User Manual (with picture on the front cover)
Contents
1. As hood design is critical to the effectiveness of an LEV system a video file explaining how hoods work has been included on the DVD which accompanies this model The video covers how the three different types of hoods work Of course you may wish to cover this in more or less detail The accompanying PowerPoint material should help you do this 6 2 Estimation of flow rate using the blockage as an orifice plate 11 Orifice plates are a common way of measuring volume flow rates through a pipe Whilst the blockage has not been designed as an orifice it does present a restriction to flow and can be used along with a manometer to estimate the flow rate through the model This can be useful as a demonstration or instruction Figure 6 below shows how to set up the orifice plate vo oes 4 L fi Uig i mrg ty J il 7 t Figure 6 Model arrangement for the estimation of volume flow rate position of blockage is shown by the arrow The flow rate can be estimated from the equation below Q 10 P Where Q Volume flow rate l min P Pressure Pa 6 3 Measurement of duct velocities By assembling the model as shown in Figure 5 it is possible to demonstrate how to measure duct velocities The insertion depths for both a single traverse and two traverses at 90 degrees to one another are given below Single traverse x positions 12 Two traverses x positions 7 Tips to getting th2. is adjustable Lamp a 10w halogen lamp used to enhance the visibility of the smoke Hinged black background screen enhances the visibility of the smoke by providing a good contrast Whisk used with the smoke machine to create an energetic source Hand held cooling fan used to demonstrate the effect of draughts on an LEV system Black non slip mat for the model Pressure Magnehelics gauges with stands used to show pressure drop across the filter and to measure static pressure ata number of locations silicone tubing used to connect manometers to pressure taps Mains powered control box used to control i operation and speed of the system fan li smoke production ili operation of the lamp iv operation of the small fan Ducting section with 75 blockage from the outside appears to be identical to the other ducting section Could be used to replace an existing section and a manometer used to find the blockage Can also be used as a crude orifice plate See section 6 2 Adaptor used to connect the large diameter duct to the fan e Large duct with access holes e Large duct e Large diameter socket with stand for joining the two large ducts 5 How to assemble the model for demonstration As each plastic component of the model is connected using identical rigid tubing sections it is possible to exclude some components depending upon what you wish to demonstrate Below are two t
3. LEV Working Demonstration Model User Manual Table of Contents l 2 3 8 9 Introduction Package contents Health and safety information 3 1 General 3 2 Smoke machine and fluid Description of the LEV model components How to assemble the model for demonstration 5 1 Full assembly 5 2 Example of partial assembly 5 3 Smoke machine 5 4 Model assembly for the measurement of duct velocities How to use the model 6 1 LEV demonstration 6 2 Estimation of flow rate using the blockage as an orifice plate 6 3 Measurement of duct velocities Tips on getting the best from the model Cleaning and maintenance Troubleshooting 10 Spare part list 11 Suppliers details 12 Guarantee and Warranty 13 Acknowledgments 14 Further reading 1 Introduction Thank you for purchasing the LEV Working Demonstration Model Local Exhaust Ventilation LEV is the most common way of controlling exposure to airborne dust fumes and gases etc that can cause ill health Unfortunately all too often it is poorly selected designed applied and maintained and doesn t protect people s health The LEV working demonstration model developed by Health and Safety Executive HSE and the Health and Safety Laboratory HSL is a powerful training tool that brings theory to life in a memorable way that people will not quickly forget From experience HSL HSE have found that the instruction on how LEV works is best shown by oscilla
4. e best from the model A smoke tube can be used in addition to the smoke machine to demonstrate how air enters a capturing hood from all directions The optional bullet camera is recommended when presenting to a large audience This allows images to be projected onto a screen to enable everyone to see the demonstration The bullet camera can be purchased from Mechanical Products Ltd 8 Cleaning and maintenance The model requires no specific maintenance However in time the filter installed in the filter housing will become blocked and will need to be replaced You will know when this occurs as the flow rate will fall as shown by the hood static pressure and pressure drop across the filter The filter is removed by undoing the bolts holding the filter housing together New filters type AEG FIL 74 with tabs removed are available from the supplier If you wish to clean any part of the model isolate from the mains supply first It is recommended that you use a damp cloth 9 Troubleshooting The fan does not operate e Check mains supply is on and the red LED on the control box is lit e Check fuse is okay Flow rate low e Check that the filter housing damper is not closed e Check the valves are open e Check that the filter is not blocked No smoke from smoke e Check reservoir is full machine e Ensure smoke machine is plugged into the control box and the switch is on and the smoke production dial set above minimum e It takes a few seconds fo
5. ng the small variable flow fan The smoke is more of a mist and doesn t easily set off smoke alarms smoke visibility is enhanced with the low wattage halogen lamp If the model is used for audiences greater than 5 it is recommended you purchase the optional extra bullet camera This allows images to be projected onto a screen so that everyone can see the demonstration 5 4 Model assembly for the measurement of duct velocities Figure 5 below shows the arrangement for measurement of duct velocities Note the duct section with the two holes 90 degrees to one another should be positioned closest to the fan A Pitot static tube not supplied can be used to demonstrate how to make duct velocity traverses This could be used as part of a demonstration instruction or as part of a test examination 10 Figure 5 Arrangement for making duct velocity traverses 6 How to use the model 6 1 LEV demonstration The model can be used to demonstrate most features of any LEV system Including e How the different types of hoods work e Why the LEV flow rate falls e g o Damage to flexible tubing inc holes and kinked tube o Out of balance dampers o Filter loading o Partially blocked ducting o Problem with fan causing a fall in flow rate e Effect of silencer e Static pressure measurements o Assessing the condition of a filter o Hood static pressure o The pressure profile throughout the system and the effect of a blockage in the system
