Overview of Triple Offset Metal Hard Seal Butterfly Valve
The sealing surface of the triple offset metal hard seal butterfly valve is a inclined cone surface, and the contact between the valve body sealing ring and the butterfly plate assembly sealing ring is a surface contact. Its working principle relies on the torque generated by the driving device to directly drive the butterfly plate assembly, causing the sealing ring of the butterfly plate assembly to make full contact with the sealing ring of the valve body, resulting in elastic deformation and sealing.
As a high-performance valve, the triple offset metal hard seal butterfly valve has advantages such as good corrosion resistance, reliable sealing, and low opening torque. For example, the DN1200 triple offset hard seal electric butterfly valve uses 1Cr18Ni9Ti for the valve body sealing ring material and a composite stainless steel plate and asbestos plate sandwich for the sealing ring material of the butterfly plate assembly. The processing quality of the valve body sealing ring and the butterfly plate assembly sealing ring directly determines the sealing performance of the butterfly valve.
Processing Technology
Considering the structural characteristics of the triple offset metal hard seal butterfly valve, the sealing ring of the butterfly plate assembly is a combination of stainless steel plate and asbestos board, while the sealing ring of the valve body is made of hard alloy with high hardness, making it difficult to control the cutting amount and achieving high roughness requirements for the processing surface. To meet the processing requirements, the process includes rough machining of the valve body or butterfly plate assembly, hard alloy welding of the valve body sealing ring, annealing to eliminate thermal stress, rough and finish machining of the sealing surface, grinding of the sealing surface with a grinding head, boring of the valve body and butterfly plate assembly, strength test, and sealing test.
Processing Fixtures
Both the sealing surface of the butterfly plate assembly sealing ring and the valve body sealing ring (processing surface) are inclined cone surfaces. The valve body sealing ring has a conical centerline angle of 8° with the vertical line of space, and the butterfly plate assembly sealing ring has a conical centerline angle of 8° with the vertical line of space, necessitating separate processing fixtures for the valve body sealing ring and the butterfly plate assembly sealing ring.
Valve Body Sealing Ring Processing
The valve body sealing ring serves as the sealing ring, welded inside the valve body. The assembled valve body, with the welded valve body sealing ring, is mounted on the valve body sealing ring processing fixture on a 2.5m lathe. The lathe tool post is rotated by 8°, and the cutting is done along the conical generator line direction until the dimension before the stainless steel is welded according to the drawing requirements. Then, stainless steel is welded, and finally, the valve body with welded stainless steel is re-mounted on the lathe for machining of the valve body sealing ring to the required dimensions. Finally, a grinding head is mounted on the lathe tool post to grind the valve body sealing ring to meet the roughness requirements of the drawing.
Butterfly Plate Assembly Sealing Ring Processing
The part of the butterfly plate assembly that serves as the sealing ring is the sealing ring, which is a conical structure with a top angle of 16° and a thickness of 13.5mm, composed of 5 layers of asbestos board and 4 layers of stainless steel plate. To prevent warping and deformation of the stainless steel plate and asbestos board in the sealing ring layer, the assembly of the butterfly plate, sealing ring, and retaining ring is done according to the drawing requirements. The processing steps include machining the various stop grooves on the butterfly plate and retaining ring, drilling holes in the retaining ring and tapping threads in the butterfly plate, drilling and tapping holes for the adjustment bolts in the butterfly plate, assembling the retaining ring, sealing ring, and butterfly plate according to the drawing, machining the conical surfaces of the retaining ring, butterfly plate, and sealing ring to the required dimensions, and finally, grinding the sealing ring with a grinding head to meet the roughness requirements of the drawing.
Valve Stem Hole Processing
After placing the butterfly plate assembly in the valve body and adjusting its relative position, soap solution is poured in, and if there is no leakage within 5 minutes, the butterfly plate assembly is pressed, and the valve body and butterfly plate holes are honed together.
This processing method for the valve body sealing ring and the butterfly plate assembly sealing ring is easy to operate, has high work efficiency, can guarantee the geometric accuracy of the sealing surface well, and meets the requirements for strength and sealing tests, demonstrating practical and promotional value.
Characteristics of Triple Offset Metal Hard Seal Butterfly Valve
The hard seal butterfly valve adopts a triple offset hard seal structure, with almost no wear between the valve seat and the butterfly plate, providing a tighter sealing function over time.
The sealing ring is made of stainless steel, providing dual advantages of metal hard sealing and elastic sealing. It exhibits excellent sealing performance in both low and high temperature conditions, with features such as corrosion resistance and long service life.
The sealing surface of the butterfly plate is built-up with cobalt-based hard alloy, ensuring wear resistance and long service life.
