TPi July 2009

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July 2009 Tube Products International 45
ConnectorsFi t t ings , Flanges &
Centring and clamping side of a Premium ▼ ▼
Coupling
means that the coupling has a clamping
side and a centring side. When two
pipes run together, the upcoming pipe-
end is automatically caught and lined up
by conical centring rolls.
The Standard Coupling has a three-point
clamping system that consists of two
fixed support feet and one adjustable
clamping foot. The adjustable foot
bridges thermal expansion and ensures
strong clamping inside the pipe. In
tests and later experience the Standard
Model performed well with smaller
diameters up to Ø 30" and under normal
circumstances.
The following circumstances demand
better performance of the coupling: large
diameters (higher pipe-weights); thin
wall thicknesses (risk of deformation);
oval pipes; curved pipes; worn out or
uneven support rolls; high velocities
of rotation; and high friction forces
between pipes.
To improve performance in these harsher
circumstances, the Advanced Coupling
was developed. This coupling has a
five point clamping system instead of
three, and all five clamping feet move
simultaneously. This ensures perfect
centring, stronger clamping and less
deformation of the pipe. For an even
stronger fixing inside the pipe-end, the
clamping feet can be covered with a heat
isolating material that also increases the
friction factor between the clamping
feet and the pipe surface.
On the centring side of the Advanced
Coupling, there is a pre-centring ring
with extra rolls that take the first blows
when the pipes are running towards
each other. Because of the extra ring
the construction of the coupling is
much stronger and the extra rolls can
handle larger radial movements of the
pipes.
Technically the Advanced Coupling
performs well, but there is one
disadvantage. For different wall
thicknesses the clamping side can be
adjusted very easily, but on the centring
side the rolls need to be exchanged
or re-positioned. This is not only time
consuming, but there is also an extra
risk of human error. The wrong rolls can
be mounted on the coupling, or rolls can
be mounted in the wrong position. To
solve this issue the Premium Coupling
was developed. This coupling is
equipped with a new clamping system
that centres both the clamping side and
the centring side of the coupling at the
same time. When force is applied on
the central screw, five clamping feet
and centring rolls automatically expand
and force themselves against the inner
pipe wall.
The Premium Coupling can clamp on
only 25mm of pipe surface, taking into
account the cutback of an internal
flowcoat. The coupling combines all
advantages in one solution and is the
result of experience with many different
coating processes worldwide.
Dhatec BV – The Netherlands
Premium Coupling with movable centring S S
rolls
Advanced Coupling inside a pipe-end S S