The series of parallel single-disc gate valves have diversion hole or non-diversion hole and adjustment structure formations which are applied to natural gas,oil products.chemical engineering,city construction and environment protection industries.The anti-sulphur product series are fit for high speed long delivery pipeline of seriously eroded natural gas which contains H2S medium and much impurity. The design features of series parallel single-disc gate valve include: The floating seat struction makes it possible to seal both director of the valve; The valve seat sealing adopts double-seats.PTFE can remove granule ad dirties to ensure a perfect sealing. Hard sealing surface is build-up welded on sealing surface with  hard alloy which results in a hardness of HRC44-52 to ensuresealing reliability. Valve with diversion hole,either full-open or full-closed,the disc will be kept in contract with seat so that the sealing surface will not be washed out directly by mediums and the valve will become more durable; The fire-resistant design of the valve complies with API 6Fa and API607 standards.