Large-sized butterfly plates adopt a lugged structure, offering high strength, large flow area, and low flow resistance.
The hard seal butterfly valve can be designed with bidirectional sealing function according to user requirements. It can be installed in any direction without being affected by the direction of the medium flow or spatial position, providing convenience for users.
The drive device can be installed in multiple positions (rotated 90° or 180°), facilitating user operation.
Common Problems of Triple Offset Metal Hard Seal Butterfly Valve:
1. Due to the multiple layers of soft and hard sealing rings fixed on the valve plate, when the valve plate is in the normally open state, the medium forms positive flushing on its sealing surface. After the soft sealing strip in the metal strip layer is flushed, it directly affects the sealing performance.
2. Due to structural limitations, this structure is not suitable for valves with a diameter below DN200 because the overall structure of the valve plate is too thick, resulting in high flow resistance.
3. The sealing between the sealing surface of the valve plate and the valve seat relies on the torque of the drive device to press the valve plate against the valve seat. When in the forward flow state, higher medium pressure results in tighter sealing. However, in the reverse flow state, if the unit pressure between the valve plate and the valve seat is lower than the medium pressure, leakage occurs.
Characteristics:
1. The valve seat sealing ring consists of a soft T-shaped sealing ring and multiple layers of stainless steel plates on both sides.
The sealing surface between the valve plate and the valve seat adopts an inclined conical structure, with wear-resistant and corrosion-resistant alloy materials deposited on the inclined conical surface of the valve plate.
2. A spring and adjusting bolt assembly between the adjusting ring pressure plate compensates for the elastic deformation of the shaft sleeve and valve stem under medium pressure, addressing sealing issues during bidirectional media transport.
3. The sealing ring, composed of soft T-shaped sealing rings and stainless steel plates on both sides, provides both metal hard sealing and soft sealing advantages, ensuring zero leakage performance under various temperature conditions.
4. Tests have demonstrated that in the forward flow state, the pressure on the sealing surface is a result of the torque of the drive device and the medium pressure acting on the valve plate. Increasing forward medium pressure results in tighter compression between the inclined conical surface of the valve plate and the valve seat sealing surface.
5. In the reverse flow state, the torque of the drive device presses the valve plate against the valve seat. As the reverse medium pressure increases, the stored deformation energy of the spring in the adjusting ring compensates for the tight compression between the sealing surfaces of the valve plate and the valve seat.
6. This new design differs from existing technologies by directly installing sealing elements on the valve body instead of the valve plate. Introducing an adjusting ring between the pressure plate and the valve seat is an ideal bidirectional hard sealing method. It has the potential to replace gate valves and ball valves.
As a high-performance valve, the triple offset metal hard seal butterfly valve has advantages such as good corrosion resistance, reliable sealing, and low opening torque. For example, the DN1200 triple offset hard seal electric butterfly valve uses 1Cr18Ni9Ti for the valve body sealing ring material and a composite stainless steel plate and asbestos plate sandwich for the sealing ring material of the butterfly plate assembly. The processing quality of the valve body sealing ring and the butterfly plate assembly sealing ring directly determines the sealing performance of the butterfly valve.
Processing Technology
Considering the structural characteristics of the triple offset metal hard seal butterfly valve, the sealing ring of the butterfly plate assembly is a combination of stainless steel plate and asbestos board, while the sealing ring of the valve body is made of hard alloy with high hardness, making it difficult to control the cutting amount and achieving high roughness requirements for the processing surface. To meet the processing requirements, the process includes rough machining of the valve body or butterfly plate assembly, hard alloy welding of the valve body sealing ring, annealing to eliminate thermal stress, rough and finish machining of the sealing surface, grinding of the sealing surface with a grinding head, boring of the valve body and butterfly plate assembly, strength test, and sealing test.
Processing Fixtures
Both the sealing surface of the butterfly plate assembly sealing ring and the valve body sealing ring (processing surface) are inclined cone surfaces. The valve body sealing ring has a conical centerline angle of 8° with the vertical line of space, and the butterfly plate assembly sealing ring has a conical centerline angle of 8° with the vertical line of space, necessitating separate processing fixtures for the valve body sealing ring and the butterfly plate assembly sealing ring.
Valve Body Sealing Ring Processing
The valve body sealing ring serves as the sealing ring, welded inside the valve body. The assembled valve body, with the welded valve body sealing ring, is mounted on the valve body sealing ring processing fixture on a 2.5m lathe. The lathe tool post is rotated by 8°, and the cutting is done along the conical generator line direction until the dimension before the stainless steel is welded according to the drawing requirements. Then, stainless steel is welded, and finally, the valve body with welded stainless steel is re-mounted on the lathe for machining of the valve body sealing ring to the required dimensions. Finally, a grinding head is mounted on the lathe tool post to grind the valve body sealing ring to meet the roughness requirements of the drawing.
