Leak-free stem seal. Primary sealing to atmosphere by multi-walled metal bellows welded to the stem. Secondary sealing to atmosphere by multiple packing rings made of graphite. Double graphite gaskets between body and bonnet (single-piece upper valve section), or between bonnet and yoke (two-piece upper valve section). Reliable sealing of body-bonnet joint: Gaskets are fitted above and below the end fitting of the bellows assembly. The lower gasket is confined by the body shoulder and the end fitting of the bellows, resulting in a longer service life. No direct contact with fluid handled. The upper gasket serves as a back-up seal preventing fluid from leaking into the atmosphere in the event of a bellows failure. Longer service life of bellows. Multi-walled bellows designed to withstand 1.5 times the nominal pressure. Positive anti-rotation device prevents bellows from twisting. Travel stop prevents excessive compression of bellows On large valve sizes the bellows is positioned well outside the flow path and thus not exposed to abrupt changes in fluid pressure. Guided valve disc (on large valve sizes) prevents bellows vibrations. Ease of service without additional cost. No cost for daily or frequent maintenance work thanks to reliable bellows seal If required, a leakage detection hole can be provided in the gland packing area. Operating reliability. Travel stop prevents valve damage caused by excessive actuating forces. Position indicator for identification of valve disc position.