FieldEngineersKitEngineering Reference & ASME Code Basis
1. Core Formula & Variable Definitions
ASTM C680 (Heat Gain/Loss — insulation thickness / surface temperature methods) · ISO 12241 (Thermal insulation for building equipment and industrial installations) · ASTM C533 / C547 / C552 / C591 (material conductivity families — screening polynomials) · ASTM C1055 (personnel protection — ~60 °C / 140 °F contact screening) · ASME B36.10M / B36.19M (pipe outside diameter for r1)
Q = (Th − Ta) / Rtot
Rtot = ln(r2/r1)/(2πk) + 1/(2π r2 ho) · ho = hc + hr
hc,nat = 1.32 ((Ts − Ta)/d2)0.25 · hr = ε σ (Ts4 − Ta4)/(Ts − Ta)
ASTM C680 / ISO 12241 radial screening · personnel Ts ≤ 60 °C (ASTM C1055)
Pipe OD from ASME B36 schedule tables (getPipeScheduleSize). Insulation k(Tm) uses ASTM C533 / C547-style polynomials at mean insulation temperature. Outer film coefficient blends ASTM C680 natural convection with a mild outdoor wind term (Churchill cube-root) plus radiation with default jacket emissivity ε = 0.90. Iterative solve for Ts. Screening only — confirm manufacturer k(T), jacketing, and site wind.
- Q (Heat Loss per Unit Length) — Radial heat loss through insulated pipe (W/m or Btu/hr·ft).
- Ts (Outer Surface Temperature) — Jacket outer surface temperature solved iteratively (°C / °F).
- R_ins (Insulation Resistance) — ln(r2/r1)/(2πk) — conduction resistance of the insulation layer.
- R_conv (Surface Resistance) — 1/(2π r2 ho) — outer convection + radiation film resistance.
- ho (Combined Surface Coefficient) — hc + hr with natural/forced convection blend and radiative hr.
- k (Thermal Conductivity) — Material k evaluated at mean insulation temperature Tm = (Th + Ts)/2.
2. Allowances, Tolerances & Standards
Field screening uses ASTM C1055 contact guidance and ISO 12241 / C680-style film models.
Pass/Fail badge follows ASTM C1055 ~5 s contact screening. Higher Ts requires thicker insulation or personnel guards.
Typical painted/metal jacket screening value. Shiny aluminum jackets may use lower ε — override in inputs.
Natural cylinder convection blended with a mild outdoor forced term so light wind does not erase the ASTM C680 natural formula; still-air cases remain natural-dominated.
Quick Reference Lookup Table
| NPS | Material | Thickness | Th / Ta | Wind | Ts (°C) | Q (W/m) | Personnel | vs bare % |
|---|---|---|---|---|---|---|---|---|
| 4 | Mineral wool | 50 mm | 200 / 25 °C | 2 m/s | 34.5 | 78.3 | Pass | 94.5 |
| 6 | Calcium silicate | 75 mm | 350 / 25 °C | 2 m/s | 43.5 | 216.7 | Pass | 96.1 |
| 3 | Mineral wool | 2.0 in | 400 / 77 °F | 4.5 mph | 34.0 (93.2 °F) | 67.0 (69.6 Btu/hr·ft) | Pass | 94.4 |
| 8 | Cellular glass | 3.0 in | 500 / 77 °F | 4.5 mph | 36.6 (97.9 °F) | 150.6 (156.6 Btu/hr·ft) | Pass | 96.2 |
| 8 | Cellular glass | 75 mm | 150 / 20 °C | 1 m/s | 26.9 | 72.9 | Pass | 95.1 |
| 2 | Mineral wool | 40 mm | 200 / 25 °C | 2 m/s | 34.9 | 58.2 | Pass | 92.9 |
| 10 | Calcium silicate | 100 mm | 250 / 25 °C | 2 m/s | 35.0 | 157.3 | Pass | 96.5 |
| 4 | Polyurethane | 40 mm | 80 / 25 °C | 1 m/s | 27.7 | 16.3 | Pass | 94.3 |
Values from the FEK iterative solver with ε = 0.90 and mild Churchill natural/forced blend (hc,forced ≈ 2.2·v^0.6/d₂^0.4). Not certified ASTM C680 lab data — confirm manufacturer k(T) and jacket emissivity for design.
3. Material & Code Limitations
k(Tm) polynomials are screening approximations of published mean curves — not mill certificates.
| Material Group | Temperature Range | Allowable Stress / Limit | Engineering Notes |
|---|---|---|---|
| Mineral wool (ASTM C547) | Hot process / steam screening | — | Common for process and steam lines; confirm binder and jacket for elevated Th. |
| Calcium silicate (ASTM C533) | High-temperature blocks | — | Higher k than mineral wool; often selected for hotter pipes and fire resistance. |
| Cellular glass (ASTM C552) | Closed-cell / cryogenic & hot | — | Moisture impermeable screening option; confirm compressive strength for supports. |
| Polyurethane (ASTM C591) | ~120 °C continuous caution | — | App warns above ~120 °C continuous service — confirm manufacturer rating. |
4. Step-by-Step Worked Example
Field VerificationShowHide
Worked Example — NPS 4 · 50 mm Mineral Wool · 200 °C
Default metric duty: NPS 4, 50 mm mineral wool, Th = 200 °C, Ta = 25 °C, wind = 2 m/s, ε = 0.90.
Resolve pipe outer radius
Set insulation outer radius and k(Tm)
Iterate jacket surface temperature Ts
Check personnel protection and savings
5. Frequently Asked Questions & Technical References
ShowHide
ASTM C1055 screening uses Ts ≤ 60 °C (140 °F) for brief (~5 s) contact. Higher Ts is flagged Fail — increase thickness or add personnel guards.
This app defaults to ε = 0.90 and blends natural + mild forced convection with site wind. Lower emissivity or still air raises Ts and changes Q — adjust ε and wind to match the duty.
No. It is a field screening solver with app k(T) polynomials. Confirm jacket emissivity, wind turbulence, and manufacturer conductivity curves for design or contractual work.
Bare Q uses the same film model on the bare OD at Th. Savings % = (Q_bare − Q_insulated) / Q_bare × 100 under identical Ta, wind, and ε assumptions.