6. r the smoke fluid to be pumped from the reservoir to the heater ensure you have left it running for a few seconds Hand held cooling fan does not e Replace the batteries work lf you are still experiencing problems contact the manufacturer 10 Spare part list e 100 ml bottle of smoke fluid e Filer unit AEG FIL 74 e Smoke tube with heater 13 11 Suppliers details Mechanical Products Ltd The Barn Pye Road Heswall Wirral CH60 ODB Telephone 44 0 151 342 2206 E mail mechanicalproducts ntlworld com 12 Guarantee and Warranty All parts are covered by a 12 months warranty 13 Acknowledgements Original concepts and early prototype developed by Dr Mark Piney 14 Further reading lf you are interested in learning more about LEV then the following publications are recommended e ACGIH Industrial Ventilation A Manual of Recommended Practice for Design hitp Awww acgih org home htm e ACGIH Industrial Ventilation A Manual of Recommended Practice for Operation and Maintenance hittp Awww acgih org home htm e Hemeon s Plant amp Process Ventilation 3rd ed ISBN 10 1566703476 e HSG 258 Controlling airborne contaminants at work A guide to local exhaust ventilation LEV ISBN 978 0 7176 6298 2 http www hsebooks co uk or available free at http www hse gov uk pubns books hsg258 htm 14
7. ting between LEV model demonstration and PowerPoint slides and video which are included with the model To fully appreciate all the features of the model please read this guide before using 2 Package contents The two cases contain the following e LEV Working Demonstration Model unassembled e User guide e DVD containing o Electronic copy of the User Guide o Video showing how to set up the model o Video giving an introduction on how to use the model o PowerPoint material that has been carefully selected to complement the working model Unique video clips that can be embedded with a PowerPoint presentation O 3 Health and Safety information 3 1 General The model control unit operates on 220 240v AC mains supply This is used to power the fan and a 12 volt transformer The transformer powers all the other electrical items i e the fan speed controller smoke machine spotlight and the small receiving fan As with all mains powered appliances there is a small risk of harm To minimise this normal safety precautions should be observed These include Unplug the mains supply before cleaning the model Fit and remove the smoke element only with the mains off Before use check for damage to cables and other electrical items Do not expose the electrical equipment to wet or damp conditions When not in use the model should be stored in the cases supplied in a dry place If the mains plug is removed for any reason it should not be re
8. tion used to create a branch e Long flexible hoses e Short flexible hose can be used to extend the long hose Ducting with hole used to join the long short hoses together Can be used to simulate damage to ducting when the flexible ducting is slid away slightly e Damper used to isolate one branch and can be used to simulate a blockage in the duct e Adjustable height damper Can be used to simulate a blockage in the duct Capturing hoods one with pressure tap one without Flange used to demonstrate the effect of adding a flange to a capturing hood Also used to hold the clear Perspex enclosures Small Perspex hood when connected to the flange can be used to demonstrate working at the face of an enclosure and can be used as a receiving hood Large hood when connected to the flange it creates an enclosure There are four positions where the smoke source can be released inside the hood e Smoke machine used to generate the source smoke that is controlled by the LEV Adjustable flow rate and adjustable height e Smoke element plugs into the smoke machine before use and is removed after use e WARNING the smoke tube gets very hot during use Allow to cool before removing 100 ml of smoke fluid Small variable flow fan used with the smoke machine to create a directional smoke laden air jet Could also be used as part of the Push of a Push pull system The fan speed
9. used 3 2 Smoke machine and fluid The smoke machine pumps fluid from the reservoir to a small heater in the smoke tube The fluid is then heated until it vaporises generating the smoke cloud WARNING The smoke tube gets extremely hot during use Do not touch during use and allow to cool before removing and packing Do not insert anything into the smoke tube as this could damage the delicate glass smoke heating element Only use the fluid supplied with the model which is available from Mechanical Products Lid to avoid damaging the smoke machine The material safety data sheet for the smoke is provided on the DVD that accompanies the model 4 Description of the LEV model components The model is supplied in two cases One case has wheels and an extendable handle the second case is designed to sit on top of the first one allowing the model to be easily transported See Figure 1 below Figure 1 Illustration of how the cases are arranged for easy transport The contents of each case are shown below in Figure 2 Figure 2 Contents of each case Identification and a description of each component is given below No Description and use Mains powered fan and housing incorporates a stand Flow rate is adjustable Interconnecting ducting with pressure tap Used to connect the different components of the model together X7 Exhaust silencer x1 Filter unit with slider to simulate filter loading Ducting Y junc
10. ypical assembly configurations 5 1 Full assembly Figure 3 shows an exploded diagram of the full model set up For instruction on how to assemble the model please see the video file How to setup the LEV Working Demonstration Model which can be found on the accompanying DVD Figure 3 Exploded diagram of the full model 5 2 Example of partial assembly If you wish to concentrate on specific parts of an LEV system then some components of the model can be excluded from the set up For example Figure 4 below shows just the fan and hood This could be used to demonstrate how the different types of hoods work Note in this arrangement the filter has been excluded See Figure 4 Other configurations are possible Figure 4 Possible model set up for demonstrating how different hoods work 5 3 Smoke machine Before switching on the model insert the smoke tube which contains the heater into the socket on top of the smoke machine After use allow to cool before removing and packing Ensure no fluid is left in the tube before packing the best way to do this is to gently shake on to a paper towel Do not insert anything into the smoke tube as this could damage the delicate glass smoke heating element To fill the smoke machine with fluid remove the white plastic cap of the reservoir and pour in the smoke fluid Replace the cap After use pour any remaining fluid back into the bottle Note The smoke cloud can be made directional usi
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