# Corrosion allowable factor

1. Aug 15, 2015

### doan

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

2. Aug 15, 2015

### SteamKing

Staff Emeritus
Corrosion factor of what?

3. Aug 15, 2015

### doan

Sorry,
I asked about corrosion allowable factor of material, which using to design pressure vessel.
Thanks!
N-Doan

4. Aug 15, 2015

### Staff: Mentor

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.

5. Aug 16, 2015

### doan

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

6. Aug 17, 2015

### Nidum

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 .

7. Aug 17, 2015

### Nidum

8. Aug 18, 2015

### doan

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