when the valve is in the closed state, the seat ring on the upstream and downstream sides cuts off the fluid and the accumulated matters in the middle cavity of the body can be excreted. The excreting device features the following functions.
1).can check if the seat ring leaks or gets damaged beforehand.
2).reduce pollution to the valve due to the medium replacement.
3).the packing on the stem portion can be re4placed when the valve is the fully opened or closed state under the working pressure.
when an abnormal pressure rise occurs with the medium stayed in the middle cavity of the valve due to rising temperature, the seat ring will come off form the ball and automatically discharge pressure or the safety valve mounted on the body ensures the system safety.
the unique sealing mode of the ball valve makes the fluid completely cut off.
4.if the Teflon seat ring is made softened and burnt in case of a fire or an abnormal temperature rise, the valve can be still reliably operated to prevent the fire from expanding and the seat ring’s support can be contacted with the ball to act as an instantaneous seal, conforming with API607.
during valve operation, the friction between the ball and the PTEE seat ring will produce electrostatic charges and they will be accumulated onto the ball. To prevent electrostatic spark from being produced, an electrostatic-proof device is mounted on the valve, which can guide the charges out through the electric path formed by both ball and body via the spring.
when the sealing parts of both seat ring and stem get damaged and thus leaks are caused, an instantaneous sealing action can be made available by injecting sealing grease through the grease injecting valve.
Two kinds: single seal and dual seal. In general, those of an automatic pressure discharge function are single seal while the dual seal means the additional safety pressure discharge to the body.
For the seat ring of the single seal structure, it depends on, after being inlaid into the support ring , the spring’s pre-tightening force and the piston effect to have both set ring and ball pressed tightly so as to form sealing. When an abnormal pressure rise occurs inside of the middle cavity of the body due to some reason, the seat ring will automatically discharge the pressure under the action of pressure differential to prevent any danger from happening, then after discharging the pressure it is reset automatically.For the dual seal structure formed with the supports of both dual seal structured seat ring and O ring, both seat ring and ball are made contacted under the spring’s pre-tightening force and sealed under the pressure differential on the upstream (downstream) side of the pipeline and the middle cavity of the body, regardless of on which side the medium’s pressure is higher, both spring’s pre-tightening force and piston effect make the seat rings on both upstream and downstream sides always tightly contacted with the ball to completely cut off the fluid and prevent leak even if any one of them gets damaged, however there is no automatic pressure discharge function, so a pressure discharger has to be mounted in the middle cavity of the body to avoid abnormal pressure rise therein.
the valve nominal diameter is identical to the inner diameter of the pipeline (which can be reduced one if so required by users) for the sake of cleaning (fig 17)
use a locker to fix the valve so as to prevent maloperation of it and keep it in the correct opened or closed position
extension of the stem is suitable for use under-ground and at low temperature, the extended size is depended on the necessity and the operation mode can be manual, pneumatic, electric, gas-hydraulic jointed or hydraulic actuation, also upon the necessity.
the relative sliding portion (seat ring and stem bearing ) of a large aperture ball valve has a small operational torque due to its use of Teflon which has a small friction coefficient and can be flexibly operated for a long time even if there is no lubrication supplied for it.
the used different and effective actuation modes include manual, pneumatic, electric, hydraulic and gas-hydraulic jointed ones.
