Numerical Method — Equation 2.1
P = Design pressure (MPa) | V = Volume (L)
Fc = Compressibility factor: 10 gas · 1 liquid · 0.1 vacuum
Ff = Contents factor: 1000 lethal · 10 very harmful · 3 harmful · 1 NHG · 1/3 NHL
Fs = Location/service factor (see inputs)
| Hazard Level Value (H) | Hazard Level | Description | Registration |
|---|---|---|---|
| H ≥ 10⁸ | A | High Hazard | Required |
| 10⁶ ≤ H < 10⁸ | B | Medium Hazard | Required |
| 10⁴ ≤ H < 10⁶ | C | Low Hazard | Required |
| 10² ≤ H < 10⁴ | D | Extra Low Hazard | Required |
| H < 10² | E | Negligible Hazard | Exempt |
Fluid Harmfulness Guide
Lethal (Ff = 1000): Very toxic / highly radioactive substances. Exposure limit ≤ 0.1 ppm.
Very Harmful (Ff = 10): Extremely/highly flammable, toxic, oxidizing, explosive, corrosive.
Harmful (Ff = 3): Combustible liquid, irritant, harmful to environment, contents above 90°C or below −30°C.
Non-Harmful Gas (Ff = 1): Air, nitrogen, CO₂ and similar inert/non-toxic gases.
Non-Harmful Liquid (Ff = 1/3): Water, non-toxic liquids between 0°C and 65°C.
Assumptions, Formulae & Notes
Uses the numerical method (Equation 2.1) from AS 4343:2014. The hazard level value H = P × V × Fc × Ff × Fs, where all factors are as defined in Clause 2.2.
Gas: Fc = 10 | Liquid: Fc = 1 | Vacuum: Fc = 0.1. This calculator covers positive pressure service only.
Non-harmful liquid with PV < 100,000 MPa.L at temperatures between 0°C and 65°C shall be classified as Hazard Level E, regardless of the calculated H value.
For multi-chamber vessels or shell & tube heat exchangers, calculate each chamber separately and select the higher hazard level per Clause 2.2.9.
Hazard Levels A, B, C and D generally require design registration. Level E equipment is typically exempt but remains subject to general plant safety regulations.
For mixed fluid contents, the harmfulness of the mixture shall be determined from NOHSC:1008 criteria (e.g. 5% cyanide in water is not classified as lethal).