Engineering Education Scheme 

Central Newcastle High School

 

Test rig design for medical vacuum flow

correction factors 

Link Engineer: Dr. Simon Bartram

Link Teacher: Mr. Andrew Morton

Team Members: Lauren Baldwin, Amelia Dickinson, Kathryn Harder, Tz-Shing Hwang

Central Newcastle High School

Contents Introduction Page 2

Summary Page 3

Background Research Page 4

Method Page 7

Results Page 8

Discussion Page 9

Conclusion Page 10

Recommendations Page 11

Bibliography Page 12

Appendix A: Test Rig Plans Page 14

B: Result Tables Page 19

C: Related Documents Page 21

D: Photographs Page 28

Acknowledgements Page 30

Page 1

Introduction The aim of the project was to design a test rig for medical sterile vacuum filters, produced by the company, Walker Filtration. The filters that Walker Filtration produces are air filters, which are often used to sterilise air used for medical and dental procedures. This tends to involve removing oil particulates that enter the air due to the oil used in lubricating machinery.

Although Walker Filtration currently has data (see fig. 8) about their filters from their own testing, the company suspects that the data, having been calculated in the 1960s, may be inaccurate. Therefore, it was felt that more accurate experimental data could be found today, using a test rig with higher resolution and more accurate machinery.

The test rig was designed to be able to measure pressure loss across the filter, temperature, humidity and air flow through the filter, in order to obtain a pressure correction factor for each specific filter. There was an additional ambition to be able to add components to the design to measure the number of particles left in air following filtration, in order to measure filter efficiency.

Pressure correction factors are specific to particular pressures, and give the fraction of maximum air flow (which is given for a filter at atmospheric pressure) that will be able to flow through a filter at a particular, not-atmospheric pressure. So, if a company that uses an air filter knows the pressure at which the filter will be used, the maximum air flow given for their particular filter can be multiplied by the pressure correction factor that corresponds to the pressure at which the filter will be used, to give the maximum air flow for their filter at their particular pressure.

The ultimate aim of the project was, inevitably, to save money for Walker Filtration. This would be achieved by making Walker Filtration’s pressure correction factors more accurate than their competitors’, either enabling them to produce smaller filters at lower cost with the same efficiency as their current filters, or to prove that they are currently producing the best type of filters that they can; both possibilities would improve their company image and could therefore increase profit.

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Summary The report follows the design of a suitable test rig, through combining research with experience of using a draught version of a test rig, to improve upon initial ideas.

The results from experiments using an early prototype of the test rig have been obtained to suggest how the completed test rig will differ in results from the data Walker Filtration has at present.

The data obtained suggests an overall change in the initial design, recommending a final design consisting of more accurate measuring instruments and additional elements to challenge the airflow.

The work done on the design and in the report to fulfil the task set will go to make differences in the company Walker Filtration and have real implications in the wider industry.

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Background Research Walker FiltrationWalker Filtration formed in 1983 by husband and wife team Brian and Carol Walker and the company has continued to successfully grow over its history. Serving a global market Walker Filtration manufactures an extensive range of high efficiency compressed air filtration and drying equipment. Other suitable uses include the compressed gas, vacuum and medical markets, and they are locally produced in Washington, Tyne and Wear.

The model used in the original test rig at the workshop was the A108, an alpha series model. Alpha Series medical vacuum filters are specially designed to protect plant installations from liquid, solid and bacterial contamination and conform to the requirements of UK Health Technical Memorandum 02-01. The medical vacuum filters Walker Filtration produced are designed and constructed using oleophobic borosilicate media and an open cell reticulated foam pre filter. This unique material construction minimises pressure drop delivering reliable filtration with improved energy efficiency. Elements are drop-fit in installation to prevent vibration and improve stability and drainage.

Filtration MethodsAir filters do not simply trap larger particles and allow smaller ones to pass through. Instead, they are often able to trap the larger and smaller particles more effectively than medium-sized particles. This is a result of inertial impaction, Brownian motion and electrostatic forces.

Inertial impaction prevents larger particles from passing through filters. Larger particles will be unable to quickly adjust their pathway (as a smaller particle might) when they reach a change in streamline direction near a filter fibre. This means that the particle will hit the filter fibre and be unable to pass further through the filter.

Brownian motion is the random movement of gas particles as a result of their frequent collisions with other particles making them have a zig-zagged pathway. The diffusion mechanism of particle capture in filters relies on Brownian motion, as smaller particles can be caught in filters because gas particles will bump into them, causing them to have a random, zig-zagging motion, which means they are very likely to collide with and stick to a filter fibre.

