Section 13 — Electrical

Electrical Tracing

IPE Engineering Practice IPE-EP-13-12-1

Document number: IPE-EP-13-12-1 · Section: 13 — Electrical

SCOPE

• This Practice and its references describes the requirements for design, fabrication, installation, testing, and inspection for the including power transformer(s), electric heat trace control panel(s), electric heat tracer(s), temperature sensors, temperature controllers, contactors, enclosures, and all necessary auxiliary equipment and controls.
• All construction and installation of heat tracing material shall be suitable for the location and the area classification involved. The extent of the hazardous (classified) and non-hazardous (unclassified) areas as shown on the area classification drawings shall govern.
• This Practice is appropriate for attachment to an inquiry or purchase document when accompanied by the referenced IPE Engineering Practices and completed Data Sheets.
• Any deviation from this Practice must be approved by the procedure described in EP 1–1–3.
• A revision bar indicates all changes made to this Revision.

REFERENCES

• Following is a listing of the Codes, Standards and Specifications referenced herein; and which shall be used with this Practice. The latest revision shall be used unless noted otherwise. In case of conflict between this document and these Codes, Standards and Specifications, the more stringent requirement shall govern unless specifically noted otherwise herein.

STANDARDS AND PUBLICATIONS

STANDARDS AND PUBLICATIONS (CONT.)

• Furnish information such as technical bulletins, typical test data, quality control procedures, drawings, etc. giving details of manufacturing, installing and testing of the equipment to be provided.

DEFINITIONS

• Contractor – Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
• Inspector – A Inflection Point Engineering, LLC appointed engineer or inspector.
• Manufacturer – The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a Manufacturer by a Contractor or the Owner. An indirect order is one issued to a Manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
• Owner – Inflection Point Engineering, LLC.
• Owner’s Engineer – A Inflection Point Engineering, LLC appointed engineer.
• Purchaser – The party placing a direct purchase order. The Purchaser is the Owner’s designated representative.

SERVICE CONDITIONS

Electric heat tracers and sensors will be installed in a typical petrochemical environment. Insulation will be applied over the electric heat tracers. Certify and warrant that the equipment will deliver rated performance and service life when subjected to any of the following conditions:

• Humidity: Relative humidity range: 0–95%
• Installation Temperatures
• Minimum: 0ºF
• Maximum: +110ºF
• Operating Ambient Temperatures
• Minimum -15ºF
• Maximum +120ºF

DESIGN, CONSTRUCTION, AND MATERIALS

• General Requirements
• The purpose of the installed electric heat tracing of a piping system is to suitably limit liquid viscosities at operating/ambient temperatures, to keep lines from freezing, and to prevent hydrate formation. In addition, certain heat trace systems are installed to maintain various processes at desired temperatures.
• The equipment and all components shall meet the material selection, construction, and testing requirements given by the industry standards listed in this Practice.
• In addition, the materials, construction and testing of the equipment and accessories supplied shall meet the quality as described in the manufacturer’s technical literature listed in the Electrical Heat Tracing Data Sheet (EP 13-12-1 DS) attached to this Practice.
• The Contractor shall furnish to the Owner information such as technical bulletins, typical test data, quality control procedures, drawings, etc., giving details of manufacturing, installing and testing of the equipment to be provided.
• Listings
• Electrical equipment, including materials, fittings, devices, apparatus that are a part of the heat tracing system shall be listed or approved by and bear the label of the Underwriters’ Laboratories (UL) and/or Factory Mutual (FM) for the service conditions and the classification for the area in which the equipment is to be installed.
• All equipment listed for hazardous (classified) locations shall be marked to show the class, division, group and operating temperature or temperature range.
• Materials
• Materials and equipment shall be standard products of established Manufacturers who have produced the type of equipment specified for at least two years. All equipment and materials shall be new and of sufficient quality to provide at least 20 years of normal operation under the service conditions described above and when installed, operated and maintained in accordance with the Manufacturer’s recommendations.
• If the Manufacturer has more than one category of manufacturing and/or materials quality and reliability such as “utility grade” and “commercial grade”, then only the materials of the highest quality shall be used.
• Design Parameters
• Where pipe maintenance temperatures are below 300ºF, heating cables shall be of the self– regulating, parallel–circuit, semi–conductive resistance type.
• Where self–regulating heaters cannot be used for pipe maintenance temperatures below 300ºF, cables shall be of the constant wattage, parallel resistance type.
• Where pipe maintenance temperatures are above the ratings for self–limiting and constant wattage type tracing, heating cables shall be of the series resistance MI (mineral insulated) type. See EP 13–2–1 Sec.15.1.
• The heat trace shall be capable of being operated in either of the following modes:

• Automatic: During automatic operation the electric heat tracing system shall maintain the temperature specified in the Electrical Heat Tracing Field Test Data Sheet for the process and miscellaneous piping system. Heat tracer energization and de–energization shall be initiated by temperature controller at preset low and high temperatures, respectively. Alarm signal shall be initiated at a preset pipe temperature (if specified).
• Manual: On manual operation, the heat tracer can be energized and de–energized by controlling the “hand–off–automatic” selector switch either to “hand” or to “off” position.
• For freeze protection a temperature of at least 10ºF above liquid pour dewpoint or freezing point is required.
• Unless otherwise specified, all equipment shall be suitable for outdoor installation.
• The heating circuit shall operate satisfactorily from a 3–phase power supply within the following tolerances:
• Frequency: 60 Hz ± 5%
• Voltage: Specified normal voltage ± 10%
• Combining heat tracing loads with power panels at the 208/120–volt level will be permitted where feasible, and with Owner approval.
• Heat loss calculation shall be made based on:
• A normal maintained pipe temperature as specified in the Electrical Heat Tracing Field Test Data Sheet under exposure to ambient conditions of –15ºF, 20–mph steady state winds, with 50–mph maximum wind gusts, and stagnant fluid flow condition.
• Actual insulation thermal conductance at applied mean temperature per insulation manufacturer’s data.
• Actual thermal properties (specific heat, heat of fusion, melt temperature, specific gravity, etc.) of fluid.
• Actual radiant and convective heat loss properties of insulation covering.
• Good contact between the insulation, weatherproofing, and the pipe.
• Manufacturer’s standard procedure for heat trace selection.
• The electric heat tracing system must compensate for additional heat losses at flanges, valves, traps, pipe shoes, supports and other components larger than line size.
• For factory fabricated heaters of the series–circuit MI cable type, field measurement of all piping and devices shall be directed by a factory representative. Isometric drawings (utilizing existing Owner drawings) shall be prepared by the Contractor which detail the required lengths for each heat–traced pipe.
• For parallel–circuit type heaters that are cut to length in the field and, thus, do not require field measurements, isometric drawings shall be made from the piping drawings. These isometrics (which will be made by the Contractor) shall specify the required heater length for each heat– traced pipe.
• In areas that contain a temperature sensitive piping and/or fluid system, e.g. an area containing FRP piping, the Manufacturer shall verify that the heat tracing element shall not have a detrimental effect on the pipe material during any mode of operation, including abnormal conditions.

• In hazardous areas, heating cables and corners, also any auxiliary devices, must be selected which comply with the area classification. The Manufacturer shall establish that the maximum heater temperature is no more than eighty percent of the auto–ignition temperatures of the combustible gases, vapors, or dust associated with the hazardous environment. Where possible, this shall be established through the use of cables having a “T–rating”, as defined in the National Electric Code.
• The maximum sheath temperature of the loaded heat trace cables shall not exceed the Manufacturer’s recommendation and must not cause adverse effects to the heat tape, the insulation material, the pipe, the fluid in the pipe, and any other equipment. The maximum sheath temperature shall be defined as the resulting temperature of the sheath achieved when the tracers are continuously operated at 100ºF ambient, zero wind velocity, design process temperature controller contacts fail and stay closed, and normal voltage is continuously applied to the heater cables.
• All cables and wiring connections shall be protected against corrosive effects of electrolysis, galvanic action, and moisture.
• System Detail Description
• General
• A completely coordinated and integrated system, when specified, shall consist of the following main subassemblies shall be furnished:
• Electric heat trace control panel with temperature controllers, contactors, meters and control devices
• Electric heat tracers
• Temperature sensors (RTD’s or thermocouples, thermostat)
• The electric trace control panel, power distribution panel, temperature controllers and contactors shall be housed in an enclosure and shall comply with the NEC and the classified area per the Owner’s specification.
• Self–Regulating, Parallel Circuit Heaters
• These heating cables shall be self–regulating, parallel circuit, semi–conductive resistance type, with heating element extruded in a continuous strip between parallel copper conductors. Heating cables shall be capable of being overlapped without overheating at overlap places.
• If the pipelines are periodically purged with up to 150 psig steam, the heater cable shall be capable of withstanding a maximum intermittent pipe temperature of 365ºF (steam temperature) for no longer than 1000 hours total accumulated time.
• If the heater cable is sometimes exposed to water, weak acids or bases, or other inorganic and organic chemicals, the cable shall be covered with an extra thermoplastic rubber or fluoropolymer jacket.
• The heater shall operate on standard voltages without the use of special transformers. Line voltage fluctuations shall not appreciably affect heater wattage output.
• The heater shall not require the use of heat transfer cement or compounds in any form.
• The heater shall vary its output in response to temperature variations along a pipe due to heat sinks such as fittings or pipe supports.

• In hazardous areas, where mechanical protection is required, or on plastic pipes, all heater cables shall be covered with a braided tinned–copper covering.
• The maximum circuit length shall be used where possible to minimize the number of power connection points and phase changes. However, this length must not exceed the maximum length recommended by the Manufacturer. The loads on the three power phases shall be balanced.
• Cable
• The heat trace cable shall be covered by an outer fluoropolymer jacket. The complete tracer assembly shall be UL listed and/or FM approved and labeled for use in the classified areas as shown on the drawings. Heat traced cable in classified areas will require a braided tinned copper shield.
• The design of the electric heat tracer shall allow it to be cut to any length in the field without changing the heat output per lineal foot and without resulting in any part of the pipe being without heat.
• The heat tracer design shall enable variation of thermal output in response to temperature variations along a pipe due to heat sinks such as pipe fittings and supports. This variable output feature shall apply to each increment of the heat tracer.
• Self–Regulating Heat Tracer for Class I, Division 1 Areas: The heat tracer system, including the connection kit, shall be Class I, Division 1 self–regulating heat tracer. Class 1, Division 1 locations must have the tracer protected with a 30 MA GFI device.
• When specified a monitor wire shall be installed.
• Constant Wattage, Parallel Resistance Heaters
• These heating cables shall be of the zone parallel type in which the heating element is an alloy resistance wire connected to the bus wire at alternate, regular intervals. This tracer provides a constant wattage at a fixed voltage.
• The heater shall be jacketed with a material suitable to protect it from its working environment.
• Heat conductive cement shall be utilized where necessary to provide proper transfer of heat to the pipe and to reduce excessive sheath temperature.
• In hazardous areas, where mechanical protection is required, or on plastic pipes, all heater cable shall be covered with a braided tinned–copper coating. An outer covering shall be provided where it is necessary to protect the braid from the working environment.
• Series Resistance MI Cables
• These heating cables shall be of the MI (mineral insulated) type with one or more resistance conductors embedded in compressed magnesium oxide insulation and enclosed in a seamless metallic sheath.
• These metallic sheaths shall be copper, stainless steel, or Inconel depending on expected temperature exposure and Manufacturer’s temperature ratings as specified on Data Sheet.
• These cables shall be completely fabricated at the factory with hot and cold sections, end caps, etc. Testing at the factory shall be completed prior to shipment.

• Heater shall be manufactured in a continuous fashion with no factory splices. Any factory splices shall be approved in writing by the Purchaser.
• No field splices shall be allowed during the design phase for MI cables.
• Electric Heat Trace Control Panel (when specified)
• General
• The control panel shall be complete with all components including a power distribution panel, thermostatically controlled space heater(s), contactors, meters, control power transformers, terminal blocks, ground bus, indicating lights, control switches, temperature controllers, relays, ground fault detection system, and power and control wiring internal to the panel. A common trouble alarm relay for remote indication shall be provided for each enclosure of group mounted controllers.
• Grouped controllers shall have an “ACKNOWLEDGE” button to silence the remote alarm. Acknowledged alarms shall not block additional alarms.
• Each enclosure shall be designed for use in the classified area as indicated in the drawings.
• The electric heat trace control panel shall be sized and detailed by the supplier. Temperature controllers, indicating lights and control switches shall be mounted on the front of the panels. Provisions shall be made such that individual heater circuits may be locked out for maintenance and testing.
• Components as a minimum shall meet the requirements of NEMA–ABI, ICS1, ICS2, ST20 and UL 489, 508 and 467.
• High temperature shutoff control is also required to prevent the fluid, the insulation material and the heat tracers from overheating, and to guard against possible failure of the low temperature control thermostats.
• Continuity: A self–regulating heater with an additional monitor wire shall be used in conjunction with an alarm relay located in the panel to monitor the continuity of each heater circuit. This alarm shall monitor the continuity of the branch circuit breaker, the heater power wiring, and the heater conductors to the end of the heater circuit. This method is not applicable for constant wattage parallel resistance or MI series resistance cables.
• Current: An ammeter or a current sensing relay shall be used to monitor the current to each circuit. This method is applicable for constant wattage parallel resistance and MI series resistance cables.
• Low Temperature: Upon contact closure of a remotely located low temperature thermostat, a signal light in the panel shall light and indicate the heater circuit that is in the alarm condition. One alarm relay shall provide a dry contact for activating the customer’s remote alarm. A diode arrangement shall be used to isolate the individual alarm signals.
• Ground Leakage: A ground leakage type circuit breaker with an adjustable trip level shall be used in conjunction with a braided ground shield on the heater to monitor physical damage to the heater. The relay provided for each circuit shall light an indicating light and energize the one common alarm relay to provide remote alarm indication.
• Contactors

• Contactors shall be open type, electrically held, normally open with 120–volt AC coil. Contactors shall be fully rated and designed to withstand in–rush currents associated with the type of heat tracer being used. Contactors shall be mounted within the electric heat trace control panel. Contactors shall be the straight–through wiring type. Contacts shall be copper alloy with silver cadmium alloy contact buttons. Contactors shall have two poles in parallel for each power lead. Overloads shall not be used for heat trace systems.
• For 120–volt short heat trace lines, thermostat contact can be used instead of a contactor and can be directly connected in series with the heat tracer if such thermostat contact has the capability to withstand the inrush current of the heat tracer.
• Temperature Controller: The temperature controller shall operate satisfactorily under specified service conditions throughout the required sensor separation distances with shielded #16 AWG copper triad cable. The controller shall be factory set “on–off”, not proportional switching mode, with set points corresponding to the minimum holding temperature indicated on the drawings. Two independent high and low set points shall be adjustable from 0ºF to 200ºF. Features shall include high and low deviation Form C alarm contacts, two LED indicating lights to show when sensor ambient is at one set temperature and another at a second set temperature. Output shall be rated to operate the contactor coils.
• Devices
• Panel mounted indicating lights, switches, auxiliary control relays, and other devices shall be provided in accordance with the electrical heat tracing elementary diagram(s)
• Pushbuttons, switches, and indicating lights shall be NEMA 4, heavy duty type. Provisions shall be made for lamp testing of indicating light while equipment is in service by means of a “push–to–test” pushbutton.
• Control relays shall have a minimum of two form C contacts rated 120–volt AC, 5 amps. The contacts shall be wired to terminal board for external connection.
• Space Heaters: When specified, thermostatically controlled space heaters shall be provided to prevent condensation inside the panels. Heaters shall be rated 240–volt AC but shall operate at the required capacity on 120–volt AC. A single molded case circuit breaker shall be provided adjacent to the thermostat for connection of the heaters to 120–volt, single phase, 60–Hz power source.
• Direction of Cable Entry: Provision shall be made for power, control and instrument cables entry(s) as indicated in the purchase documents.
• Painting and Finish
• Each assembly shall be cleaned, primed and painted with a minimum of two coats of paint.
• Enclosure interiors shall be finish painted matte white. Exterior surfaces shall be finish painted per Manufacturer’s standard. Light grey similar to ANSI 61 is the preferred exterior finish.
• Supply paint, matching each color used, for field “touch–up” after installation of the equipment. Two one–pint aerosol spray cans of each color shall be supplied per assembly.
• Field Devices and Accessories
• Temperature Sensors

• Temperature Sensor (RTD) Assembly: When specified, a compensated RTD assembly shall be furnished with a 36–inch long jacketed armored cable connected to watertight junction box. The RTD shall be platinum, 100 ohms at 0ºC and 0.00385 ohm/ohm per C, mounted in a stainless steel tube suitable for strapping or fastening with adhesive tape to the pipe. The RTD leads shall be connected to the armored jacketed cable with a suitable termination. The armored jacketed cable shall consist of triad cable, #16 AWG minimum conductor size, teflon insulation, and teflon jacket covered with coated interlocking metal armor. The cable shall be terminated at the junction box in a threaded connector (1/2 inch NPT) and 9–inch exposed leads.
• The junction box shall be furnished with an internal ground terminal and provisions for mounting on flat steel plate. Wire nuts shall be included to hook up the insulation twisted lead connection to #16 AWG wires.
• When specified, a temperature sensor thermocouple assembly, type J or K thermocouples shall be provided for temperature control, low temperature alarm and indication.
• Maximum limit of error of the sensors shall be ±3ºF between the temperature range of –0ºF and +200ºF.
• When specified, thermostats with ambient sensing bulbs and capillary tubing shall be used to control short and non-critical heat traced lines. For critical pipe, inline sensing shall be required for low temperature alarm. Exposure temperature range of thermostat sensor shall be –30ºF to 140ºF.
• Temperature Sensor Wiring Junction Boxes
• Temperature sensor wiring connection boxes shall be as indicated in the purchase documents.
• Connection boxes shall be furnished as a complete assembly with two sets of rail mounted terminal blocks with terminals for terminating #16 AWG stranded copper wires.
• Connection boxes shall be provided with a nameplate. The nameplate legend will be provided by the Owner.
• Heat Tracer Power Junction Boxes (PJB’s)
• For self–regulating heat tracer, power junction boxes shall be mounted on the upper quandrants of the pipe with stainless steel pipe straps.
• The box cover shall be accessible after insulation has been installed on the pipe.
• Unless otherwise specified, NEMA 4X stainless steel boxes shall be used for unclassified areas.
• Boxes shall have required number of predrilled holes for entrance of heat tracers. Each hole for heat tracer entrance shall be provided with fitting equipped with blank grommet suitable for the specified enclosure.
• Boxes shall have provisions for grounding each heat tracer shield inside the box.
• Physical strain relief shall be provided for the heater element.
• Heat Tracer Splice Box
• The splice box for self–regulating type heat tracer shall be the low–profile type. The splice box shall include mounting base and a gasketed removal cover. The mounting base shall have provision for grounding and shall be suitable for mounting on top of the pipe and under the pipe insulation.
• Properly sized grommets shall be furnished for the type of heat trace (with tin copper braid and outer jacket covering shield) being used.

• Heat Tracer End Seal: Tail pilot light shall not be used for monitoring the heat trace system, unless specified on the Data Sheets.
• Power Feed Cable
• Unless otherwise specified, conduit shall be used for running power feeder along pipe.
• All power cables/wires shall be color coded as indicated in Table 1, using pigmented or dyed insulation on conductors #6 AWG and smaller.
• Grounding
• An external grounding connection shall be provided on each separate enclosure. It is preferred that the external frame grounding consists of a 3/8–16 bronze, hex head, cap screw tapped into the metallic frame or enclosure. Tapped holes shall not penetrate or weaken sealed enclosures approved for hazardous locations and shall not compromise the specified NEMA enclosure standards.
• Grounding and bonding equipment shall be constructed and approved in accordance with UL Standard 467 and be assembled as required by the National Electrical Code.
• Nameplate and Tagging Requirements
• Major electrical components and control devices shall be labeled in accordance with the supplier’s electrical drawings.
• Engraved laminated nameplates (white faces and black core) shall be used for the purpose of labeling. Nameplates shall be permanently attached with screws or rivets without compromising the required enclosure classification.
• Each segment of the heat tracer shall be factory tagged with an identification sequence number stamped on the heater itself. Each heater segment shall be designated by a manufacturing sequence number to assure traceability.
• All segments of the same pipe run shall have a common identifier label on a stainless steel tag for ease of sorting, handling and assigning the packaged components.

