Lined Valves
Lined Valves Designed for Worldwide Industrial Uses
Lined valves are the unsung heroes of fluid handling, designed specifically to tackle the most challenging and corrosive media. Instead of manufacturing the entire valve body from expensive, exotic metals, a lined valve uses a standard, cost-effective metal housing with a corrosion-resistant plastic or elastomer liner on all wetted surfaces .
This design provides a “best of both worlds” solution: the metal body provides the mechanical strength and pressure containment, while the plastic liner provides the chemical resistance
Technical Specifications
When selecting a lined valve, you need to look beyond just the material. Key technical specifications include:
Size Range: Typically available from NPS ½” up to 24″ (DN 15 to DN 600), depending on the valve type .
Pressure Ratings: Most are rated for ASME Class 150 and PN10/16, which translates to lower-pressure applications (typically up to 16-20 bar) due to the limitations of the plastic liner .
Temperature Range: This is dictated by the liner material. For fluoropolymers, the range can be from -29°C up to 260°C. Elastomers like polyurethane have a much lower upper limit .
Liner Thickness: A critical factor for preventing permeation (migration of gas or liquid through the liner). Standard liners are often ~3mm thick, with “high permeation” liners available up to 5mm for handling very hazardous gases like chlorine .
Design Standards: Lined valves are manufactured to various standards like API 609, MSS SP-67 (butterfly), MSS SP-81 (knife gate), and ASME B16.5 for flange dimensions .
Why Choose Lined Valves?
The primary advantage of lined valves is their exceptional ability to handle highly corrosive and hazardous fluids cost-effectively. Here’s a breakdown of their main benefits:
Superior Corrosion Resistance: The inert liners, especially fluoropolymers like PTFE, PFA, and FEP, are chemically resistant to nearly all types of acids, caustics, solvents, and other aggressive chemicals .
Cost-Effective Alternative: They are significantly more economical than using solid high-alloy materials like Hastelloy, Monel, or titanium, which offer similar corrosion resistance but at a much higher cost .
High Purity and Non-Contamination: The smooth, inert liner surface prevents the fluid from contacting the metal body. This ensures no metallic ions leach into the media, making them ideal for ultrapure water, pharmaceuticals, and food processing .
Reduced Inventory and Installation Errors: A single lined valve with a specific fluoropolymer liner can handle a wide range of chemicals. This reduces the need to stock different expensive alloy valves for each specific application, simplifying inventory and avoiding costly mistakes .
Leakage Prevention: Modern lined valves feature advanced sealing technologies, such as live-loaded stem seals and fully encapsulated discs, to provide bubble-tight shutoff and prevent hazardous fugitive emissions
Types of Lined Valves?
Lined valves are available in various configurations to suit different flow control needs.
Lined Ball Valves: Use a rotating ball with a bore to start or stop flow. They provide reliable shut-off and are often combined with fusible links for fire safety, automatically closing when a set temperature is reached .
Lined Butterfly Valves: Feature a rotating disc and are compact, lightweight, and ideal for large pipe diameters. They offer bubble-tight shutoff and are popular in chemical, semiconductor, and water treatment plants .
Lined Plug Valves: Use a tapered or cylindrical plug with a passage. Known for their simple design, high flow capacity, and easy in-line maintenance, as they can be adjusted without disassembly from the pipeline .
Lined Check Valves: Allow flow in only one direction to prevent backflow. They are self-actuating, using the flow’s pressure to open and automatically closing when the flow stops or reverses .
Lined Diaphragm Valves: Use a flexible diaphragm to pinch or block the flow. The liner is integrated into the body, and the diaphragm isolates the bonnet and stem, making it excellent for slurries, viscous fluids, and corrosive services .
Lined Knife Gate Valves: Designed for shut-off in thick slurries and viscous media. A sharp gate cuts through the fluid to close, with a liner that fully protects the body from abrasion and corrosion .
Lining Materials
he choice of lining material is critical and depends on the specific chemical, temperature, and abrasiveness of the application. The table below compares the most common options.
| Lining Material | Key Properties | Max. Temperature | Typical Applications |
|---|---|---|---|
| PTFE | Excellent chemical resistance, low friction, non-stick, but soft and prone to permeation. | ~180°C | Broad chemical resistance, general-purpose corrosive fluids . |
| PFA | Very similar to PTFE but can be melt-processed. It is tougher, smoother, and has lower permeability. | ~200°C to 260°C | High-purity applications, handling strong oxidizing agents at high temperatures . |
| FEP | Excellent chemical resistance, good anti-stick properties. More permeable than PFA. | ~150°C to 200°C | A cost-effective alternative to PFA for many corrosive chemicals . |
| PVDF | Good chemical resistance, high mechanical strength and abrasion resistance. | ~120°C | Ultrapure water systems, acids, and applications requiring mechanical durability. |
| Polyurethane | Exceptional resistance to abrasion and wear, good flexibility, poor chemical resistance. | ~90°C | Slurries, mining, wastewater, and other highly abrasive media . |
| EPDM / Hypalon | Flexible, good resistance to water, dilute acids, and alkalis. Incompatible with oils and solvents. | ~130°C | Water treatment, dilute chemicals, and as a seat energizer behind other liners . |
