High Temperature Induced Draft Fan for 1000 C Service

Overview

1000 C is the limit of conventional centrifugal induced draft fans and is a custom design. Impellers are usually cast in heat resistant steel ZG40Cr25Ni20, casing internals use 253MA or Inconel 601, and the lining reaches 150 mm of composite insulation with divided expansion joints, monitored by multiple thermocouples.

Material Selection at 1000 C

This band exceeds the long term limit of conventional austenitic grades, so each element is selected for its own duty.

Location	Material / process	Basis
Impeller	Heat resistant cast steel ZG40Cr25Ni20 (HK40 type) or 253MA	Casting allows complex blade shapes with creep resistance
Casing and internals	253MA, Inconel 601 (UNS N06601)	Good scaling resistance at 1000 C
Surface treatment	Anti-oxidation coating with pre-oxidation	Extends the replacement interval
Bearing assembly	Water cooled housing, oil circulation unit, thermal sleeve	Multi-stage isolation of the heat source
Instrumentation	Thermocouples with alarm and interlock	Detects over-temperature and lining damage

Structural Measures at 1000 C

Location	Material / process	Basis
Composite lining	150 mm composite insulation with divided expansion joints	Keeps the metal wall within its limit
Local water cooling	Bearing housing and local cooling panels	Handles intense radiant heat
Shaft thermal isolation	Sleeve with air or water cooling passage	Reduces the temperature gradient
Multi-point temperature monitoring	Thermocouples wired to alarm and interlock	Early detection of hot spots
Start-up curve	Controlled heating and cooling rates	Protects lining and impeller on start

Applications

Applications include yellow phosphorus tail gas, hazardous waste incineration, special kilns and high temperature gas circulation test rigs.

This band is a custom design: material and structure are calculated from the actual gas composition, dust load and continuous operating hours.

Because the duty is outside standard product ranges, the technical agreement should define the heating and cooling curves, the allowable wall temperature limit and the inspection window.

Acceptance and Verification

Standard	Title	Purpose
GB/T 20878	Stainless and heat-resisting steels - Designation and chemical composition	High temperature and corrosion resistant grades
GB/T 3003	Refractory fibres and products	High temperature lining material and acceptance
GB/T 12777	General specification for metal bellows expansion joints	Expansion compensation for hot ducts and casing
GB/T 9239.1 / ISO 21940-11	Mechanical vibration - Balance quality requirements for rigid rotors	Impeller balancing grade
JB/T 10563	General purpose centrifugal fans - Technical specifications	General technical conditions and works acceptance

Please provide gas composition, temperature, dust load, continuous operating hours and air flow. The design is calculated for the actual duty.

FAQ

Why is a 1000 C fan a custom design?

This temperature exceeds the long term service range of conventional austenitic stainless steel. Material, lining, cooling and monitoring all have to be engineered for the specific duty, so a standard model cannot cover it.

Should the impeller be cast or fabricated?

Complex blade shapes favour cast ZG40Cr25Ni20; thin section and high accuracy blades favour a fabricated 253MA structure. Both require a creep assessment for the duty.

How is the maintenance interval set at this level?

Not by a fixed period. Thermocouples and infrared measurement track wall temperature in service, while lining and impeller thickness are measured during shutdowns, and the interval is adjusted from the measured data.

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