Electrostatic forces of attraction between filter fibres and particles can enable the particles to be trapped in the filter. This can happen because both the fibre and particle are charged (oppositely) and so are attracted to each other. A neutral particle can also be attracted to a charged fibre by induced dipole-dipole attraction, just as a charged particle can be attracted to a neutral fibre.

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Bourdon Pressure GaugeThe Bourdon pressure gauge uses the principle that a flattened tube tends to straighten or regain its circular form in cross-section when pressurized. Although this change in cross-section may be hardly noticeable, and thus involving moderate stresses within the elastic range of easily workable materials, the strain of the material of the tube is magnified by forming the tube into a C shape or even a helix, such that the entire tube tends to straighten out or uncoil, elastically, as it is pressurized

Bourdon tubes measure gauge pressure, relative to ambient atmospheric pressure, as opposed to absolute pressure; vacuum is sensed as a reverse motion. Some aneroid barometers use Bourdon tubes closed at both ends (but most use diaphragms or capsules, see below). When the measured pressure is rapidly pulsing, such as when the gauge is near a reciprocating pump, an orifice restriction in the connecting pipe is frequently used to avoid unnecessary wear on the gears and provide an average reading; when the whole gauge is subject to mechanical vibration, the entire case including the pointer and indicator card can be filled with an oil or glycerine.

Valve Selection for the New Test RigGlobe valves can be used to control air flow, and are appropriate for gradually adjusting how much air can pass through a system, as (unlike other types of valves) they are seldom damaged when partially opened. They are operated by turning a handle that moves a plug up or down, thereby changing the size of space through which air in a system can flow. This means that they can be very useful for air flow control, although pressure is affected more significantly by adjusting them than for other valves, because the pathway through the valve is ‘s’ shaped. Globe valves can also be damaged by closing them too far.

Gate valves are appropriate for controlling whether access through a pipe is open or closed. They work (like a gate) by lowering the gate to obstruct air flow, or lifting the gate to allow more air flow. Gate valves are used less often than globe valves to control air flow, because they can be damaged when partially open, however can be used to open or close off a particular route.

A pneumatic valve is used to ensure that the air in a pipe or system does not flow backwards, but stays in the desired direction, thus controlling the flow of the air.

Valves are often either 2-port or 3-port (although higher numbers are also possible). A 2-port valve has 2 openings, and some form of mechanism to adjust air flow within, where air tends to enter by one opening and leave by another.

A 3-port valve will have 3 openings- either 2 paths for air to enter and one to leave, or vice versa. So, a 3-port valve can be used to bring two pipes together, or to split air flowing through one pipe into 2 separate routes. The ports of a 3-port valve can generally be opened and closed independent of each other.

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Laskin NozzleA Laskin nozzle produces a high concentration of liquid droplets in a polydisperse aerosol, which means that the aerosol contains particles of a variety of sizes. The particles that can be added to the aerosol include motor oils, meaning a Laskin nozzle can be used to test a Walker filter, since motor oils are commonly what they must remove. This would improve the design of the test rig, by creating a similar situation to that in which the filters would be used, rather than the previous design, which involved very little for the filters to remove.

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Method Following initial research a basic plan for the test rig was begun (see fig. 1) and was refined through communication with the link engineer to include more specialized equipment so more precise measurements could be taken.

At the university, the improved test rig design (see fig. 2) was constructed with the materials available. However, as only certain components were available it meant the constructed rig was a more basic version. This rig enabled any primary issues in the design to be identified and the solutions to these were then discussed.

After the rig was assembled, results were recorded (see fig. 6). This was achieved by controlling the variables of pressure (mBar) and air flow simultaneously using gate valves, which affected the temperature, humidity, and differential pressure.

The test rig consisted of a vacuum pump sucking air through a series of pipes and measuring devices across a filter, belonging to Walker Filtration, this allowed for measurements of the differential pressure across the filter using a barometer that calculated difference in pressure before and after air had flowed across the filter.

The residential workshop began with recording rough measurements and logging the data. This enabled comparison to the original results, where it was discovered that the lowest differential pressure value was 2%, which created a target to obtain this 2% value, or as close as possible, at all pressures in the second experiment.

This was done by setting the vacuum pump on a particular pressure, and adjusting the pressure in the pipes by adjusting gate valves on either side of the filter, which changes the airflow. To measure a particular pressure, the team had to drill/insert a new valve into the system which allowed the measuring devices to measure air flow in two different location, one before the filter and the second after the filter. When the differential pressure was shown to be 2% of the pressure of the overall system results were recorded for all the variables. This process was repeated several times. Once the results were compiled, graphs were produced (see results page) which were plotted in comparison to the walker filtration correction factors.

