Page 518 - Corrosion Engineering Principles and Practice

484 C h a p t e r 1 2 C o r r o s i o n a s a R i s k 485

Management information is typically required on predicted costs of
problems, the risks involved, the remaining life of the affected
equipment and what can be done to improve or eradicate these
problems.
The KPIs described in the following sections were developed
specifically to estimate the effect of corrosion on the technical and
financial performance of assets involved in oil and gas production
facilities and to address the performance of particular critical
corrosion-related systems [8]. The same approach can be generalized
and adapted to many other high-risk systems.

12.4.1 Cost of Corrosion Key Performance Indicator
The cost of corrosion KPI allows converting the amount of corrosion
damage sustained during a given period into a monetary figure in
order to provide a clearer focus on corrosion management
performance. Factors considered within this KPI are existing damage
sustained prior to the period in question, the cost of repair or
replacement, and the remaining service life of plant. Performance can
then be computed in terms of the cost of damage in the last period
examined, the annual damage cost, and/or life-cycle costs. The cost
of corrosion damage (C corr ) sustained in a given period can be derived
with the following Eq. (12.2):

 N ⋅ R   D 
p
C corr =  C FL cost    365   (12.2)
   
where C corr is cost of corrosion damage in a specific time period
N is estimated number of replacement cycles to end of
C
service life
R cost is replacement cost (including lost product cost)
FL is required remaining field life (years)
D is days in monitoring period (days)
p
If, however, the calculated remaining life of a component (RL ) as
C
defined in Eq. (12.4) is greater than the field life (FL), C corr can be
assumed to be zero. This is based on the assumption that the KPI is a
performance indicator reflecting the effect on operating costs (Opex)
and does not consider depreciation against the initial capital cost
(Capex). The number of replacement cycles (N ) can be estimated
C
with Eq. (12.3):
  FL − RL C 
N = 1 +   RL  (12.3)

C

 R 