Type A PTFE Envelope Gasket

If you are looking for high quality Type A PTFE Envelope Gasket, you can choose Taifno as your supplier and long-term partner. This product has a soft filler core wrapped in a PTFE jacket with a slit cut from the outer edge to the inner bore. Available in sizes up to DN500. Gasket factor m=2.5, minimum seating stress y=20 MPa.

What Is Type A PTFE Envelope Gasket?

A Type A PTFE envelope gasket consists of a PTFE outer jacket with a soft filler core inside. The PTFE jacket is slit from the outer edge inward to the inner bore, allowing the filler core to be inserted.

Structure:

PTFE Jacket: Made from PTFE sheet or tubing (typically 0.8-1.0mm thick), slit from the outer edge to approximately 1.5-2mm from the inner bore

Filler Core: Non-metallic material such as asbestos-free rubber sheet, compressed fiber, or graphite composite sheet

Type A Construction: The slit design makes insertion of the filler core simple — reducing manufacturing complexity and cost

Key characteristics:

PTFE jacket: Provides universal chemical resistance (pH 0-14), non-stick surface, and protects the filler core from chemical attack

Filler core: Provides compressibility, resilience, and the ability to conform to flange irregularities

Economical: Lower manufacturing cost than Type B or C — cost-effective for general chemical service

Comparison and Selection Guide

Type A vs Type B vs Type C vs Solid PTFE

Quick Selection Guide

Primary Applications

Technical Specifications

Type A PTFE Envelope Gasket Properties

Available Sizes

Quality Assurance

100% Virgin PTFE Resin — consistent quality, batch after batch

Full Traceability — material certificates available on request

Multiple Filler Options — asbestos-free rubber, compressed fiber, graphite composite

Custom Sizes — available in standard flange sizes and custom dimensions

Lead Time — standard sizes in stock (24-48 hours); custom sizes 5-10 days

FAQ

Q: When should I use Type A PTFE envelope gasket?

A: A Type A PTFE envelope gasket consists of a PTFE jacket with a slit cut from the outer edge to the inner bore, with a soft filler core inserted inside. The PTFE jacket provides universal chemical resistance (pH 0-14), while the filler core provides compressibility and resilience.

Use Type A when: You need chemical resistance for low-to-medium pressure corrosive service (up to 4.0 MPa) and cost is a consideration.

When NOT to use Type A: High-pressure or critical services where sealing integrity is paramount, consider Type B or C.

Cost comparison: Type A costs 30-50% less than solid PTFE gaskets of the same size, making it the preferred choice for general chemical service.

Q: Type A vs Type B vs Type C, which one should I choose?

A: Type A (slit) is the most economical, best for low-pressure general chemical service.

Type B (machined) offers better sealing integrity with a full PTFE envelope and no slit, best for medium-high pressure critical service.

Type C (corrugated metal) provides the highest pressure rating and blowout resistance, best for high pressure and thermal cycling.

Quick rule:

Up to 4.0 MPa, general chemicals → Type A.

Higher pressure, critical service → Type B.

High pressure, thermal cycling, blowout risk → Type C.

Size note: Type A recommended up to DN500; for larger diameters, Type C is preferred.

Q: What are the limitations of Type A envelope gaskets and what are the most common mistakes?

A: Temperature: Up to +200°C.

Pressure: Up to 4.0 MPa (40 bar).

Chemical: pH 0-14 universal resistance, NOT compatible with molten alkali metals or elemental fluorine at high temperatures.

Three common mistakes: 

(1) Using Type A in high-pressure service: above 4.0 MPa, the gasket may deform or fail; use Type B or C. 

(2) Over-tightening: excessive compression can damage the PTFE jacket at the slit, exposing the filler core to chemical attack. 

(3) Using in applications with media that permeate PTFE: some chemicals (nitric acid, chlorine, ethylene oxide) can permeate through PTFE over time and attack the filler core. For these services, replace gaskets regularly or use solid PTFE gaskets.