• Article Written By Woodcock & Wilson | 3 of 6 Articles
  

Woodcock & Wilson are specialist manufacturers of independently certified ATEX fans and IECEx industrial fans for the ventilation of hazardous area locations and potentially explosive atmospheres.

Below is Part 3 in a series of 6 Articles by Woodcock & Wilson discussing fans, the laws, common problems, troubleshooting the main performance issues and getting your fan started again if you encounter any issues.

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”.

Factors That Influence Fan 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

Some Do’s & Don’t’s When For Fan Installations

LEADERS IN ATEX INNOVATION

T&D are your first-choice provider of innovative and competitive solutions to ensure ATEX & IECEx Compliance for Hazardous Area Electrical, HVAC & Process Instrumentation Equipment to your UK and international projects.

Key Product Groups

Control Panels | Plugs | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace | Gas Detection | Flame Detection | Process Instrumentation | Process Heating | Ventilation Fans | Security Access Control 

• Article Written By Woodcock & Wilson | 2 of 6 Articles
  

Woodcock & Wilson are specialist manufacturers of independently certified ATEX fans and IECEx industrial fans for the ventilation of hazardous area locations and potentially explosive atmospheres.

Below is Part 2 in a series of 6 Articles by Woodcock & Wilson discussing fans, the laws, common problems, troubleshooting the main performance issues and getting your fan started again if you encounter any issues.

The fans are used to determine theoretical performance data for varying combinations of impeller speed, diameter and air densities.

Here we will only consider the relationship and effect of speed on volume, pressure and power for a constant impeller diameter handling air at a constant density.

When speed is varied on the same size, handling constant density air (e.g. fan used with frequency inverter drive).

Fan Laws Further Explained

Flow Rate varies directly as the speed.
Q2 m³/s = (rpm2/rpm1) x Q1 m³/s

Pressure varies as the square of the speed.
P2 Pa = (rpm2/rpm1)² x P1 Pa

Power varies as the cube of speed.
Power2 kW= (rpm2/rpm1)³ x Power1 kW

Performance Curve Showing Speed Variation

Maximum speed : 1480 RPM.

Reduced speeds :
• 1110 RPM (75%)
• 740 RPM (50%)

Here we will only consider the relationship and effect of fan diameter on volume, pressure and power for a constant impeller speed handling air at a constant density:

Flow Rate varies as the cube of the diameter.
Q2 m³/s = (D2/D1)³ x Q1 m³/s

Pressure varies as the square of the diameter.
P2 Pa = (D2/D1)² x P1 Pa

Power varies as the fifth power of the diameter.

Power2 kW= (rpm2/rpm1)5 x Power1 kW

Pressure and Power vary directly proportional to gas density, combining speed, diameter and density we have the following :-

Q2 = Q1 x (n2/n1) x (D2/D1)³
P2 = P1 x (n2/n1)² x (D2/D1)² x (ρ2/ ρ1)
W2 = W1 x (n2/n1)³ x (D2/D1)5 x (ρ2/ ρ1)

Where:

Q = flow rate
P = pressure (total, static, or dynamic)
ρ = gas density
n = fan rotational speed
D = impeller diameter
W = impeller power

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LEADERS IN ATEX INNOVATION

T&D are your first-choice provider of innovative and competitive solutions to ensure ATEX & IECEx Compliance for Hazardous Area Electrical, HVAC & Process Instrumentation Equipment to your UK and international projects.

Key Product Groups

Control Panels | Plugs | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace | Gas Detection | Flame Detection | Process Instrumentation | Process Heating | Ventilation Fans | Security Access Control 

• Article Written By Woodcock & Wilson | 1 of 6 Articles
  

Woodcock & Wilson are specialist manufacturers of independently certified ATEX fans and IECEx industrial fans for the ventilation of hazardous area locations and potentially explosive atmospheres.

Below is Part 1 in a series of 6 Articles by Woodcock & Wilson discussing fans, the laws, common problems, troubleshooting the main performance issues and getting your fan started again if you encounter any issues.

What is a Fan?

A fan is a machine for transferring energy into moving air. The performance of a fan can be described in terms of Volume Flow, Pressure, Power Absorbed & Efficiency.

Three Main Fan Types

• Axial Flow
• Centrifugal
• Mixed Flow

💡 Hazardex 2020 Conference Paper – Non-Electrical (Mechanical) Equipment Compliance With IECEX Certification

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 & outlet
• Bifurcated Axial – internal tunnel or pod for mounting the motor out of the airstream-used for hot or corrosive gasses

It may come as a surprise that most modern jet engines incorporate a large axial fan. Here the Rolls Royce Trent first stage fan can be seen in all its glory. The fan contributes to around 90% of the thrust generated by the engine and absorbs around 100 MW of power….that’s a big power fan!!

