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Tracing overview 

Tracing (commonly referred to as "Heat Tracing") is one of the most maligned and misunderstood activities the piping designer is asked or required to perform.  Many pipers consider it to be "scutwork" and either refuse to do it or grumble as they put forth a less than their best effort.  The definition of the term scutwork is "(–noun) menial, routine work, as that done by an underling. Example: the scutwork of scrubbing pots and pans." 
This attitude needs to change. 

 
The word "Heat" as used in this application is a relative term.  The actual heat application may be "Hot" or "Cold".  Most applications are "Hot" tracing to prevent freezing due to weather conditions or unwanted cooling of the product and the resulting lowering of viscosity.  On the other hand, there are also some fluids/processes where the fluid is "Exothermic" and needs constant cooled.  The identification of weather related tracing requirements is both the Process and Piping Department responsibility.  The identification of all other heating or cooling tracing requirements is the responsibility of the Process Engineer.  The tracing need and identification is communicated via the P&ID (Piping & Instrument Diagram) and must clearly define the type, manner and temperature for all pipe line tracing requirements.   

The amount of heat tracing on some projects may be minimal or even nonexistent.  On other projects, heat tracing may be required on as much as 40 to 50 percent of the process lines.  Heat tracing on these projects is vital for the successful and cost effective operation of the plant.  This can mean, if the heat tracing is not done properly the plant will not work at all, or the plant will be strangled by the excessive cost of down time and expensive maintenance.   

Properly designed and installed heat tracing systems are the piping designer's responsibility.  It should not be assigned just to "underlings" as suggested in the definition of the term "scutwork".  It is okay to have a few people involved in the work who have no prior heat tracing experience with only two or three years experience in piping, but the total effort needs to be staffed by mostly experienced piping designers with 10 to 15 years in the piping business including heat tracing.  The leader of the heat tracing effort (large or small), needs to have extensive experience on one or more projects with extensive heat tracing. 

What is "heat tracing"? 

Heat tracing is the supplemental application of heat (or cooling) to a primary piping system, vessel, pump or other object to ensure temperature control. 

Supplemental heat is used for two reasons:

1) Environmental (Winterization) - to keep a fluid from freezing caused by atmospheric conditions

2) Process – the control of the process viscosity so it can be pumped without setting up in the pipe or equipment.

The manner and medium are two factors of prime importance in Heat Tracing. The application of the heat for the Tracing includes the manner of delivering the heat and the fluid media is the heat source to be delivered. 

Manner (noun) "the style or customary way of doing or accomplishing something" is the hardware that becomes the tracer that physically transports the heat medium fluid.

    Manner types may include: 

  • Single bare tube tracer (tubing 1/2", 3/4" etc).
  • Multiple bare tube tracers (tubing 1/2", 3/4" etc).
  • Single or multiple tube tracers with a Heat Transfer compound.
  • "ControTrace," formed channel shaped to fit the pipe.
  • Jacketed Pipe, pipe inside another pipe.
  • Electric Tracing, electric resistance cable wrapped around pipe or strapped to pipe and valves.

Medium (noun) "an intervening substance, as air, through which a force acts or an effect is produced" is the fluid used to provide the supplemental heat.  Each media may have one or more levels of temperature.  Each of these media will also have both a supply and a return for each temperature level.  On very complex Heat Tracing projects it is not unusual to have 5 or 6 tracer media.

    Media types may include: 

  • Steam – There could be two or more temperatures of Steam
  • Hot Oil – There could be two or more temperatures of Hot Oil
  • Hot Water – There could be two or more temperatures of Water
  • Chilled Water –  There could be two or more temperatures of Chilled Water

 

Key Issues related to the design of Heat Tracing

Piping Tracing Team Supervisor: This effort needs to be lead by the most experienced designers available. The person in the position to lead the Heat Tracing Design Team needs to be assigned early and be active on the project.  This means they are busy with other piping activities until it is time for the actual tracing work.  But when there is a task related to Tracing, the person must be able to drop what ever task they are doing and give attention to the Tracing issue.  The other people assigned to tracing only need to be present when it is time to start the actual Tracing work.  The proper time to do the Tracing work is when the fabrication and installation piping Isometrics have been issued.

Staffing: Who should be assigned to do Heat Tracing? Heat Tracing is not a simple task and should not be all assigned to lower skilled pipers.    It can be a learning experience for some but 50% or more of the people assigned should have past experience in Heat Tracing.

Scheduling: When to start the Tracing design? If there is tracing on a project it should be discussed early and often.  Questions for the early discussions regarding Tracing should include the actual installation responsibility, the level of design detail, purchasing responsibility, etc. 

