PNSC0035 tracing

August 2002

Process Industry Practices Piping

PIP PNSC0035 Steam Tracing Specification

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice. This Practice is subject to revision at any time by the responsible Function Team and will be reviewed every 5 years. This Practice will be revised, reaffirmed, or withdrawn. Information on whether this Practice has been revised may be found at www.pip.org.

© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas 78759. PIP member companies and subscribers may copy this Practice for their internal use. Changes, overlays, addenda, or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP.

PIP will not consider requests for interpretations (inquiries) for this Practice.

Not printed with State funds

August 2002

Process Industry Practices Piping

PIP PNSC0035 Steam Tracing Specification Table of Contents 1. Introduction .................................. 3 1.1 1.2 1.3 1.4

Purpose ............................................. 3 Scope................................................. 3 Tracing Systems................................ 3 Supporting Documents ...................... 3

2. References.................................... 3 2.1 Process Industry Practices................ 3 2.2 Industry Code and Standards............ 3

3. Definitions .................................... 4 4. Mechanical Criteria ...................... 7 4.1 Tracing System Temperature Control ............................................... 7 4.2 Steam Supply Design/Layout ............ 7 4.3 Steam Trap Selection ........................ 7 4.4 Steam Pressure Selection ................. 7 4.5 Selection of Tracer Type ................... 8 4.6 Size and Number of Tracers ........... 10

5. Materials ..................................... 11 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9

General ............................................ 11 Preinsulated Leads.......................... 11 Tracer Material ................................ 11 Copper Tubing................................. 11 Stainless Steel Tubing..................... 12 Preinsulated Tracers ....................... 12 Tracer Tubing Fittings...................... 12 Steam Traps .................................... 12 Insulation System ............................ 12

Process Industry Practices

5.10 Selection and Application of Heat Transfer Compounds....................... 13

6. Installation.................................. 13 6.1 6.2 6.3 6.4

Tracer Tube Cutting and Shaping ... 13 Tubing Unions ................................. 13 Steam Supply Layout ...................... 13 Trap and Condensate Return Systems ........................................... 14 6.5. Tracer Location and Routing ........... 14 6.6 Trap Station Installation................... 15 6.7 Tracing Identification ....................... 16 6.8 Tracers on Valves and Pumps ........ 16 6.9 Tracers on Vessels.......................... 17 6.10 Tracing on Instruments.................... 17 6.11 Heating Systems for Instruments Enclosures....................................... 17 6.12 Process Piping Supports ................. 18 6.13 Preinsulated Lead Supports ............ 18 6.14 Tracing Installation Sequence ......... 18 6.15 Surface Preparation of Piping ......... 19 6.16 Surface Preparation of Tracers ....... 19 6.17 Tracer Securement to Process Lines ................................................ 19 6.18 Pressure Testing and Cleaning ....... 19 6.19 Insulation Installation ....................... 19

7. Inspection ................................. 20 7.1 Inspection Access............................ 20 7.2 Inspection Requirements................. 20

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PIP PNSC0035 Steam Tracing Specification

Attached Detail Drawings PIP ST01 – Typical Steam Tracing System Arrangement PIP ST02 – Pressure Gauge or Switch, Liquids & Steam PIP ST03 – Typical Arrangement for Typical Bare Steam Tracing Circuit PIP ST04 – Typical Arrangement for 12 Station -3” – Class 150 – Steam Distribution Manifold PIP ST05 – Typical Detail for Condensate Manifold PIP ST06 – Typical Detail for Steam/Condensate Manifold Mounting Bracket PIP ST07 – Typical Arrangement for Trap with Separate Strainer PIP ST08 – Typical Arrangement for Trap with Integral Strainer PIP ST09 – Details for Tracing Identification Tags on Steam Supply Line PIP ST10 – Details for Tracing Identification Tags on Steam Condensate Line PIP ST11 – Details for Tracing Identification Tags on Steam Manifold PIP ST12 – Details for Tracing Identification Tags on Condensate Manifold PIP ST13 – Typical Tracer Arrangements PIP ST14 – Typical Tracer Arrangements PIP ST15 – Convection Tracing for Piping PIP ST16 – Typical Arrangement Details and Tracer Expansion Loops PIP ST17 – Arrangements Details for Tracer Penetrations in Insulation PIP ST18 – Typical Arrangement Detail PIP ST19 – Maximum Accumulated Rise Data for Tracers PIP ST20 – Steam Tracing Control Valve Stations PIP ST21 – Typical Tracing of Flanged Valves

