pipe thikness, min, load consideration 1

[anservices]

It is interesting to know about these sites, in which we could get Some constructive and formative information, because my experience In piping and pressure vessels also.

But my idea is comment the actual approaches for the thickness in these Equipments and components, as you know mostly STD guides and the Practice sees only the pressure problem, but the real problem is not in This way (the pressure and velocity of flow it is needed in process eng.
In order to estimate the diameter and a near thickness for thermal Proposals), I think it is needed to take into account the bending, torsion, The no linear effects, the environmental material degradation, etc.

This is, considering the application of the API rp 579 and BS 7910, in the Level 1, the LTAs etc. I think that this is not useful without considering The concepts mentioned before in last paragraph.
I remember the ANSI B31.G, which I didn’t like because the assessment
Of pipe thickness when corrosion exist near the 90% of material, was this
Ok for those calculations? It showed YES.
And what if exist bending moments, thermal effects, torsion etc?, where
Were its taken into account?


ANoriega

 

[JoeTank]

I am not exact sure what your question is about, but I believe you may be disappointed that API-579, B31G, etc do not give you guidance on all of the load criteia you desire. In this instance, you must rely upon your engineering skills to assess each of these loads. Do not be disappointed that the Codes leave part of the work to you to perform. No design Code gives you everything needed... that's why engineers are required for such evaluations. You must evaluate and assess each load condition based on how it affects the pipe cross section.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[Cockroach]

Von Mises-Hencky Equation will reference the internal loads as tri-axial state of stress. You can work these out yourself from first principles using the hoop, radial and longitudinal stress relations from Thick Wall Pressure Vessel Theory. To that, add the external loading, which will alter one or more principle stresses of the system. There is a lot of math involved, but it is very simple and easy to get to the end result found in textbooks dealing with Advanced Mechanics of Materials.

As far as wall loss due to corrosion, I have always used the Hencky Equation and iterated for 10% wall loss in order to maintain an acceptable Factor of Safety. If cost bore out safety concerns, then the results were acceptable. Of course you may have alternate criteria, but as principle designer, that is your perogative.

There is no subsititue for seasoned judgement. I suggest you contact a person with skilled art in the field.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[anservices]

I think it is needed to take into account the bending, torsion, The no linear effects, the environmental material degradation, etc.
as you know mostly STD guides and the Practice sees only the pressure problem, but the real problem is not in This way.
I think it is not so easy to say combined stress mises etc. if we take in account that exist flaws, cracks, holes,
pitting and high corrosion,gouges,bad material,etc.
It isn't continuum media!, but approacched one.
the actual art engineering goes with api 579, 1060,bs 7910
etc.( the best at all is fitness for service, is not the new design)
ANoriega

 

[Cockroach]

Anservices, I have absolutely no idea what you are talking about. Bending and torsional loads are applied are boundary terms external to wall material losses. Therefore the computation accounts for bending and torsion AS AN EXTERNAL SYSTEM APPLIED LOAD WHICH VARY FROM CASE TO CASE, AS FIELD CONDITIONS DICTATE.

Metallurgical conditions such as pitting and high corrosion rates are consideration of SELECTED MATERIAL and not physical design per say. In other words, the design can be solid but the material performance is not a function of bending, torsion, normal, shear, etc. Design the system for load, then select the material according to application.

When you're talking about flaws, cracks, holes, etc, these are yet again beyond the intent of design. I would broadly classify these as quality, since they bring into play craftsmanship, merchantability and warranty. These are also beyond the consideration of design for load and material selection.

There is not a single industrial specification that would address all the issues. I think that seasoned judgement as a Professional Engineer, the extension of sound education and field exposure over SEVERAL years would cover the bases.

So again, you're mixing in several independent streams of thought into "design".

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[anservices]

sir(s):

My claim in this group or forum is to get some constructive and formative comments in the actual tools
for mech. eng. like f4s, fracture assesments in industries.

Mr. kockoar--, all is ok. but I prefer don't touch the word
"DESIGN" and forget it in this subject, because I´d say
the better way in "post design" or "operating environment".

I formerly said the central ideas, but everybody take it as their work do or their experience.


ANoriega
anservices