A Guide To Fume Extraction Systems & Components

Objectives & Aims Of This CPD Presentation

1 – Fan Selection - What situations require fume extraction systems- What information is needed to correctly select a fan?

2 – Specification Standards - How standards influence selection- Understanding how Current Legislation relates to fume extraction systems

3 – Fan Control - Methods & Importance of Control- Understand Contact & Variable air volume systems

4 – Fan Installation – Recognise the importance of correct installation

An Introduction To Fume Extraction: Fan SelectionEquipment That May Require A Fume Extract Fan

“All require the safe, efficient and correct selection of components including fan and controls taking into account air changes and pressurisation by supplying the correct amount of air”

Extract Arms, Fume Cupboards, Sinks, Hoods & Storage Cupboards

Required Fume Cupboard InformationStandards EN14-175

1 – The Sash Opening SizeThe sash width and the test height (usually 500mm)

2 – The Required VelocityRanges from 0,3m/s to 0,7m/s dependson the Fume Cupboard typeStandard cupboard is usually 0,5m/s Sash

3 – Any Special Requirements 0,3m/s to 0,7m/sComply with Atex regulationsConstant air volume (CAV) or Variable air volume (VAV)

An Introduction To Fume Extraction: Fan Selection

For LEV equipmentyou should refer to the

manufacturers recommendedair velocity or air volumes.


Types Of The Fume Cupboards AvailableStandards EN14-175

1 – Constant Air Volume (CAV)Constant air volume entering the cupboard, cupboard is fitted with a by-pass so a constant velocity through the sash and by-pass

By-pass2 – Variable Air Volume (VAV)

Variable air volume entering the cupboard, sash velocity remains constant for any sash position

Sash3 – Ducted Low Flow Fume Cupboards

Designed to work at lower sash velocities typically 0,3m/s

4- Ductless Re-Circulating Fume CupboardsDesigned to pass air through a filter and back into the room.


Information Required For The Ductwork systemEN14-175 & DW standards

1 – Select The Duct Diameter In duct velocity should be between 5,5m/s to 7,5m/s. This is to keep the noise level down

2 – What Is In The Duct RunLength of the duct run. How many Fume Cupboardsor other equipment are in the system. How many bends or other fittings such as tees etc

3 – Calculate The System’s ResistanceEach item in the system has a resistance. Bends, tees, straight duct run and the discharge. The Fume Cupboard has approximately 60Pascals resistance, bends, tees, other fittings and straight duct can be seen on the next two slides.


Pressure lossesfor Various duct fittings


System pressure losses in straight sections


Ductwork InstallationStandards EN 14175 and The DW standards

1 - Duct work material shall be self supporting and PVC, Polypropylene or Stainless Steel depending on the application

2 - Discharge stack shall finish the required height above the building (3m). The discharge size should give a velocity of 10m/s

3 – The system is to ensure Containment / Protection Mode through the Fume Cupboard


Fume Cupboard - Example Fan Selection

1 – Fume Cupboard, (1,8 nominal 1,5 actual width with 0,5m/s velocity)Airflow , Sash width 1,5m x 0,5m (test height) x 0,5m/s (velocity) = 0,375m³/s (1350m³/h).

2 – Duct work, 2 bends 90°, 1 Fume Cupboard, 10m straight duct (diameter to be specified). Resistance, Fume Cupboard 60Pascals, induct velocity (5,5 to 7,5m/s) 7,5m/s Ø250 (top of the range) 2Pascals per metre 20Pascals in total, 7,5m/s through a 90°Bend 12Pascals per bend 24Pascals total,

3 – Discharge, 10m/s velocity 0,375m³/s at 10m/s is Ø225 discharge size 60Pascals in total

4 – Total resistance 60Pa + 20Pa + 24Pa + 60Pa =164Pascals at 1350m³/h

5 – Fan would usually be a 4pole.


LEV - Example Fan Selection

1 – LEV equipment use manufacturer’s recommended air velocity or air volume.

2 – Duct work velocities may vary depending the equipment used.

3 – Discharge, 10m/s

Fans for these applications can usually be 2pole speed to overcome higher pressures.


Review Information Required

1 - You now have the airflow (m³/h) 2 - You now have the system resistance (Pa)

3 - Using a fan curve you can select a fan allowing a the required margin in performance. Many specifications will show how much margin is required.

