EXTERNAL LOADS AND MOMENTS FOR FLANGE 3

[skengg]

hello,
Can someone guide me how to calculate external axial force and bending moment on bolted flange connection. I have all the flange design input parameter, Design as per ASME SEC. VIII, but I also need to consider external load and bending moment acting on flange in the calculation, Anyone have reference of external loads and moment, like for ASTM A105 material, CLASS 1500 flange at 140 kg/cm2 Design pressure and 93°© Design temprature.
Thanks

 

[Snickster]

Using a piping stress analysis program such as Caesar you create a node at the flange location and model as an internal anchor point. This will provide forces and moments at that point.

 

[XL83NL]

UG-44. Or EN 1591 which is (one of) the best analytical methods currently available.

Huub
- You never get what you expect, you only get what you inspect.

 

[skengg]

Thanks Snickster for replying but I don't have any FEA software to calculate, need any calculation reference.
Thanks XL83NL,let me look at these references you mentioned. After that if any doubt arises, will revert to you.

 

[Snickster]

Are you designing a custom piping flange for some kind of process line? I had to do that once for a special flange design in a large vent stack. In that case the forces and bending moments at the flange could be determined since they were basically due to wind load. I used certain reference books and calcs which were per ASME.

If you have flanges in the pressurized pipeline with thermal expansion then you would need to determine with a computer stress analysis. There are also manual methods if you can get hold of them and take the time to understand. Other than that I don't know of any values off hand to plug into those unknown piping loads to get a conservative value. Maybe there is a rule of thumb for estimated external loads to apply to flanges in design.

 

[skengg]

Thanks Snickster for sharing the experience,
It's actually non-standard Subsea flanges for offshore applications, CL-1500 A105 flange.can u give me any handbook or code reference for study about what type of forces need to consider, need only conservative values to accommodate with internal pressure.

 

[Snickster]

I believe you need to know what the values of Fe and Me (external forces and moment) for to plug into the ASME equations is that correct? I don't know off hand how you would estimate that for underwater piping. I would think that external forces and moments would be very small due to thermal expansion and external loads such as wave. I would think the pipeline would be rather fixed on the subsea flow and would not move much if at all. The temperature also I assume would be rather constant. That being said I will still try to include something for these external loads. I will see if I can find something on this tommorrow in my references'

Attached is a example calculation spreadsheet in metric in accordance with ASME. With an estimate of the Fe and Me loads you can solve being that you have all the other parameters availabe. Of course you should have a copy of the ASME code calculation to review so you understand that the attached calculation is correct and giving you the correct answer. It has been years since I used it.

 

[skengg]

Thanks a lot Snickster for attaching Excel sheet for reference, I have copy of ASME code, will check and review for sure.
till then I am also looking for any study material to make some sense and yeah I'm looking for Fe and Me values to plug in the ASME Equation.

 

[Snickster]

Here is a copy of the Kellogg method. This was used back in the day before the digital age as a way to estimate if a flange loading was OK. Caesar II has this as a method along with ASME method built into their stress analysis program. When we did flange checks we first used the simple Kellogg method. If the flange passed by this method then we did not do ASME check since the Kellogg method is very conservative. If it failed the Kellogg method we then checked with the ASME method. I would do the ASME in any case if it is a very critical flange but the Kellogg method will give you a validity check and will get you a better understanding of the flange calculations in general.

I think the paper by Peng attached reflects the Kellogg method in the more recent article. Peng was the main author for Kellogg methods of piping design.

Attached is a spreadsheet for the method. I copied from a larger workbook with links to other sheets. I believe you can still use it by manually filling in some of the missing information for flange configurations rather than using the links which would automatically fill them in.

 

[Snickster]

I need to attach the files separately as I do not know how to attach them all to one post.

 

[Snickster]

Last one.

 

[Snickster]

I attached a duplicate abovee - here is the Peng article.

 

[LittleInch]

Snickster,

If the pipeline is subject to thermal changes then you can get huge movements and forces. Most subsea connections use a Z spool or similar to take the movement out but this creates moments and forces which the flange sees and is quite complex to calculate by hand.

Design temp is 93C!! A105 is going to de rate as well.

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

 

[skengg]

Littelinch,
it's actually de-rated flange, can u give me more information about de-rating of flange because this is something i haven't studied before.
in the enquiry sheet they have mentioned that Derrating as per DNV-OS-F101, what's this interpret?

 

[LittleInch]

skengg,

I'm confused - you say its a class 1500 flange, presumably to ASEM B 16.5?, but then quote ASME VIII

Flanges to B 16.5 commonly fail under the ASME VIII calculation.

I think OS F101 has a derating chart for common materials. The worst is Duplex, but carbon steel has a curve as well.

See section 5 C304.

At 100C you lose 30Mpa stress derating.



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

 

[skengg]

thanks snickster for providing all information. i will look at it

 

[skengg]

littleinch, it's actually CLASS 1500 ring joint type swivel flange but not exactly as per B16.5, bolt circle dia, hole dia and ring joint dimensions all taken from B16.5 but flange thickness and other stress and moment calculation as per ASME SEC. VIII. at given design temprature and pressure which makes it de-rated flange.

 

[Snickster]

The link below is for book that give a very detailed complete chapter on design of flange connections to the ASME codes, also has design of other process equipment. I have used it as a reference and have a hard copy.

https://www.thriftbooks.com/w/desig...1ad1d38c086991c#idiq=31940873&edition=6058272

If your pipe really heats up to 93C then there will be alot of thermal expansion and loading at changes in direction. For straight runs there will be just axial loading mostly. I have never designed a subsea pipeline so I have no experience in how they are installed to handle the loads such as using z-bends that little inch suggested.

 

[Snickster]

The attached DNV provides requirements and guidance for designing subsea pipelines.