Chlorine Resistant Centrifugal Fan

Overview

Chlorine fan material selection starts with one question: dry chlorine or wet chlorine. Dry chlorine with very low moisture is relatively mild to carbon steel. Once moisture is present, chlorine forms hydrochloric and hypochlorous acid and attack rises sharply, so titanium, PVC/CPVC, FRP or PTFE lining must be used. Copper and aluminium are not suitable in chlorine service.

Material Selection by Moisture State

Moisture content is the decisive boundary. Where condensation or moisture ingress during start-up and shutdown is possible, the duty should be treated as wet chlorine.

Location	Material / process	Basis
Impeller and casing, dry chlorine	Carbon steel with strict moisture control	Mild attack at very low moisture; avoid condensation
Impeller and casing, wet chlorine	Titanium (GB/T 3620.1)	Good resistance in wet chlorine
Casing and duct, wet chlorine	PVC/CPVC, FRP or PTFE lining	Non-metallic option avoids chloride attack
Fasteners and shaft	Titanium or sheathed parts; no copper or aluminium	Chlorine reacts with copper and aluminium
Sealing	PTFE	Chlorine resistant and reliable

Grade 316L is not suitable for wet chlorine: chlorides break down the passive film and cause pitting and crevice corrosion. Moisture content, temperature and condensation risk should be written into the technical agreement.

Structural and Process Measures

Measure	Practice	Purpose
Condensation control	Casing insulation; inlet above dew point	Prevents dry chlorine becoming wet
Drainage	Low point drain in the casing	Removes condensate
Weld treatment	Inert gas shielding for titanium; passivation for stainless	Maintains weld corrosion resistance
Leak control	PTFE seal with leak drainage	Chlorine is toxic and must not escape
Earthing	Equipotential bonding per GB 12158	Static control
Enclosure rating	IP grade per GB/T 4208	Outdoor and washdown protection

Applications

Typical duties include chlorine handling in chlor-alkali plants, chlorine liquefaction tail gas, sodium hypochlorite and bleaching stages, water treatment chlorination rooms, PVC and chlorination reaction off gas, and chloride process titanium dioxide tail gas.

Corrosion risk in these duties comes from moisture and temperature rather than dust load. Even at low temperature, moisture ingress during start-up and shutdown must be prevented; once condensation occurs, a dry chlorine duty quickly becomes a wet chlorine duty.

Chlorine is toxic and strongly oxidising. Ventilation and emergency provisions must be confirmed against the site hazardous area and occupational hygiene requirements; this page covers material selection only.

Acceptance and Verification

Standard	Title	Purpose
HG/T 20679	Design code for external anti-corrosion of chemical equipment and piping	Anti-corrosion design basis
GB/T 3620.1	Titanium and titanium alloy designations and chemical composition	Titanium grade confirmation
GB/T 4237	Hot rolled stainless steel plate, sheet and strip	Stainless base material acceptance
GB/T 1236	Industrial fans - Performance testing using standardized airways	Air flow and pressure test
GB/T 9239.1 / ISO 21940-11	Mechanical vibration - Balance quality requirements for rigid rotors	Balancing, typically G6.3

Fan size, air flow, pressure and motor power are calculated for the actual duty. Please provide chlorine moisture content, medium temperature, condensation risk and available space.

Lining Processes and Application Limits

A steel lining is not a single coating. The process chain runs from grit blasting to Sa2.5, adhesive application, sheet or hot pressing, vulcanisation (autoclave or ambient), spark testing, thickness measurement, to flange turn-up and weld treatment. A failure at any step shows up later as blistering, debonding or a local perforation.

Chlorine duty splits into dry and wet service: wet chlorine mainly uses PTFE-lined and PE-lined construction and normally avoids rubber lining, while dry chlorine with moisture control may allow carbon steel.

Lining type	Base and lining	Typical temperature	Media and process notes
Rubber lining	Steel + natural or butyl rubber	Usually up to 80 C	Dilute acids and abrasion; sheet applied after blasting, autoclave cured
Plastic lining	Steel + PP, PE or PVDF	Commonly 60 to 120 C	Acids, alkalis and salts; hot pressed or loose lined, flanged seal
PP-lined	Carbon steel + polypropylene	Commonly up to 100 C	Acids, alkalis and salts; sheet or roll lining, double welded seams
PE-lined	Carbon steel + polyethylene	Commonly 60 to 70 C	Abrasion and low temperature; ambient solids bearing media
PTFE-lined	Carbon steel + PTFE	Commonly -180 to 260 C	Strong acids, alkalis and oxidisers; isostatic or loose lining, flanged seal
Natural rubber lining	Carbon steel + natural rubber	Commonly up to 70 C	Dilute acids and solids; bond strength checked after cure
Butyl rubber lining	Carbon steel + butyl rubber	Commonly up to 90 C	Good gas tightness and weathering; suitable for gas bearing media

Concentration, temperature, solids content and oxidising components should be written into the technical agreement. After lining, the fan is performance tested to GB/T 1236, balanced to GB/T 9239.1, and the lining is spark tested and thickness checked.

FAQ

Why do dry and wet chlorine need different materials?

Dry chlorine lacks the moisture needed for sustained attack, so carbon steel can be used. Moist chlorine forms hydrochloric and hypochlorous acid and becomes far more aggressive, requiring titanium or a PVC, FRP or PTFE lined solution. Moisture content and condensation risk decide the case.

Why is 316L not used for chlorine fans?

Chlorides in wet chlorine break down the passive film of 316L and cause pitting and crevice corrosion, so service life is unpredictable. Titanium is preferred for wet chlorine; where metal is not desired, PVC/CPVC, FRP or PTFE lining can be used.

What else matters in chlorine duty?

Chlorine is toxic and strongly oxidising: shaft sealing must control leakage, the casing needs a low point drain and insulation against condensation, and earthing follows GB 12158. Ventilation and emergency provisions follow the site hazardous area classification.

Related pages: Anti-corrosion fan range  Hydrochloric acid resistant fan  Product range