the stress calculations.

Just make sure to check the "Perform Flange Calculation" and "Include Corrosion in Flange Thickness Calculations"

Hold on first... What do you mean by..

"......... or rather I should say that you won't know until you run the calculations."

Are you tryin to say that i'm a kind of engineer that fully depends on software?

I dont know about you but i'd design A LOTS of vessel since past 5 years.

"Dont always look down people eventhough they are new"

I dont know which statement that made confusion right now.

My question is simple.

Does Vessel with C.A. > R.F. value allowed to use standard Blind from ASME B16.5.
Guest is always say to run with Appendix 2.

From software " current i use PVelite". If manways or any nozzles with blind, we just check on blind. Never give caution that blind need to justify with appendix 2.

So far, i am designing vessel for c.s. vessel, i never do appendix 2 for manway blind or any nozzle with blind.

I think other designer did'nt practice this either. A.I. or RPE also never bring up this issue. Which we are worried about.

Wooooooo !! Easy now - I apologize if you took offense to my responses - I think you have taken them the wrong way. I did not mean to come across as belittling. I wasn't trying to "say" anything about you.

But the fact is I sometimes post quick responses without fully thinking them through as I bounce around in my day-to-day life/job and then sometimes need to post quick follow-up clarification/questions/answers when I get back to this site.

Please accept my apologies if my posts came across as terse. Maybe I should have said "......... or rather I should say that no one will know until you or I run the calculations."

The thickness of the raised face is almost meaningless - it has nothing to do with the thickness of the cover itself - except for the fact that it imparts a edge moment. With a blind flange it is a "bonus" to have the raised face thickness across the bore because this acts as a corrosion allowance. If however, you corrode through this thickness and take away the "t" dimension in flange calculations - then you need to determine if you have enough thickness.

So to get get back to your specific question - it is possible to use a class 150 blind flange with a 3mm corrosion allowance IF (and I hate to say this) it passes the calculations.

Lastly, please accept my profuse apology for any misunderstanding.

............. oh yeah - to follow-up I must admit I can be quite snarky with some responses because it just floors me at times after reading repeated questions of the form:

I need to design a pressure vessel for 3000 psi, could someone tell me how thick of wall I need?

or if there are repeated basic questions from the same person who is obviously not knowledgeable with what they are tasked with doing and can lead to grave harm to people.

But in your question - I wasn't trying to be snide. This is a common question/problem that a lot of people don't understand. There is even a line of thinking that you don't need to include corrosion in flange calculations - but I do not fall into that crowd.

...... there I go again - I shouldn't have said that the raised face is a "bonus" - that's not entirely true - another case of my fingers faster than my brain. I double checked UG-34 (I got caught focusing on appendix 2) and the thickness of the cover "t" is included.

Regardless, you should still perform the calculations (or have PVElite do it for you)

.. PVelite also one thing..

since u mentioned about UG-34. When got opening on blind it is already not a standard blind. So need to do appendix-2. But appendix-2 not covered if any opening on it. Then it should perform another analysis which is UG-34(c) bolting cover. Compress got it but PVelite does not include this.

One funny thing is.

There one case with my A.I. before,

It is true if we have made modification or anything on B16.5 standard flanges / blind,

It will not covered by code already. So that A.I. has bring up if there are any welding on it. It should performed Appendix 2. So all the manways that cleats/davit support are required to weld on it.

We insist not to do. Then he get scared when this item stucked b'coz of this issue. Lastly he approved.

Yeah - A.I.'s can be a pretty funny bunch, but it's best to stay on their good side.

My dear guest..

Blame shall be on me to missunderstood your word. Please forgive me..

It is fun to have colleague like yourself in the same field to share opinion.

I have to say that i agree, If c.a. has corrode the blind thickness, it will not cover by B16.5 anymore.

But.. in other way, my thought is, Blind or Flanges thickness is always govern by Loads from Bolts "maybe gasket type" coz of edge moment that will bend the thickness. Not from internal pressure.

So.. the corroded portion shall be on the center area only. Outside area can consider unharm.

Still.. justification.. No body ask b4.

I wonder.. dear guest, are you pressure vessel Designer?

If yes, do you always check for appendix 2 for c.s. blind for each size?

Yes, I am design engineer - vessels, piping, mechanical, etc ................... as my company sees fit and I fight back (other duties as assigned).

And yes, I do Appendix 2 in every case - just to be sure and thorough - I am not a pressure vessel "production" designer - I only do about 2-3 a year.

The thickness of the flange depends on both the pressure and bolt load in the operating case while- please download this example from CASTI for a thorough explanation.

http://ifile.it/5m2o3bc

And yes, it is always great to converse with others regarding similar work (or even unsimilar for that matter). So please do stick around and enjoy CR4 - at the very least you can correct my mistakes of typing before thinking

I should salute you if you do performed appendix 2 for each and every size nozzles with blind in every calculation you done.

Last time i did do that when i was a beginner. Then my boss insist not to do. If i do means it will take a longer time and also this will effect on other designer that might required to follow.

I don't want to be irresponsible to my design. That's why i always dig out issue like this.

I'm design engineer at AMC"M" Sdn. Bhd. (Pressure Vessel Fabricator) also a freelance doing design and fabrication drawings.

Thanks Soo Much for your kind assistance.

I just feel better doing the flange calculations for them all - like I mentioned I only do 2-3 vessels a year, so the extra time doesn't significantly add up. My boss supports it - he is "old-school" and very thorough. But I appreciate the fact that in "production" design/fabrication it is not really necessary - I work in a plant environment where our focus is not on volume production of pressure vessels. Thanks for the contact info - where abouts are you located? I am in western Canada.

Oh - I found your company's web page - it appears you are in Malaysia. I have never been there but would like to visit one day.

Come here my friend. Have a nice holiday here..

But not now. Now is flood season. heheee..

What is great about my company is.. we always get bottle neck order that required delivery around 2~3 month. even for columns & thick vessel.

Nowadays, since ASME VIII Ed, 2007 released. I dare not to try for Div.2. ASME audit is nearly comin. Need to prepare myself to it.

I'm From Malaysia.

How exactly CR4 work?

Did anybody else can see our discussion?

I wonder others seems not interested to this thread.

I'm very interested to hear from guy named Guru.

Ok.. Guest. " why still you use this nickname?"

heheh..

Just e-mail me if us required anything.

Yeah - other people can see/read this thread - but I have found that there is only really one other person on here that is quite knowledgeable and replies to pressure vessel questions. His name is Abdel Halim Galala and is located in Egypt - it is only 7 am there right now - so he probably won't see this for a little bit - at which he may grace this thread with his presence. He is very astute and his answers are always well thought out and written, not like my broken answers . I don't really have a good explanation why I don't register and lose the Guest stigma. Maybe it's because I reply too quick and say some stupid things that no one can trace it back to me . I also don't like the whole concept of "Good Answers" and would rather not keep score. Plus the title "Guru" is rather pointless - I believe it is just based on the number of replies you have made and has nothing to do with the content of the answers.

Oh yeah, don't come to Canada right now either - it is the snowy season.

Hi "Guest" here again - I figured I would finally signup and now my answers will have more merit . Thanks for helping me come to my senses. (unfortunately I had to add a period to my name as straight 'Guest' is apparently reserved)

Post #2 - on my way to being a Guru!!!!!! ...................... I've gotta get a life.