Exproof Fan Maintenance: Periodic Inspection Guide for Hazardous Areas
Correct selection of an exproof fan is the beginning of safety; maintaining that safety throughout operation depends on inspection and maintenance. An unsuitable intervention in a hazardous area can weaken the certified protection features of the equipment.
Why is maintenance different from a standard fan?
Maintenance of equipment in hazardous areas is not performed only to prevent loss of performance. Loose connections, corrosion, damaged cable entries, loss of earthing, bearing deterioration or mechanical rubbing can become potential ignition sources.
A simple “does the fan run?” check that may be used on a conventional fan is not sufficient here. The inspection must also consider whether the certified construction, nameplate information and the mechanical and electrical conditions specified by the manufacturer are still being maintained.
Hazardous-area maintenance and inspection should therefore be carried out by competent personnel using plant procedures and manufacturer documentation. Where relevant, applicable hazardous-area electrical inspection standards may also be referenced in the maintenance plan.
What should be checked during periodic inspection?
Depending on the product and site conditions, periodic inspection may include the following points:
- Deformation or rubbing marks on the fan casing, impeller and guards
- Physical condition of the motor, terminal box, cable glands and electrical connections
- Condition of earthing and equipotential-bonding connections
- Unusual increase in bearing noise, vibration or temperature
- Loose parts, wear, corrosion or evidence of external impact
- Legibility of the nameplate, certificate information and equipment identity
The inspection scope can vary according to the fan protection concept, manufacturer instructions and site risk assessment. Work that requires measurement or disassembly should be carried out under the appropriate procedure.
Why is cleaning important?
Dust and dirt accumulation can do more than reduce fan performance. It may reduce cooling and create imbalance on the impeller, increasing vibration, bearing loads and, in some cases, surface temperatures.
Cleaning is particularly important in combustible-dust processes. Dust layers and deposits must be considered as part of the plant explosion-risk assessment. The cleaning method should not damage the equipment or introduce a new electrostatic or mechanical-spark hazard.
The use of compressed air, solvents or other cleaning chemicals should be decided in accordance with manufacturer instructions and plant procedures. The objective is not simply a clean appearance, but the preservation of the equipment’s designed operating conditions.
Take care when replacing parts
The protection integrity of exproof equipment can be compromised by unauthorised modifications. When replacing a motor, cable gland, connection part, bearing, impeller or other critical component, the manufacturer instructions and certificate conditions must be followed.
“We installed a part with the same dimensions” is not always an adequate justification. Material, tolerance, protection concept or certificate scope may differ. Flameproof enclosures and exproof connection details in particular should not be treated as ordinary workshop modifications.
After repair, equipment identification, labelling and maintenance records should be kept up to date. Where there is uncertainty, verification from the manufacturer or authorised technical support is the safer approach.
How should a maintenance plan be created?
The inspection interval should be based on operating conditions rather than a single fixed calendar. Corrosiveness of the environment, dust loading, daily operating hours, vibration level, temperature, previous failures and the plant risk assessment all influence the appropriate frequency.
A good maintenance record identifies the equipment, inspection date, observed findings, work carried out and responsible person. This makes it possible to track developing vibration, corrosion or connection issues on the same fan over time.
The purpose of maintenance is not only to extend fan life. It is also to preserve, throughout operation, the safety conditions that existed when the equipment was originally selected. For exproof fans, maintenance should therefore be regarded as a continuation of the purchasing and engineering process.