Envelope Gaskets

PTFE Envelope Gaskets

A trouble-free sealing solution

CHEMISEAL® PTFE envelope gaskets offer positive, trouble-free sealing in most applications, ranging from mild to severely corrosive environments. PTFE envelope gaskets are available in a broad range of standard sizes and configurations, as well as custom sizes upon request. PTFE envelope gaskets are ideal for use in equipment employing flanges made from alloy, standard steel, glass-lined, plastic, ceramic, conical-end glass pipe and more.


Slit Envelope Gaskets

These are essentially ring gaskets with .020" thick leaves slit from the OD to approximately 3/64" from the ID. The OD of the jacket extends and nests within the bolt circle. The jacket ID is the nominal ID of the pipe. The bearing surface is determined by the filler dimensions as the jacket requires clearance between the filler ID and the jacket slit diameter. These slit envelope gaskets are the most widely used gasket type. Available in sizes 1" to 50" OD.

Milled Envelope Gaskets

Made from premium PTFE cylinder stock, the milled envelope jackets are machined from their OD to within 3/64" of the ID leaving a shield of approximately .020" top and bottom. The flat ID of the jacket fits flush with the pipe ID while the jacket OD nests within the bolt circle. Milled envelope gaskets are available in standard sizes as well as special sizes up to 50" OD.

Double Jacket Envelope Gaskets

These envelope gaskets are recommended for vacuum service. Their design completely covers the filler material with two overlapping virgin PTFE jackets for optimum protection from corrosive attack.


Style 6300

1/16" or 1/8" thick filler for maximum softness, formability and low compressive bolt loading.

Style 6302

Corrosion resistant, corrugated stainless steel between two layers of conformable, soft filler for pressures up to 300 psi (pounds per square inch).

Style 6303

Adapter steel core with 1/8" thick conformable, soft filler on each side.

Style 6305

Same configuration as Style 6300, using 1/16" or 1/8" Garlock BLUEGUARD® 3000 filler.

Style 6326

3/16" or 5/16" total thick Garlock BLUEGUARD® 3000 filler between two layers of material.


Designed for severe service conditions. CHEMISEAL® GZ envelope gaskets are soft, easily compressible, chemically inert PTFE. The combination of chemical resistance and very low permeability make the CHEMISEAL® GZ envelope gasket a superior gasket for severe corrosive service in glass lined equipment where conventional envelope gaskets will not meet the requirements.

Designed to seal from cryogenic temperatures to 500°F (260°C) and conform to all FDA specifications. Additional features include a stress free envelope, low torque sealing, and no fiber or filler.

Standard Dimensions = ASA Dimensions. Also available in ANSI Dimensions




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