Ball valve for a pipe system for conveying liquid or gaseous media

1. A ball valve for a line system for conveying liquid or gaseous media comprising:

a housing which has a ball plug and seat rings, and the seat rings contact the ball plug to provide a seal therebetween;

a hydraulic pressure system, which is independent of pressure of the liquid or gaseous medium flowing through the line system, and the hydraulic pressure system provides a pressure to and controllably varies contact pressure of at least one seat ring of the seat rings against the ball plug; and wherein

the hydraulic pressure system comprises at least one pressure channel for feeding a pressurized medium to, or discharging said pressurized medium from, a rear side, of the at least one seat ring of the seat rings, averted from the ball plug to vary the contact pressure exerted by the at least one seat ring of the seat rings on the ball plug; and wherein

an annularly encircling annular space with which the at least one, pressure channel corresponds, is formed between the rear side of the at least one seat ring of the seat rings and an adjacent inner wall surface, facing toward the at least one seat ring of the seat rings, of the housing; and wherein

the hydraulic pressure system has a bypass line to produce a pressure equalization between the annular space and a dead space which is situated between the seat rings and a top side of the ball plug and an inner all of the housing; and wherein

the hydraulic pressure system has at least one shut-off element to open and close the bypass line.

2. The ball valve as claimed in claim 1 , characterized in that the annular space is delimited by a first seal and a second seal which are arranged such that the pressurized medium fed from the pressure channel generates a pressure force which acts directly on the rear side of the at least one seat ring of the seat rings.

3. The ball valve as claimed in claim 2 , and wherein the first seal is arranged between the inner wall surface of the housing and the at least one seat ring of the seat rings and seals off the annular space with respect to the dead space, and wherein, during operation of the line system, a pressure prevails in the dead space which corresponds to the pressure in pipelines, of the line system through which the liquid or gaseous medium is transported.

4. The ball valve as claimed in claim 2 , and wherein the first seal is a piston seal has an O-ring and a slide ring seal, and wherein the O-ring is arranged on the rear side, of the slide ring seal, averted from the inner wall surface.

5. The ball valve as c aimed in claim 1 , and further comprising:

a sealing and pressure-exerting device; and

the sealing and pressure-exerting device is inserted in the annular space of the ball valve proximate an outlet opening of the pressure channel.

6. The ball valve as claimed in claim 1 , characterized in that the pressure that acts on the rear side of the at least one seat ring of the seat rings can be set to the pressure that is the same as the pressure in the line system and can be set to a pressure that is different from the pressure in the line system.

7. The ball valve as claimed in claim 6 and further comprising:

a control device for controlling the pressure applied to the rear side of at least one seat ring of the seat rings independently of the liquid or gaseous media flowing through the line system.

8. The ball valve as claimed in claim 7 , characterized in that the control device reduces the pressure at the rear side of the at least one seat ring of the seat rings to a pressure below the pressure in the line system.

9. The ball valve as claimed hi claim 1 , characterized in that, for the at least one seat ring of the seat rings, a spring is provided for pushing the at least one seat ring of the seat rings against the ball plug.

10. A method for adjusting a ball valve as claimed in claim 1 , and wherein the ball valve is integrated into a line system for conveying liquid or gaseous media, and the ball valve is adjusted to open and close pipelines, in which method, for the adjustment of the ball valve, a pressure which is generated by a hydraulic medium, and which acts on a rear side, of at least one seat ring of the seat rings averted from a ball plug is variable such that the pressure acting on the rear side is reduced to a pressure below the pressure in the pipelines.

11. A method for sealing a ball valve as claimed in claim 1 and further comprising the steps:

providing ball valve that is integrated into a line system having pipelines, for conveying liquid or gaseous media and the ball valve is adjusted in order to open and close the pipelines; and

the ball valve has a ball plug and seat rings that communicate with the ball plug to provide a seal therebetween; and

providing a hydraulic pressure system that is independent from pressure in the pipelines, and the hydraulic pressure system generates a pressure which is fed to at least one seat ring of the seat rings so that the at least one seat ring of the seat rings is pressed against the ball plug so that a contact surface between the ball plug and the at least one seat ring of the seat rings is sealed off, even if a sealing surface of the at least one seat ring of the seat rings is damaged.

12. The ball valve as claimed in claim 1 , and further comprising: a sealing and pressure-exerting device and the sealing and pressure-exerting device is proximate an outlet opening of the pressure channel.

13. A method for leading a pig through a ball valve inserted into a line system for liquid or gaseous media, and wherein the ball valve has an adjustable ball plug, and seat rings which contact the adjustable ball plug to provide a seal therebetween, the method comprising the steps:

providing a pressure system that communicates with the ball valve, and the pressure system is independent of a pressure in the line system generated by the liquid or gaseous media; and

the pressure system generates and controls a pressure that is communicated to the ball valve, and the generated and controlled pressure presses at least one seat ring, of the seat rings against the adjustable ball plug, and the generated and controlled pressure is sufficient for pressing at least one seat ring of the seat rings against the adjustable ball plug and holding the at least one seat ring of the seat rings in contact with the adjustable ball plug which the pig passes therethrough; and

leading the pig through pipelines of the line system into which the ball valve is inserted.

14. The method as claimed in claim 13 characterized in that, after the pig has been led through the ball plug, the pressure which is generated by the pressure system and which presses the at least one seat ring of the seat rings against the ball plug is reduced so that the at least one seat ring of the seat rings lifts off from the ball plug.

15. A method for cleaning a ball valve, in which method the ball valve ( 1 ) is integrated into a line system for conveying liquid or gaseous media and is adjusted in order to open and close pipelines ( 2 a , 2 b ), in which method the ball valve ( 1 ) has a ball plug ( 4 ) and seat rings ( 5 , 6 ), in which method a pressure system ( 7 ) is provided which is designed to, independently of the pressure in the pipelines ( 2 a , 2 b ), generate a pressure which is fed to at least one of the seat rings ( 5 , 6 ) such that the at least one seat ring ( 5 , 6 ) is acted on with a force which pushes the seat ring ( 5 , 6 ) away from the contact surface on the ball plug ( 4 ) and wherein the pressure generated by the pressure system ( 7 ) is fed to a dead space ( 18 ).

16. The method as claimed in claim 15 , characterized in that the pressure generated by the pressure system ( 7 ) is equal to or higher than the pressure in the pipelines ( 2 a , 2 b ).