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ZWICK TRIPLE OFFSET VALVES FOR MOLTEN SULPHUR & SULPHUR TAIL GAS
Product News Wednesday, June 5, 2019: Valve & Automation (Pty) Ltd
Molten Sulphur or Sulphur Tail gas applications have many challenges. If you work with this media, 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.
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 Zwick 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.
- Triple offset 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 88” (DN50 to DN2200)
- 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”