Introduction to Fluorine lined Butterfly Valve

Fluorine-lined Butterfly Valve Introduction

At present, fluorine lined butterfly valves and rubber lined butterfly valves have been widely used in many fields such as petroleum, chemical, metallurgy, hydropower, etc. as components used to achieve on/off and flow control of pipeline systems. In the known butterfly valve technology, the sealing form often adopts a sealing structure, and the sealing material is rubber, polytetrafluoroethylene, etc. Due to structural limitations, it is not suitable for industries that are resistant to high temperatures, high pressures, corrosion, and wear. The existing comparative butterfly valve is a three eccentric metal hard seal butterfly valve, with the valve body and valve seat as integrated components, and the sealing surface layer of the valve seat is welded with heat-resistant and corrosion-resistant alloy materials. The multi-layer soft stacked sealing ring is fixed on the valve plate. Compared with traditional butterfly valves, this butterfly valve has the advantages of high temperature resistance, easy operation, frictionless opening and closing, and compensating for sealing with the increase of torque of the transmission mechanism when closing, which improves the sealing performance and extends the service life of the butterfly valve. This type of valve should generally be installed horizontally in pipelines. The butterfly plate of the fluorine lined butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis at an angle between 0 ° and 90 °. When it rotates to 90 °, the valve is fully open.

The material used for the fluorine lined butterfly valve

Perfluoroethylene FEP (F46)
Applicable medium:
Any organic solvent or reagent, dilute or concentrated inorganic acid, base, ketone, aromatic hydrocarbon, chlorinated hydrocarbon, etc.
Operating temperature:
-85~150
Characteristics: The mechanics, electrical properties, and chemical stability are basically the same as F4, but the outstanding advantage is dynamic impact toughness
High, with excellent weather resistance and radiation resistance.
Polytrifluoroethylene PCTEF (F3)
Applicable medium:
Various organic solvents, inorganic corrosive liquids (oxidizing acids)
Operating temperature: -195~120
Features: Heat resistance, electrical and chemical stability second only to F4, mechanical strength, creep performance, and hardness better than F4
Polypropylene: RPP
Applicable media: aqueous solutions of inorganic salts, dilute or concentrated solutions of inorganic acids and bases.
Operating temperature: -14~80
Characteristics: One of the lighter plastics, its yield, tensile and compressive strength, hardness are superior to low-pressure polyethylene, it has outstanding rigidity, good heat resistance, easy molding, and excellent cost. Modified mobility, fluidity, and bending elasticity.
Polyvinyl chloride: hard PVC
Applicable media: water-resistant, concentrated alkali, non oxidizing acids, chain hydrocarbons, oil, ozone, etc.
Operating temperature: 0-55
Features: high mechanical strength, excellent chemical stability and dielectric properties, good oil resistance and anti-aging resistance, easy to fuse
And bonding, with a lower price.
Polytetrafluoroethylene PTFE (F4)
Media used: strong acid, strong alkali, strong oxidant, etc.
Operating temperature: -200~180
Characteristics: It has chemical stability, high heat and cold resistance, low friction coefficient, and is an excellent self-lubricating material. However, its mechanical properties are low, its flowability is poor, and its thermal expansion is large.
Polyvinylidene chloride PVDF (F2)
Medium of use: resistant to most chemicals and solvents,
Operating temperature: -70~100
Features: The tensile and compressive strength of the product is better than that of F4, and it is resistant to bending, weather, and radiation. It is resistant to light and aging, and its major characteristics are good toughness and easy molding.
Polyolefin: PO
Applicable media: various concentrations of acid-base salts and certain organic solvents.
Operating temperature: -58~80
Characteristics: It is currently one of the most ideal anti-corrosion materials in the world and has been widely used for lining large equipment and pipeline components in rotary molding.
C， Several classifications of performance for fluorine lined butterfly valves
1. Classified by structural form
(1) Center sealed butterfly valve
(2) Single eccentric sealed coal valve
(3) Double eccentric sealing butterfly valve
(4) Triple eccentric sealing valve
2. Classified by sealing surface material
(1) Soft sealed butterfly valve.
1) The sealing pair is composed of non-metallic soft materials.
2) The sealing pair is composed of metal hard materials and non-metal soft materials.
(2) Metal hard sealed butterfly valve. The sealing pair is composed of metal hard materials.
3. Fluorine lined butterfly valves classified by sealing form
(1) Forced sealing butterfly valve
1) Elastic sealed butterfly valve. The sealing pressure is generated by the compression of the valve seat by the valve plate when the valve is closed, and the elasticity of the valve seat or valve plate
2) External torque sealed butterfly valve. The sealing pressure is generated by the torque applied to the valve shaft externally
(2) Pressure sealed butterfly valve. The sealing pressure is generated by the pressurization of the elastic sealing element on the valve seat or valve plate
(3) Automatic sealing butterfly valve. The sealing pressure is automatically generated by the medium pressure.
4. Fluorine lined butterfly valves classified by working pressure
(1) Vacuum butterfly valve. Butterfly valves with working pressure lower than the atmospheric pressure of the standard reactor.
(2) Low pressure butterfly valve. Butterfly valve with nominal pressure PN<1.6MPa.
(3) Medium pressure butterfly valve. Butterfly valves with nominal pressure PN ranging from 2.5 to 6.4 MPa.
(4) High pressure disc valve. The nominal pressure PN is 10. Butterfly valve with a pressure range of 0-80.0MPa.
(5) Ultra high pressure butterfly valve. Butterfly valves with nominal pressure PN>100MPa.
5. Fluorine lined butterfly valves classified by operating temperature
(1) High temperature butterfly valve. t> 450 ° C butterfly valve
(2) Medium temperature disc valve. 120 C (3) Room temperature butterfly valve. 40C (4) Low temperature butterfly valve. One hundred (E) Ultra low temperature butterfly valve. Butterfly valve with t<100 ° C
6. Fluorine lined butterfly valves classified by connection method
(1) Clamp type butterfly valve
(2) Flange butterfly valve
(3) Ear type butterfly valve
(4) Welded butterfly valve
Precautions for fluorine lined butterfly valve:
Due to the multi-layer soft stacked sealing ring being fixed on the valve plate, when the valve plate is in a normally open state, the medium forms a positive flushing on its sealing surface, which directly affects the sealing performance after being flushed.
2. Due to structural limitations, this structure is not suitable for valves with diameters below DN200, as the overall structure of the valve plate is too thick and has high flow resistance. Fluorine lined butterfly valve product usage: D371F46 Clamp type fluorine lined butterfly valve FEP is suitable for use in pipelines with various concentrations of aqua regia, sulfuric acid, hydrochloric acid, hydrofluoric acid, as well as various organic acids, strong acids, and strong oxidants from -50 ℃ to 150 ℃. FEP is also suitable for use in pipelines with various concentrations of strong alkaline organic solvents and other corrosive gases and liquid media.
Characteristics of fluorine lined butterfly valve:
When in reverse flow state, the seal between the valve plate and the valve seat is pressed against the valve seat by the torque of the driving device. As the reverse medium pressure increases, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the regulating ring after being loaded compensates for the tight pressure on the sealing surface between the valve plate and the valve seat, playing an automatic compensation role. Therefore, unlike existing technologies that install soft and hard multi-layer sealing rings on the valve plate, this utility model directly installs them on the valve body, and adding an adjusting ring between the pressure plate and the valve seat is an ideal bidirectional hard sealing method. It will replace gate valves and globe valves

