Corrosion allowance with FBE lining water pipe
Corrosion allowance with FBE lining water pipe
(OP)
We need to guarantee a service life of 50+ years for carbon steel water pipe carrying potable water. Specification is Fusion Bonded Epoxy lining plus a corrosion allowance.
Are we likely to get localised failure of the FBE and deep pitting corrosion, perhaps causing penetration, of the pipe wall or can we anticipate local failure of the FBE will result in undercutting and relatively large area corrosion ?
Are we likely to get localised failure of the FBE and deep pitting corrosion, perhaps causing penetration, of the pipe wall or can we anticipate local failure of the FBE will result in undercutting and relatively large area corrosion ?





RE: Corrosion allowance with FBE lining water pipe
gr2vessels
RE: Corrosion allowance with FBE lining water pipe
RE: Corrosion allowance with FBE lining water pipe
On a previous project for the same client FBE plus a 3mm corrosion allowance was used. The 50 year life is total life. There is no residual value. The pipe can collapse at 50.1 years.
The question is does the corrosion allowance have any value.
Brian
RE: Corrosion allowance with FBE lining water pipe
Personally, I am sceptical of the above assessment and I prefer engineering judgement. In reality, the internal and external linig and cathodic protection will only minimize the corrosion and the piping break down.
I would start estimating a corrosion rate for the un-lined pipe, calculate for 50 years and add some percentage for unknown conditions. Add this to the pipe minimum thickness as corrosion allowwance, select the next up pipe schedule. Then provide the best corrosion protection (internal/external) for your pipe and work out some thickness monitoring system for the next 10 - 15 years, in order to have an idea of how the system works and maintains it's integrity.
However, as you mentioned, 3 mm corrosion allowance is a symbolic inclusion, rather than engineering calculation, hence no real value, unles confirmed by corrosion rate estimates as per above.
cheers,
gr2vessels
RE: Corrosion allowance with FBE lining water pipe