Instrument tubing freeze protection: plan for the coldest operating case
Cold weather, low flow and shutdowns can change what an instrument line needs. Start with the operating cases before choosing a traced tubing bundle.
Start with the conditions, not a heater rating.
An exposed instrument line may behave differently when a plant is running, operating at low flow or shut down. A warm process does not necessarily protect fluid that is left stationary in a small tube. Before specifying freeze protection, identify when the line can cool and what must remain available during those periods.
Record the minimum ambient temperature, normal and minimum fluid temperatures, fluid composition and the consequence of a blocked or damaged line. A freezing point is only one part of the enquiry. The required operating temperature and the time spent in each condition also matter.
Protect the line. Review the whole route.
Electric tracing supplies heat alongside the process tube. Its suitability depends on the complete assembly, available power, controls and the duty being specified.
Insulation reduces heat loss; tracing adds heat.
Pre-insulated tubing provides a thermal barrier around the process tube. It has no integral electric heater. Where a defined cold-weather duty requires added heat, electric-traced tubing is a family to consider. Marmon lists electrically traced constructions for freeze protection and temperature maintenance, with different heater options.
Treat a published heater limit as a component or family characteristic. It does not establish the temperature that an installed line will maintain. The proposed construction needs to be considered against the fluid, ambient conditions and installation.
Include connections and shutdown arrangements.
Describe the full route, including exposed sections, supports, valves, terminations and transitions into cabinets or buildings. Ask how each part will be protected and how the installation will be inspected. Provide the available voltage, control arrangement and any area-classification requirements.
Confirm what happens if power is unavailable, the line is isolated or the process stops. Drain-down or another operating measure may be relevant to the site procedure. PMA can help bring those requirements together for an assembly-specific enquiry.
Explore the related guidance.
Explore instrument-line freeze protection
Product information
Manufacturer references: electric traced. Confirm the exact assembly and documentation for your enquiry.
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