What is 4F board for chemical equipment lining
Information summary：Chemical equipment lining 4F board refers to the lining of polytetrafluoroethylene (PTFE, commonly known as "4F") board inside chemical equipment, which utilizes its excellent chemical stability, corrosion resistance, and high temperature resistance to protect the equipment body from strong corrosive media and extend the service life of the equipment.
1、 Core material: Polytetrafluoroethylene (PT
Chemical equipment lining 4F board refers to the lining of polytetrafluoroethylene (PTFE, commonly known as "4F") board inside chemical equipment, which utilizes its excellent chemical stability, corrosion resistance, and high temperature resistance to protect the equipment body from strong corrosive media and extend the service life of the equipment.
1、 Core material: Polytetrafluoroethylene (PTFE/4F)
Chemical characteristics:
Resistant to strong acids (such as sulfuric acid and nitric acid), strong bases (such as sodium hydroxide), strong oxidants (such as aqua regia), and organic solvents (such as benzene and ketones).
Extremely inert, almost does not react with any chemical substances, only molten alkali metals (such as lithium and sodium) may slowly erode.
Physical characteristics:
High temperature resistance: Long term use temperature -196 ℃~260 ℃.
Smooth surface: Low friction coefficient (0.04), not easy to adhere to media, easy to clean.
Insulation: Low dielectric constant and dielectric loss, suitable for anti-static scenarios.
2、 Lining process and structure
1. Common lining methods
Loose lining method: Cut and splice PTFE plates according to the equipment size, then loosely fit them onto the inner wall of the equipment and fix them with flanges or welding.
Advantages: Simple process and low cost;
Disadvantage: Easy to cause displacement of the inner lining due to temperature differences, suitable for atmospheric or low-pressure equipment.
2. Tight lining method (molding/winding):
By using mold pressing or spiral winding, PTFE plates are tightly adhered to the inner wall of the equipment, and bonding agents (such as glass fiber and graphite) are used to enhance adhesion.
Advantages: tight fit, resistant to negative pressure and temperature fluctuations;
Disadvantages: The process is complex and requires specialized equipment.
3. Welding lining:
Use hot melt welding (such as hot air welding, hot wedge welding) to splice PTFE plates into a single lining layer and fix it to the inner wall of the equipment.
Advantages: seamless, strong sealing, suitable for high corrosion and high purity requirements scenarios (such as pharmaceuticals and high-purity acid preparation).
2. Key points of structural design
Weld seam treatment: The weld seam needs to be polished flat to avoid corrosion caused by medium retention;
Corner reinforcement: Equipment bends, tees, and other areas that are prone to erosion require thicker lining layers (such as double-layer PTFE or composite fiberglass reinforcement);
Exhaust hole: Reserve exhaust holes under high temperature conditions to prevent the lining from bulging due to gas expansion.
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