Corrosive & Toxic Specialty Gases
Corrosive and toxic gases turn valve selection into a safety exercise. The wetted alloy, diaphragm material, stem seal and fail position all need to be matched to the gas before a panel is built.
Valonix supplies bellows sealed valves for aggressive or hot services and UHP diaphragm valves for cleaner distribution lines, with material compatibility reviewed against the declared gas list.
Gas-by-gas considerations
Chlorine and hydrogen chloride attack many elastomers and require compatible alloys; ammonia is corrosive in the presence of moisture; silane is pyrophoric; NF3 is a strong oxidiser at process conditions. Moisture ingress during installation often causes more damage than the gas itself.
- Cl2 / HCl: halide-compatible alloys
- NH3: keep the system dry
- SiH4: pyrophoric, normally closed
- NF3: oxidiser, clean and degreased
Primary containment
A welded metal bellows gives a hermetic stem seal with no elastomer in the gas path. A diaphragm valve gives the lowest dead volume for distribution. Both are helium leak tested; the choice depends on temperature, aggressiveness and purity target.
- Bellows: hermetic stem, aggressive/hot service
- Diaphragm: lowest dead volume, UHP lines
- Both helium leak tested
Interlocks and safe state
Every actuated valve on a toxic gas line should be normally closed, with position feedback wired into the gas detection and emergency shutdown system. Purge and vent legs need check valves to prevent reverse migration.
- Normally closed on loss of air or power
- Position feedback to gas detection / ESD
- Check valves on purge and vent
Recommended valve families
Bellows Sealed Valves
Bellows sealed valves for toxic, corrosive and high temperature specialty gases
UHP Diaphragm Valves
Ultra high purity diaphragm valves for specialty gas delivery. 316L VIM/VAR bodies
High Purity Check Valves
High purity check valves and non-return valves for specialty gas systems
Frequently Asked Questions
Which valve type for chlorine service?
A bellows sealed valve with halide-compatible wetted materials is normally specified; declare concentration and temperature.
What does normally closed mean here?
The valve closes automatically when instrument air or electrical power is lost, which is the required safe state for toxic gas lines.