Anti-corrosion Wear-resistant Centrifugal Fan

Overview

Where corrosion and abrasion occur together, a scheme that is best for one risk is often poor overall: ceramic is hard but does not tolerate fluoride bearing media or coarse particle impact, while duplex stainless resists chloride pitting but has limited hardness. The practical answer is to allocate materials by zone so that each area addresses its dominant risk.

Combination by Zone

Separating the high velocity erosion zone from the low velocity corrosion zone is the basic design approach for this type of duty.

Location	Combination	Basis
Impeller	Duplex 2205 body with local ceramic composite	Combines pitting resistance and wear resistance
Volute casing	316L body with replaceable liner	Worn parts are replaced rather than the machine
Inlet cone	Ceramic tile or hardfacing	Chosen by whether fluorides are present
Shaft	Duplex stainless with sheathing	Resists chloride pitting
Fasteners	Duplex or sheathed bolts	Avoids crevice corrosion

Manufacturing and Maintenance

Location	Combination	Basis
Zoning	Areas divided by velocity and medium distribution	Puts material only where it is needed
Weld passivation	Pickling and passivation of stainless welds	Restores weld corrosion resistance
Replaceable liners	Designed as removable components	Reduces maintenance effort
Shutdown washing	Wash and keep dry after shutdown	Reduces wet corrosion
Thickness measurement	Periodic measurement and visual inspection	Rolling replacement interval

Applications

Applications include wet flue gas after desulphurisation, chloride bearing dust, chemical powder conveying, salt spray and coastal environments and wet dust laden gas.

Where the medium contains fluorides, ceramic should not be used alone because the glass phase is attacked; another wear solution or an isolating layer is required.

Failure in this type of duty usually starts with corrosion reducing the substrate strength and wear then accelerating it, so maintenance assessment should look at both thickness and corrosion morphology.

Acceptance and Verification

Standard	Title	Purpose
GB/T 4340.1	Metallic materials - Vickers hardness test - Part 1	Coating and hardened layer hardness
ASTM G65	Standard test method for measuring abrasion using the dry sand/rubber wheel apparatus	Relative abrasive wear resistance
HG/T 20679	Design code for external anti-corrosion of chemical equipment and piping	Anti-corrosion design for chemical media
GB/T 1236	Industrial fans - Performance testing using standardized airways	Air flow, pressure and efficiency testing
GB/T 9239.1 / ISO 21940-11	Mechanical vibration - Balance quality requirements for rigid rotors	Impeller balancing grade

Please provide medium composition including chloride and fluoride content, dust concentration, particle hardness, medium temperature and air flow.

FAQ

Is ceramic lining resistant to acid?

Ceramic tolerates most acids but its glass phase is attacked by fluoride bearing media and it does not tolerate coarse particle impact. Fluoride or high impact duty should use duplex stainless, nickel alloy or hardfacing instead.

How are wear and corrosion resistance combined?

Allocate by zone: use wear protection in the high velocity erosion area, corrosion resistant material in low velocity and crevice areas, and design the wear prone parts as replaceable liners so that the whole machine is not scrapped.

What are the limits of duplex stainless steel?

Duplex grades resist chloride pitting well and are widely used in chloride bearing media, but they have an upper service temperature because brittle phases form during prolonged exposure. The exact limit depends on grade and medium conditions.

Related pages: Non-standard fan range  Wear-resistant fan range  Anti-corrosion fan range