Miscellaneous Design Guide
Winterizing
Chapter from the Miscellaneous Design Guide.
WINTERIZING & HEAT TRACING DESIGN
Heat Tracing Types
| Type | Medium | Max Temp | Maintenance Temperature | Advantages | Limitations | Typical Use |
|---|---|---|---|---|---|---|
| Electric — self-regulating | Polymer/carbon matrix | 300-500°F | Up to 300°F | Self-limiting, easy install, zones | Limited max temperature | Instrument lines, small pipes |
| Electric — constant wattage | Mineral insulated cable | 1,000°F+ | Up to 1,000°F | High temperature capability | Requires thermostat, can overheat | High-T process maintenance |
| Electric — skin effect | Ferromagnetic tube + conductor | 400°F | Up to 400°F | Long runs, uniform heat | Complex installation | Long pipelines |
| Steam — external tracing | Tubing on pipe exterior | 50 psig: 298°F | 220-300°F typical | Simple, reliable, high duty | Steam supply needed, condensate return | Most refinery process piping |
| Steam — jacketed pipe | Steam jacket around process pipe | 150 psig: 366°F | Up to 350°F | Highest heat input | Expensive, complex fabrication | Sulfur lines, heavy residuum |
| Hot oil tracing | Hot oil in tracing tube | Per HTF limit | Up to 600°F | Higher temp than steam | Separate hot oil system needed | High-T applications |
Winterization Design Checklist
Instruments:
• All DP transmitters: heat trace impulse lines, insulate, drain/seal legs
• Level bridles: heat trace, insulate, verify drain valves
• Control valves: heat trace actuator if pneumatic (prevent moisture freeze)
• Pressure gauges: remove or heat trace if water service
Piping:
• All dead legs >12" long: heat trace or slope to drain
• Pump casings: heat trace and insulate (especially standby pumps)
• Relief valve inlet/outlet: verify no liquid accumulation points
• Drain lines: heat trace, slope to drain point
• Cooling water lines: insulate exposed sections, trace if stagnant risk
Equipment:
• Cooling tower: design for freeze protection (bypass, heaters, windscreen)
• Air coolers: louvers, recirculation, VFD fans
• Steam traps: verify operation before winter — failed trap = frozen line
• Fire water: heat trace headers, drain test connections after use
Source: Miscellaneous_Design_Guide_v1.xlsx · sheet “Winterizing”
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