Focus On Triple Offset Butterfly Valve 

Introduction to Flanged Butterfly Valves

Flanged butterfly valves introduce the concept of self-sealing design, in which the patented design withdrawal pin structure is used to connect the disc to the valve shaft.The main features of the valve are reliable sealing, bidirectional sealing, tight connection, no loosening, and long service life of the valve.Its features are as follows:

Bi-directional seal

Conventional butterfly valves usually fail to seal well under working pressure in opposite direction (unfavorable sealing direction) due to their structural and other reasons. At present, there is no mandatory requirement for bidirectional sealing in relevant national standards.This is due to:

  1. Adopt self-sealing design concept

The disc sealing ring is directly embedded in the disc with rubber in a zigzag shape and does not need to be fixed with a pressure factor or bolt, thus avoiding the problems of uneven force on the sealing ring, bolt shedding and premature damage to the sealing ring caused by traditional bolt-type seals.Under the action of working pressure in opposite direction, the sealing ring produces self-sealing force, which increases the specific pressure of the seal and compresses the valve seat. The higher the working pressure in opposite direction, the greater the self-sealing force will be, thus tightening the sealing ring to the valve seat and achieving the effect of two-way sealing.

2 Disc is rigid and not easily deformed

The discs above DN300 of butterfly valve are double-plate truss flow structure with small flow resistance and good rigidity. It is not easy to deform under working pressure in the opposite direction, so that the sealing ring will not be separated from the best sealing point of the valve seat with the deformation of the disc, thus ensuring the sealing effect of the sealing ring.

3 Long service life of rubber sealing ring

(1) Due to the self-sealing design concept, the smaller interference between the rubber ring and the stainless steel seat only maintains the initial seal, so the specific pressure required for the seal increases with the increase of the system pressure.

(2) In addition, there is a so-called breathing groove in the zigzag groove for the elastic retraction of rubber, which allows the rubber to have a certain space to expand under pressure so that elastic fatigue will not occur in long-term work.Therefore, the service life of the sealing ring is greatly increased compared with the traditional type.

Unique design pull-out structure

In general, butterfly valves in service, because of the traditional pin connection, the pin passes through the center of the valve shaft, which not only reduces the strength of the valve shaft, but also generates clearance between the valve shaft during long-term use, resulting in an impact load on the valve when it is switched, which is much greater than the normal compressive and shear stresses.The pin is often seriously deformed or broken during service, which makes the valve not close tightly or fail, and greatly reduces the service life of the valve.If the newly manufactured valve uses a uniquely designed pull-out pin structure instead of the pin connection between the shaft and disc, the pull-out pin does not pass through the center of the valve shaft, not only does not weaken the strength of the shaft, but also greatly increases the fitting surface with the valve shaft. By tightening the pull-out pin nut, a preload is generated between the pull-out pin and the joint surface of the valve shaft, so that the disc shaft is tightly joined without gaps.There is no shock load when opening and closing the valve, which makes the disc rotate smoothly and thus achieves reliable sealing.

Design of bottom axial adjustment locking device

In butterfly valves above DN300 specification, due to the reliability of butterfly plate self-weight seal, the position of the disc on the valve seat is in the best sealing state by precise adjustment and fixing of the axial position during manufacture.For disc sag that may occur during long-term use, further adjustment of locking is also facilitated to achieve zero leakage during long-term use.

Easy replacement of sealing rings

When the sealing ring needs to be replaced, it is not necessary to remove the valve disc, just open the valve fully, remove the key in the operating device, maintain the connection with the main valve key after the operating device is turned to closed state, and then continue to turn the handwheel towards the opening direction until the seal stops at the sealing side of the valve body to replace the seal.

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