Ball valve with removable means for retaining the axial seal

1. A ball valve comprising:

a valve body with a seat for housing a ball provided with a coaxial through-opening and able to be rotationally operated from a closed valve position into an open valve position and vice versa;

two opposite end flanges which are constrained to the valve body on opposite sides of the ball and provided with a respective, coaxial, internal hole and are suitable for connection to respective pipe sections;

sealing means arranged between the valve body and the ball and comprising an annular member which is coaxial with the longitudinal axis (X-X) and carries a single axial seal housed inside an associated axial seat of the annular member inside which it is partially inserted in order to interfere with the outer surface of the ball;

a coaxial retaining ring axially constrained to the annular member and interfering in the transverse direction (Y-Y) with a front surface portion of the axial seal in order to retain the latter in the axial direction; and

springs axially inserted inside corresponding seats of the end flange against which the springs react,

wherein said axial seal is formed by a plurality of layers of sheets of pure graphite reinforced with a metal strip.

2. The valve according to claim 1 , wherein said coaxial retaining ring is removable.

3. The valve according to claim 2 , wherein said coaxial retaining ring is constrained to the annular seal-carrying member by means of screws which are axially screwed into the latter.

4. The valve according to claim 1 , wherein said annular member has a radial extension with a diameter greater than the diameter of the surface of the ball interfering with the axial seal.

5. The valve according to claim 4 , wherein the screws for fixing the coaxial retaining ring for axially retaining the seal are screwed into said radial extension.

6. The valve according to claim 1 , wherein the coaxial retaining ring for retaining the axial seal has an annular body with a diameter corresponding to that of the radial extension of the annular member and an outwardly inclined undercut able to be arranged substantially parallel to the tangent of the outer surface of the ball opposite the said undercut.

7. The valve according to claim 1 , wherein the metal strip is made of stainless steel.

8. The valve according to claim 1 , wherein the metal strip has a thickness of between a few hundredths and a few tenths of a millimeter.

9. The valve according to claim 1 , wherein the coaxial retaining ring is housed inside a corresponding axial seat of the seal-carrying member.

10. The valve according to claim 1 , wherein the axial seal is able to produce a fluid-tight seal both in the axial direction by means of contact with the outer surface of the ball and with the end wall, parallel to the transverse direction (Y-Y), of the associated axial seat of the annular member against which it makes contact and a cylindrical circular seal along the coaxial annular surface of the same axial seat of the annular member.

11. The valve according to claim 1 , wherein the annular member carries radial seals able to interfere with the flanges or the valve body are associated with said annular seal carrying member.