Industrial axial fans come in all shapes and sizes…here are some of them:

Principles of Operation

Axial fans work by generating lift within the rotating blades. Newton’s third law states that for every action there exists an equal & opposite reaction. In this case the upward lift force on the blade is balanced by an equal and opposite force making the air flow in the opposite direction.

• Generally suited for moving large volumes of air at low pressures
• Generally low efficiencies- 50%-60%. Larger special designs can achieve static efficiencies in the upper 80’s %
• Larger pitches can have a pronounced stall & can be inherently unstable if selected too far to the left of the fan curve. Should be selected well to the left of peak pressure or select a larger fan at a lower pitch angle

Centrifugal Fans

Air enters the fan axially and exits at 90°.

• Single inlet-all air is drawn in through one inlet. (SISW)
• Double inlet-equal amounts of air drawn in through two opposing inlets. (DIDW)
• Fan case is an expanding volute shape, which assists static pressure regain and directs the airflow in one direction

Double Inlet Double Width (DIDW)

Centrifugal Fan

Principles of Fan Operation

Unlike axial flow fans, which rely on aerodynamic lift from blades, centrifugal fans rely on dragging air round in circles and using centrifugal force to generate air flow.

Different types of centrifugal fan impellers:

• Backward bladed
• Forward curved
• Radial bladed

Backward Bladed

• Flat backward inclined, backward curved & double skin aerofoil
• High efficiency > 80% static
• Non overloading power characteristic-power absorbed reaches a peak near the maximum efficiency & then becomes lower towards higher flows
• Can exhibit stall characteristics to the left of peak pressure-this could result in instability & vibration. Fan selection point should always be on the steep part of the curve to the right of peak pressure
• Can cope with medium erosive gasses in arduous applications
• Used in HVAC and industrial applications

Forward Curved (Multivane)

• Comparable selections often give a smaller diameter fan than a backward inclined
• Usually used for large flow rates, low pressure HVAC and air handling unit applications
• Volume / Pressure characteristic less steep than backward bladed fan
• No pronounced stall, so can operate over a wider span of the characteristic curve
• Exhibits overloading power characteristic – power rises continually towards higher flows
• Poor efficiency-typically 50% to 60%

Radial Bladed (Paddle Bladed)

• Open paddle, Backplate paddle or Shrouded paddle
• The unshrouded version has the highest mechanical strength of all centrifugal types
• Suitable for heavy dust burdens and high temperatures
• The characteristic is stable over the whole range of flows
• Exhibits overloading power characteristic – power rises continually towards higher flows
• Narrow types are suitable for high pressure applications such as pneumatic conveying

Mixed Flow Fans

• Hybrid centrifugal and axial fan
• Impeller rotation imparts both an axial & a centrifugal component. The flow from the impeller discharges into an annular chamber
• Where stationary vanes reduce the whirl component and recover static pressure
• Higher pressures achievable than an axial fan
• Mixed flow fan impellers, which are shrouded are more robust than an axial fan and have a less severe stall

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LEADERS IN ATEX INNOVATION

T&D are your first-choice provider of innovative and competitive solutions to ensure ATEX & IECEx Compliance for Hazardous Area Electrical, HVAC & Process Instrumentation Equipment to your UK and international projects.

Key Product Groups

Control Panels | Plugs | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace | Gas Detection | Flame Detection | Process Instrumentation | Process Heating | Ventilation Fans | Security Access Control 

T&D’s online library of Drum, IBC & Tank Heating applications is now updated to include the following : using IBC jacket to maintain water within a storage facility for washing system equipment.

Visit Silicone Heating Products for details of electric surface heating solutions – flexible silicone heaters can be applied to heat the most complex shapes, geometries, curves and pipes.

Specified Product Solution : IBC Heaters

HeatING JACKET Type

• Drum
• IBC ✓
• Bespoke

area Classification

• Safe Area ✓
• Hazardous Area (Zone 1 & Zone 2)

HEATING FLUID, MEDIUM, CONTENTS

• Water
• Oil
• Wax
• Chemicals
• Petrochemicals (Solvents, Detergents, Adhesives, Other)
• Food Ingredients (Liquid, Powdered, Granulated)
• Other ✓ Soap

Chemical HEATING APPLICATION

• Frost Protection
• Reduce Viscosity
• Temperature Maintenance
• Low Temperature Heating (0-20 degrees Celsius)
• Medium Temperature Heating (21-50 degrees Celsius)
• High Temperature Heating (50 degrees Celsius+)
• Other ✓ Water for cleaning/wash down

