African Petrochemicals- 16.1 2019

ZWICK FOR MOLTEN SULPHUR OR SULPHUR TAIL GAS
If you work with Molten Sulphur or Sulphur Tail gas, please take time to read more.
Design engineers at Zwick in Germany have looked at solving on-going problems being
experienced with valves on sulphur units.
Typical valve problems on large bore line sizes range from seizing of the packing to severe
seat damage when valve need to be operated after long periods of time of inactivity.
Valves should be specified as steam jacketed valves as this is a standard mandatory type of
valve requirement.
Generally a standard valve may be suitable in an ideal line were
there are never any shutdowns or upset conditions as once the
valves body temperature has reached that of the hot sulphur or
tail gas passing through it will not allow for any solidification,
however in an upset condition were the valve body cools down
with sulphur cooling also, then this will solidify in the bearing /
shaft areas which will consequently generate a seizure of these
elements.
Based on international experience, Zwick engineers recommend the use
of steam jacketed valves as these would maintain the critical areas under a
constant temperature, thus eliminating any potential seizure.
Zwick are capable of supplying valves in both wafer and double flanged style
with steam jackets, and we can also apply a steam traced trim (stem and disc).
Zwick Tri-Con series valves come with bearing protectors, which
reduce the ingress of the medium into the critical areas, which
coupled with the bearing flush purge ports constitute a true
cleansing and protection of these critical areas.
The following explanation highlights the technical differences
between the Zwick Tri-Con valve and other manufacturers of valves ranging
from double eccentric to unjacketed valves which will fail in this type of application.
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The Zwick Tri-Con series valve is a specially designed process isolation, on/off and control
valve, which has a wide range of application uses limited only by that of the actual
materials used, in fact Zwick manufacture valves for applications which range from -196ºC
up to +815ºC. Valves can be manufactured in any machinable form of alloy available on
the market for specific client requirements.
The Zwick Tri-Con series valve is a triple offset valve with true cone in cone design which
totally eliminates any rubbing of the seats, hence eliminates any wear and tear which
would generate leakages across the seat, this is technically not possible for other typical
high performance valves, which means it is limited to a double eccentric design, rubbing
sealing in the last 15-18º which will generate leakage as the time goes by.
The other standard double eccentric are not designed for these severe applications
therefore any attempt to use it for particular process applications may result in a
problematic outcome.
Self Centering disc
With it’s unique self centering temperature compensating disc, the Tri-Con series
construction guarantees the optimal position of the laminated seal against the seat.
Jamming due to thermal expansion is therefore eliminated.
The torque transmission with keys
The disc is keyed to the shaft and not pinned, providing equal torque transmission and
eliminating the danger of pins sheering off.
Ideal lamination and disc design
The strong disc with it’s elliptical supporting surface offers the best fixing of the
lamination. The zero leakage is achieved by the special machining of thre lamination.
Supporting bearing bushing
The optimal position of the bearing reduces the bending of the shaft. This guarantees
bi-directional tightness under maximum pressure.
General characteristics
• Triple eccentric design
• Metal seating
• Zero leakage
• Pressure classes
• Full bi-directional shutoff tp
API & DIN, ZERO Leakage
• Temperature range -196ºC up
to +815ºC
• Size range 2” to 72” (DN50 to
DN1800)
• Friction free opening and
closing
• Vacuum tight
• Laminated seal and seat made
of stainless steel
• Anti blow-out shaft to API 609
• Steel casting, stainless steel
and special alloys
• Fire-safe acc. To BD 6755 and
API 607 for both flow directions
• Fugitive emission control acc.
To “TA-Luft II”