API 650 Flange class selection 2

[RBKN]

I am designing an API 650 tank for the first time and have loads given for a 4" nozzle with RFWN flange. Is there a section in API 650 giving guidelines to select the class of flange to be used?( if it were ASME section VIII Div 1 I would have to use a 300# under these conditions) I looked at Appendix - P but I cant see how it will help in selecting which class of flange should be used? I want to check if I can get away with 150# by API 650 standards.

 

[mk3223]

The pressure class of the nozzle flanges can be based on ASME B16.5 for API-650 tanks as well as BPVC vessels. Typically, the 150# class flange is suitable for API-650 tank nozzle.

 

[RBKN]

@mk3223, so if the BPVC calculations shows that I have to use class 300 flange, I have to use class 300 for API 650 tank as well?

 

[TGS4]

You seem to be dancing around your actual issue.

What "calculation" for an API 650 tank that generates pressure due only to hydrostatic head would force you into a Class 300 flange to ASME B16.5?

 

[LittleInch]

I don't understand this either.

API 650 is for "atmospheric pressure" storage.

Your nozzle can't see any pressure higher than that generated by the liquid head.

So unless your tank is several hundred metres high, in terms of pressure you won't need anything higher than class 150.

Can you explain yourself a bit more and why you keep talking about ASME VIII when you refer to an API 650 tank?? Doesn't make sense.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SnTMan]

... and have loads given for a 4" nozzle with RFWN flange.

It appears to me that OP has nozzle loads applied and is taking the flange itself into consideration. Perhaps applying one of the equivalent pressure methods. I am completely unfamiliar with API 650 and so cannot comment on the Apx P reference, or what methods may be allowed.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[JStephen]

I don't think there's anything in the code that addresses external loading on a flange itself.
Usually, the flange class is specified by the purchaser, and is nearly always 150#.
In probably the majority of cases where external loading on a nozzle was specified and was a problem, it was also a case where those loads were not realistic. Either they were arbitrary loads pulled off somebody's "standard nozzle loading" chart or they were derived assuming infinite stiffness in the nozzle. In either of those cases, if the flange itself appears to be inadequate, consider taking a second look at where those loads came from. Presumably, the piping designer would have the same issue on the matching flange, right?

 

[SnTMan]

JStephen, no, it never affects the piping, only the equipment the piping is attached to

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[RBKN]

@LittleInch and @TGS4 I am sorry for being vague.

I understand that the nozzle will see only the pressure due to fluid column in an API 650 tank, but that's not what I am worried about. There are Force components and Moment components given (External Loads) acting on the flange and I am unable to find any Section in API 650 which accommodates these external loads on the flanges. As a result of this, to be safe, I did the calculations as per ASME Section VIII Div 1 ( because I am relatively familiar with this code). These calculations showed that due to external loads (again, not because of the pressure loads), Class 300 Flanges should be used.

That is why I want to know if someone who has been designing tanks can guide/suggest me as to where to find the information or how are the external loads on flanges dealt with in API 650?

 

[SnTMan]

Nishanksp9, what do you mean when you say "...I did the calculations as per ASME Section VIII Div 1..."?

Sec VIII, Div 1 itself contains no means to evaluate the effect of external loads on flanges. There is a Code Case by which external loads can be evaluated. There are also several "industry standard" methods to do so.

Also, if Sec VIII, Div 1, Appendix 2 methods are applied to ASME B16.5 flanges these usually fail, even in the absence of external loads.

So, what are you referring to?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

Nishanksp9

You appear to have missed Appendix P? This lets you calculate the nozzle loads the tank can take.

Normally these allowable flange loads are really small hence why you don't normally need a higher class flange because the issue isn't the load on the nozzle flange, it's the loads on the tank that are the limiting factor.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

Did you check API-650 Annex P, Allowable External Load on tank shell opening?
Can the connecting pipe be supported to comply with the tank nozzle allowable load requirement?

 

[RBKN]

@SntMan

What I meant was, I calculated MAWP reduction due to external loads. And according to that class 300 flange was safe to use.

 

[RBKN]

@LittleInch

In my very first post I wrote ".... I looked at Appendix - P but I cant see how it will help in selecting which class of flange should be used?..." It appears you missed that.
Anyways, if you know how it will let me make a selection of class of flange, please enlighten me.

 

[SnTMan]

Nishanksp9, I am curious, how did you do so?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

sorry, I missed that.

I think the point though is that you seem to be doing this the wrong way around.

There is no point looking at the forces on the flange in isolation if the nozzle to which the flange is attached can't take the loads that you're putting into the flange.

Normally you would find out what the flange can take (generally pretty low for an API 650 tank) and then use this as the basis for the flange connection study. That's what you use App P for.

I don't think I've ever seen a flange on an API650 tank needing to be increased in rating because the loads are too high. A pressure vessel maybe, but not a tank.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TGS4]

What I meant was, I calculated MAWP reduction due to external loads. And according to that class 300 flange was safe to use.

So, how, exactly, did you perform this calculation? What exact method did you use? Details, please, because I think that you are doing something that is very wrong.

 

[84Volumex]

Did the flange loads you were given take into account the flexibility and movement of the tank? or was the tank nozzle assumed to be an anchor?
Nozzles near the base of the tank have a nasty habit of rotating as the tank fills up. This should be taken into consideration when the pipe stress calcs are done.
In the refinery I work at, the use of Class 300 flanges for instruments on tanks is common.

 

[RBKN]

Everyone, Code case 2901. This is how I did it and my question is that does API 650 has something similar?

@TGS4 and @SnTMan

Please follow this link.

https://www.youtube.com/watch?v=Ld_OHq_G24Y#action=share

@LittleInch I have seen only 2 tanks till now and they didn't require external loads to be considered. This third one is the first time I am dealing with external loads in nozzles in API 650. I have no experience whatsoever with the API 650 tanks so you have my respect. But I think you still don't understand what my query is.

I have considered App-P for my tank and my tank meets the requirements, it is the FLANGE that I am concerned about.

And again, if you have never seen something doesn't imply it is wrong or it doesn't existent. It simply means you haven't seen it.

See, for @84Volumex it is a common thing.

@84Volumex, My client just provided me the resultant loads that he wanted me to consider, I don't know if he compensated for all the factors you mentioned.
Regarding if he considered the flexibility of the tank or as an anchor, I would like to look into it. Thanks.

 

[TGS4]

Glad that you are using CC2901. I am having a difficult time believing that you are still having to up-rate the flange using that method. Care to share you calculation?