TPi March 2016

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March 2016 Tube Products International 39
products & developments
Ultrasonic • High Pressure • Steam
Tube, Wire, Strip & Cable Cleaning Systems
GEO-REINIGUNGSTECHNIK GmbH
Mechanical Cleaning
with Textiles or Brushes
Dry or Liquid Supported Cleaning
Wire, Cable, Tube
WIRE 2016
11/A32
booth
Dual-function valves
Among zero-leakage valves for open/
close function, triple eccentric butterfly
valves are on the rise. This type of
construction can provide advantages
that include 100 per cent zero leakage,
compactness, easy and frictionless
functioning, and long maintenance-free
operation.
For fixed limits, triple eccentric butterfly
valves can be used for control and/
or throttling applications. To extend
the range and create an efficient high-
performance control valve, Zwick and
Yeary Controls developed the Tri-Shark
triple offset butterfly valve.
In collaboration with Yeary Controls,
Zwick developed the patented
Sharktooth throttling trim cartridge,
which is used to turn the triple offset
butterfly valves into control valves. This
revised design is claimed to be equal
in control performance to a globe valve
or rotary plug valve, while incorporating
better shut-off capabilities. By
combining the Sharktooth throttling trim
cartridge with the Tri-Con triple offset
butterfly valve series, Zwick created
the Tri-Shark zero-leakage shut-off and
control triple offset butterfly valve.
This control valve combines the benefits
of a triple eccentric butterfly valve
with the special qualities of a control
valve, enabling just one style of valve
to be used for both on-off and control
applications. The throttling trim
cartridge is close to the pivoting motion
of the valve’s disc to keep the flow
between disc and cartridge as low as
possible. The cartridge is manufactured
with multiple optimised slots that divide
the flow and clear an exact calculated
cross section while opening or closing
the valve.
With the throttling trim cartridge, the
valve’s flow is changed to an equal
percentage flow, which is a preferred
inherent flow characteristic for many
control applications. Tri-Shark’s flow
characteristic ensures that the valve
is able to provide an effective control
range at 5° to 30° of travel – the control
area where traditional triple eccentric
butterfly valves seem to reach their
limits. Typical butterfly valves have good
control limits between 30° and 70° of
travel. Tri-Shark valves extend this range
through the throttling trim cartridge.
Further advantages of Tri-Shark valves
are anti-cavitation properties. The flow
is divided through the slots and reduces
cavitation, because the occurring steam
bubbles in the cartridges slots’ area
reach a smaller dimension by the smaller
flow rate of each channel. Therefore the
occurring energy is less when the steam
bubbles implode.
Especially at small opening angels, Tri-
Shark valves are able to conduct water
jets concentric to the pipeline’s centre,
converting kinetic energy to a smaller
level in fluid prior to contacting the pipe
wall. This can reduce the occurrence of
damage, eg at the pipe wall.
As the mass flow is divided into smaller
parts through Sharktooth’s throttling
slots the sound frequency rises, and
the sound can be absorbed more
easily through the pipeline because the
frequency is in a region where human
ears will notice it less.
Another important aspect of the throttling
trim cartridge is that the dynamic torque
is reduced by the changed pressure
field. At critical opening angles and flow
conditions with regards to the occurring
dynamic torque, a smaller actuator with
less torque can be used.
Tri-Shark can be supplied in different
types. In addition to the standard lug-
type design and Sharktooth (DN900),
integrated versions such as double
flange (DN200) and valves with butt
weld ends (DN800, DN700 Trim) are
available.
Zwick Armaturen GmbH – Germany
Sharktooth disc clearance
Butt weld Tri-Shark