The fluorine lined butterfly valve still has the following problems during use:

1、 Due to the multi-layer soft and hard stacked sealing ring fixed on the valve plate, when the valve plate is in a normally open state, the medium forms a positive flushing on its sealing surface. The soft sealing tape in the metal sheet interlayer is directly affected by the flushing, which directly affects the sealing performance.
2、 Due to structural limitations, this structure is not suitable for valves with diameters below DN200, as the overall structure of the valve plate is too thick and has high flow resistance.
3、 Due to the principle of rubber lined butterfly valves, the sealing between the sealing surface of the valve plate and the valve seat is achieved by the torque of the transmission device, which presses the valve plate against the valve seat. In the positive flow state, the higher the medium pressure, the tighter the sealing compression. When the medium in the flow channel flows backwards and the unit positive pressure between the valve plate and the valve seat is less than the medium pressure as the medium pressure increases, the seal begins to leak.
4、 High performance fluorine lined butterfly valve,
Characterized in that the valve seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of a soft T-shaped sealing ring.
The sealing surface between the valve plate and the valve seat is a slanted cone structure, and a heat-resistant and corrosion-resistant alloy material is welded on the slanted cone surface of the valve plate; The structure in which the spring fixed between the adjusting ring pressure plate and the adjusting bolt on the pressure plate are assembled together. This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body, as well as the elastic deformation of the valve stem under medium pressure, solving the sealing problem of the valve in the bi-directional exchange of medium transportation process
The sealing ring is composed of multiple layers of soft T-shaped stainless steel sheets on both sides, which has the dual advantages of metal hard sealing and soft sealing. It has zero leakage sealing performance in both low and high temperature conditions. The experiment proves that when the pool is in a positive flow state (the direction of medium flow is the same as the direction of butterfly plate rotation), the pressure on the sealing surface is generated by the torque of the transmission device and the effect of medium pressure on the valve plate. The tighter the compression between the inclined conical surface of the valve plate and the sealing surface of the valve seat when the positive medium pressure increases, the better the sealing effect.
When in reverse flow state, the seal between the valve plate and the valve seat is pressed against the valve seat by the torque of the driving device. As the reverse medium pressure increases, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the regulating ring after being loaded compensates for the tight pressure on the sealing surface between the valve plate and the valve seat, playing an automatic compensation role.
Therefore, unlike existing technologies that install soft and hard multi-layer sealing rings on the valve plate, this utility model directly installs them on the valve body, and adding an adjusting ring between the pressure plate and the valve seat is an ideal bidirectional hard sealing method. It will replace gate valves and globe valves.