1 Scope

1.1 These requirements cover test procedures and performance criteria for the evaluation of nonmetallic gasket and seal materials such as elastomers, composite gasket material, flexible cellular material, thermoplastics and thermoplastic elastomers for specific end products.

1.2 The general use of these gasket and seal materials is to exclude or hold within an enclosure materials that are liquid, gas, or vapor.

1.3 The materials covered in this standard are incomplete in certain construction features or restricted in performance capabilities, and are intended for use as components in complete equipment.

1.4 This standard covers gaskets and seals as:

a)    Elastomers, thermoplastics and thermoplastic elastomers in the form of solid sheets, flexible cellular sheets, slabs, rolls, or parts, "O" rings, seats, shaft seals, and special forms.

b)    Composite gaskets in the form of sheets, rolls and cut forms of the types described in 3.2.

c)    Coated fabrics in the form of elastomers reinforced with fabrics in sheets or diaphragm form.

1.5 The material composition of these gaskets and seals excludes metals.

1.6 The gaskets and seals are evaluated for various properties to provide profile information - see Table 4.1. They are also evaluated for specific end-use applications - see Table 4.2. Table 4.3 specifies the oven aging required for establishing the maximum temperature for an expected use.

Summary of Topics

This revision to UL 157 includes the following changes in requirements:

• Clarification of Profile Test Applicability

• Deletion of Drinking Water End-Use Gasket Requirements

• Deletion of Compressibility, Recovery, and Sealability Test in Section 12

• Revision of ASTM References for Ozone Exposure

• Update and Removal of Dates on References to Outside Standards