PFA Lined Globe Valve

Size: 1/2" - 8" (DN15 - DN200)

Pressure: Class 150 - 300 / PN 10-40

Standard: MSS SP-111, manufacturer-specific

Body Materials: Carbon steel (A216 WCB) or ductile iron outer body; PFA (perfluoroalkoxy) full-body liner (3-5mm) covering all wetted surfaces — body bore, seat ring area, disc contact surface, bonnet interior up to packing area

Seat: PFA liner extends to seat ring area for disc shutoff contact; disc is PFA-encapsulated — metal core for structural strength, PFA shell for corrosion isolation

Design: Globe valve body with PFA liner; disc lifts off seat for throttling and shutoff; PFA covers every wetted surface — no exposed metal in the flow path

Why PFA, Not PTFE, for Globe Valves

Both materials are chemically inert to the same range of corrosive media. PTFE is cheaper, proven, and it works. Most lined valves in the industry use PTFE liners. So why specify PFA for a globe valve?

It comes down to how globe valves operate. They throttle. The disc doesn't just snap open and closed like a ball valve — it modulates flow, sliding across the seat surface on every cycle. Hundreds of cycles. Thousands of cycles. And every time that disc contacts the PTFE liner at the seat, two problems show up.

First: cold flow. PTFE creeps under sustained mechanical load. The seating force compresses the PTFE at the disc-seat contact zone. Over hundreds of cycles, that compression thins the liner until it can't hold shutoff pressure. You see it as increasing seat leakage over time — the liner is literally being squeezed thinner with every close cycle.

Second: surface finish. PTFE liners are compression-molded or paste-extruded. The surface isn't as smooth as it could be. Rougher surface means higher friction at the disc-to-seat sliding contact, which accelerates wear on both the disc encapsulation and the seat liner area.

PFA solves both. It has roughly 10x less creep under load compared to PTFE — the seat area holds its dimensional shape through thousands of throttling cycles. And PFA's melt-processability produces a smoother, more uniform liner surface that reduces sliding friction at the disc-seat interface.

The tradeoff is cost. PFA liner material runs 30-50% more than PTFE. But for a throttling globe valve in corrosive service where the disc-seat pair cycles thousands of times, that cost difference buys you a liner that survives more cycles before seat leakage forces replacement. That's the calculation — not which material is cheaper per kilogram, but which material keeps the valve in service longer between liner replacements.

The Disc Is Part of the Lining System

The globe disc isn't just PFA-lined on the contact face. It's PFA-encapsulated — metal core, PFA shell covering the entire disc surface. The disc lives inside the process fluid just like the body bore does. A disc with PFA only on the seat face would leave metal exposed to corrosive media everywhere else. That's not full isolation. PFA encapsulation means the disc is as chemically isolated as the body liner — no metal, no corrosion, no contamination from the disc either.

Throttling Where Nothing Else Survives

PFA lined globe valves sit in corrosive throttling service where metal-seated globe valves can't operate — acid concentration control, caustic flow modulation, pharmaceutical solvent metering, chemical reactor feed regulation. The service demands both corrosion resistance and throttling precision. PFA on the liner and disc gives you the corrosion barrier. The globe disc-to-seat geometry gives you the throttling control. Together they handle the job that neither a lined ball valve (great isolation, poor throttling) nor a metal globe valve (great throttling, zero corrosion resistance) can do alone.

A: You can, but it's over-specified for that role. If you need shutoff only in corrosive service, a PTFE lined ball valve is simpler and costs less. Globe valves earn their place when throttling is part of the requirement.

A: It depends on the seating force, disc travel distance, and process temperature. In typical acid throttling service at ambient to moderate temperatures, PFA liners hold dimensional stability through several thousand full cycles. Monitor seat leakage — when it trends upward beyond Class IV, the liner at the seat zone is thinning and replacement is due.

A: Essentially yes. PFA and PTFE resist the same range of corrosive media — strong acids, oxidizers, halogens, organic solvents. PFA's maximum continuous service temperature is slightly lower than PTFE's (260°C vs 280°C), but within that range the chemical resistance profile is equivalent.

A: PTFE or PFA packing above the bonnet liner zone, with a corrosion-resistant stem that's also PFA-covered where it passes through the bonnet bore. The packing zone is the transition point — the liner covers the bonnet interior up to the packing area, and packing seals the stem above that point.

A: Not in the field. PFA liners are molded into the body cavity — removing and replacing the liner requires factory re-lining. Monitor seat leakage trends and plan valve replacement or factory re-lining when leakage exceeds acceptable limits.