TPI November 2015

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56 Tube ProducTs INTerNaTIoNal November 2015
Orbital welding solutions:
offshore umbilicals
Tube production
The process begins with the super-duplex tubing.
A first method consists of joining tubes at least 12m in length
and with an inside diameter ranging from 25.4 to 88.9mm
(1" to 3½"). Following tube end preparation in the workshop,
the tubes are butt welded to form a several-thousand-metre-
long pipe coiled on an enormous spool.
To tackle this job, Polysoude proposes its MU range of
open-head orbital TIG welding equipment with arc voltage
control (AVC) and torch oscillation control (OSC) to produce
a flawless weld seam over the entire thickness. This head is
generally combined with a P6-type power source and a wire
feeder. A PC 300 power source can be selected for particularly
demanding applications in terms of quality and productivity.
It must be emphasised that
only the TIG (GTAW) process
can guarantee the integrity
of the material by controlling
the energy input rate. The
high level of flexibility of
the TIG process lies in the
fact that filler wire speed is
independent of the welding
current.
Obviously qualification of the
welding procedure must meet
quality requirements relating
to the weld and continuity in
the mechanical and physical
I n the field of offshore oil exploration, vital links between
the platform or FPSO units and the seabed equipment are
provided by umbilical cables. Understandably, these key
components must offer impeccable quality and flawless
reliability.
Umbilical cables – or ‘umbilicals’ – are assemblies
consisting of duplex, super-duplex or even hyper-duplex
steel tubes, electric wiring harnesses, hoses and fibre-optic
cables bundled together in a steel tube with a protective
polyethylene casing. The final outside diameter ranges
from 75 to 300mm.
Umbilicals supply the electrical and hydraulic power
required by the control functions of the wellhead, subsea
wellhead equipment and manifold. They are also used for
injecting chemicals designed to improve fluidity or eliminate
the formation of scale and hydrates in the production
stream. Two-way communication or data transfer between
several platforms and the subsea installations is also
conducted via umbilicals.
Numerous items of Polysoude equipment are used at the
various stages of umbilical construction, from the assembly
of tubes coiled on spools to the assembly of connectors
joining the umbilicals to the equipment. Once in position
on the seabed, especially in very deep water, they are
practically impossible to repair. Quality is therefore a crucial
requirement, and the customer and the manufacturer must
have total confidence in the manufacturing process.
Spool of butt-welded umbilical
cable tubing
Library of
qualified
welding
procedures
Quality assurance with parameter monitoring and storage