The new results showed what conditions the filter could withstand. This allowed a new plan for a new test rig to be designed (fig. 4), testing the filter under varying conditions, such as with more power or a dirtier vacuum and with different filter sizes, and including equipment to measure other factors, for example a particle counter, which we could use in the previous rig.

Results Page 7

From the tests that were done at the residential, air flow corection factors were calculated (see fig. 6) which are plotted on the graph below.

The graph demonstrates a positive correation between air pressure and pressure correction factors; at higher pressures tested (those closer to atmospheric pressure) a greater volume of air could flow through, meaning the pressure correction factor is larger. So, the maximum air flow at higher pressures is a larger percentage of the maximum air flow at standard conditions of pressure, temperature and humidity.

The results follow a linear pattern, and show very strong correlation, all lying on the line of best fit on the graph, implying that the results are precise. The pattern also shows that, up to atmospheric pressure, pressure correction factors and pressure are close to directly proportional.

In addition, the data shows the test rig to be very efficient as the points are generally lower than, or, as at 900 mBar, equal to, the points obtained by Walker Filtration.

0 100 200 300 400 500 600 700 800 900 10000

0.10.20.30.40.50.60.70.80.91

Relationship between Pressure and Pressure Correction Factor

Walker correction factorsOwn correction factors

Pressure (mBar)

Pre

ssu

re C

orre

ctio

n F

acto

r

Discussion The data appears reliable and accurate as the correction factors calculated from the results obtained during the residential workshop have a line of best fit that is very close to all of the plotted points. This shows there is little random error in the methodology.

The results are quite different from the Walker Filtration factors, which suggests that the test rig designed gave more accurate results than the test rigs previously used. The pressure correction factors gained at the residential are lower than those of Walker Filtration, which is likely due to the use of more recent methods of measurement (the Walker Filtration values were found C. 1960.) This means it is likely that the affects of pressure loss over the filter have been taken into account more by the residential pressure correction factors.

After each trial experiment, more elements were added to the pipe system to create more challenges. For example, different measuring instruments with different degrees of accuracy and different types of valves to restrict airflow to different degrees.

The initial test rig plan will be redesigned with more accurate measuring instruments and the removal of bends in the pipe system.

Overall the aim described in the brief title is achieved as a test rig was successfully planned and built as well as used to obtain sufficiently accurate air flow correction factors for the air filters.

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Conclusion The final design (see fig. 4), contains the most effective components for testing the filters, and would be capable of testing many different sizes of filters, the design fulfils the criteria which was set at the start of the project as it has components for measuring:

Airflow: a digital air flow measuring device is located at the inlet, as it is more accurate placing it later on in the system, and is more accurate than using an analogue system which would be easy to obtain human error from.

Humidity: The humidity is measured with two hygrometers, which is a precise method for measuring humidity. By taking two readings the resulting difference in humidity can be analysed, can provide more information regarding the filter. Data loggers are also going to be used so that measurements can be recorded without human error.

Differential Pressure: A digital barometer has been included, located across the filter, so it can automatically calculate the pressure difference across the filter.

Temperature: A digital thermometer will be inserted into the pipe after the filter, so that the temperature within the system can be measured (this is more effective than having the thermometer outside the test rig, as less other external variables could differ the result form its true value.

Oil content in air: will be measured in the test rig by two different deviceso An air sample would be collected in a device which had an oil solvent within

it, the oil solvent would remove oil from the system, and this oil would be able to be detecting by weighing the solvent before and after

o A particle detector, this would digitally calculate the different sized particles in the air passing the device, using software provided by walker filtration

Moreover, the new test rig consists of a vacuum pump to draw air through the test rig and filter, which is essential for the design to work.

Pipe adaptors will be inserted into the rig to make it more compatible for various types of filters with different diameters to be tested. As shown in the background research a selection of different valves were chosen as these ensure more controlled air flow, which ultimately give more accurate results.

The results show through the difference the pressure correction factors obtained by the walker filtration results and the results obtained from the research, that the newly designed test rig, will produce more current data, which can be used by Walker Filtration, which allows the company to sell a small filter to its customers, over more this would reduce costs in production, and give a larger margin in profit.

Therefore the test rig that has been designed meets the engineer’s project scope effectively and accurately.

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Recommendations Following the results gained at the residential, the test rig could be improved by making changes to the pipe system and vacuum, the measurement devices and to use equipment that will challenge the filter.