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August 2002

PIP ST22 – Typical Steam Jacketed Valve Tracing PIP ST23 – Typical Single Tubing Steam Tracing PIP ST24 – Arrangement Details for Installation of Vessel Tracing PIP ST25 – Arrangement Details for Tracing on Pumps, Valves, & Cone Bottoms PIP ST26 – Steam Tracing for Pressure Transmitter Liquid or Steam Service PIP ST28 – Jacketed Level Glass – Typical Arrangement Details for Installation of Instrument Tracing PIP ST27 – Flanged D/P Level Transmitter – Typical Arrangement Details for Installation of Instrument Tracing PIP ST28 – Jacketed Level Glass – Typical Arrangement Details for Installation of Instrument Tracing PIP ST29 – External Float Level Instrument – Typical Arrangement Details for Installation of Instrument Tracing PIP ST30 – D/P Level Instrument on Vessel – Typical Arrangement for Installation of Instrument Tracing PIP ST31 – Liquid Remote Pressure Gauge – Typical Arrangement for Installation of Instrument Tracing PIP ST32 – Remote Mounted D/P Instrument – Typical Arrangement Details for Installation of Instrument Tracing PIP ST33 – Line Mounted D/P Instrument – Typical Arrangement for Installation of Instrument Tracing PIP ST34 – Pressure Transmitter Detail – Typical Arrangement for Installation of Instrument Tracing PIP ST35 – Pressure Switch or Pressure Gauge in Steam Traced Lines – Typical Arrangement for Installation of Instrument Tracing

Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

1.

Introduction 1.1

Purpose This Practice provides a guideline for the design and installation of steam tracing systems with process fluids that require heating to prevent condensation, freezing, unacceptable viscosity, crystallizing, separation, or temperature control.

1.2

Scope This Practice covers minimum requirements for design, materials of construction, installation, leak testing, and inspection of steam tracing systems on equipment, piping, and instruments including steam supply piping, steam tracers, tracer traps, and condensate collection.

1.3

Tracing Systems Systems requiring additional steam tracing specifications beyond this specification shall be covered by the purchaser’s documentation.

1.4

Supporting Documents Use of this Practice for contractual purposes requires the purchaser to make specific choices and assemble additional supporting documents. Listing of or reference to supporting documents within this Practice does not imply suitability for specific designs.

2.

References Applicable requirements in the latest edition (or the edition indicated) of the following Practices, industry codes and standards, and detail drawings shall be considered an integral part of this Practice. Short titles will be used herein when appropriate. 2.1

Process Industry Practices (PIP) – PIP INSH2000 - Installation of Hot Service Insulation Systems – PIP INSH2002 - Documentation Requirements – PIP PN50SA0L01 – Piping Material Specification 50SA0L01, 304/304L Stainless Steel, 0.000” C.A., Process Tubing – PIP PN50SD0L01 – Piping Material Specification 50SD0L01, 316/316L Stainless Steel, 0.000” C.A., Process Tubing

2.2

Industry Code and Standards – ASTM B68-99 - Standard Specification for Seamless Copper Tube, Bright Annealed – ASTM B75-99 – Standard Specification for Seamless Copper Tube – ASME B31.3 – Process Piping

Process Industry Practices

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PIP PNSC0035 Steam Tracing Specification

3.

August 2002

Definitions For the purpose of this Practice, the following definitions apply: air convection tracing: Tracers attached to the pipe without the use of heat-transfer compounds. Tubing can be bare or may have a polymer jacket. A tracer is attached to the pipe with hightemperature tape, tie-wires, or bands. Heat transfer is by means of air convection movement of heat in the annular space between the thermal insulation and the heated pipe. ambient temperature: The temperature of the air in the surrounding atmosphere condensate: Water that is formed in the steam tracer tube when latent heat from the steam is given up to the heated pipe or equipment conduction tracing: Tracer tube that is thermally bonded to the heated pipe or equipment by heat-transfer compound when the primary heat transfer means is by conduction directly into the metal wall of the pipe or equipment being heated contractor: Party that is responsible for furnishing and/or installing the insulation system dry steam: Steam containing no moisture; it may be either saturated or superheated. heat loss: The rate at which heat flows from a hot surface such as a process pipe to a cooler atmosphere, usually stated in Btu/h feet (kcal/m) of length of pipe. The heat loss is generally from the pipe through the pipe insulation to the cooler atmosphere, but may also be from conduction through hangers and supports. heatsink: A surface or mass such as a flange or valve that is at a lower temperature than the warm pipe heat tracing: The application of hot liquid, vapor, steam tracing tubes, electric heating cables, or tapes to pipes, fittings, valves, pumps, tanks instruments, or instrument lines to offset the heat loss through thermal insulation heat-transfer compound: A heat-conductive material with highly efficient thermal characteristics for use on any steam or fluid tracer tube. The heat-transfer compound is used to establish a broad, heat-conductive contact surface, for heat-transfer purposes, between the tracer tube and the surface to be heated. heated pipe: Any process, service, or utility pipe that is heat traced heating media: Dry-saturated steam that flows from the point of supply on the steam main through to the inlet of the tracing circuit steam trap heat-up: A steam tracing application in which process pipe or equipment requires the addition of heat to raise its temperature from a lower to a higher level high-pressure steam: Steam at a pressure of 250 psig to 600 psig (1,723 kPag to 4,136 kPag) inline instruments: Instruments that are installed in the piping. These instruments are normally traced with the same tracing circuit as the piping.

