130 www.stauff.com/6/en/#130 G Sealing Variations Two-Way Ball Valves (Type LBV) This valve has a floating ball. The ball seats act as bearing seats for the ball. Sealing is achieved by the ball being pushed against the downstream seal due to the pressure p1at . Without pressure the sealing is guaranteed by the preloading of the sealing elements. This valve has a trunnion ball. The sealing element seals from the upsteam side. The sealing is guaranteed under all pressure conditions. It is achieved by the sealing element being forced against the ball. X3:1 Multi-Way Ball Valves Three-Way Ball Valves (Type CBVL) The selector ball valve has 2 seats and a floating ball. If the shut-off port is pressurised and p1 is higher than p2, then the ball is being forced against the opposite sealing element. A gap forms and the ball valve is leaking. p1 p2 p1 p2 p1 p2 Three-Way Ball Valves (Type CBVSL) p1 p2 Gap X3:1 The selector ball valve has 2 front side sealing seats and a floating ball. p1 > p2 Due to the forming of the ring surface „f1“ and the pressure (p1-p2) the left sealing element will be forced against the ball and consequently the sealing is achieved. The „floating“ ball moves against the right sealing surface - the ball valve remains sealed. Pressure inlet possible from all ports! Must be operated without pressure! Gap X3:1 p1 < p2 Due to the ring surface „f2“ and the pressure (p2-p1) the right sealing element will also be forced against the ball and consequently the sealing is achieved. The „floating“ ball moves against the left sealing surface - the ball valve remains sealed. Pressure inlet possible from all ports! Must be operated without pressure! p1 p2 Special Protected Seats For compressible and abrasive media special protected seats are utilised. During the first part opening of the ball valve, standard plastic seats are located unprotected in the critical cross sectional area. During gas applications and with all kinds of compressive media this narrowest cross section can result in a very high flow rate that cause erosion of the seats. If media contain solids, for example paint, the abrasion risk in the first opening section is extremely high. Ball valves with standard seats can quickly become inoperative. For this application, STAUFF has designed a sealing version with erosion protection ring. This ring is made of special material and keeps the high flow forces and the abrasive solids away from the plastic seals. Tests and long term experience with this application have shown that ball valves with this sealing system provide substantially improved life times. Times of non-use as well as maintenance and repair times are therefore reduced. A further increase of the lifetime is possible by using metal seating elements. The ring is made of special material and protects the seats against erosion. Catalogue 6 § Edition 06/2024 Technical Appendix
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