4 – Decide the fan pedestal and electrical supply required.

You should now have enough information to select the best fan


European Fume Cupboard StandardsEN14-175

Part 1: Vocabulary in 7 languagesPart 2: Safety and performances requirementsPart 3: Type test methodsPart 4: On site test methodsPart 5: Recommendations for installation and maintenance Part 6: Variable air volume fume cupboards

DuctworkDuct work shall be installed to meet EN14175 and DW series of standards

An Introduction To Fume Extraction: Standards

Polypropylene Fan

1 – Scroll moulded UV treated recyclable polypropylene

2 – Centrifugal impeller in moulded polypropylene electronically balanced to ISO 1940

3 – Direct drive units fitted with IP55 motors. Available in single phase and three phase. Complete with outdoor box pedestal in polypropylene

or indoor pedestal in dipped galvanized.

4 – Fans available as none Atex rated or Zone 2 rated.

5 – Performance based on tests conducted in accordance with AMCA 210-85 and ISO 5801

An Introduction To Fume Extraction: Standards

Understanding CAV & VAV System Control

1 - Constant Air Volume SystemThe fan will have a starter with on/off buttons. This must be fitted

with an overload relay to help protect the fan motor for overloading. A damper will then need to be fitted to allow the required duty to be achieved.

2 - Variable Air Volume SystemThe fan will be controlled using an inverter speed controller as part of the fume cupboard control system or mounted separately. This will allow the duty to be achieve and help save energy. As the sash is opened and

closed the fan speed will change to keep the sash velocity set a the commissioning of the cupboard.

An Introduction To Fume Extraction: Control Your Fan

Speed Control Methods

1 – Direct on line, use a starter and overload relay.Basic stop and stop with overload relay.

2- Inverter speed control (IP20) panel mounted Fan speed control day/night running Energy saving, the motor turns enough to do the job required Works with fume cupboard controllers

3 - Inverter speed control (IP66) mounted away from control panel (not outdoors)

An Introduction To Fume Extraction: Fan Control

Fume Cupboard Control

1 – Fume Cupboard Controllers, Labair ‘A’Available as an alarm with a light, fan switches towork with external relays. High and Low airflowindicators.

2 – Fume Cupboard Controllers, Labair ‘C’Available as an alarm with a light, fan switches towork with external relays. High and Low airflowindicators. It has an output signal to enable it through aninverter to speed control the extract fan.


Fume Cupboard Control

3 – Controllers are available with digital display if required.

4 – Factory pre-calibration and easy to finalise settings on site when installed into the fume cupboard.

5 - Sash high contact.

6 – Alarm relay and battery back up.

7 – Available in vertical or horizontal versions


Installation

1 - Fan and pedestal will need to be stable and care must betaken to ensure the weight of the stack does not rest on the fan scroll as this can cause the fan togo out of shape.

2 – Consider anti vibration mountings and flexible connectors to reduce noise and vibration.

3 – The fan motor as any electric motor must be fittedwith an electrical isolator in the event of maintenancework to be carried out.

An Introduction To Fume Extraction: Fan Installation

Installation

4 – The fan stack should not be fitted with a discharge cowl Which means it is possible rain may get into the stack and gather in the fan scroll. The water needs to be drained as it may cause extra resistance for the impeller and motor unit causing a reduction in fan performance. Fit a scroll drain.

5 – When the fan is installed and the system is been commissioned ensure the fan rotates the correct way. If not you will lose performance.


Installation

6 – The position of the fan should be as close to the end of the ductwork runas possible. The reason been that the duct is under negative pressure so in

the event of a leak fumes will not be blow out but surrounding air will be draw in.

7 – Air been taken out by the fume extract system must be replaced with air into the area. Failure to replace extracted air may result reduce performance of the fume cupboard.


Summary – We Have…1 – Applied fume extraction to different types of equipment including Hoods, Sinks, Fume Cupboards & LEV

2 - Applied relevant & current standards to fume extraction systems

3 - How to Correctly select fans to suit the LEV/Fume Cupboard with the required ductwork

4 - Understood the need for Control within a fume extraction system

5 - Recognise the importance of correct and safe fan installation within the extraction system.

An Introduction To Fume Extraction

A Guide To Fume Extraction Systems & Components

Engineering

Transcript of A Guide To Fume Extraction Systems & Components