WELDING
A pump manufacturer that set up its own
cleanroom for sensitive welding processes has
had 98.82% of 339 welding joints pass strict
inspection for integrity and surface contamination
I n June 2016, the operator of a
sulphur recovery plant in the
United Arab Emirates asked
the experts at LEWA Nikkiso
Middle East for 13 chemical
injection packages. One of the
packages presented a particular
challenge: it was intended for
pumping sodium hypochlorite
solution at a temperature of
85 °C, a highly corrosive fluid,
which meant that wetted parts
had to be manufactured from
titanium.
Based on the stringent
specifications of the customer,
the subsidiary of the Germanbased
LEWA GmbH decided
to build its own climatecontrolled
45 m² clean room
to create an appropriate
environment for titanium
welding. All relevant welding
parameters such as current,
gas flow rate and temperature
were jointly tested and adjusted
by in-house welding engineers
and appointed welders to
meet all requirements. The
customer wanted to ensure
the quality and longevity of
all welding joints. This was
done by adding an extra
requirement that a careful
visual inspection be carried out
after each welding joint was
completed. Special attention
was paid to prevent potential
surface contamination in the
heat-affected zones. 98.82
percent of all welding joints
passed the rigorous visual and
radiographic inspections. The
titanium chemical injection
package was successfully
accepted and delivered in
January 2019.
The chemical injection
package designed and built for
pumping sodium hypochlorite
(NaClO) solution was delivered
by LEWA Nikkiso Middle East
Welding clea
to Zirku Island in the United
Arab Emirates. It was part of
an order that included a total
of 13 injection packages. The
two-compartment sodium
hypochlorite tank was made
of fibreglass-reinforced plastic
(FRP). All other wetted parts
were made from corrosionresistant
titanium material.
This material is especially wellsuited
for the pumped fluid
at the design temperature of
85 °C. In addition to two API
675-compliant NaClO dosing
pumps, the package is fully
equipped with titanium valves,
strainers and a complete set of
instruments.
These pumps are
hydraulically-actuated
diaphragm metering pumps
of the type Ecoflow LDC1
from LEWA. Thanks to their
robust design and the resulting
longevity, they can be used for
difficult application conditions
and fluids. Moreover, the
pumps are hermetically tight
to ensure safe handling of
hazardous fluids. “For the
project in the United Arab
Emirates, we made the wetted
parts – such as the pump heads
and piping – out of titanium, to
further increase the resistance
of the units,” explains Senthil
Nathan, Project Manager at
LEWA Nikisso Middle East.
The material used for piping is
titanium material (Grade 2), in
total 58 meters of pipe ranging
from ½ to 2 inches diameter
with 339 welded joints have
been completed.
Manufacturing the piping
system from titanium was the
biggest challenge involved
in this project. “Welding
titanium is very different from
welding any other material,”
explains Nathan. “During the
welding process, the material
is extremely sensitive to
surrounding conditions, in
particular to temperature and
cleanliness. In addition, the
necessary inert gas atmosphere
around the welding point is
very specific and requires
constant attention in order
to obtain a satisfactory
result.” However, the German
pump manufacturer and
system integrator LEWA had
already gained the necessary
28 Issue 2 2020