ISO 4437-3:2014 specifies the characteristics of fusion fittings made from polyethylene (PE) as well as of mechanical fittings for piping systems in the field of the supply of gaseous fuels.

It also specifies the test parameters for the test methods referred to in this part of ISO 4437.

In conjunction with ISO 4437-1, ISO 4437-2, ISO 4437-4, and ISO 4437-5, it is applicable to PE pipes, fittings and valves, their joints, and joints with components of PE and other materials intended to be used under the following conditions: the maximum operating pressure (MOP) is based on the design stress, determined from the compound minimum required strength (MRS) divided by the C factor, and taking into account rapid crack propagation (RCP) requirements; and a temperature of 20 °C is taken as reference temperature for the design basis.

ISO 4437-3:2014 is applicable for fittings of the following types: electrofusion socket fittings; electrofusion saddle fittings; spigot end fittings (for butt fusion using heated tools and electrofusion socket fusion); socket fusion fittings; and mechanical fittings.