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Information required to optimise a fan selection

Information required to optimise a fan selection. Howard Brooke, Chief Engineer. Woodcock & Wilson Ltd. Objectives. To have a basic understanding of the information required by a fan engineering company to enable the selection of a suitable fan. K ey Areas of Coverage.

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Information required to optimise a fan selection

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  1. Information required to optimise a fan selection Howard Brooke, Chief Engineer. Woodcock & Wilson Ltd.

  2. Objectives To have a basic understanding of the information required by a fan engineering company to enable the selection of a suitable fan.

  3. Key Areas of Coverage • A - Information relevant to basic fan selections. • B - Ancillary Equipment. • C - Information required to avoid system effects. • D - Information required for an ATEX-Certified fan.

  4. A - Basic Fan Selection • Flow Rate – Actual, Standard and Normal • Units (m³/s, m³/s, m³/min, cfm, l/s) • Fan Pressure • Units – Pa, kPa, mbar mmWg, insWg Static Pressure orTotal Pressure - Temperature related to the specified pressure - Pressure split between fan inlet and discharge

  5. Climatic Conditions • Temperature • Humidity • Altitude

  6. Operating Conditions • Maximum operating temperature • Requirement for cold start would also need to be known. • Minimum fan efficiency ? • Is the fan handling corrosive or erosive gases? • Material Handling • Type and Size of Material • Concentration

  7. Operating Conditions • Power supply (Voltage/Phase and Frequency) • Is the fan to be driven by inverter? • Is fan subject to cyclic operation? • Thermal or Speed? • Any noise limitations • Fan Finish and Colour

  8. B - Ancillary Equipment • Inlet and Discharge Flexible connectors • Anti-Vibration Mounts • Inlet/Discharge Dampers • Instrumentation(Vibration/Temp/Speed) • Sealing Arrangements

  9. C - Information required to ensure that fan is free from system effects • Select a fan type most appropriate to your installation.

  10. Fan Types • Axial Fans • Air Enters and exits axially • Long case, Short case or Plate mounted • Tubular Case- can be as with a portable man cooler, ducted on either inlet, outlet or both inlet and outlet. • Bifurcated axial – internal tunnel or pod for mounting the motor out of the airstream – Used for hot or corrosive gases

  11. Fan Types • Centrifugal Fans • Air enters axially & exits at 90° • Single Inlet. All airis drawn through one inlet (SISW) • Fan case is an expandingvolute shape, which assistsstatic pressure regain & directs the airflow in one direction

  12. Fan Types • Centrifugal Fans • Double Inlet Double Width (DIDW) • Air is drawn from both sides

  13. Fan Arrangements & Handings • Select the most appropriate handing to suit the site conditions

  14. System problems • Fans will only meet the duty point shown on the performance curve under “ideal” installation conditions. • Ideal conditions are seldom obtainable in practice consequently there will always be some “SYSTEM EFFECT”.

  15. SystemProblems Factors that influence system effect: • Elbow or bend too close to fan inlet or outlet • Abrupt duct transition • Pre swirl of the incoming air due to duct design. (Swirl in same direction as rotation). • Dampers not fully open. • Damper location • Poorly designed fan drives – large drive pulley - solid rather than spoked. • Fan inlet or outlet too close to wall or bulkhead. • Fan inlet box design • Bend orientations at discharge • Free discharge – abrupt expansion. • Weather cowls and hoods

  16. SOME DO’S & DONT’S FOR FAN INSTALLATIONS

  17. SOME DO’S & DONT’S FOR FAN INSTALLATIONS

  18. Fan Discharge Orientation Good Bad Good

  19. Fan Inlet Swirl COUNTER-ROTATION AIR SWIRL IN OPPOSITE DIRECTION TO IMPELLER ROTATION

  20. Section D Information required to select ATEX-Certified Fans

  21. ATEX ZONE • Fan Category • Temperature class (Gas Only) • Gas or Dust Group • Max Allowable surface temperature • Ignition Temperature of Dust • How fan is installed • Description of Operation • Details of extreme environmental conditions

  22. Thank you very much for listening. Any Questions?

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