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Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

instruments: Devices that are either used separately or in combination to measure, analyze, or monitor the various aspects of a process instruments piping: All piping, tubing or tubing bundles, valves, and fittings used to connect instruments to process piping and to other instruments and apparatus for measuring, analyzing, or monitoring purposes isolated tracing: Tracing for sensitive piping and processes where the tracer tube is separated from the pipe or equipment by a low conductive material. This tracing includes preinsulated tubing with a polymer protective jacket. Heat transfer is primarily by air-convection movement of heat in the annular space between the thermal insulation and the heated pipe. low-pressure steam: Steam at a pressure of 15 psig to 50 psig (68 kPag to 344 kPag) medium-pressure steam: Steam at a pressure of 50 psig to 250 psig (345 kPag to 1,722 kPag) owner: Principal end user pockets: Bends, loops, or dips in a tracer tube circuit where condensate can collect and prevent the tracer circuit from being self-draining process maintenance temperature: The temperature level that must be held on plant process pipes and equipment to keep the contents from solidifying, condensing, crystallizing, separating, or becoming too viscous to pump NOTE: The term is often used to refer to all traced utility, service, or process pipes. process piping: Piping used to transport fluids between storage tanks and within process units per ASME B31.3 purchaser: Owner or the owner’s authorized agent remote instruments: Instruments that are installed at a location that is remote from the piping. These instruments are traced with a tracing circuit that is separate from the tracing circuit(s) used to trace the piping. saturated steam: Steam at the temperature at which vaporization takes place for that pressure and is free of moisture service piping: Piping used to transport water, brine, steam, air, or other substances to process piping or equipment to bring about the successful completion of the process steam supply manifolds: Modular prefabricated steam supply distribution manifolds designed specifically for supplying steam to tracing circuits steam and condensate manifolds: Modular prefabricated steam supply and condensate collection units designed specifically for steam tracing circuits steam and condensate return leads: Preinsulated tubing with a weather-protective jacket that is used to interconnect headers to manifolds and manifolds to tracers for steam supply and condensate return. Referred to as leads, runs, lines, and takeoffs.

Process Industry Practices

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PIP PNSC0035 Steam Tracing Specification

August 2002

steam boiler: A closed vessel in which water is vaporized into steam to provide mechanical power and process heat such as steam for tracing circuits steam header: The principal steam line supplying steam to all users in an area including tracer circuits that is assumed to be supported on overhead pipe rack and may have several branches. steam-out: A process for cleaning residue from piping by passing steam through the piping. It is necessary to select a tracer material that can withstand exposure to the steam-out temperature. Steam traced piping: All references to steam traced piping throughout this Practice is meant to imply all steam traced piping, fittings, valves, pumps, tanks, vessels, instruments, instrument lines and any other materials or equipment requiring steam tracers. steam tracing: A tube or small pipe carrying steam, which is placed parallel and attached to the surface of the pipe or equipment to be heated. The tube is referred to as the “tracer,” “tracer tube,” or simply “tracing.” steam tracing condensate subheader: A line that collects and returns condensate from one or more tracer circuits via a condensate collection manifold to the condensate header steam tracing subheader: A branch from the steam header to the steam distribution manifold for tracer circuits steam trap: Automatic device used to hold steam in a steam tracing circuit until it has given up its latent heat and allows condensate, air, and other gases to pass while preventing the passage of steam superheated steam: Steam at a temperature higher than that at which vaporization takes place for that pressure temperature controllers: Automatic devices used to control steam pressure and/or flow to maintain pipe temperature for freeze protection or process temperature control thermal insulation: For steam tracing purposes, it refers to materials used to retard the flow of heat from piping and equipment to the surrounding atmosphere. utilities piping: Piping that transports the primary plant commodities such as fuel gases, fuel oil, water, air, steam, and condensate vessel: The term “vessel” in this specification refers to any large surface such as tanks, towers, drums, reactors, or exchangers. weather barrier: A protective material covering the outer surface of thermal insulation to repel rain, snow, sleet, hose wash-down, or any other substance that might negatively affect the thermal insulation wet steam: Steam containing moisture winterization: Sometimes referred to as “freeze protection” or “warming services,” winterization is the preparation of piping and equipment for operation in winter weather, including cold temperatures, high winds, snow, and ice.

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Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

4.

Mechanical Criteria 4.1

Tracing System Temperature Control Proper temperature control based on an assessment of the actual system needs should be provided when economically practical.

4.2

4.3

4.4

Steam Supply Design/Layout 4.2.1

Steam used to supply steam tracing must be from a constant source that can be maintained independently of plant operations. The steam supply should be taken from a source that is continuously available even during normal shutdown periods when possible. Steam should be distributed at the highest pressure and reduced to the design requirements of the tracer system using a pressure-reducing valve.

4.2.2

To help ensure the quality of the tracing steam, all steam supply manifolds and tracer circuits shall have a separate steam trap station installed.

4.2.3

Tracing steam shall be dry saturated steam of a pressure that furnishes the tracing design heat input requirements.

4.2.4

The tracing supply header shall be adequately sized to provide the maximum tracer design load (steam pounds per hour) and trapped at its low points.

4.2.5

The number of tracer connections on a manifold should be held to a maximum of 12. A minimum of two of these connections should be designated as spares.

4.2.6

Vertical type manifolds should be utilized when possible.

Steam Trap Selection 4.3.1

Effective removal of condensate and air is essential to achieving uniform temperatures and maximum heat-transfer rates from steam tracing circuits.

4.3.2

Consult trap manufacturers for information for the selection and sizing of the steam traps as well as for sizing and proper installation techniques to provide trouble-free winter performance.