  • Who is going to install it?
  • Will this be by direct hire specialist under the supervision of someone on the EPC Construction Superintendent's staff?
  • Will this be a Sub-Contract let to a Contractor qualified and experienced in doing Tracing? 
  • Will the design and installation be Sub-contracted to a Specialty Company that does this and only this? 
  • What level of detail is required on the Tracing Isometrics?  Who will do the MTO (material take-off)?
  • Who will purchase the material?

The answer to these questions will impact how the in-house work is executed.  Regardless of who executes the actual installation, the Heat Tracing will have a prominent place in the Project Scope of Work (SOW).  It also will need to have sufficient definition so as to be included in the piping Labor Estimate (Man hour) and the piping Control Level Schedule of piping activities.

Scope: For the purpose of this article we need to create a hypothetical project.  This Project is intended to help you to understand the magnitude of effort involved where there is a lot of tracing.  Here is our sample project criterion.  The total plant is a mega-project "Grass-Roots" (Green Field) chemical complex.  There are seven major units including the Utility Complex plus Feed Tankage, Intermediate Product Tankage along with Storage for bulk and bagged palletized finished product.  We will focus on one of the major processing units.  Unit 16 is the largest unit and has complex equipment and 3550 line numbers.  The breakdown of these lines is shown in Table "A" & "B" (See Appendix). 

Tables A & B reflect the number of lines and tracer isometrics for our project.  It also shows the number of Supply and Return manifolds required.  The number and type of manifolds allows for 25% futures tracers and 8 connections per manifold.  Once these numbers have been determined, even if they are estimates, additional planning can be done.

Defining the number, manner of tracer systems and media (High Pressure Steam, Low Pressure Steam, High Temp Water, Glycol/water, Hot Oil, Chilled Water, etc.) is very important. This needs to be defined early in the project and has an impact on the planning of the number of lines on the pipe rack, the sizing of the rack and number of levels of the rack. Each of these commodities is the first required in the unit for start-up and the last needed for shut-down.  If you have five (5) tracing mediums there will be ten (10) additional lines not showing up on the average P&ID.  The tracing media lines are all insulated.  These lines are all going to be subject to thermal expansion.  These lines will have anchors and guides that will result in loops and added forces to the pipe rack design. 

Pay particular attention to the total manifold requirement. Each manifold will require a minimum footprint of 3'-0"x 1'-6" (1meter x .5 meters).  This space is defined as the space for just the hardware.  Operator and maintenance space in front of the manifold is required but can be coexistent with an aisle or other clear space.  This is important because space must be allowed for and reserved during Plot Plan development and not used by normal piping layout.  The manifold space must be protected from infringement and use by other disciplines during the design process. If a 3D CAD system is used for the design, a blocked out area (with a designated color) should be inserted into the plant layout and identified.

Heat Tracing Specification and Standard Details: Regardless of who installs the tracing (direct hire or Sub-contract) the Specification and Standard Details need to be well written detailed and complete.   
 
Tracing Files & data: There are multiple items necessary and helpful to the Heat Tracing activity. These may include:

  • P&ID's: For a unit the size of our sample project there may be as many as 80 to 90 (or more) P&IDs.  All issues and revisions must be collected, properly controlled and reviewed for Tracing related changes
  • Client criteria (Tracing related) : What does the Client want or not want.  Does the Client have existing Standards?  All such items should be requested from the Client and evaluated for the project.
  • Correspondence (Tracing related): The Tracing Team leader should be on distribution for all correspondence (letters, memos, etc) related to Tracing.
  • Specification (Tracing related): Normally this is a modification and update making a generic Tracing Specification specific for the current project.  If the Engineering Company does not have a basic generic specification then one needs to be developed.  Nothing should be left to interpretation.  Items that need to be covered in the Specification include; material for each type of tracing mediums; manner of the tracing; if Heat transfer compound is to be used; how much compound and how the compound is applied. 
  • Standards (Tracing related): The objective is to have a Standard to refer to, eliminating the need to detail repetitive situations on every Tracing Isometric.  These may include Manifold Support; Manifold Piping and Valving; Supply/Return Tracer Supports; Single Tracer Positioning; Multi Tracer Positioning; Tracer Expansion Loops; Valve Tracer Positioning; and any other repetitive situation. The Standard Details need to show placement of the tracer on the process pipe; maximum distance a tracer can travel; design of tracer expansion loops; locating jumpers around non-traced objects etc.
  • Vendor Data and Drawings (Tracing related): Example: Prefabricated Manifolds, Steam Traps, etc.
  • Heat Tracing Isometric Samples: Develop a sample of different situations, use them for team orientation and require compliance for quality & unity of design.
  • Sample Tracing Supply & Return lines: Show how the tracing supply/return line attaches to the manifold. Include the Manifold number and the connection "Letter" designation, show how the pre-insulated tubing is supported and how it connects to the "on-pipe tracer".  Be sure to include proper reference to the continuing documents.
  • Project specific statistical data (see Table A & B, Appendix)
  • Tracing Circuit Index Form: This is an issued document that the Client (Operators and Maintenance Staff) will use in the operation of the unit. (See sample Index Form, Appendix)
  • Isotrac: This is not the same as the Tracing Circuit Index.  Isotrac is the control document used for listing and tracking development and issue of all piping isometrics on the project.

