1.1 This specification covers the requirements for direct and indirect reading sight liquid level indicators for general applications. General applications for indirect reading sight glasses are water and fuel service at working pressures 2.07 MPa (300 lb/in.²) and below, temperatures of 149°C (300°F) and below. General applications for direct reading sight glasses are applications in which the temperature does not exceed 66°C (150°F).

1.2 Direct reading sight glass indicators may consist of glass or plastic tubes with fittings including shutoff valves. Glass tubes may be used for low shock direct reading sight glass indicators in which the fluid is not compatible with plastic.

1.3 Indirect reading indicators may consist of a sealed chamber with a magnetic float or flag indicator.

1.4 Special requirements for naval shipboard applications are included in the supplement to this standard.

1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.