Double seat valve with cleanable seats

A double seat valve with cleanable seats, with two closure members (4, 5) mounted in series and movable relative to each other which prevent overflow of fluids from one valve housing element (1, 2) to another (2, 1) when the valve is in the closed position, which delimit in both the closed and the open position a leakage cavity (11) between the closure numbers, the leakage cavity being connected to the vicinity of the valve by way of a tubular shaft (4e;

• 5c) connected to one of the closure members (4, 5), a first of the closure members (4) being in the form a slide valve piston with an end section provided with radial sealing agents (6, 7) being received, when the valve is in the closed positions so as to effect sealing in a cylindrical valve seat surface (3a) of a connecting hole (3, 3a*) joining the valve housing elements (1, 2) and being received during its opening movement so as to effect sealing in a recess (9) provided in a second of the closure members (5) in alignment with the cylindrical valve seat surface (3a) before the second closure member (5) is also transferred to the open position by the first closure member (4), and with each of the closure members (4, 5) being transferrable independently of the other closure member to a seat cleaning position for the purpose of rinsing of its seat surfaces (3a, 3b) by a partial valve stroke of the width of a gap, characterized in that
• the end section of the slide valve piston (4) has two radial sealing agents (6, 7) spaced axially relative to the longitudinal axis of the slide valve piston,
• between these two radial sealing agents there are provided in the slide valve piston (4) passage openings (4b) which connect the vicinity of the slide valve piston (4) on the jacket surface side to the leakage cavity (11) by way of a discharge outlet (4a, 4a*) opening into a tubular shaft (4e, 5c),
• in that the two sealing agents (6, 7)
• are received into the cylindrical valve seat surface (3a) so as to effect sealing when the double seat valve is in the closed position, as well as in the seat cleaning position of the second closure member (5), and
• are moved into the recess (9) in the open position where at least the sealing agent (6, 7) on the valve housing side seals against the circumferential wall of the recess (9),
• and in that, when the slide valve piston (4) is in the seat cleaning position, the slide valve piston is displaced by the amount of a partial valve stroke in the direction of its opening movement in such a way that the passage openings (4b) are open to the valve housing element (2, 1) adjacent to the cleared seat surfaces and in the process the sealing agent (7) of the slide valve piston (4) on the leakage cavity side remains in the cylindrical seat surface (3a) so as to effect sealing,
• and in that, when the second closure member (5) is in the seat cleaning position, the second closure member is displaced by the amount of a partial stroke in the direction of its opening movement, whereby the valve housing element (1, 2) adjacent to the cleared seat surface is connected with the discharge outlet (4a) by way of the leakage cavity (11).