1. Three Streams Engineering
HEAT TRACE DESIGN

2. AGENDA PIPE HEAT TRACE THEORY HEAT TRACE CABLE TYPES AND USES
CONTROLS AND MONITORING
HEAT TRACE DESIGN
LEARNINGS AND FAQ

3. 1. PIPE HEAT TRACE THEORY Heat Trace design is based on the IEEE 515
(Recommended Practise for the Testing, Design, Installation and Maintenance of
Electrical Resistance Heat Tracing for Industrial Applications.

4. Considerations for Calculating Heat Loss
(INFORMATION ON LINE LIST AND P&ID)
Pipe Size
Insulation Type (mineral wool, fiberglass, calcium silicate)
Insulation Size (always calculate as oversized)
Min Ambient Temperature ( -40°C as per Cenovus pipe spec)
Maintain Temperature (Freeze protection = 10°C)
Wind Speed (standard = 40km/h)
Safety Factor (25%)
IMPORTANT – with pipe heat trace systems – we do not usually care what type of fluid is in the pipe or pipe thickness (some systems we need to be aware of fluid due to sheath temperatures of heat trace – such as polymers). This is relevant to other types of heat trace design (tanks, vessels)

5. 2. HEAT TRACE CABLE TYPES AND USES
Mineral Insulated Cable
Series cable
Stainless Steel outer sheath
Up to 600vac (long lengths) – 3 phase designs possible
High heat exposure (500°C)

6. B. Series Constant Wattage (TEK)
Series cable
Cut –to Length
Up to 600vac (long lengths)
1 phase or 3 phase cable
Only available from Thermon

7. C. Sect Heat Trace System
Extreme long lengths (up to 20 miles)
High watt density (20w/ft per tube)
Voltage is based on length
Expensive but bulletproof.
Specialty design – usually used on pipes that cannot be accessed in the future (under water)

8. D. Self-Regulating Thermon Types
BSX - used when low sheath or T class temperature is required
HTSX – most commonly used. Will take min LP steam (204°C with power off)
D. Self-Regulating
Overlap installation (not a good practice)
Cut-to Length
Can be operated without RTD control
Stock item
Lower voltages only – 120vac to 277vac

9. E. Constant Wattage Thermon Types Cut-to Length Requires RTD control
Stock item
Voltage – 120vac to 600vac
Zone Construction
Thermon Types
FP – not in Cenovus spec
HPT – power limiting cable (120/240vac only) – rarely used. Very expensive
Drexan
CMH Pipe Guard. – can be used on high heat lines – not in Cenovus spec yet

10. 3. Controls and Monitoring
Nextron
Tracemate (single or 2 point) – can be used as power kit. Built-in RTD
MasterTrace (up to 9 point controllers – dual RTD control capability) 30amp rating on 2pole relays
B. Thermon
TC-101A (single point)
TC-201A (single point – dual RTD control)
TC-202A (dual point – single RTD control)
TC-1818A (18 control points – single RTD control – can be configured for 9 control points with dual RTD control) – 15amp rating on 2pole relays. If we use 2 single pole relays – can achieve 30amp rating but much larger heat sinks.
C. RTD control
RTD placement important. Watch for dead legs or block-ins. Flow pattern important
Dual RTD maybe required for lines with take-off for instrumentation. Tubing to be separate circuit for all MI circuits.
Ambient Control – only used with Self-regulating cable.
D. Setpoint List
For Thermon or Nextron Master Trace controllers – need to do a controller setpoint configuration list (see template)

11. 4. Heat Trace Design
Step 1
- Acquire P&ID’s, Line List and Piping Iso’s. (iso’s not really required for a self-regulating or constant wattage heat trace circuit – distance can be estimated because except to keep circuit below 30amp breaker max
Go through Iso’s (based on what is heat traced from the P&ID’s) and makeup your preliminary heat trace circuits. Instrument double block a bleed – sometimes not shown on piping iso (smaller than 1” not shown) – review P&ID and check with piping design on length if not shown.
Determine maintain temperatures from line list. Required info for heat loss is:
Pipe Size – on P&ID also.
Insulation Type (mineral wool, fiberglass, calcium silicate)
Insulation Size (always calculate as oversized) – on P&ID also
Min Ambient Temperature ( -40°C as per Cenovus pipe spec)
Maintain Temperature (Freeze protection = 10°C)
Wind Speed (standard = 40km/h)
Safety Factor (25%)
Determine the voltages that can be utilized. It has been a standard at TSE to use 208vac as a min unless the 120vac source is very close.
IMPORTANT – heat trace manufacturers recommended max watt/meter for any cable is 49 watts/m (15w/ft) - (this is to keep the sheath temperatures at a nominal temperature) In keeping with this – the following is a recommended cable allowance during preliminary design.
3/4” to 4” – single pass
6” to 10” – dual pass
12” to 16” – 3 passes or more.