 

HEATING JACKET VOLTAGE

• 110 Volt
• 230 Volt ✓
• Low Voltage

HEATING APPLICATION : DRUM, IBC, TANK OR VESSEL

• 25 Litres
• 50 Litres
• 105 Litres
• 205 Litres
• 1000 Litres ✓ Schutz
• Other

VESSEL MATERIAL

• Steel
• Stainless Steel
• Plastic
• Cardboard
• Other

HEAT UP TEMPERATURE

• 0-5 degrees Celsius
• 5-20 degrees Celsius
• 20-50 degrees Celsius ✓
• 50-70 degrees Celsius
• 70+ degrees Celsius
• N/A (Frost Protection)

HEAT UP TIME REQUIREMENT

• 0-4 Hours
• 4-12 Hours
• 12-24 Hours
• 24-48 Hours ✓
• N/A

Contact T&D for specification, support and sales of Electrical Heating Equipment for safe, industrial and hazardous area plant and equipment – we provide process temperature heating and pipework frost protection (Winterisation) products for pipework, valves, IBC’s, drums and tanks. Complete range of heating cables and trace heating cables are available for process temperature maintenance.

T&D – Largest UK Stockist of Heat Tracing Cables. UK & International Delivery.

EXPERTS IN EQUIPMENT FOR EXPLOSIVE ATMOSPHERES

T&D are your first-choice provider of innovative and competitive solutions to ensure ATEX & IECEx Compliance for Hazardous Area Electrical, HVAC & Process Instrumentation Equipment to your UK and international projects.

Control Panels | Plugs | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace | Gas Detection | Flame Detection | Process Instrumentation | Process Heating | Ventilation Fans | Security Access Control 

T&D’s online library of Drum, IBC & Tank Heating applications is now updated to include the following : heating up oil in small pots for use laboratory testing.

Visit Silicone Heating Products for details of electric surface heating solutions – flexible silicone heaters can be applied to heat the most complex shapes, geometries, curves and pipes.

Specified Product Solution : Bespoke Heaters

HeatING JACKET Type

• Drum
• IBC 
• Bespoke ✓

area Classification

• Safe Area ✓
• Hazardous Area (Zone 1 & Zone 2)

HEATING FLUID, MEDIUM, CONTENTS

• Water
• Oil
• Wax
• Chemicals
• Petrochemicals (Solvents, Detergents, Adhesives, Other)
• Food Ingredients (Liquid, Powdered, Granulated)
• Other ✓ Soap

Chemical HEATING APPLICATION

• Frost Protection
• Reduce Viscosity
• Temperature Maintenance
• Low Temperature Heating (0-20 degrees Celsius)
• Medium Temperature Heating (21-50 degrees Celsius)
• High Temperature Heating (50 degrees Celsius+) ✓
• Other

 

HEATING JACKET VOLTAGE

• 110 Volt
• 230 Volt ✓
• Low Voltage

HEATING APPLICATION : DRUM, IBC, TANK OR VESSEL

• 25 Litres
• 50 Litres
• 105 Litres
• 205 Litres
• 1000 Litres
• Other ✓ Custom size 700 x 1550 to suit 450mm Diameter

VESSEL MATERIAL

• Steel ✓
• Stainless Steel
• Plastic
• Cardboard
• Other

HEAT UP TEMPERATURE

• 0-5 degrees Celsius
• 5-20 degrees Celsius
• 20-50 degrees Celsius
• 50-70 degrees Celsius ✓
• 70+ degrees Celsius
• N/A (Frost Protection)

HEAT UP TIME REQUIREMENT

• 0-4 Hours ✓
• 4-12 Hours
• 12-24 Hours
• 24-48 Hours
• N/A

Contact T&D for specification, support and sales of Electrical Heating Equipment for safe, industrial and hazardous area plant and equipment – we provide process temperature heating and pipework frost protection (Winterisation) products for pipework, valves, IBC’s, drums and tanks. Complete range of heating cables and trace heating cables are available for process temperature maintenance.

T&D – Largest UK Stockist of Heat Tracing Cables. UK & International Delivery.

EXPERTS IN EQUIPMENT FOR EXPLOSIVE ATMOSPHERES

T&D are your first-choice provider of innovative and competitive solutions to ensure ATEX & IECEx Compliance for Hazardous Area Electrical, HVAC & Process Instrumentation Equipment to your UK and international projects.

Control Panels | Plugs | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace | Gas Detection | Flame Detection | Process Instrumentation | Process Heating | Ventilation Fans | Security Access Control