Impedance heating of pipelines and equipment - General, testing, marking, and documentation requirements

1.1 General

This standard is divided into seven clauses that cover requirements for impedance heating when installed in ordinary locations as well as in hazardous (classified) locations. Clause 1 provides the scope, purpose, and typical applications. Clause 2 lists normative references to other standards that are indispensable in applying this standard. Clause 3 provides definitions that are not found in other standards or have been modified for use with this standard. Clause 4 establishes general system requirements for impedance heating. Clause 5 provides both type and routine testing requirements for insulated impedance conductors and other impedance system components. Clause 6 covers marking requirements. Clause 7 details additional documentation requirements.

This standard also contains annexes. Annex A provides bibliographical references. Annex B provides requirements for installations that are in explosive atmospheres classified using the Division method of area classification. Annex C provides additional requirements in explosive atmospheres classified using the Zone method of area classification. Annex D covers impedance heating design verification methodologies. Annex E provides reference tables associated with insulated impedance conductor testing in Clause 5. Annex F provides the formula for calculating insulation resistance. Annex G provides alternative national markings.

1.2 Scope

This standard applies to general, testing, marking, and documentation requirements for impedance heating systems for steel or steel alloy pipe or equipment, rated up to and including 132 Vac. These heating system components are intended for installation in accordance with CSA C22.1, Canadian Electrical Code, Part I (CE Code); NFPA 70, National Electrical Code® (NEC®) in the USA; or with any other national electrical installation code, as applicable.

This standard applies to impedance heating systems that are intended to be installed in ordinary and hazardous locations. The hazardous location installations are limited to 30 Vac and include the following:

- In Canada: Zone 2; Zone 22; or Class I, Division 2; Class II, Division 2; Class III, Division 2 as described in CSA C22.1; and
- In the USA: Class I, Zone 2; Zone 22; or Class I, Division 2; Class II, Division 2; Class III, Division 2 as described in the NEC.

This standard also applies to power connection points and control methods used with impedance heating systems.

NOTE 1— Requirements for certification of insulated impedance conductors with insulation temperature ratings above 105 °C may be considered under a special investigation by an accredited certification body.

NOTE 2— Information on isolation transformers, power distribution, and control components can be found in IEEE Std 844.4/CSA C293.

1.3 Purpose

This standard provides testing, marking, design, and documentation requirements for impedance heating system components. Impedance heating systems that follow the component requirements as outlined here are intended to:

a) Maintain design temperature; and
b) Provide electrical, thermal, and mechanical durability and reliability.

1.4 Typical applications

1.4.1 General

Impedance heating systems provide heating for pipes and equipment in order to maintain or raise the temperature in the following typical applications.

1.4.2 Solidification prevention

Systems can be used to prevent the fluid in a pipe or equipment from solidifying. These include water, aqueous solutions, crude oil, pitch, asphalt, metals, sulfur, and other chemicals. The heating system compensates for pipe heat losses in order to maintain the temperature of the contents above the solidification point.

1.4.3 Viscosity maintenance

Systems can be used to maintain viscosity of a fluid in a pipe or equipment. Viscous materials such as heavy fuel and crude oil are generally heated to achieve optimum pump efficiency and pipe sizes. Usually these materials are preheated to a temperature that provides the desired viscosity and pumped to their destination through heated pipes designed to maintain that temperature.

1.4.4 Process heating

Systems can be used to maintain the temperature of fluids when process parameters require it. Systems can also be used to raise the temperature of process fluids flowing in the pipe or equipment, but they require increased heat input capacity.

1.4.5 Condensation prevention

Systems can be used to prevent gaseous materials from condensing. Some gases condense at low temperature and require heating to maintain their gaseous state during transportation. If pressure is significantly reduced during gas flow, such as through a valve, increased heat input capacity might also be required.

1.4.6 Re-melting solidified fluids

Systems can be used to re-melt solidified fluids. Some heating applications do not require heat during pumping, but only supply heat to re-melt pipe contents and bring them up to temperature prior to pumping. A typical example is an infrequently used loading or unloading pipeline.

1.4.7 Terminology

In this standard, shall is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; should is used to express a recommendation or that which is advised but not required; and may is used to express an option or that which is permissible within the limits of the standard.

Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.

Notes to tables and figures are considered part of the table or figure and may be written as requirements.

Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.