Due to a very large flow passage DAFRAM control ball valves can grant high flow coefficients compared to other valve types. Thanks to their operating principle, quarter-turn ball valves are able to control fluid flow at very small openings and to open at high differential pressure. They are also able to maintain low fluid velocity thus lower noise and vibration to the pipeline. In addition, control ball valves allow tight and fast shut-off in case of emergency.
DAFRAM control ball valves assure excellent flow characteristic and provide accurate, reliable control in a wide range of applications, such as chemical, power and oil, both on gas and liquid service.
MAIN STANDARD FEATURES
High capacity (Cv)
The unrestricted flow passage in fully open position provides high Cv combined with relatively small overall dimensions and light weight compared to the same size globe valves: a given size ball valve can grant a Cv coefficient even three times greater than a same size globe valve. This ensures a smaller and lighter valve, a smaller and lighter actuator, smaller pipeline supports and overall a money-saving application compared to standard linear valve solutions.
High rangeability, characterization and precise modulation are granted thanks to trim special design. The DAFRAM valves inherent rangeability is kept between the acceptance limits stated in IEC 60534 specification by means of CFD calculation and lab testing based on customers specification and flow conditions.
When required, tight shut-off is obtained thanks to the well experienced on-off design (spring-loaded, pressure assisted floating seats with trunnion mounted ball) against any differential pressures, from very low to extremely high levels. Outstanding tightness capability is granted also when metal seats are required. For trunnion mounted valves the double block and bleed features is a DAFRAM standard, allowing cavity draining and basic maintenance operations. On request seats double sealing configuration is available.
Special design for sensitive control
Spring loaded seats design assures scraping action and continuous contact between seat and ball: dirty fluids do not stick and jam on the ball surface. Trunnion construction and special low-friction bearings assure low operating torque. So a smooth fluid control is assured for the whole valve service life.
Body construction, special design for stem and actuator connections eliminate free-play (backlash) and assure great resistance even against piping forces.
Low emission stem packing
Special design of stem sealing assures low emission performance to meet Fugitive Emission and “TA-Luft” requirements. Advanced solution have also been developed when very low emission levels are required (i.e. ISO 15848 rate A)
Fast operating time
Quarter turn design allows to use fast actuating devices which can perform emergency operation in a few second to improve the safety of the plant.
DAFRAM control ball valves can be supplied with API6FA, API 607 and BS 6755 part 2. Fire safe test certificates are available on request.
Adjustable stem packing
In order to improve the life time of stem sealings DAFRAM can provide adjustable packing to meet the most stringent requirements during the whole valve service time. Stem packings are available in PTFE, RPTFE and expanded graphite.
Customized seal arrangements
DAFRAM can provide different sealing systems both for static and dynamic application according to customer’s specifications.
Grease injection fittings
If necessary ball, seats and stem sealing can be equipped with grease injections systems to reach the maximum service life. The same system may be used for emergency sealant injection to restore proper tightness and avoid emissions to the environment if damage occurs on the sealing surfaces.