Source of Tracing Media: The source of tracing media may be from inside the unit but more likely it will come from outside the unit.  If more than one unit requires tracing then it is logical that a central site (Utility Plant or other) would be dedicated to providing the required services.  An example of this is the Steam for Steam Heat tracing.  The Main Steam for the plant is generated in the Utility Plant and supplies the total facility.  Steam at various pressures is created in the Utility Plant.  It may be generated specifically for tracing or thru a reducing station used to create medium or low pressure steam for the other uses. The requirement for tracer steam could be supplied from outside the unit via a dedicated line with a pressure control station and pressure relief valves to guarantee the supply and protect the tracing systems.  The tracer condensate may be collected inside the unit and exported from the unit via a dedicated line.  Each of the other commodity mediums may also be supplied from a central source and have a dedicated supply and return line in the unit.

Identification of lines targeted for tracing: A task normally accomplished by the Unit Process Engineers while developing the P&IDs.  However, they are human and will often miss little things that will cause trouble.  These "little" things include equipment items such as pumps and instrumentation.  Piping should do an extensive survey of the P&IDs looking at all instrumentation and equipment to which traced lines are associated.   

Identification of maintenance breaks of the pipe lines or equipment: This is the piping designer's responsibility.  The designer needs to look at any line or part of a line that can or will be removed as a part of routine maintenance.  An example of this is found in pump suction and discharge lines at paired pumps.  If one pump breaks down the spare pump must take over and the damaged pump must be taken out of service.  When this situation is present, the common suction line, the operating pump and the common discharge lines must continue to operate.  Therefore, the tracing for these must also continue to operate.  The suction line and discharge lines inside the block valves must be shut down, drained and cleaned.  The tracing is then shut off so the pump can be disassembled or removed completely.  In a case like this there is one tracer circuit on the common suction line (from the source tank to the suction block valves at each pump.  There are two tracer circuits; one on each suction/discharge lines inside (pump side) the block valves. Then there are one or more tracer circuits on the common discharge line depending on the length and complexity.  At a control valve manifold there is one tracer circuit on the common line to cover both up stream and down stream piping including the bypass.  The part of the manifold inside the block valves including the control valve itself must be on a separate circuit so it can be removed in case major maintenance or replacement is required.  Similar thinking must be carried out for every line and each piece of equipment.

Some design options that should be considered in any Unit with heavy tracing involve piping or instrument components. 

  • Strainers in pump suction lines should be the "T" type or "Y" type strainers.  These allow the changing or cleaning of the screen without dismantling the suction line (and the tracing) when the "Conical" type strainer is used. 
  • Drilling of a small (¼" +/-) hole in the pump discharge check valve to allow some backflow through the pump when it is on "Standby" mode. 
  • Discussions with the Instrument Engineer need to cover all instruments including Pressure Instruments (PI's).  PI's should be looked at with the possibility using only the "Diaphram" protected type so the critical process fluid does not get into the "PI" piping and require heat tracing.

Defining the number of tracing circuits: The number of tracing circuits required in each Unit is determined by a detailed review of the P&IDs by the piping designer.  The number required is a constantly moving target.  Early in the project a count for the purpose of the SOW (Scope of Work) and estimate will executed.  P&ID development is a dynamic activity and therefore two or three months later another count should be completed to update the number of circuits and prepare a RFQ (Request for Quote) for Manifold assemblies.  If the updated number is significantly different (higher or lower) than the SOW count it is appropriate to follow the procedure to adjust the piping labor estimate.

Defining the number of supply and return manifolds: As shown in Table "B" (Appendix), some very simple math will accomplish this task.  The math considers the total number of tracer circuits, the number of connections on each standard manifold and the percent utilization for initial installation vs. future needs.  Table "B" uses an eight (8) connection standard manifold.  Manifolds with 8 connections, 10 connections or 12 connections are available.  However, there is a trade off that must be considered between using fewer manifolds and longer supply and return runs.

