Calculating Corrosion Allowable Factor for SA516-70 Material?

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Discussion Overview

The discussion revolves around determining the corrosion allowable factor for SA516-70 material, particularly in the context of designing pressure vessels. Participants explore various aspects of corrosion factors, their calculation, and implications for pressure vessel design.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants question the broadness of the initial inquiry regarding corrosion factors, suggesting that it lacks specificity.
  • A participant notes that determining the corrosion factor depends on various design factors, including material properties, service life, and expected corrosion types.
  • One participant shares a specific approach to calculating corrosion allowance based on maximum allowable wall thinning and service conditions, emphasizing uniform corrosion assumptions.
  • N-Doan provides a list of corrosion allowances for different applications, seeking validation of this information for use in pressure vessel wall thickness calculations.
  • Another participant warns about the unpredictability of corrosion in pressure vessels and suggests using corrosion-resistant materials and rigorous inspection schedules instead of relying solely on calculated allowances.
  • There is mention of the necessity for pressure vessels to conform to established standards, such as the ASME Boiler and Pressure Vessel Code.

Areas of Agreement / Disagreement

Participants express differing views on the approach to calculating corrosion factors, with some emphasizing the need for specific context and others advocating for general guidelines. The discussion remains unresolved regarding the best practices for determining corrosion allowances in pressure vessel design.

Contextual Notes

Participants highlight the complexity of corrosion behavior and the importance of considering specific service conditions, which may not be fully addressed in the discussion. There are also references to standards that may influence design decisions.

doan
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Dear all,
I have one question about corrosion factor. How to find it? (may be have 1 table to determine it? )
thanks!
N-Doan
 
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Corrosion factor of what?

You're asking a very broad, yet vague question.
 
Sorry,
I asked about corrosion allowable factor of material, which using to design pressure vessel.
Thanks!
N-Doan
 
As SteamKing indicated, "I have one question about corrosion factor. How to find it?" is a very broad and vague statement.

It depends on a number of factors that go into design.

I've determined it for a very specific case/application (including a specific material with known range of yield/tensile strength), and it was derived from the maximum allowable wall thinning over the service life, in conjunction with minimum wall thickness and maximum pressure (stress) allowed. The corrosion was assumed to be uniform, so it would not apply for a case where pitting or crevice corrosion might occur.
 
Dear "Astronuc",
I've never see the formula contained time service of pressure tank (Service life). Could you determined for me to understand?
And I had some information. Is it correct? Can I use it to calculate wall thickness of other parts in pressure vessel?

Corrosion allowance for carbon steel pipes (Ca) mm


Superheated steam = 0.3


Saturated steam = 0.8


Steam coils in cargo tanks and liquid fuel tanks = 2.0


Feed water for boilers in open circuit systems = 1.5


Feed water for boilers in closed circuit systems = 0.5


Blow-down systems for boilers = 1.5


Compressed air = 1.0


Hydraulic oil = 0.3


Lubricating oil = 0.3


Fuel oil = 1.0


Thermal oil = 1.0


Fresh water = 0.8

Sea water = 3.0

Cargo systems for oil tankers = 2.0

Cargo systems for ships carrying liquefied gases = 0.3

Thanks,
N-Doan
 
Doan - your original question puts us on difficult ground before we start - corrosion and pressure vessels is a bad combination .

If the situation were absolutely unavoidable I would seek information about out what type and rate of corrosion was commonly found in the particular type of pressure vessel and work from there .

Problem is that extent , depth and rate of corrosion can be very unpredictable in a real situation . If you expect corrosion to be a problem then the only answer is overkill on thickness and a very rigorously applied schedule of inspection .

Far better to use proper pressure vessel materials which are corrosion resistant and proven to be suitable in use intended - there are many to select from .

Don't want to be unhelpful - tell us more about what you are actually doing and perhaps we can come up with better answers .
 
Thanks,
We have designed steam system with SA516-70 material.
and the choose corrosion allowable is very important in this case.
Could you teach to me in this case (Ca value).
N-Doan
 

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