34
Tube Products International October 2012
products & developments
Increasing life expectancy of pipelines
Alan Robinson, managing director of
Arc Energy Resources, discusses the
benefits of weld overlay cladding to
protect the internal surfaces of pipe
systems, and reviews the options
available using corrosion resistant
alloys.
Corrosion is the ultimate dirty word,
leading to a waste of precious natural
resources and creating problems for
those entrusted with the containment
and handling of aggressive liquids and
ecologically damaging toxins.
Paints and coatings are readily available
to protect the external surfaces of
piping systems and equipment from the
atmosphere; but what can engineers
do to ensure the integrity of the internal
surfaces and maintain an efficient and
reliable service, when the transported
media can, for chemical or mechanical
reasons, degrade pipes, valves and
other equipment?
In such applications, what techniques
are available to enhance the life of new
plant or refurbish worn or corroded
equipment, and what are the cost
benefits compared to expensive base
materials and/or replacement parts?
Engineers have a number of options
when considering corrosion protection
for the wetted surfaces of a pipeline
system. However, the final solution
will depend in part on an evaluation
of factors such as the presence of
chemically aggressive compounds; the
level of suspended solids, if any, in the
product; the installation deadline; and
budget restraints.
Where budget is not a constraint,
engineers can simply specify
components in corrosion or wear
resistant alloys known to withstand the
specific service conditions. However,
this is rarely the case and other, more
cost-effective options must be sought.
Where standard, off-the-shelf carbon
steel components such as pipe, flanges
or fittings are used, weld overlay cladding
is certainly the most versatile option,
providing the assurance of a heavy-duty
metallurgically bonded protective layer
that will not be undermined or dislodged
in service.
After first identifying the areas within
the system that need to be protected,
and the properties of the medium from
which protection is required, engineers
can choose from a number of welding
processes and a wide range of cladding
alloys. The final choice will depend on the
size and geometry of the components
to be clad and the alloy best suited to
combat the surface degradation.
Even in systems that do not suffer
anything worse than normal aqueous
attack and where pipes are internally
protected by other methods, it is well
worth considering the application of
weld overlay cladding to the system’s
seal areas. For example, on flange seal
faces where mechanical damage may
be caused during construction and
subsequent maintenance activities, a
conventional and inexpensive stainless
steel deposit would be adequate.
Where the medium is more corrosive or
can be variable in content, the use of
either a higher grade stainless steel or
oneof themorecomplexnickel chromium
alloys is normally recommended. Whilst
these may be prohibitively expensive for
use in solid form, a 3mm thick layer on
the affected surface will offer the same
working performance and could lead to
significant savings from the extended
life of the equipment.
Mechanical wear is normally limited to
areas where a directional change of flow
takes place – for example at a bend or
diversion point, or where the medium is
physically propelled by pumping or other
means. In these areas of wear, weld
overlay cladding offers clear advantages
because protection can be applied
specifically to the areas under attack.
The overwhelming advantage of weld
overlay cladding is its versatility.
Whatever the shape or size of the
component there is a process that can
be applied, and whatever the medium,
there is an alloy to counteract its
corrosive or abrasive properties.
Significant developments by equipment
suppliers to improve productivity and
quality have helped to ensure that weld
overlay cladding is now widely accepted
as a versatile and economically viable
process with which to protect pipe
systems against corrosion.
Arc Energy Resources
– UK
6m pipe cladding
Steel pipe from China
Tianjin Nolite Steel Co, Ltd is a manufacturer of ERW, SSAW and LSAW steel
pipe and strip steel. The company supplies high quality petroleum and gas
line pipe, water pipe and construction pipe.
The company’s ERW steel pipes range from 21.3 to 457.2mm
(½" to 18")
o
utside diameter, and 1.5 to 14.27mm wall thickness. SSAW steel pipe is
available in outside diameters from 219.1 to 3,048mm (8" to 120"), with wall
thickness ranging from 5 to 30mm. LSAW steel pipe OD ranges from 219.1
to 1,820mm (8" to 72").
Tianjin Nolite Steel Co can manufacture according to certificates API 5L
PSL2, API 5CT, EN 10217-1, 2, 5, EN 10219-1, and ISO 9001:2008.
Tianjin Nolite Steel Co, Ltd
– China