4.3.3

Preassembled steam trapping stations with universal connectors are preferred. The type of traps selected shall meet the design and efficiency requirements of the tracing system.

Steam Pressure Selection The following criteria must be considered when selecting the steam pressure that can be utilized to meet the steam tracing design requirements: a. Desired maximum allowable number of tracers on a line b. Desired maximum allowable length of the tracer tubing that is connected to the line c. Elevation differences between the location of the steam manifold and traced piping d. If process fluid or piping material is sensitive to conduction or localized heating

Process Industry Practices

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PIP PNSC0035 Steam Tracing Specification

August 2002

e. Plant site environmental design criteria (summer and winter design temperatures and mean wind velocity) f.

Pressure differential between steam trap discharge and the condensate return header including any static pressure head

g. Pressure of plant steam that is dedicated for steam tracing h. Required maintenance temperatures (allowable minimum/maximum temperature range for traced piping) i.

Safety factor for drops in steam pressure

j.

Size and desired maximum length of all steam supply and condensate return leads

k. Traced piping size (outside diameter [OD]) and material of construction l.

Tracing size and type (air convection, conduction, or isolated tracing)

m. Type and thickness of the insulation system 4.5

Selection of Tracer Type 4.5.1

The selection of the steam tracer for each heated pipe and piece of equipment must be based on the process sensitivity and the temperature to be maintained along with the heat load demand, tracer capability, and the results of the design scenarios.

4.5.2

Isolated tracing should be considered for the following operating conditions: a. When reduced thermal risk is important to aid in compliance with applicable safety standards b. When a controlled, predictable heat-transfer rate must be maintained to prevent corrosion or other unacceptable temperature-related conditions c. When sensitive products such as caustics, acids, amines, resins, and aqueous fluids that require low uniform heat for freeze protection

4.5.3

Convection tracing should be utilized for the following operating conditions: a. When only one convection tracer is needed to hold the required temperature b. When winterization is needed for lines carrying such material as air, water, gases, or other noncorrosive aqueous solutions c. When low heat density and flexibility is necessary for high-maintenance valves, pumps, and other such equipment

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Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

d. For process lines in which ambient temperature fluctuations or emergency shutdown and heat-up requirements do not necessitate more heat than the convection tracer supplies NOTE: Multiple convection tracers usually cannot be economically justified when one tracer with heat-transfer compound will suffice because of the additional steam supply connections and trap assemblies required. However, a convection tracer may be doubled back when allowable pressure drops are not exceeded. The use of doubled-back tracers should be held to a minimum. Spiraled convection tracers are not permitted, unless otherwise noted, because circumferential expansion reduces the heat-transfer coefficient by increasing the air gap between the tracer and the pipe and the increased number of pockets on horizontal runs requires more frequent trapping. 4.5.4

Tracers with heat-transfer compound may be utilized for the following operating conditions: a. When more than one convection tracer is required b. When fast heat-up is essential after an emergency or a planned shutdown c. When a more even temperature distribution is required d. When high heat density and flexibility is required at valves, pumps, and other such equipment e. When it is desirable to keep the required number of tracers to a minimum

4.5.5

Preinsulated instrument tubing bundles and high-density polyurethane instrument enclosures are recommended for the following situations: a. When closely predicted thermal characteristics are required for pressure and differential pressure transmitters, process analyzers, emissions analyzers, and other such applications b. When space is limited, pretraced and insulated bundles can be shaped to allow layout via the shortest distance with simple supports in locations where field-fabricated lines are not practical c. When factory-applied polymer weather protection is preferred on critical lines

4.5.6

Tracing with self-acting, off-on, or pressure-reducing control valves with sensors that respond to the pipe wall or ambient temperature should be considered for: a. Piping that operates intermittently b. When it is essential to prevent overheating of the product c. When constant viscosity is required for instrumentation d. When energy efficiency is a key requirement e. Piping that requires process heat-up

Process Industry Practices

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PIP PNSC0035 Steam Tracing Specification

August 2002

f. Piping that requires freeze protection during shutdown periods NOTE: When the process fluid is sensitive to over heating, self-acting off-on in steam tracers may not be suitable. 4.6

Size and Number of Tracers 4.6.1

To facilitate designing a cost-effective tracing system, minimize the number of tracer circuits. To establish the number and size of tracers required to supply the required heating, the following six factors must be taken into consideration. Three factors are given and three factors are variable. The variable factors must be balanced to establish an appropriate design. Given factors: a. Nominal pipe size b. Desired pipe temperature c. Lowest ambient temperature and highest wind speed Variable factors: a. Tracer type, size, and number b. Steam inlet pressure and temperature c. Insulation type and thickness

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4.6.2

All flow diagrams shall be reviewed to determine the steam tracing requirements for each line. Isometric drawings identifying steam supply headers, tracer supply manifolds, tracer routing, tracer trap stations, and condensate return lines will be provided to facilitate proper design and installation of the tracing system.

4.6.3

The tracer size and number of tracer circuits required to supply the heating requirement on a line or equipment item should be determined by calculation, manufacturer’s data, or the use of a computer program developed for steam tracing design.

4.6.4

The maximum trapping length and the maximum vertical rise for each tracer circuit shall be determined from calculation, manufacturer’s data, or the use of a computer program developed for steam tracing design.

