1.1 This specification covers direct buried underground pre-insulated, hot water piping systems with an upper temperature limit of 250 °F (121 °C) used to convey pressurized fluids for district heating. In the pre-insulated pipe industry and in this standard, this temperature range is called “low temperature hot water”.

1.2 This specification shall not be used for low-pressure steam systems, steam trap discharge or pressurized condensate systems, since there is a high risk of exceeding the upper temperature limits. Pumped condensate return lines that are vented to atmosphere are considered to be low temperature hot water and are acceptable for this application.

1.3 This specification covers only piping systems insulated and jacketed with bonded polyurethane (PUR) rigid foam. A piping system consists of both straight sections of pre-insulated piping as well as pre-insulated fittings and field closures of the insulation system, and all materials required to ensure a water tight insulation system which will preclude water from entering the insulation from the surrounding soil. This specification does not encompass insulating or jacketing materials, or insulation methods, which do not produce factory, pre-fabricated, insulated and jacketed units for assembly at the field site.

1.4 The insulated piping systems covered by this specification do not possess an air gap between the carrier pipe and the insulation nor between the insulation and jacket. For straight pipe sections of the piping systems covered by this specification, these three components are bonded together.

1.5 The carrier piping that is part of the insulated piping system covered by this specification shall be designed, fabricated, and tested to the requirements of ANSI/ASME B31.1 (Power Piping).

1.6 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered to be the standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.