Location of supply and return manifolds: All supply and return manifolds should be located as close to the user as is reasonably possible.  It may be better to have more but smaller (fewer connection) manifolds than fewer larger (more connection) manifolds.  Fewer manifolds will automatically lengthen the supply and return run causing more heat loss.

Design of Tracing hard piping: Hard piping (Tracing media  supply and return headers in the pipe racks; the branches to & from the supply headers and the manifolds) can and should be designed along with all other piping in the Unit.  Pipe runs will likely be shop fabricated and shipped to the field. 

Manifold identification: Identification of manifolds is not a standard and is usually what the Client /Operator requests.  It may be something they are accustomed to and use in one their existing plants.  If there is no Client preferred system, a system must be developed.  Whatever system that is utilized, it needs to be simple, logical and consistent.  A simple system you might consider is the following: 

  • If a plant is a horizontal plant having all (or most) equipment grade mounted.  Consider starting with SM 001, S= Supply, M= Manifold, 001= simple numeric identification for the manifold.  Return Manifold would start with RM 001. 
  • If a plant is a vertical plant having equipment on multiple levels, consider a manifold designation structured for ease of the operators locating the manifolds.  For multiple level plants you might use SM 1-001 for the first or ground level and SM 2-001 for the second level, etc.

Next is the need for a designation system for each manifold connection point.  The best way for this is, as you face each manifold (Supply and Return) start at the upper left connection with "A" then across from that is "B" at the upper right and so on down the manifold.  Each of the manifolds shown in Illustration 1, would have tracer connections labeled "A" through "H". See "Sample Tracer Numbering" (Appendix). 

    Illustration 1

Steam Tracer Manifolds
Supply Manifold  (left) & Return Manifold (right)
8 connections each
(Note: individual tracer block valves are not shown)
From Spirax Sarco

 

Executing the Tracing work

How do you do this? I could start by saying "Very Carefully" but I am sure that you will do that.  So the real answer is, don't start until the piping Isometrics have all been issued for construction.  You do not want to have some Tracing work done and then find that the piping design has been revised and tracing must be redesigned.  Also, now that the piping is complete, designers will be available for the Tracing effort.  The "How To" includes creating the Tracing Supply isometric, locating the tracing on the process line and creating the Tracing Return isometric. 

The Tracing Supply isometric is very much like a standard CAD or manual drawn isometric but is shown as pre-insulated tubing.  The tubing must be supported and must have basic dimensions for material purchase and the installer can estimate the work giving a realistic price.  The tracing on the actual process line is bare tubing running the length of the pip[e (considering breakout sections) and then connecting to the return isometric.  The Return Tracing Isometric is similar to the Supply Isometric.  It shows pre-insulated tubing, supports and basic dimensions. 

As each Tracing Circuit is being designed, the "Heat Tracing Index" must be filled out to document the complete system for Client operators.  In addition to the Tracing Index, there needs to be a simple tool to organize and control the work and prevent multiple designers from using the same manifold connection on different tracer circuits.  This is achieved by creating a simple sketch of a standard manifold.  Example: If using the numbers shown in Table "B" (Appendix), print out one copy for each Supply and Return manifold and label them sequentially.  When a designer starts a circuit he or she is required to sign out the two connections required. No exceptions Use it or Lose it.  

After reading this article it should be clear that Tracing is not "Scutwork".  Tracing is complex and demands experience, planning, organization and proper execution.  When the Tracing effort is completed and installed, the next thing is the successful start-up.  If all the recommendations of this article were followed you can be assured that the start-up will be smooth and the Client will be happy.  
 
 
 
 Acknowledgements: With deep appreciation to A. R. Legvold for the significant technical input and for the editing of the whole article, thank you. 
 
 

James O. Pennock has more than forty-five years in the process plant design profession.  He has been involved in both home office and job site assignments on refinery, chemical, petrochemical, power and other projects. His experience ranges from entry level designer to engineering manager.  Much of this was with Fluor.  He is also the author of the book "Piping Engineering Leadership for Process Plant Projects." He is now retired, living in Florida, USA and does only occasional consulting work.  Mr. Pennock can be contacted via E-Mail at This email address is being protected from spambots. You need JavaScript enabled to view it..