4.6.5

The maximum length of the tracing circuit shall not exceed the calculated maximum trapping length for the tracer that must include the supply and return leads.

4.6.6

Maximum tracer length shall be applicable to the length of the tracer that is attached to the line. The tracer length should be measured from the point where the tracer first contacts the line to be heated to the point where it connects to the return lead that is routed to the trap station.

4.6.7

Pressure losses for preinsulated tubing that runs from the steam manifold to the tracer circuit, from the tracer to the condensate manifold, and from the manifold to the condensate return header will be calculated separately if the length of these runs exceeds 100-feet (30-m) total.

Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

5.

Materials 5.1

5.2

5.3

5.4

General 5.1.1

All materials used to construct steam tracing components shall be new and in accordance with this specification and its references. Refer to PIP piping and line class specifications as required for piping details.

5.1.2

Steam supply, condensate return, and tracer tubing wall thickness shall be in accordance with ASME B31.3.

5.1.3

Steam supply subheaders and tracing steam distribution manifolds shall be of the same materials as the steam header.

5.1.4

Condensate return subheaders and tracing condensate collection manifolds shall be of the same materials as the condensate return header.

Preinsulated Leads 5.2.1

Tubing shall be insulated with approved thermal insulation and jacketed with plastic rated for 105ºF (40ºC) or higher.

5.2.2

Sufficient insulation shall be furnished to provide a maximum surface temperature of 140ºF (60ºC) during operation. The sensible temperature and wind speed for the location as well as the maximum steam temperature and pressure expected for the particular application unless otherwise noted.

Tracer Material 5.3.1

The tracer in a steam tracing system must be as flexible as possible for the ease of installation and conformance to the shape and layout of the pipes and equipment being heated and must act as a leak-proof carrier of the heating media. Tubing should be used rather than pipe for tracing whenever possible.

5.3.2

The tracer shall be selected to fulfill the thermal and installation requirements as determined by the process pipe material, temperature of the process pipe and tracer, pressure of the heating media, and the environment. The tracer should be of metal close to the potential of the process pipe so as to minimize galvanic corrosion.

Copper Tubing 5.4.1

Bare copper tubing tracers shall be soft-annealed grade 122 and meet or exceed ASTM Standard B68 and ASTM Standard B75. Copper tubing shall be used if the saturated steam pressure or the item being traced does not exceed 400°F (204°C) and there is no corrosion or other deterrent for using copper.

5.4.2

Tubing thickness shall be: a. 3/8-inch (9.52-mm) OD x 0.035-inch (.89-mm) wall b. 1/2-inch (12.7-mm) OD x 0.035-inch (.89-mm) wall

Process Industry Practices

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PIP PNSC0035 Steam Tracing Specification

August 2002

c. 3/4-inch (19-mm) OD x 0.049-inch (1.24-mm) wall NOTE: 1/4-inch (6.35-mm) OD tracers should only be used when absolutely necessary for heating relatively small tubes or similar application. 5.5

Stainless Steel Tubing 5.5.1

Bare stainless steel tubing shall be PIP PN50SD0L01 316/316L stainless steel tubing and shall be used if the saturated steam pressure or the item being traced has a maximum temperature between 400°F (204°C) and 800°F (427°C), and there is no corrosion or other deterrent for using stainless steel.

5.5.2

Tubing thickness shall be: a. 3/8-inch (9.52-mm) OD x 0.035-inch (.89-mm) wall (minimum) b. 1/2-inch (12.7-mm) OD x 0.035-inch (.89-mm) wall

5.6

5.7

Preinsulated Tracers 5.6.1

The material requirements for preinsulated tracer tubing shall be the same as specified herein for bare tracers.

5.6.2

Preinsulated tracers shall be covered with a flexible insulation and a weathertight flexible jacket. Flexibility of the jacket shall be adequate to allow for bending required to fit the preinsulated tracer to typical installations.

Tracer Tubing Fittings The tracer tubing fittings shall be suitable for the pressure of the steam that they contain. Fittings shall be compression type. The fittings shall be made of material that is compatible with the tracer construction material.

5.8

Steam Traps Steam traps shall be sized for the maximum calculated condensate load in the expected operating pressure range and furnished with an integral strainer, air vent, and blow-off valve.

5.9

Insulation System 5.9.1

The next largest pipe-size rigid insulation (calcium silicate, expanded Perlite, cellular glass, etc.) shall be selected; however, insulation of the actual pipe size may be used if board sections are cut to fit the longitudinal joint to compensate for the steam tracer.

5.9.2

The insulation material to be used on steam traced piping and equipment shall be selected with care and shall comply with PIP INSH2000 and PIP INSH2002. Important aspects to be considered are: a. Thermal insulating characteristics b. Mechanical strength characteristics c. Chemical stability characteristics under both normal and abnormal conditions

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Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

d. Moisture absorption characteristics e. Personnel health and safety aspects f. Installed cost 5.10

Selection and Application of Heat-Transfer Compounds Various formulations of heat-transfer compounds are available to cover a wide range of tracing applications. The selection of the proper formulation involves consideration of all the following: a. Minimum and maximum temperatures to which heat-transfer compounds will be exposed under both normal and abnormal operating conditions b. Ambient conditions under which installation of heat-transfer compounds must occur c. Piping and equipment size and configuration d. Total installed cost for the heat-transfer compounds e. Feasibility of performing start-up curing procedures when required f.

