How to select thermic fluid heating system components wisely?
Thermic fluid heating system is used in many fields, do you know how to select its components?
System components comprise piping, threaded installations, flanges, gaskets, studs, nuts, insulation, valves and pumps. When specifying components for a hot oil heating system, be sure that they are designed for hot oil systems and for temperatures that exceed your system’s bulk temperature.
Thermic Fluid Heating System
Piping. Welded installations are recommended. If you use threaded installations, back-weld all connections or use thread sealant.
Flanges. Select flanges with the following characteristics:
- 300 lb forged steel construction
- welding neck
- 1/16″ raised face, Schedule 40 bore
- ASTM A 181 rating.
The use of backing rings at pipe-to-flange welds is recommended.
Gaskets. Select spiral-wound, graphite-filled or expanded/filled PTFE gaskets.
Studs. Choose alloy steel, continuously threaded, ASTM A 193, Grade B7 or higher studs.
Nuts. Use heavy hex nuts, ASTM A 194, Grade 2H or higher.
Insulation. Calcium silicate or fiberglass rated to 850oF (454oC) is acceptable where the potential for leaks is minimal. Closed-cell foamed glass is recommended within several feet of flanges, valves, pipe taps or other potential leak points. Flanges should be left uninsulated to ease leak detection.
Valves. Select cast or forged carbon steel valves with a socket weld or flanged (300 lb) design. Graphite or expanded/filled PTFE valve-stem packing or bellows seal is recommended. Isolation valves should be ball-type valves; for these uses, control valves or globe valves are recommended. Install valve stems pointing down to allow any leaking fluid to drain away from the insulation.
Pumps. For positive-displacement pumps, select those made of alloy steel with a gear-within-a-gear or sliding-vane design. For centrifugal pumps, be sure the pump selected has ductile or cast iron wetted parts. For the pumps’ mechanical seals, select bellows type. For applications with low particulate loading, carbon seal faces are recommended over silicon or tungsten carbide seal faces. For applications with high particulate loading, use tungsten carbide seal faces rather than silicon carbide.