The valve needs to be lined with the typical scene
1. Corrosive media
Strong acid (sulfuric acid, hydrochloric acid, hydrofluoric acid, etc.), strong alkali (sodium hydroxide, potassium hydroxide, etc.), organic solvents (such as acetone, chloroform).
- Example: Valves conveying concentrated sulfuric acid in chemical production need to be lined with PTFE (polytetrafluoroethylene) or PFA (perfluoroalkoxy resin) to prevent corrosion.
2. High or low temperature media
High temperature (>200 ° C) or deep cold (<-50 ° C) environment, ordinary metals are easy to deformation or embrittlement.
- Examples: high-temperature steam pipeline valves lined with ceramic or high-temperature alloy; liquid nitrogen valves lined with low-temperature rubber.
3. Highly abrasive media
Containing solid particles (such as slurry, mud, catalyst powder) or high-speed fluid.
- Example: slurry conveying valves lined with wear-resistant ceramics or tungsten carbide (such as tungsten carbide).
4. Clean or sterile requirements
Food, pharmaceutical, semiconductor industry, need to avoid metal ion contamination or bacterial growth.
- Example: Pharmaceutical pure water system valves lined with EPDM (EPDM) or PTFE.
5. Electrochemical corrosion risk
Medium and metal valve material electrochemical reaction (such as seawater, salt water).
- Example: seawater desalination valve lined with Hastelloy (Hastelloy) or rubber lining.
Selection recommendations
1. clear media parameters: list the composition of the medium, concentration, temperature, pressure, flow rate and particle content.
2. matching material performance: priority to meet the most critical needs (such as strong corrosion scenarios preferred PTFE, wear-resistant scenarios selected ceramics).
3. Verify compatibility: refer to material corrosion tables (e.g. ISO 12944 or manufacturer's datasheets). 4. Consider maintenance costs.
4. Consider maintenance costs: cost-effective solutions (e.g. PP lined valves for mildly corrosive scenarios).
5. Customised for special conditions: extreme environments (e.g. nuclear radiation) require special alloys or composite linings.
Key factors in the selection of lining materials
| Consideration | Direction of material selection | Source material |
| Corrosion Resistance | Selection of inert materials according to the chemical properties of the medium | PTFE, PFA, PVDF, EPDM, Fluoroelastomer, Ceramic, Hastelloy |
| Temperature Range | Ceramic or alloy for high temperature; cold resistant rubber or PTFE for low temperature. | Ceramic (1200°C resistance), EPDM (-50~150°C) |
| Abrasion Resistance | Highly rigid materials (ceramics, tungsten carbide) or elastic materials (rubber) | Alumina ceramics, silicon carbide, ultra-high molecular weight polyethylene (UHMWPE) |
| Pressure Rating | High-pressure environments require high-strength linings (metal alloys or composite layers). | Inconel, Duplex Stainless Steel |
| Hygiene Requirement | Non-toxic, easy to clean, smooth surface | PTFE, EPDM, 316L stainless steel + EPDM composite lining |
| Cost | Balancing performance and economics (e.g. PP is cheaper than PTFE but has lower temperature resistance) | PP (polypropylene), FRP (fibreglass reinforced plastic), natural rubber |
Common lining material characteristics and applicable scenes
1. Rubber lining (EPDM, NBR, fluorine rubber, etc.)
Applicable: water treatment, weak acid and alkali, temperature <150°C working conditions.
- Advantages: good elasticity, impact resistance, low cost.
- Disadvantages: not resistant to high temperature and strong oxidising medium.
2. Plastic lining (PTFE, PFA, PP)
Suitable for: concentrated sulphuric acid, chlor-alkali industry, food and pharmaceutical industry.
- Advantages: strong corrosion resistance, smooth surface (anti-adhesion). Disadvantages: low mechanical strength, not resistant to high temperature and strong oxidising media.
- Disadvantages: low mechanical strength, not resistant to high pressure.
3. Ceramic lining (alumina, silicon carbide)
Applicable: mineral slurry, grey slag, high temperature medium containing particles.
Advantages: super wear-resistant, high temperature resistant, corrosion resistant.
- Disadvantages: brittle, not resistant to impact.
4. Metal alloy lining (Hastelloy, titanium, monel)
Application: deep sea oil and gas, nuclear industry, strong corrosive and high pressure environment.
- Advantages: high strength, high temperature and pressure resistance.
- Disadvantages: high cost, complex processing.
5. Composite lining (such as PTFE + glass fibre, rubber + ceramic sheet)
Applicable: extreme working conditions (such as high temperature corrosive media containing particles).
- Advantages: optimised overall performance (wear + corrosion resistance).
- Disadvantages: complex process.
Precautions
1. Installation requirements: lined valves need to avoid violent installation to prevent cracking of the lining.
2. Sudden change of temperature: Plastic or rubber lined valves need to slowly raise and lower the temperature to avoid thermal stress damage.
3. regular inspection: high pressure or corrosive environment is recommended to check the thickness and integrity of the lining layer annually.
Through the rational choice of lining material and valve type, can significantly extend the valve life, reduce maintenance costs, and ensure process safety.