6.

Solubility resistance of the heat-transfer compounds

Installation 6.1

Tracer Tube Cutting and Shaping Tracer tube bends shall be free of kinks, wrinkles, or flattening. Bends shall be made with a mechanical tubing bender. Bend radii should generally be from four to ten times the outside diameter of the tube. The largest functional radius should be used. A tube cutter or hacksaw shall be used to cut the tracer tubes. Guide blocks shall be used with a hacksaw cutting to assure a square cut. Outside diameter (OD) and inside diameter (ID) deburring shall be performed using a file for the OD and a deburring tool for the ID.

6.2

Tubing Unions Tubing unions shall be installed in tracers where necessary to permit removal of equipment such as pumps, relief valves, instruments, control valves, and strainers. Tubes shall be formed to join with true alignment to the centerline of the fittings without distortion or tension.

6.3

Steam Supply Layout 6.3.1

Process Industry Practices

The tracing supply header shall be located as close as possible to the point of use. If three or more tracers are supplied from a common header, prefabricated manifolds should be considered.

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PIP PNSC0035 Steam Tracing Specification

6.3.2

August 2002

Each tracer supply line (subheader) from the steam header shall be: a. Equipped with an isolation valve. These valves shall be located where they are accessible to the plant operation personnel. b. Routed from off the top of the tracer supply header at the highest point possible flowing downward to the tracer steam supply distribution manifold subheader.

6.3.3

Preinsulated tubing with factory-applied insulation and a polymeric weatherprotective jacket may be used for steam supply and condensate return leads.

6.3.4

Preinsulated leads shall be routed as follows: a. From the distribution manifold block valve outlet to where the tracer that is attached to the piping enters the insulation. b. From the point of connection where the tracer piping exits the insulation to the inlet connection of the steam trap station located on the condensate collection manifold. c. All lines should be routed symmetrically and run together when possible to maintain a neat appearance. Pockets shall be avoided when possible. d. To ensure a cost-effective design, the length of the supply and return leads must be kept to a minimum, preferably from 25 feet (7.6 m) to 70 feet (21 m) in length.

6.4

6.5.

6.3.5

Steam supply manifolds shall be strategically located along the tracing route and shall be accessible from grade, platform, or permanent ladder.

6.3.6

Steam supply manifolds shall be fitted with an isolation valve.

6.3.7

Supply manifolds shall be drained via a trap and discharged to the atmosphere directed to a safe location when condensate is not returned.

Trap and Condensate Return Systems 6.4.1

Steam trap condensate manifold assemblies shall be provided with an internal siphon tube for freeze protection of traps that are shut off and a freeze protection valve that senses condensate temperature to drain the manifold if the condensate cools to a given set point.

6.4.2

Steam trap manifold assemblies shall be placed in an accessible location when possible to simplify maintenance.

6.4.3

Manufactured steam trap, steam distribution, and condensate collection manifolds designed specifically for steam tracing applications are preferred.

Tracer Location and Routing 6.5.1

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Tracers serving the same or adjacent items shall be grouped and supplied from a common manifold to facilitate maintenance. Condensate shall be returned to a common return manifold.

Process Industry Practices

PNSC0035 Steam Tracing Specification

August 2002

6.5.2

The steam supply should start at the highest point of the lines to be traced, and the tracers shall be arranged so that flow is generally downward avoiding pockets as much as possible. The accumulated vertical tracer rise (pocket height) in feet should not exceed 15% of the steam supply pressure without specific permission of the owner.

6.5.3

Each tracer shall be continuous from the supply manifold to the trap with no vents, drains, or dead-end extensions at intermediate points. In general, branch connections shall be avoided. If branches are required, each branch that is used shall have its own trap.

6.5.4

All tracers shall be installed parallel to and against the heated pipe or equipment and shall be placed on the most accessible surface location in regard to supports, ease of installation, connection, and thermal insulation. Multiple tracers shall be equally spaced around the circumference of the pipe.

6.5.5

Expansion of bare (convection) tracer tubes shall be absorbed at elbows and flanges when possible. For long straight runs, a 12-inch (.305-m) diameter horizontal loop shall be provided at 60-feet to 100-feet (18-m to 30-m) intervals, preferably midway between fittings. Tracer loops provided specifically for expansion should not contain unions.

6.5.6

Tracer loops around flanges shall be horizontal so as to drain on shutdown, and unions shall be provided so tracers can be disconnected at valves, pumps, tanks, or other flange-connected equipment.

6.5.7

Tracing shall be included on dead legs and similar heatsinks along the traced line.

6.5.8

Each tracer circuit shall have a separate trap station installed at the end of the tracer circuit.

6.5.9

Slots shall be provided in the thermal insulation to accommodate expansion of the tracer where it joins and leaves the traced line. See detail drawing ST-17 for arrangement details.