12. - Keep in mind that for long lines (208vac to 600vac) – a 3phase circuit can be used (do not do on pipe smaller than 6”)
Check line list (depends on design, operating and maintain temperatures) and site conditions to determine what type of cable to use (it has been an unwritten directive from Cenovus to use MI as much as possible). All maintain heat trace circuits should be MI (self-regulating does not work good for this).
Review P&ID’s for instrumentation heat trace requirement. The instrumentation requirement will probably not show up on the iso’s – just the take off valves.
All circuits designed with min 30amp breaker. It has been a standard at TSE to use 208vac as a min unless the 120vac source is very close.
Multiple circuits can be used on the same line – insure RTD control is used and each circuit is controlled. You can connect each heat trace circuit in parallel to common power circuit or have multiple power circuits.
Step 2
Use standard heat trace length calculation sheet (“HT CALC SHEET”) to calculate heat trace circuit length. Use this sheet to calculate MI set lengths also. Copy the template to your directory then change it to reflect your design parameters (cable type), Job number and directory to store the calculation sheets.
Each heat trace circuit to have a calculation sheet file.
When using the calculation sheet – enter all the lengths in the sheet as much as possible – do not use a calculator to add all the lengths and then input in the sheet – it is impossible for anybody to check in the future especially if changes in the future are done to the piping ios and the heat trace circuit needs to be revised. The use of this sheet is important to determine proper equipment allowances and cable variance.
MI set lengths to be 75 meters max (manufacturers recommendation)

13. Step 3
Use calculation program to determine heat trace circuit. For today – we are going to use Computrace (Thermon). Review of Drexan.
Insure that your min ambient is properly inputted. This effects your max (inrush) current requirement.
Remember you have calculated your entire length – disable all allowances in the program.
For most circuits – you can let the program automatically pick the cable but for lines with 2 passes or more – you will probably need to use the override function or keep your pipe size smaller.
You may have to use the cable override function to determine the proper cable due to you having 2 separate heat trace circuits on the line. To insure you get a proper cable sheath temperature – adjust the pipe size to be able to determine this.
When designing a 3 phase circuit – never use the override function.
In the settings tab- insure you are using a 30amp breaker – the type of control you are using and for MI design – set the overvoltage to 500%
Remember – in the end you want a cable design that makes up the heat loss.
It is important (especially for MI cable design) that we export the calculation sheet into your working directory – vendor requires them and it is good for future information.
As a standard – heat trace circuit tags are derived from the pipe number (PG-BAA H-ET1) = HT-PG-9810.

14. 5. Heat Trace Learnings and FAQ
Improper Insulation. Open area’s on pipe
Wet Insulation – worse than no insulation at all
Improper Heat Trace install – especially allowances
Heat trace to long can be as bad as heat trace to short with MI cable. (especially on small pipes)
Sensing RTD in wrong location (dead legs)
Dual RTD control required.
MI Heat trace of instrument tubing should be on separate circuit due to during design – we do not know the length required.
Diaphragm instruments do not require EHT. P&ID can show dashed line around instrument – this may mean heat trace or enclosure – you need to find out from instrumentation if tubing requires heat trace. Do not trust P&ID diaphragm symbols.
The use of steam and self-regulating cable. If there is a chance for steam – do not use self-regulating. (remember even cleaning)
All heat trace circuits require 30mA GFCI protection min (not a standard GFCI breaker – 5mA) – this is due to every heat trace circuit has a small ground fault.
Heat Trace designed for non-operating systems only (stagnant)
Heat Trace is not designed for heat-up applications – maintain only – the process needs to heat up the product. Heat trace should not be energized until process is running at the beginning. (in other words –if it is frozen – heat trace will not thaw effectively)
Every manufacturer of heat trace has different equipment allowances. There is no standards for allowances (company specs only)
Ambient RTD control on MI and constant wattage – can it be used?
All scratch designs should have EHT schedule – existing EHT schedules should be revised.

15. Solid State versus Mechanical Relays in Heat Trace Controllers – more cost effective to use mechanical and spec does not specify solid state – only reason for solid state is if ambient proportional control is utilized (it never has as yet). Life span of relay is relatively the same (supplier is saying) – solid state also generates unwanted heat – mechanical does not require heat sinks on panel.
Cut to length parallel cables (constant wattage or self-regulating) – anything above 3 meters – install a TEE kit. Below – just loop. Drexan CMH Pipe Guard cable is large – very difficult to loop on small diameter piping.

16. HEAT TRACE EDL HEAT TRACE CALCULATION SHEET (HT CALC SHEET)
HEAT TRACE SCHEDULE TEMPLATE
HEAT TRACE ISO TEMPLATE
HEAT TRACE CONTROLLER TEMPLATES
NEXTRON MASTERTRACE SET-POINT LIST
THERMON SET-POINT LIST
THERMON HEAT TRACE CABLE CUT SHEETS
NEXTRON 10, 20, 30 CCT CONTROLLER TYPICAL DWGS
THERMON CONTROLLER TYPICAL DWGS