Butterfly Plate Assembly Sealing Ring Processing
The part of the butterfly plate assembly that serves as the sealing ring is the sealing ring, which is a conical structure with a top angle of 16° and a thickness of 13.5mm, composed of 5 layers of asbestos board and 4 layers of stainless steel plate. To prevent warping and deformation of the stainless steel plate and asbestos board in the sealing ring layer, the assembly of the butterfly plate, sealing ring, and retaining ring is done according to the drawing requirements. The processing steps include machining the various stop grooves on the butterfly plate and retaining ring, drilling holes in the retaining ring and tapping threads in the butterfly plate, drilling and tapping holes for the adjustment bolts in the butterfly plate, assembling the retaining ring, sealing ring, and butterfly plate according to the drawing, machining the conical surfaces of the retaining ring, butterfly plate, and sealing ring to the required dimensions, and finally, grinding the sealing ring with a grinding head to meet the roughness requirements of the drawing.
Valve Stem Hole Processing
After placing the butterfly plate assembly in the valve body and adjusting its relative position, soap solution is poured in, and if there is no leakage within 5 minutes, the butterfly plate assembly is pressed, and the valve body and butterfly plate holes are honed together.
This processing method for the valve body sealing ring and the butterfly plate assembly sealing ring is easy to operate, has high work efficiency, can guarantee the geometric accuracy of the sealing surface well, and meets the requirements for strength and sealing tests, demonstrating practical and promotional value.
Characteristics of Triple Offset Metal Hard Seal Butterfly Valve
The hard seal butterfly valve adopts a triple offset hard seal structure, with almost no wear between the valve seat and the butterfly plate, providing a tighter sealing function over time.
The sealing ring is made of stainless steel, providing dual advantages of metal hard sealing and elastic sealing. It exhibits excellent sealing performance in both low and high temperature conditions, with features such as corrosion resistance and long service life.
The sealing surface of the butterfly plate is built-up with cobalt-based hard alloy, ensuring wear resistance and long service life.
Large-sized butterfly plates adopt a lugged structure, offering high strength, large flow area, and low flow resistance.
The hard seal butterfly valve can be designed with bidirectional sealing function according to user requirements. It can be installed in any direction without being affected by the direction of the medium flow or spatial position, providing convenience for users.
The drive device can be installed in multiple positions (rotated 90° or 180°), facilitating user operation.
Common Problems of Triple Offset Metal Hard Seal Butterfly Valve:
1. Due to the multiple layers of soft and hard sealing rings fixed on the valve plate, when the valve plate is in the normally open state, the medium forms positive flushing on its sealing surface. After the soft sealing strip in the metal strip layer is flushed, it directly affects the sealing performance.
2. Due to structural limitations, this structure is not suitable for valves with a diameter below DN200 because the overall structure of the valve plate is too thick, resulting in high flow resistance.
3. The sealing between the sealing surface of the valve plate and the valve seat relies on the torque of the drive device to press the valve plate against the valve seat. When in the forward flow state, higher medium pressure results in tighter sealing. However, in the reverse flow state, if the unit pressure between the valve plate and the valve seat is lower than the medium pressure, leakage occurs.
Characteristics:
1. The valve seat sealing ring consists of a soft T-shaped sealing ring and multiple layers of stainless steel plates on both sides.
The sealing surface between the valve plate and the valve seat adopts an inclined conical structure, with wear-resistant and corrosion-resistant alloy materials deposited on the inclined conical surface of the valve plate.
2. A spring and adjusting bolt assembly between the adjusting ring pressure plate compensates for the elastic deformation of the shaft sleeve and valve stem under medium pressure, addressing sealing issues during bidirectional media transport.
3. The sealing ring, composed of soft T-shaped sealing rings and stainless steel plates on both sides, provides both metal hard sealing and soft sealing advantages, ensuring zero leakage performance under various temperature conditions.
4. Tests have demonstrated that in the forward flow state, the pressure on the sealing surface is a result of the torque of the drive device and the medium pressure acting on the valve plate. Increasing forward medium pressure results in tighter compression between the inclined conical surface of the valve plate and the valve seat sealing surface.
5. In the reverse flow state, the torque of the drive device presses the valve plate against the valve seat. As the reverse medium pressure increases, the stored deformation energy of the spring in the adjusting ring compensates for the tight compression between the sealing surfaces of the valve plate and the valve seat.
6. This new design differs from existing technologies by directly installing sealing elements on the valve body instead of the valve plate. Introducing an adjusting ring between the pressure plate and the valve seat is an ideal bidirectional hard sealing method. It has the potential to replace gate valves and ball valves.
