In chemical plants the bigger fear than high pressure is corrosion. An ordinary stainless valve may perforate in days in concentrated HCl; strong alkali ages seals fast.

Against strong corrosion the usual answer is not pricier metal but a protective lining — fluorocarbon. This article explains lined valves.

1. What Is a Lined Valve

A lined valve has an inner fluoropolymer layer (usually PTFE, PFA, FEP) so corrosive media contact only the plastic, not the metal substrate.

  • Metal provides pressure strength;
  • Fluoropolymer provides chemical resistance;
  • Together they are safe and economical.

2. Why Fluoropolymer Resists

PTFE (polytetrafluoroethylene) reacts with almost nothing, the plastic king:

  • Resists strong acid, alkali, oxidizer;
  • Wide temperature, PTFE around 200 C;
  • Low friction, less fouling.

PFA performs close to PTFE but is melt-processable for uniform lining; FEP is tough for complex shapes.

3. Common Lined Valve Types

Type Feature Use
Lined ball Good seal, fast On-off, zero leak
Lined butterfly Large bore, cheap High flow, low/mid pressure
Lined diaphragm No packing, no extern leak High-purity, toxic
Lined globe Good throttling Small-bore trim

4. Example Media

  • HCl, dilute H2SO4, HF (special lining);
  • Caustic soda, liquid alkali;
  • Sodium hypochlorite, bleach;
  • Most organic solvents.

Real compatibility depends on concentration and temperature, not name alone.

5. Limits and Cautions

Lining is not universal:

  • Not for the extreme high-temp/pressure ends (plastic has a ceiling);
  • Strong oxidizers (e.g., fuming nitric) may not apply;
  • Vacuum or negative pressure needs special design to avoid lining collapse;
  • High particle content wears the lining.

6. Negative Pressure and Vacuum Risk

Under vacuum the lining can be sucked loose or wrinkled by pressure difference, causing leakage or blockage. Lines that may be evacuated need specially designed vacuum-rated lining.

7. Installation and Maintenance

  • Avoid impact and welding heat conducting to the lining;
  • Tighten flange bolts evenly to avoid cracking the lining;
  • Do not pry the lining with metal tools during service.

8. Quick Selection

Confirm: medium name and concentration, working temperature, vacuum or not, particle content, pressure class, on-off or throttling.

Give these to the supplier to fix lining material (PTFE/PFA/FEP) and valve structure.

9. Common Myths

  • Myth: stainless resists all acid/alkali. HCl and chlorides attack ordinary stainless fast.
  • Myth: lining resists everything. Temperature and oxidizers have limits.

Summary

For strong corrosion choose lined valves: metal for pressure, fluoropolymer for resistance, good value. The key is stating concentration, temperature and vacuum clearly, and picking the right lining and structure so the valve works long-term in acid and alkali.

Wuxi Quankong Valve & Fluid Control Co., Ltd.
Industrial Valves | Valve Selection | Actuator Packages | Fluid Control Solutions
Email: [email protected]

在化工车间里，最怕的不是高压，而是腐蚀。一台普通不锈钢阀门，碰到浓盐酸可能几天就穿孔；碰到强碱，密封迅速老化。

对付强腐蚀，常用办法不是换更贵的金属，而是给阀门“穿一层防护服”——衬氟。这篇文章讲清衬氟阀门怎么用。

一、什么是衬氟阀门

衬氟阀门在阀体内部衬一层氟塑料（常见 PTFE、PFA、FEP），让腐蚀性介质只接触氟塑料，不接触金属基体。

  • 金属负责承压和强度；
  • 氟塑料负责耐化学腐蚀；
  • 两者配合，既安全又经济。

二、氟塑料为什么耐腐蚀

PTFE（聚四氟乙烯）几乎不跟任何化学品反应，被称为塑料王：

  • 耐强酸、强碱、强氧化剂；
  • 使用温度宽，PTFE 可达 200℃ 左右；
  • 摩擦系数低，不易结垢。

PFA 与 PTFE 性能接近，但可熔融加工，衬里更均匀；FEP 韧性好，适合复杂形状。

三、常见衬氟阀门类型

类型 特点 适用
衬氟球阀 密封好、开关快 切断、零泄漏
衬氟蝶阀 大口径、经济 大流量、中低压
衬氟隔膜阀 无填料、无外漏 高纯、剧毒介质
衬氟截止阀 调节性好 小口径节流

四、适用介质举例

  • 盐酸、稀硫酸、氢氟酸（需特殊衬里）；
  • 烧碱、液碱；
  • 次氯酸钠、漂白液；
  • 多数有机溶剂。

具体兼容性要看介质浓度和温度，不能只看名称。

五、局限与注意

衬氟不是万能：

  • 不耐高温高压的极限工况（氟塑料有温度上限）；
  • 强氧化性介质（如发烟硝酸）可能不适用；
  • 负压或真空工况要特别设计，防止衬里脱壳；
  • 颗粒含量高会磨损衬里。

六、负压与真空风险

衬氟阀门在负压下，衬里可能因内外压差被吸脱、起皱，导致泄漏甚至堵塞。真空或可能抽空的管线，要选专门设计的负压型衬里。

七、安装与维护

  • 避免敲击、焊接时高温传导到衬里；
  • 法兰螺栓均匀紧固，防止衬里被压裂；
  • 检修时不要用金属工具硬撬衬里。

八、选型速查

确认：介质名称与浓度、工作温度、是否负压、颗粒含量、压力等级、需要切断还是调节。

把这些交给厂家，才能定下衬里材料（PTFE/PFA/FEP）和阀门结构。

九、常见误区

  • 误区：不锈钢能扛所有酸碱。 盐酸、氯离子环境会迅速腐蚀普通不锈钢。
  • 误区：衬氟能耐一切。 温度和氧化性介质有上限。

总结

强腐蚀介质首选衬氟阀门：金属承压、氟塑料防腐，性价比高。关键是把介质浓度、温度和是否负压说清，选对衬里材料和结构，阀门才能在酸碱里长期稳定工作。

无锡泉控阀门流体控制有限公司
工业阀门 | 阀门选型 | 执行机构配套 | 流体控制解决方案
技术咨询：[email protected]