Valves for Hydrofluoric Acid (HF) Service
Hydrofluoric acid is one of the most hazardous industrial chemicals. Even dilute HF can cause deep tissue burns and systemic fluoride poisoning through skin contact. Refinery alkylation units use concentrated HF or sulphuric acid. Valve specifications follow CCPS and API 751 guidelines.
Pressure Range
1–20 bar
Temperature
Ambient to 70°C
Industries
Petroleum refining (alkylation), Semiconductor etching, Fluorochemical production
Key Properties — Hydrofluoric Acid (HF)
- Penetrates skin — causes deep tissue damage and systemic toxicity
- IDLH: 30 ppm (immediately dangerous to life)
- Attacks glass and many ceramics (used for etching)
- Anhydrous HF is a gas above 19.5°C — requires pressure vessels
- Refinery alkylation uses anhydrous or concentrated aqueous HF
Material Compatibility — Hydrofluoric Acid (HF)
Ratings are indicative. Actual compatibility depends on concentration, temperature, velocity, and presence of contaminants. Always consult corrosion tables or a materials engineer.
| Material | Rating | Notes |
|---|---|---|
| Monel 400 (N04400) | Excellent | Industry standard for HF alkylation service. Resists anhydrous and aqueous HF. |
| Carbon Steel | Good | Forms iron fluoride passivation layer. Acceptable for anhydrous HF and high concentrations. Not for dilute aqueous HF. |
| SS 304/316 | Not Recommended | Not acceptable for HF service — corrosion and SCC risk. |
| PTFE | Good | Acceptable for aqueous HF up to ~50% at ambient. Fuming HF attacks PTFE at elevated temperature. |
| Hastelloy C-276 | Fair | Only for dilute aqueous HF — not for anhydrous or hot concentrated HF. |
| Nickel 200/201 | Good | Good for aqueous HF in some concentration ranges. |
Recommended Valves
Monel 400 globe valve (NACE MR0175)
HF alkylation unit — API 751 compliant design
Monel 400 ball valve
Isolation in HF service — Monel wetted parts throughout
Bellows-sealed globe valve
Zero fugitive emission design — HF is lethal at low concentrations
ESD valve with remote actuator
Remote operation mandatory — no manual operation in HF area
Valves to Avoid
SS 304 or SS 316 in any HF service
Non-fire-safe or non-bellows-sealed valves
Any valve with glass or ceramic components
Valves not rated for Category M lethal service
Special Considerations
Applicable Standards
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