How is pipe-run volume calculated?

In Pipe run mode, volume is V = π/4 · ID² · L using the ASME B36 inside diameter for the selected NPS and schedule. Add vessel or tubing volume separately when it is a meaningful share of the pressurized envelope.

What does R₀ = 45 ft mean?

R₀ = 45 ft per lb TNT is the unprotected personnel screening standoff corresponding to roughly ~1 psi side-on overpressure. Barriers, occupied buildings, and AHJ rules often require a larger zone than this screening value.

Is this an ASME calculator for pipe stress?

No. It does not run pipe-stress / flexibility analysis. It screens pneumatic test safety distance. For stress/flexibility, use thermal expansion / loop tools or CAESAR II.

Can I use this for a paid PDF / inspection package?

Yes as a starting sheet. Export the results into your test package, then have an authorized inspector / NDE firm complete barrier layout, procedure, and witness deliverables for B2B clients.

Why prefer hydrostatic testing?

Liquid water stores far less elastic energy than compressed gas. Codes and good practice prefer hydrotest whenever the process and materials allow.

Pneumatic Test Safety Distance — 150 psi · 50 ft³ | FieldEngineersKit

Parameter	Value
Test pressure	150 psi g
Volume under test	50 ft³
Test gas	Air

1. Core Formula & Variable Definitions

ASME PCC-2 (Repair of Pressure Equipment & Piping) — Article 501 Pneumatic Testing · ASME B31.3 (2022 Edition) · Chapter VI — pneumatic test authorization & limits (companion) · ASME B36.10M / B36.19M — ID for pipe-run volume mode

E = [P₁·V / (γ − 1)] · [1 − (P₀/P₁)^((γ−1)/γ)]

D = R₀ · (E / E_TNT)^1/3 · R₀ = 45 ft per lb TNT

ASME PCC-2 Article 501 Nonmandatory Appendix energy method (screening)

Standard PCC-2 Art. 501γ air/N₂ 1.40R₀ 45 ft / lb TNTOutput D · E · TNT eq.

Pneumatic tests store elastic energy in the compressed gas. This calculator evaluates ideal-gas expansion to atmosphere (γ = 1.40 for air/N₂, 1.67 for He), converts energy to TNT equivalent (1 lb TNT ≈ 1.4×10⁶ ft·lbf), and scales an unprotected personnel standoff with R₀ = 45 ft (~1 psi side-on). Volume may be entered directly or from NPS × schedule × length (B36 ID). Prefer hydrostatic testing when practical. Screening only — not a stamped blast or AHJ package.

P₁ (Absolute test pressure) — Gauge test pressure + atmospheric (Pa absolute).
P₀ (Atmosphere) — 101.325 kPa absolute reference for expansion.
V (Pressurized volume) — Pipe / vessel / tubing envelope under test (m³ or ft³).
γ (Ratio of specific heats) — 1.40 air/nitrogen · 1.67 helium.
E (Stored energy) — Ideal-gas expansion energy released to atmosphere (J / MJ).
D (Min. safe distance) — Unprotected personnel exclusion radius from cube-root scaling.

2. Allowances, Tolerances & Standards

Distance screening does not replace barriers, stepwise pressurization, or written authorization.

Prefer hydrotestWhen practical

Water stores little elastic energy vs gas. Use pneumatic only when hydrotest is impractical.

B31.3 Pt limit≤ 1.1 × P × (St/S)

Resolve pneumatic test pressure separately (Hydro / Pneumatic Pt calculator), then screen D here.

R₀ basis45 ft / lb TNT

~1 psi side-on unprotected personnel screening. AHJ / barrier layouts may require larger zones.

PDF / inspection packageExport screening sheet

Use Export for the field package start; formal PCC-2 Article 501 documentation is a paid inspection deliverable.

Quick Reference Lookup Table

Illustrative air-test screening distances (this app, R₀ = 45 ft)
P (gauge)	V	D (approx.)	Focus
5 bar	1 m³	9.3 m	Small envelope
10 bar	2 m³	15.5 m	Default app case
15 bar	5 m³	24.6 m	Larger envelope
20 bar	10 m³	34.6 m	High stored energy
150 psi	50 ft³	45.8 ft	Imperial SEO case

3. Material & Code Limitations

Ideal-gas screening for air, nitrogen, and helium. Not for reactive / toxic release modeling or confined blast.

Material Group	Temperature Range	Allowable Stress / Limit	Engineering Notes
Air / nitrogen	γ = 1.40	N/A — energy method	Default pneumatic media for most plant tests.
Helium	γ = 1.67	N/A — energy method	Higher γ changes stored energy vs air at the same P·V.
Pipe-run volume	Ambient screening	Uses B36 ID	Add vessel / tubing volume separately when significant.

Code Applicability & Safety Boundaries

Field screening only — does not satisfy a formal blast study, barrier design, or stamped PCC-2 Article 501 procedure.
ASME B31.3 still requires written authorization, barriers, and stepwise pressurization for pneumatic tests.
R₀ = 45 ft assumes ~1 psi side-on unprotected exposure; occupied buildings and roads may need larger zones.
Export / PDF output is a screening sheet for packages and B2B inspection handoff — not a certified report by itself.

4. Step-by-Step Worked Example

Field VerificationShow

Step-by-Step Worked Example: 10 bar g · 2 m³ air

Screen the unprotected personnel exclusion distance for a 10 bar gauge air pneumatic test on a 2 m³ pressurized envelope (ASME PCC-2 Article 501 energy method, R₀ = 45 ft per lb TNT).

Test pressure:10 bar g (P₁ = 11.013 bar a)Volume V:2.0 m³Gas:Air · γ = 1.40P₀:1.01325 bar aR₀:45 ft per lb TNT

1

Form absolute pressure and energy

E = \frac{P _{1} V}{γ - 1} [1 - (\frac{P _{0}}{P _{1}})^{(γ - 1) / γ}]

P₁ = 1.101325 MPa · V = 2 m³ · γ = 1.4 → E ≈ 2.722 MJ (2.722×10⁶ J).

Result:E ≈ 2.722 MJ

2

Convert to TNT equivalent

W = E / E_{TNT}

E_TNT ≈ 1.4×10⁶ ft·lbf/lb ≈ 1.898 MJ/lb → W ≈ 2.722 / 1.898 ≈ 1.43 lb TNT.

Result:W ≈ 1.43 lb TNT

3

Scale exclusion distance

D = R_{0} \cdot W^{1/3}

D = 45 ft × (1.43)^{1/3} ≈ 45 × 1.13 ≈ 50.8 ft ≈ 15.5 m.

Result:D ≈ 15.5 m (50.8 ft)

Keep non-essential personnel outside this radius during pressurization and hold unless an engineered barrier plan says otherwise.

Conclusion: For 10 bar g × 2 m³ air, this app’s PCC-2 Article 501 screening gives D ≈ 15.5 m. Open /10-bar-2-m3, export the sheet for the test package, and escalate barrier / AHJ documentation to your inspection contractor.

5. Frequently Asked Questions & Technical References

Show

This tool implements the stored-energy → cube-root distance screening used with ASME PCC-2 Article 501 pneumatic testing guidance: compute E, convert to TNT equivalent, then report an unprotected personnel exclusion radius D.