ASSET INTEGRITY AND CORROSION MANAGEMENT

1. A LIFE CYCLE APPROACH TO
CORROSION MANAGEMENT AND ASSET INTEGRITY.
A case study on steel fabrications in oil and gas service.
Esegine Okeme. A
esegine_okeme@yahoo.com
ABSTRACT
Over the years industrialization and the need to satisfy wants has necessitated the
conceptualization and engineering of systems and processes to achieve pre-determined goals.
The chemical and process industry has not been left behind. A lot of items (fluids, chemicals,
metals, stones etc) are found in nature and may require processes to be engineered to transform
them from the way they occur naturally into phases and forms in which they can meet certain
needs, attain certain performance objectives or conform to certain safety and regulatory
standards. These processes are carried out within pipes, vessels, fractionating columns, kettles,
heat exchanger etc as required. In most cases, the aim of the process, which may be heating,
cooling, extraction, separation etc, is usually of so much importance that all efforts are targeted
towards the success of the process.
INTRODUCTION
Corrosion, material degradation and various
damage mechanisms would affect the
Integrity and consequently the reliability of
the facility (pipes and equipment’s) as a result
of the process being supported. The
unfortunate thing about corrosion is its
autocatalytic nature, once corrosion
commences then that is it. In practice, the best
way to prevent the spread of corrosion is to
prevent it from starting at all! Given the cost
of engineering, procurement and construction
of process installations, the ultimate
successful facility is one that remains in the
intended service for as long as possible. Re-
engineering the process is a viable option for
optimizing and exploring economic
alternatives to achieve process objectives
while ensuring the integrity and longer service
life of installed facilities. The global cost of
corrosion is in the region of USD 5bn
(NACE). How is the cost of corrosion really
computed and how can this be validated?
Practically, the cost of corrosion is the sum of
the cost of coating, corrosion monitoring,
Cathodic protection, corrosion inhibition,
water treatment and all other corrosion
preventive activities and the cost of
rehabilitation, shut down and asset failure. To
buttress the effect of corrosion corroded
specimens of bolts/nuts and angle bars were
taken from a turnaround maintenance site for
yield and tensile strength testing along with
new components of the same material
specification for comparism. The reduction in
the load applied before failure (pressure
withstanding strength) of the members give an

2. idea of how corrosion can compromise the pressure retaining capability of the member.
Members 65 x 65 x 6mm Angle bars 16M bolts
Strength of new un-corroded
member YS 335.24 N/mm²
UTS 431.99 N/mm²
YS 601.02 N/mm ²
UTS 801.37 N/mm²
Strength of corroded member
YS 280.33N/mm²
UTS 373.77 N/mm²
YS 565.44 N/mm²
UTS 753.21 N/mm²
Application
Roof hand rails for tanks,
stiffening rings for tanks,
stiffeners for pressure vessel,
supports for pipes and small
vessels etc
Bolting and flange
connection
Mitigation proper blasting and painting use galvanized bolts
THE BELOW ARE RECOMMENDABLE LIFE CYCLE SOLUTIONS TO CORROSION
AND INTEGRITY RELATED ISSUES.
1. DESIGN
The design of an asset is one of the most critical
phases in the life of the asset. Over time, project/
construction/ inspection engineers have found
out that brown field expansion, rehabilitation,
de-bottle necking and tie-in projects especially
where there no pre-designed tie-in and expansion
provisions are the most critical type of projects
safety wise. Major operational plant issues if
envisaged at the time of the design are easier to
execute when the need arises. Design flaws like
a Tower with less than optimal amount of trays
resulting in condensate leaving with high
concentration in the outgoing stream, lack of
High and low points for pipelines, line size too
small for flow conditions, Dead legs within
piping configurations, elbows over 5 – 7 D
bends at directional change for pipelines, lack of
drain points for tank foundations etc.