6.5.10 Extra tracer lengths are not generally required at pipe hangers, piping tees, and ells. 6.5.11 Design shall include extra tracer length for valves or large pieces of equipment. The engineer will indicate on critical service if pipe supports or flanges require additional tracer length. Insulated pipe supports will be considered on critical temperature maintenance situations. 6.5.12 All tracers should be arranged to accommodate maintenance and removal of traced valves, instruments, and other equipment. 6.6

Trap Station Installation 6.6.1

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The steam trap shall be installed below the tracer circuit when possible and at a condensate manifold located so as not to interfere with the operation and maintenance of equipment or obstruct access ways.

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PIP PNSC0035 Steam Tracing Specification

6.7

6.8

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August 2002

6.6.2

Each tracer circuit shall be trapped individually at the tracer termination point determined from the circuit design information. A new tracer shall be installed for continuing the tracing if the pipe-run exceeds the specified maximum trapping length.

6.6.3

Isolation valves shall be installed to accommodate servicing of the trap.

6.6.4

When condensate will be discharged to an overhead return line or against a lift, a swing check valve shall be installed in the discharge line just beyond the trap at the bottom of the lift if the trap does not have an integral check valve or is not otherwise designed to prevent back flow. The discharge line from the trap shall feed into the top of the return main.

6.6.5

The pressure due to the lift shall be added to the pressure in the overhead return line to determine the total back pressure against which the trap must discharge. Use 0.5 psi per vertical foot of lift (11.31 kp/m) to calculate the pressure due to lift. The back pressure shall not exceed the allowable limit of the selected trap.

6.6.6

A test tee should be installed just downstream of the trap to allow checking of the trap performance.

Tracing Identification 6.7.1

Each tracer circuit shall be identified by two corrosion-resistant identification tags. One tag shall be installed on the steam supply valve at the steam distribution manifold and the other tag shall be installed on the isolation valve located on the steam trap assembly.

6.7.2

Steam tracer supply stations and condensate trap stations shall be given line numbers. An isometric piping erection drawing will be made for each station. These stations will be assigned numbers that are to be located on the plot plan and the model to indicate unit number, station number, and whether they are supply or trap stations.

6.7.3

The identification tags shall be fabricated from 16-gauge corrosion-resistant material suitable for the environment and attached to the supply valve and steam trap assembly valve with No. 16 gauge corrosion-resistant wire.

6.7.4

Identification tags shall be stamped with 1/4-inch (6-mm) numbers and letters using the identification system established for the project.

Tracers on Valves and Pumps 6.8.1

Tracing for valves and pumps shall be tubing in the form of hairpin loops so that the tracer makes the least amount of complete circles. The number of feet of tracer to surface area of valve or pump shall be sufficient to obtain the same ratio or higher of feet of tracer per unit of surface area as on the straight pipe surface area.

6.8.2

Unless otherwise specified, hairpin tubing loops shall be attached to the valve or pump surface with 1/2-inch x .020-inch (12-mm x .5-mm) stainless steel bands, high-temperature fiberglass tape or No. 16 gauge stainless steel wire. (See detail drawings ST-20, ST-21, and ST-25 for arrangement details.)

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PNSC0035 Steam Tracing Specification

August 2002

6.9

6.10

Tracers on Vessels 6.9.1

External tracing for vessels should be prefabricated stainless steel heating panels formed to the required radius or hairpin loop tubing panels, unless otherwise specified. (See detail drawings ST-24 and ST-25 for arrangement details.)

6.9.2

Prefabricated stainless steel heating panels should have a layer of factoryapplied nonhardening heat-transfer compound between the vessel surface and the back of the heating panel.

6.9.3

Small equipment with an outside radius of curvature less than 7 inches (178 mm) and vessel bottoms with compound curved surfaces may be traced with tubing in the form of hairpin loops in lieu of heating panels.

6.9.4

Hairpin circuits shall be embedded in heat-transfer compound, unless otherwise specified.

6.9.5

Each tracing panel shall have a separate steam trap station.

6.9.6

Tracing systems on equipment shall be systems that are separate from the tracing systems dedicated for the piping.

Tracing on Instruments 6.10.1 Tracing for instruments and instrument impulse lines shall conform to information provided in the attached details. 6.10.2 Tracing shall be installed so that instruments can be removed for maintenance without interruption or removing the tracing. 6.10.3 Tracing shall be applied only to the process-wetted parts of instruments, not to electronic or pneumatic parts. 6.10.4 Tracer sizes shall be as follows: a. 1/2-inch (12-mm) OD tubing shall be used for gauge glass and external displacer level instruments. b. 3/8-inch (10-mm) or 1/2-inch (12-mm) OD tubing shall be used for meter leads.

6.11

Heating Systems for Instruments Enclosures 6.11.1 Pressure gauge enclosures shall be heated with the heat from the process line by installing heat conservation insulation up to the enclosure or by continuing the tracer at the gauge connection. 6.11.2 Differential pressure transmitters with partial enclosures shall be heated by a steam heater block installed under the instrument. The heater shall have its own flexible thermal insulation cover and be installed where it will not interfere with removal of the transmitter. 6.11.3 Preinsulated tubing bundles may be used in lieu of field-traced and insulated instrument lead lines. Transmitters, controllers, recorders, etc., with complete polyurethane enclosures shall be heated with a separate finned steam heater connected by tube fittings to the steam tracer.

