Double block and bleed Ball Valve
In case of fire during the use of valve, the seat ring made of PTFE or other non-metal material will be decomposed or damaged under high pressure and cause higher leakage.
The double block bleed valve and Bleed Ball Valve require two isolation in one line and a bleed function. It is applied to control the flow between the two ‘ball valves’ cavity in order to block the downstream pipeline in a safety way. The double block is playing the role of venting the pressure safety during maintenance by a valve stead of two bolted valves.
1. Double Block and Bleed (DBB)When the valve is closed and the middle cavity is emptied through the discharge valve, the upstream and downstream seats will independently block the fluid at the inlet and outlet to realize double block function. Another function of the discharge device is that the valve seat can be checked if there is any leakage during the test.
2. Fireproof Structure DesignIn case of fire during the use of valve, the seat ring Created of PTFE or other non-Steel Elements will be decomposed or Broken Below Higher Stress and Trigger Increased leakage. The fireproof seal ring is set between ball and seat so that after the valve seat is burnt, the medium will push the ball rapidly towards
the downstream metal seal ring to form the auxiliary metal to metal sealing structure, which can effectively control valve leakage. In addition, the middle flange sealing gasket is made of metal wound gasket, which can ensure sealing even under high temperature. The fireproof structure design of floating valves conforms to requirement in API6FA, BS 6755 and other standards.
3. Reliable Sealing of Valve StemThe stem is provided with the should at its bottom so that it will not be blown out by the medium even under the extreme conditions such as abnormal pressure rise inside the valve cavity, failure of gland plate and etc. In addition, to avoid leakage after the stem packing is burnt in case of fire, the thrust bearing is set at the place where the stem shoulder and body contact to form reverse sealing seat.