By altering the pipe system, such as removing any bends from the pipe system and increasing the pipe length the air flow becomes less turbulent. This means that the results for air flow will be more accurate. Adding reducers and adaptors into the pipework means that the system could be used to test various filters, instead of the single filter that was tested. Additionally, to test the larger filters a larger vacuum pump would be needed because the current vacuum pump is unsuitable for filter sizes of 3”.

Measurements of the system could also be improved by recording the results using data loggers, which would digitally record a wider range of values, meaning the values do not need to be read out and so less time is used. In addition, better measurements could be taken if: a hygrometer, a digital device which measures humidity, and a particle detector, which would record how efficient a filter was at removing waste particles, were added.

Challenging the system is another way the rig could be improved, because it would allow filters to be tested in replicated real-life situations, as the system may have an older, dirtier vacuum, or the filter may be wet out (it cannot take any more) and so this would test the limits of the filters in inadequate situations.

It is recommended that the system should be adjusted in the future to include these changes.

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Bibliography Vacuum VIP, Filter for Medical Vacuum, 2010. Bea Technologies. [18/12/13]

A Beginner’s Guide to Humidity Measurement, October 2011. Stephanie Bell. [04/12/13]

Vacuum Pump Protection Filter, 07/06/13. f & t. [18/12/13]

Measurement of Oil Mist from mineral oil-based metalworking fluids, June 1997. Health and Safety Executive. [12/12/2013] http://www.hse.gov.uk/pubns/mdhs/pdfs/mdhs84.pdf 

Method for measuring oil contained in Air-conditioning components, 2010. University of Illinois at Urbana-Champaign group. http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2034&context=iracc       [12/12/2013]

Medical Sterile Filters, unknown. Nano Purification Solutions. [17/11/13]

Breathing Air Purifiers, 2010. Parker Domnick-Hunter [18/12/13]

Oil X-Evolution, 2007. Parker Domnick-Hunter [18/12/13]

Medical Vacuum Filters, 2002. Parker Domnick- Hunter. [18/12/13]

Calculation of correction factors for variable area flow metres at deviating working conditions, unknown. Georg Rollmann. [17/11/13] http://kt-web.de/pdf/physik/korrekturfaktorenberechnung_gb_2.2.pdf 

Humidity Sensors and Signal Conditioning Choices, 13/10/2011. Steve Taranovich. http://www.digikey.com/us/en/techzone/sensors/resources/articles/humidity-sensors-and-signal-conditioning-choices.html [04/12/13]

Mechanisms of Filtration for High Efficiency Fibrous Filters, 29/08/12. TSI Incorporated. [10/12/13] http://kt-web.de/pdf/physik/korrekturfaktorenberechnung_gb_2.2.pdf 

Medical Sterile Filters, 2003. Walker Filtration. [17/11/13]

What is isokinetic sampling? 25/09/13. John Zactruba http://www.brighthubengineering.com/power-plants/98903-what-is-isokinetic-sampling/ [17/02/14] 

Page 12

http://www.allied-grp.com/warrenalloy/products/valves/globe-valves [8/12/13]

http://www.valvias.com/types-of-valves.php [8/12/13]

http://www.tlv.com/global/TI/steam-theory/types-of-valves.html [8/12/13]

http://en.wikipedia.org/wiki/Piping_and_plumbing_fitting [16/01/14]

http://www.pipingstudy.com/reducer.html [16/01/14]

http://en.wikipedia.org/wiki/Hygrometer [04/12/13]

http://www.filterintegrity.com/PTAS/PandS/Products/LiquidPartGen/plgmain.html  [18/01/14]

http://www.parker.com/portal/site/PARKER/menuitem.de7b26ee6a659c147cf26710237ad1ca/?vgnextoid=fcc9b5bbec622110VgnVCM10000032a71dacRCRD&vgnextdiv=&vgnextcatid=177247&vgnextcat=PRECISION%20PRESSURE%20REGULATORS&vgnextfmt=default [18/01/14]

http://www.atitest.com/html/products/details/documents/6DSpecs.pdf [21/01/14]

http://www.walkerfiltration.com/ [various]

http://www.tsi.com/airflow-instruments/ [04/12/13]

http://en.wikipedia.org/wiki/Pressure_measurement [04/12/13]

http://www.tsi.com/indoor-air-quality-meters-and-instruments/ [04/12/13]

http://www.palmerwahl.com/digi-stem-fixed-thermometers.php [04/12/13]

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Appendices Appendix A: Test Rig Design Plans

Fig. 1: First Design of Test Rig

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Page 14

Fig. 2: Second Design of Test Rig

Page 15

Fig. 3: Third Design of Test Rig

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Fig. 4: Final Design of Test Rig

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Fig. 5: Oil Measuring Device for Final Design of the Test Rig

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Appendix B: Test Results

Fig. 6: First Results from the Test Rig

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Fig. 7: Second Results from the Test Rig

Appendix C: Related Documents

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Fig. 8: Walker Filtrations’ Correction Factors

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Project: Test Rig Design for Medical Vacuum Flow Correction Factors

Risk assessment completed by: 4/12/20131. Who might be harmed?