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PIP PNSC0035 Steam Tracing Specification

6.12

August 2002

Process Piping Supports Process piping supports shall be designed to allow for ease of installation of steam tracers and insulation.

6.13

Preinsulated Lead Supports 6.13.1 The installation and support of preinsulated instrument tubing bundles and preinsulated steam supply and condensate return lines shall be in accordance with the manufacturer’s specifications. 6.13.2 Routing and support is to be determined in the field. Lines shall be run together as much as possible for common support. Preinsulated tubing shall be spaced and located in accordance with the following considerations: a. Ability to place a durable support at some desired location b. Keep sag in the line within limits that will permit drainage c. Avoid bends that exceed the minimum bend radius as recommended by the manufacturer d. Allow for heat dissipation by keeping a 1/2-inch (12-mm) space (minimum) between the preinsulated lines

6.14

Tracing Installation Sequence After the process pipe has been installed with proper supports and hangers to allow for correct application of tracers and insulation, the following major steps are used for installations of the tracer system: Step 1: Ensure that all leak testing of the piping has been completed. Step 2: Ensure that all the required coatings have been applied on the pipe. Step 3: Perform surface preparation of process piping. Step 4: Perform surface preparation of tracer. Step 5: Perform installation of tracer and its securement. Step 6: Perform pressure testing of tracer. Step 7: Perform application of heat-transfer compound (when required). Step 8: Ensure curing of heat-transfer compound (if required). Step 9: Inspect the tracer system in accordance with the requirements specified herein. Step 10: Perform application of thermal insulation system in accordance with PIP INSH2000. Step 11: Perform inspection of insulation system in accordance PIP INSH2000.

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PNSC0035 Steam Tracing Specification

August 2002

6.15

Surface Preparation of Piping All tracer tubes and pipes or equipment to be traced shall be reasonably clean before installation of steam tracers. For noncoated surfaces, dirt, rust, and scale can be removed with a wire brush. Oil and grease films on coated or noncoated surfaces may be removed with a rag and suitable solvent. For coated surfaces, use clean compressed air, brushes, or rags to remove all loose dirt or dust. Preparation for the application of heat-transfer compounds shall be done in accordance with the manufacturer’s instructions.

6.16

Surface Preparation of Tracers All tracers shall be free of dirt, grease, oil, loose scale, or any other nonspecified material before installation on piping and equipment and before application of heattransfer compound when applicable.

6.17

Tracer Securement to Process Lines 6.17.1 Provide for expansion where required to prevent stress in the tracer tubing by properly securing the tracer to the process pipe. 6.17.2 Tracers shall be fastened to piping and equipment with wire, bands, or hightemperature tapes. 6.17.3 Covering the tracer with galvanized or stainless steel channels before final attachment may be required to protect the tracer from impacts. 6.17.4 Each method of tracing in this specification shall be installed in accordance with the attached drawings. 6.17.5 Care shall be taken to use fastening materials that are galvanically compatible with the pipe and tracer materials. High-temperature tapes shall be free of chlorides or halides if used to secure stainless steel pipe or tubing.

6.18

Pressure Testing and Cleaning 6.18.1 Steam supply headers and pipe or tubing runs to tracers shall be blown clean with steam or air before connection to trap assemblies. 6.18.2 After all tracer connections to the supply header and trap have been completed, the circuit shall be tested for leaks by subjecting it to a steam pressure equal to or greater than that to be used in the system or by suitable hydrostatic tests. 6.18.3 All leaks shall be repaired and the system retested before the installation of heat-conducting compound (when used) and insulation. 6.18.4 Performance of traps, gauges, pressure-relief valves, and pressure- and/or temperature-controlling devices shall be periodically checked at prescribed intervals during start-up and during the first 48 hours of normal operation.

6.19

Insulation Installation Installation of the insulation system shall be in accordance with the requirements of PIP INSH2000 and PIP INSH2002.

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PIP PNSC0035 Steam Tracing Specification

7.

August 2002

Inspection 7.1

Inspection Access The purchaser’s inspector and the tracing or insulation manufacturer’s representative shall be given full access to all stages of the work upon request.

7.2

Inspection Requirements The inspectors shall ensure that all phases of the installation are in accordance with the materials and application specifications. The inspector shall make certain that: a. All materials used are as specified and in good condition. b. All materials are stored in accordance with recommendations. c. Surface preparations are as specified. d. Tracer systems are installed in accordance with the design. e. All tracing supply headers, preinsulated supply and condensate tubing runs, tracer tubes, and manifolds are cleaned before they are connected to trap assemblies. f.

All tracer circuits and process pipe runs are pressure tested after all connections are completed.

g. Heat-transfer compounds are installed in accordance with these specifications. h. Heat-transfer compounds are properly cured. i.

Water-soluble heat-transfer compounds are protected from rain and other moisture before installing the thermal insulation and weather barrier.

j.

High-temperature insulation is of proper thickness and installed in accordance with specifications.

k. Insulation was dry when installed and protected from rain and moisture until weather barrier was installed. l.

All insulation on vessels is properly supported.

m. Suitable insulation expansion joints are installed. n. Weather protection is of type specified, installed in accordance with specifications and recommendations, and dry thickness of mastic is of specified dimension. o. All weather barriers are watertight, and projections and terminations are properly sealed.

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