TPT July 2011

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78 July 2011 ›
Technology Update
Orbital tube-
to-tubesheet
welding
AXTON Incorporated, located near
Vancouver, Canada, has been
manufacturing heat exchangers and other
industrial equipment since the 1980s.
Its list of projects includes the
structural engineering and fabrication of
the Vancouver 2010 Cauldron for the
Vancouver 2010 Olympic Games. Axton
was restructured in 2002-2003 and at
that time the owners decided to update
some of their operations. After careful
consideration they purchased a Model
227 orbital welding power supply and
Model 6 orbital tube-to-tubesheet weld
head from Arc Machines Inc in California,
USA. Although orbital welding is generally
considered to be welding of tube or pipe,
orbital welding is defined as “machine
or automatic welding in which the arc
rotates around a stationary weld joint”
and this includes orbital tube-to-tubesheet
welding.
While the company had some previous
experience with orbital welding, they
gladly accepted the opportunity to refresh
their skills by having an AMI factory
trainer come to their facility to train their
lead welders.
Axton is a truly international company
that exports a significant amount of
their production to countries outside of
Canada including Mexico, Africa and
others worldwide. Industries served
include mining, oil and gas, chemical,
acid manufacture, petrochemical, power,
transportation and pulp and paper.
They are currently fabricating a large
stainless steel exchanger for export.
The tubesheet on this unit has 990
tubes 1¾" (44.45mm) diameter with a wall
thickness of 0.084" (2.1mm). The vessel
is 50ft (15.24m) long and 140" (3.55m) in
diameter with tubesheets on both ends.
The model 227 weld power supply is
microprocessor controlled and stores weld
programs, or schedules, consisting of all
the programmable weld parameters in the
power supply memory. The operator enters
the program each time the power supply is
turned on. The weld schedule specifies
primary and background amperage, travel
speed (rotation), pulse times, wire feed
speed and other parameters. Thus, if
other factors such as tube end preparation,
cleanliness and purge flow are constant,
there is a very high degree of repeatability
from weld to weld.
The weld head features a chill follower
linked mechanically to the torch that is
spring loaded to the ID of the tube. This
causes the torch to maintain a constant
distance from the tube OD even when
there is some degree of ovality in the
tubes. The chill follower as well as the
entire torch block is water cooled, which
removes heat from the ID of the tube. This
allows the application of additional heat
to the weld resulting in better penetration
without melting through the tubes. The
power supply’s arc gap control (AVC)
enables the torch to maintain a constant
distance between the tungsten electrode
and the weld joint. The welding operator
may make small changes in the AVC
setting during the day to adjust for changes
in ambient temperature or humidity.
Axton Incorporated – Canada
Email:
Website:
Acid fume extraction system
ARVIND Anticor Ltd manufactures and
exports industrial fume extraction systems
and fume gas exhaust systems. Anticor ‘FES’
is designed to offer the highest collection or
removal efficiency. All equipment is fabricated
using quality thermoplastics and fibreglass.
The company’s services cover
conceptualisation to design, selection
of anti-corrosive plastics materials for
construction, manufacture, procurement of
purchased items such as pumps, motors,
instrumentation and control, supply,
erection, commissioning and handing over
with guarantees for quality and integrity of
the supplies and performance of the system
conforming to specified parameters.
The most important basis for calculations
is the determination of the exhaust air volume
with fume capture and the resistance and
losses of air. Process tanks have inbuilt fume
exhaust slot incremental duct section to have
uniform exhaust all over the length, thus
creating a fumeless atmosphere near the
tank. The fume extraction system is offered
with scrubber facility. The exhaust system
meets all regulatory environment standards,
and the system is suitable for pickling mild
steel, stainless steel and other non-ferrous
tubes and pipes.
The fume extraction plants can be used
not only in encapsulated pre-treatment
plants but also for lateral suction channels
on pickling tanks as well as process tanks.
Arvind Anticor Ltd – India
Website: