Flat-plate Gate Valve

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Products design features 1、Cast and weld two structures with the body. 2、The seat ring uses the floating seat ring structure with o-seal ring sealed and pre-tightening force applied to have inlet and outlet dual-way sealed; and the open-close moment with this structure is 1/2 that of the common valves only, able to lightly open and close valve. 3、The seat ring uses the sealing face inlaid with PTFE, so has dual seals of PTFE to metal and metal to metal, the PTFE sealing face also acts as removing the dirt on the wedge disc. 4、For the valve with the metal to metal seal, there is grease injector outside of it, grease gets into the sealing face through the injector and the seat ring to have the valve up to null leak. 5、The wedge disc of the valve with flow guide hole is always fitted with the sealing face whether in full open or full close status to have the sealing face protected without being directly eroded by the medium so as to extend the duration. 6、When fully opened, the valve's channel is smooth and linear, with an extremely small flow resisting coefficient and no pressure loss, and the pipeline can be cleaned with hair-ball through it. 7、This valve uses the packing structure with the ability of self-seal, needs no constant adjustment, features very light open and close and a reliable seal. An assisting sealing grease injection structure is set in the packing to have the sealing performance reliable and get a true null leak, settling the problem for the packing place of universal valves to be easiest leak outward. 8、Automatic removal of the high pressure in the internal cavity when the valve is about to close (see the working principle diagram for the details) so as to ensure safety. 9、Fully sealed structure leaves a good protective property, suitable for the requirement of 24-hour duty. 10、An indication rod or viewing window is set with the valve to show the open-close condition. Working principle 1、With equal pressure throughout the valve(and the gate in closed position), and initial seal (1) is formed with the raised PTFE ring on the faces of the seats. (The seat-inserts clean both sides of the gate each time the valve is opened or closed). 2、As line pressure (2) is applied to the valve. it acts on the gate, forcing it against the PTFE ring on the downstream seat, compressing it until the seat against the steel seat. Thus, a double seal is formed...first, a PTFE-to-metal seal; then, metal-to-metal. The seat is also forced firmly into its recess. The O-ring (3) prevents any downstream flow at this point3、Upstream seal is provided when valve cavity pressure is bled off. This is caused by the force of line pressure acting against the upstream seat (4) moving the seat against the gate and providing a tight PTFE-to metal seal at this point. At the same time. the O-ring (5) forms a tight sea with the seat recess. 4、Valve automatically relieves itself of excessive valve cavity pressure. When valve cavity pressure exceeds line pressure...from such causes as thermal expansion...the upstream seat is forced back into its recess and the excess pressure in the valve cavity is bled between the seat and the gate into the line.Flow characteristic The flow characteristic of flat gate valves with a diversion hole is equal to that of pipelines of the same specification. The characteristic is shown in per centum form. As for valves without a diversion hole its cavity fly span is smaller than that of wedge gate vales and it is a regular cylindrical object, therefore, characteristics of the valves are similar except that they have a larger pressure loss. Besides, their flux adjustment behavior is better than that of the ones with a diversion hole.

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Beijing St. Ocean Engineering Technology Co.,Ltd.

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