Centrifugal fan

01

Components / BOM reference

The wheel, housing and drive assembly are illustrated in Greenheck’s IP manual. The following is a functional component reference, not a manufacturing BOM with quantities, material grades or replacement part numbers [3].

Material grades and replacement-part dimensions depend on the selected model; they are not established by this category reference. The illustrated IP arrangement contains additional drive and installation parts [3].

02

Keep the rating and its conditions together

These 13 specification fields are what to record or ask for on a fan enquiry. They are not verified ratings for a supplied model, and no universal value applies to centrifugal fans.

The request fields for enclosure protection and construction materials are open procurement inputs, not manufacturer specifications or claims of suitability. A sound-pressure figure also depends on the receiver location and surroundings [4].

03

Specify the duty at the real gas conditions

Catalogue performance is based on standard air density of 0.075 lb/ft³, air at 70 °F at sea level and 50% relative humidity [1].

Flow

Volumetric flow at inlet conditions. The density comparison below assumes the same fan, unchanged speed and corresponding operating points [1].

Pressure and power

Pressure and shaft power scale with density in that comparison; changed system resistance can shift the operating point [1].

Density inputs

Barometric pressure, wet and dry bulb temperatures and elevation; for a gas other than air, its composition [1]

Application

State the use: Shandong Bofeng lists workshop ventilation, dust collection, material conveying and boiler and kiln air supply for its industrial centrifugal fans [2]

04

Use the fan laws for speed changes

Twin City Fan sets out the three fan laws [1].

The +10% speed example compares the same fan at corresponding operating points and unchanged gas density: 1.1, 1.1² = 1.21 and 1.1³ = 1.331. These are calculated ratios, not a guarantee for a changed duct system. Check the motor margin before increasing speed [1].

05

Avoid system effects at inlet and outlet

Fans are tested with smooth inlets and straight ducts; poor connections in the field make a fan perform below its curve [1].

1. Send the duct layout

   Include the inlet and outlet arrangement, not only the duty point.

2. Ask for system-effect allowance

   The system effect must be added to the system resistance when selecting speed and power [1].

3. Use straighteners where spin is unavoidable

   Turning vanes in elbows or straighteners upstream of the inlet break up swirl [1].

Outlet duct length

AMCA's 100% effective duct length is at least 2.5 equivalent duct diameters for outlet velocities up to 2,500 fpm, plus 1 diameter per additional 1,000 fpm [1]

Outlet connection

FE-100 describes an AMCA laboratory arrangement with outlet area at 95–105% of the fan outlet and transition slopes no greater than 15° converging or 7° diverging [1]. Confirm the applicable test setup for the supplied fan.

Inlet elbows

An elbow at the inlet makes flow uneven, more air entering on the outside of the bend [1]

Drop boxes

Flow losses as high as 45% have been observed; a purpose-designed inlet box has minimal, predictable effect [1]

Swirl

Counter-rotating swirl raises power sharply for little extra pressure; pre-rotating swirl lowers pressure and power; avoid duct shapes that cause spin [1]

Obstructions

Undersized inlet ducts, butterfly valves or belt guards close to the inlet, and inlets close to walls all cause losses [1]

06

Judge a field test against the right tolerance

Twin City Fan’s FE-100 illustrates a laboratory tolerance band equivalent to approximately a 3% speed change, evaluated along the system line [1]. This is not a blanket acceptance limit for an installed fan. Agree the applicable test standard, edition, measurement conditions and acceptance criteria in the purchase specification.

• Compare test points along the system line, not at constant flow or constant pressure [1]
• Average fluctuating readings and record measurement locations; probe placement can change readings [1]
• Correct to the actual gas density before comparing with the catalogue [1]
• Ask the maker for its factory run test records: Bofeng states each fan is trial-run and tested for vibration and noise before packing [2]

Data from Twin City Fan's case study; the swirl leaving the cyclone turned in the impeller's direction, lowering pressure, flow and power until straighteners were added [1]. Field tests are rarely as accurate as laboratory tests [1].

07

Trace vibration through the wheel and drive train

Greenheck’s Model IP manual links maintenance to the actual assembly. Use the supplied model’s instructions and isolation procedure; this reference is not a substitute for them [3].

Wheel and housing

Inspect deposits, wear, corrosion and loose fasteners. Uneven dirt accumulation can unbalance the wheel [3].

Belt drive, where fitted

Check belt wear, tension and sheave alignment. Both excessive and insufficient tension can contribute to vibration [3].

Bearings and motor

Obtain the lubrication instructions for the fitted components; permanently lubricated motors do not require added grease. Do not apply a single interval to every fan [3].

Before corrective work, isolate and lock out the power supply and secure the impeller against rotation, including windmilling. Unexplained vibration needs qualified diagnosis [3].

08

Copy this RFQ and fill in the brackets

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Product: industrial centrifugal fan, quantity [ ]
Duty: flow [m³/h] at inlet conditions, static pressure [Pa] at the fan
Gas: [air / flue gas / dusty air], temperature normal / max / cold start [°C], density [kg/m³], elevation [m], dust load [g/m³]
Arrangement: drive [direct / belt], rotation and outlet angle, inlet box [yes/no]
Ducts: drawing of inlet and outlet connections (elbows, cyclone, dampers)
Motor: power with margin for cold start and +[ ]% speed, supply [V/Hz], VFD [ ]
Materials: impeller and casing [carbon / stainless / wear liner], max temperature [°C]
Tests: factory run test, vibration and noise records; performance curve at our density
Delivery to [country], target date [date]

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