Appendix:

Line Count

Pipe Line Breakdown

Gross Numbers

Percent

Total Line Count

3550

 

Total Process Lines

2130

60%

Total Utility Lines

1420

40%

Total Lines Traced

639

18%

Percent Process lines Traced

 

30%

 
 
 
 
 
 
 
 
 
 

Table "A"
 
 

Tracing Media Type Breakdown

 

Media Type

Lines per Tracing Type

Percent Per Tracer Type

Minimum Iso's per Line

(1) (2)

Estimated Tracers Iso's

(5)

Supply Positions

Manifold Req'd

 

(3)

Return Positions

Manifold Req'd

 

(4)

H. P. Steam

202

39.6%

4

808

269

45

269

45

L. P. Steam

182

28.5%

4

728

243

40

143

40

Hot Oil

127

19.9%

3.5

445

169

28

169

28

Hot Water

63

9.9%

3.5

221

84

14

84

14

Warm Water

65

10.2%

3.5

228

87

14

87

14

Glycol

(30 degree F)

0

0.0%

0

 

 

 

 

 

Chilled Water

(42 Degree F)

0

0.0%

0

 

 

 

 

 

Other

0

0.0%

0

 

 

 

 

 

Total

639

100%

----

2429

852

142

852

142

 

Table "B"

 

Table “B” notes:

  1. Minimum tracing isometrics per line includes one (1) tracing isometric from the Supply Manifold to the Process Line, a minimum of one (1) tracing isometric for the tracing on the Process Line and one (1) tracing isometric for the return line to the Return Manifold. Process line tracing requires one tracing isometric for every original construction isometric.
  2. Some process lines may require more than one tracing circuit depending on the length, complexity or temperature requirements.
  3. Supply Manifold requirements are based on 8 connection manifolds and 75% initial utilization with 25% future.
  4. Return Manifold requirements are based on 8 connection manifolds and 75% initial utilization with 25% future.
  5. Manual vs. CAD execution methods may result in differing quantities of fabrication isometrics and tracing isometrics.

 

 

Sample Tracer Numbering

16 – 1234 – 1/3 – SM22 – C – RM40 – D

Legend:

16 – Unit number

1234 – Process line number

1/3 – Number of circuit / total circuits required for this process line

SM22 – Number ID of Supply Manifold for this circuit

C – Supply manifold connection letter designation for this tracer

RM40 - Number ID of Return Manifold for this circuit

D - Return manifold connection letter designation for this tracer

Unit No.

Line No.

Tracing Circuit Count

Supply Manifold Number

Supply Manifold Conn. Position

Return Manifold Number

Return Manifold Conn. Position

Heat Media

Process Line Commodity

Min. Process Line Req’d

(Deg. F)

Remarks

Assigned to:

Date

16

0011

1 of 3

SM34

A

Rm29

C

Hot Water

Raw Feed

180

 

ARL/ 25Mar11

16

0012

4 of 4

SM02

B

RM03

F

HP Steam

Stage 1 Base Prep

400

Critical Line

 

16

0030

3 of 3

SM02

B

RM20

A

HP Steam

Stage 2 Base

400

 

 

16

0048

1 of 1

SM60

D

RM68

B

Hot Oil

Poly Prop.

300

 

ARL/ 25Mar11


Sample Tracing Circuit Index

 

(Index Title, Document Number and Project Identification omitted here)

Note: An excel work book containing Tables “A” & “B” and the Tracing Circuit Index (w/ 1000 circuits) is available by contacting J. O. Pennock at This email address is being protected from spambots. You need JavaScript enabled to view it.

Related reading and resources:

 
Standard Manifold, Supply Manifold (for all tracer medium and Return Manifold for non-Steam Tracers) - http://bayportvalve.com/bayport2/pdffiles/Spirax%20Sarco/vertical%20steam%20distribution%20manifold.pdf

Condensate Return Manifold- http://bayportvalve.com/bayport2/pdffiles/Spirax%20Sarco/vertical%20condensate%20collection%20manifold.pdf

Installation Instructions - http://www.thermon.com/us/installinst.aspx

For more on this subject see:http://www.csiheat.com/

Spirax Sarco Tracing and Manifold details - http://www.spiraxsarco.com/resources/cad/applications/steam-trapping/steam-tracing-and-manifolds.asp

Controls South East, ControTrace - http://www.csiheat.com/products/controtrace.aspx


Acknowledgements: With deep appreciation to A. R. Legvold for the significant technical input and for the editing of the whole article, thank you.


About the Author

Jop

James O. Pennock has more than forty-five years in the process plant design profession. He has been involved in both home office and job site assignments on refinery, chemical, petrochemical, power and other projects. His experience ranges from entry level designer to engineering manager. Much of this was with Fluor. He is also the author of the book "Piping Engineering Leadership for Process Plant Projects." He is now retired, living in Florida, USA and does only occasional consulting work.

Mr. Pennock can be contacted via E-Mail at jopennock@netscape.net.

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