Thermal Fluid System Design From MultiTherm®

Welded installations are recommended:


  • Up through 1 1/2" - ASTM 106 Grade B Schedule 40 seamless carbon steel pipe.

  • 2" through 24" - ASTM A 53 Type S Grade B Schedule 40 seamless carbon steel pipe.

  • Mill scale and protective coatings should be removed prior to installation.

  • Use of backing rings at pipe to pipe welds is recommended (Robvon or equal).

Threaded installations:

  • Up through 1" - ASTM A 106 Grade B Schedule 80 seamless carbon steel pipe.

  • 1" to 2" - ASTM A 106 Grade B Schedule 40 seamless carbon steel pipe.

  • Greater than 2" - ASTM A 53 Type S Grade B Schedule 40 seamless carbon steel pipe

  • Back weld all connections or use thread sealant (Felpro HPS, Copalite, X-PANDO or equal).


300 lb. forged steel; welded neck: 1/16" raised face, Schedule 40 bore, ASTM A 181. Use of backing rings at pipe-to flange welds in recommended.

Spiral wound graphite filled (Grafoil, Flexitallic or equal) or expended/filled PTFE (Goretex, Gylon or equal).

Alloy steel continuous threaded, ASTM A 193, Grade B7 or higher.

Heavy hex nuts, ASTM A 194, Grade 2H or higher.


Calcium silicate or fiberglass rated to 850°F is acceptable where potential for leaks is minimal. Closed cell foamed glass (Pittsburgh Corning or Equal) is recommended within several feet of flanges, valves, pipe taps or any potential leak point.


Note: Flanges should be left uninsulated to facilitate the detection of leaks. If flanges must be insulated after startup, closed cell formed glass is recommended.


Cast or forged carbon steel; socket weld or flanged (300 lb.). Graphite or expanded/filled PTFE valve stem packing or bellows seal recommended.


  • Isolation Valves: Ball valves recommended (Orbit or equal)

  • Control Valves: Globe valves recommended


Note: Install valve stems pointing downwards to allow leaking fluid to drain away from insulation.



  • Positive Displacement: Alloy steel; gear-within-a-gear (Viking or equal) or sliding vane (Blackmer or equal).

  • Centrifugal: Ductile or cast iron wetted parts: ( Sihi, Dean brothers, Goulds, ITT, MP Pumps, or equal)

  • Mechanical Seals: Bellow type; carbon vs silicon/tungsten carbide seal faces recommended for low particulate loading; tungsten carbide vs. silicon carbide seal faces recommended for high particulate loading (BW/IP, A W Chesteron, John Crane, Durametallic, or equal)

  • Canned Motor: (Crane Chempump, Sundyne or equal)

  • Magnetic Drive: (Caster, Dickow, Kontro or equal).


MultiTherm® Technical Articles

Fluid Analysis | Fluid Life | Handling of MultiTherm Fluids | Material Safety Data Sheets | MultiTherm vs Synthetic
Processes That Use MultiTherm Fluids | Technical Articles | TechTeam Form | Thermal Fluid Filtration |
Thermal Fluid Safety Issues | Thermal Fluid System Cleanout | Thermal Fluid System Layout |
Typical MultiTherm Industrial Users | Typical System Design & Components



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