TESTING AND INSPECTION

• General Requirements

Testing and inspection of heat tracing equipment are specified to ensure that:

• All equipment is fabricated and installed in conformance with the dimensional, material and functional requirements specified in this Practice.
• Satisfactory workmanship is performed during the fabrication of the heat tracing equipment.
• Required conformance verifications are performed as prescribed with the quotation.
• Factory Tests
• Testing shall be accomplished after the installation is complete and all systems have been completed in accordance with all applicable specifications, codes and regulations having jurisdiction.
• Normal manufacturing quality control tests shall be carried out in accordance with the Manufacturer’s standard procedures.

• All equipment shall be inspected, cleaned, checked for electrical and/or mechanical operation, and all circuits free from shorts, grounds or faulty connections, before turning over to the Owner.
• Temporary power (24–volt DC, 120–volt AC and 480–volt AC) shall be provided as necessary to perform the required tests and functional checks.
• All test reports and records shall be submitted to the Owner.
• In making any test on equipment, the equipment Manufacturer’s instructions regarding recommended test and checkout procedures, special precautions and the like shall be strictly observed. Where the test provisions of this Practice conflict with the Manufacturer’s recommended instructions, the latter shall take precedence.
• All parts, components, etc., found to be faulty as a result of the tests and checkouts shall be brought to the attention of the Owner.
• Heat trace control panel shall undergo complete operational and alarm testing at the factory with the power applied to the panel.
• Continuity and megger tests shall be performed for pre–installed self–regulating heat tracer after the insulation has been completed. Megger test shall be at 1000–volt DC from each bus wire to the sheath. The resistance shall be at least 20 megohm.

6.3 Witness Testing

When witness testing is specified, the Owner shall witness complete testing of all items required per the data sheets and the contract documents.

DRAWINGS AND DATA

The drawings and data requirements shall show the equipment as ordered and built. Typical drawings are not acceptable, unless revised to show as–built equipment and identify the specific equipment ordered. Owner’s name, job order, P.O. number and item number shall accompany all drawings and data.

• Data To Be Supplied With Quotation
• Complete list of materials, specification for materials and drawings for all items being offered.
• All exceptions to this Practice.
• All items requested by this Practice to include but not limited to:
• Paragraph 5.4.9
• Paragraph 5.4.10
• Provide complete field test procedures.
• Minimum heat output vs. temp from –15ºF to 70ºF in watt/ft.
• Power requirements per circuit including recommended circuit breaker size per circuit.
• Maximum maintained temperature, minimum maintained temperature.
• Typical installation procedures for products quoted.
• Drawings and Data to be Submitted to Owner for Approval after Receipt of Order

(Refer to Manufacturer document requirements in requisition for additional requirements)

• All items in paragraph 7.1 of this Practice
• Test reports/data for all specified tests
• Detailed installation drawings and instructions

• Certified Data (to be supplied prior to shipment)
• All items in paragraph 7.2 of this Practice
• Instruction and maintenance manuals
• Complete renewal parts list
• Material list

SPARE PARTS

A complete Spare Parts Recommendation based on the total purchase order is required. It shall be confirmed that spare parts will be available for the anticipated life of the equipment. The spare parts recommendation shall include:

• A complete spare parts list, including part numbers, source location, diagrams or drawings.
• A separate price list for any special tools that may be required for maintenance/installation.
• A list of parts for the purchased equipment not kept in stock and the delivery time for each part.

SHIPPING

• General

“Preparation for Shipment” shall be in accordance with Manufacturer’s standards, unless otherwise noted on the “Request for Quotation” and/or “Purchase “Order”. The Manufacturer shall be solely responsible for the adequacy of the “Preparation for Shipment” provisions employed with respect to materials and application, to ensure that materials reach their destination in ex–works condition, when handled by commercial carrier systems.

• Self–Regulating and Constant Wattage Type Heat Tracer

Each reel shall contain only one continuous length of cable. The ends of the heat trace cable shall be protected from moisture contamination of the core material. Reels shall be of substantial construction to withstand multiple handling during storage and transit. Each reel shall be shipped totally enclosed in a suitable shipping carton. The reel and associated carton shall indicate the purchase order number, tracer type, voltage rating and actual length, have both ends accessible.

10.0 TABLES

TABLE 1

COLOR CODING FOR POWER CABLES

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