3. 2. MATERIAL SELECTION AND
METALLURGY
Most people think asset management and
corrosion control measures are largely
implemented at the in-service stage.
Contrarily, these phenomenal are best
controlled at the asset conception and
material selection phase. The material has to
be selected in view of the process that the
asset would support. As a rule of thumb,
materials with carbon content above 3% are
not advised for welded and pressure
retaining fabrications. For high temperature
process, it is best chromium-Molybdenum
(chro-Mo) materials are specified. For
corrosive services, chromium content of the
steel would be important. For low
temperature services, steel specifications
with high level in Nickel (NI) contents are
recommended. Over time, ASTM A 36
(Structural steel) has been widely used for
construction of above ground storage tanks
which may either be in crude, refined
product or even potable water service. For
pressure vessels, A516 Gr 60 or 70 has been
widely used with global acceptability. This
is not to mean engineering design should not
be carried out for the above said type of
assets. Before commencement of
construction, the steel MTC and factory
quality documents has to be checked and
confirmed that the steel materials supplied
steels meets project specifications.
Cleanliness (no inclusion) and uniformity
(no laminations) of supplied material are
also essential.
3. CONSTRUCTION
During construction, welding process and
welding procedures are a good medium to
control some process induced damage
mechanisms. Low hydrogen processes
(SMAW and TIG) are the most
recommended for oil and gas fabrication.
Electrode selection also pays and important
role. Low hydrogen electrodes (E 7018 etc)
are specified over rutile and cellulosic
electrodes. Although same strength can be
achieved with any type of
Electrode, the low hydrogen advantage reduces
the risk of HICC. When cellulosic electrodes
(stove piping) are used for pipeline
construction, heating has to be introduced (pre
heating and post weld heat treatment) and this
complicates the construction procedure. For
lower strength materials, one can be a bit
careless with the construction however with
high strength low alloy steel (HSLA) a little
more restraint has to be exercised during
construction. With X65, X72 and above,
random tacks and arc striking are outlawed.
The fast cooling of these misdemeanors
increases localized hardening and maybe
cracking which should be excavated, MT’d,
appropriate electrode filled and ground flushed
at the minimum. This is a key consideration
because the weld seams are the main areas of
focus during welding inspection. Most facility
owners, especially at the management level

4. always have the impression that painting
campaigns are for aesthetic and branding
purposes. On the contrary, coating is as
important an asset integrity management
activity as any other. A precursor to painting
which is the blasting and painting has to be
done to specification (Swedish standards)
before coating. The 3 coat system which is a
zinc rich primer, and intermediate MIO and 2
coats of the poly Utherane top coat has proven
to be adequate for marine locations.
4. OPERATIONS
For any process facility, an operating
envelope has to be established. With time
over the operating life of the asset, this may
be revised to accommodate prevailing
conditions. The envelope specifies critical
parameters within which the asset should
operate. Adhering to pre-determined
operating upper and lower temperature
limits, flow velocity, pressure range, various
stream concentrations, water and/or feed
quality etc are very important to asset life.
Operating outside of specified window may
lead to increased corrosion, increased
vibration, and un-reliability among other
things. In power plants, refineries and other
asset in which a boiler is intricate to
operation, water quality has to be monitored.
The demineralization and treatment process
if handled with laxity can result in system
inefficiencies in processes where a phase
change (liquid to steam) would cause
concentration of impurities. The effect of
this is frequent exchanger fouling, scaling
within the tubes, particle impingement on
turbine blades etc. Processes rich with
Hydroxide (OH) compounds, wet
H2S/aqueous solutions, Sulphur, Hydrogen,
dissolved O2 and CO2, chlorides etc are to
be monitored for various damage
mechanisms. Equipment’s and piping
systems with operating windows where heat
transfer conditions allows for concentration
and precipitation are to be subjected to a
special inspection plan.
5. ASSET MANAGEMENT
My approach to asset management is a
sequence I would call Inspection, Integrity
and reliability (IIR). Inspection and
condition monitoring would answer the
question what is the status of the equipment
at the moment. This may require some NDT
procedures to be carried and the equipments
may be on or off stream. Integrity answers
the question is the equipment safely operate
given the specified operating window.
Reliability answers the question for how
long would the equipment remain in safe
operation if the operating envelope is not
changed. The concepts explained above are
high level summaries. The parameters that
define the asset management approach to be
adopted are the type of asset and the process
that the asset supports. Insulated piping
systems are at a CUI risk unlike exposed
configurations. Some process fluid requires

5. more attention than others. Intervals, asset
location (Marine, industrial, rural), type and
extent of inspection are detailed in API 570
for piping systems, API 510 for pressure
vessels and API 653 for Above ground
storage Tanks. Cathodic protection
monitoring should also be in the mix. With
proper inspection programs where
degradation indicators are properly
identified and monitored, the service life of
assets can be extended reasonably
SUMMARY AND CONCLUSION.
From design to quality construction management, routine inspection and properly executed
shutdowns, the success of any mechanical integrity or asset management program is the
acknowledgement of its administrators that adopting a life cycle approach gives the asset a better
shot at reliability. Reliability is the degree to which an asset would give a consistent response for
a given operating condition. The asset integrity team should comprise of individuals with a rich
mechanical and chemical/process engineering background and an in-depth knowledge of the
operating process. For an asset integrity engineer to properly manage an asset, design implication
on operation and expansion, damage mechanism identification, degradation indicators, remaining
life calculations, validating inspection intervals, documentation etc are soft skills that should be
at his fingertips.
REFERENCES
1. H.-P. Berg corrosion mechanisms and their consequences for nuclear power plants with light water reactors.
R&RATA # 4 (Vol. 2) 2009 December
2. Viswanathan, R. and Stringer, J., 2000, Failure Mechanisms of High Temperature Components in
Power Plants, ASME, J. of Engg. Materials and Technology, 122, July 2000.
3. BS 4449:1998 BS stansdard for testing steel plate sheet strip
4. National Accociation of Corrosion Engineers United states cost of corrosion study 2002