The team members are susceptible to injury

The technicians are susceptible to injury

Lead Engineer: Dr. Simon Bartarm is susceptible to injury

2. Hazards: Please list in the boxesprovided below a l l of the hazards associated with the project activities to be carried out at the workshop. (A hazard is anything with the potential to cause harm eg. sharp objects, heavy loads, slips, trips or falls, electricity).

3. Please assess the severity of potential injury andlikelihood of accident happening for each hazard listed

Severity of potential injury Likelihood of accidenthappening

1 2 3 1 2 3

Minorinjury

Majorinjury

Fatality Unlikely Possible Likely

i. Burns from equipment at high temperatures

X X X

ii. Falls when working X X

iii. Scratches & grazes from building the rig

X X

4. Considerations and control measures: Please think about what checks you will put in place for

each hazard identified above to avoid accidents. eg. the wearing of safety goggles, attending appropriate briefings, keeping workspace tidy).i. Wearing gloves and hand protection when working with hot equipment

ii. Attending the briefings so instructions and hazards are clarified

iii. Keeping the workspace tidy in order to avoid slips, trips and falls

iv. Taking care when using tools and equipment to avoid injury

v. Wearing sensible clothing and footwear to avoid snagging and injury

We have considered the severity of the hazards and the likelihood; however, the considerations (above) seem appropriate.

Fig. 9: Final Gantt Chart

Fig. 10: Risk Assessment

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Page 23

EES Minutes: Meeting with Walker Filtration 15/11/13

Project Title: Test rig design for medical vacuum flow correction factors.

Project Scope: Build and implement a test rig that can provide relevant data for determining flow correction values for systems operating at various pressures.

Equipment that we will need to measure:

1. System pressure 2. Pressure loss across filter3. Air flow rate4. If possible- filtration efficiency (preferably bacterial)

Specifically of interest are the flow characteristics of a medical vacuum system, so this project should be based on air flow at a pressure below 1 bar (absolute)

Project Deliverables:

1. Test rig, (workshop at Newcastle University can be used to investigate requirements/limitations to be considered for the design)

2. Sourcing parts and assembly of test rig (WFL to carry out this part)3. Standard operating procedure documentation4. Test results relevant to medical vacuum application5. Competitor analysis

Equipment needed for testing

Compressors Vacuum pump Particle detector (if possible) Systems to contain the air and to move the air Measurers for air flow Thermometers Humidity measurers Purity measurers Pressure measurers Bacteria to challenge filters (if possible) Valves, fittings and pipes

To research

Medical sterile filters Pressure flow correction values

EES Minutes: Company Visit to Walker Filtration 29/11/13

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Prior to the tour of the company, more was learnt about the ethos and values of the company and the way in which their filters worked via a brief presentation

Questions about the project, including expectations, deadlines, rig size and more information on the vacuums used, were answered

A rough plan of the work planned during the residential was decided upon- the test rig would be built, measurements taken, improvements decided and the test rig improved

A discussion of the hazards was also undertaken and the main hazard was found to be the heat of the machinery

A tour showed the vacuums that would be used and how the filters were produced

It was confirmed that the flow correction factors are multiplied by the generic flow values according to the pressure of the filter system to give their specific flow value.

Actions for next meeting:

Create a draft flow-diagram for the design of the test rig. Research into: impaction, inertial, Brownian motion and electrostatic.

EES Minutes: Flow Chart Design and Risk Assessment Form 4/12/13

The variables that would be recorded from the rig were decided: -System Pressure-Pressure loss across filter- Air Flow rate-Particle count-Temperature-Humidity

A rough flow chart was then made Next the devices needed to measure the above were researched, these were:

-Pressure- Barometer-Air Flow- digital timer, air flow detector-Purity – particle counter/ detector-Temperature – digital thermometer-Humidity – Capacitive sensors or resistive sensors humidity

The risk assessments and the word document the university required were completed

The universities equipment requirements online form part 2 were filled in A neat flow chart on Microsoft publisher was made Finally, the Gantt chart was updated

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EES Minutes: Residential Preparations and Research 10/12/13

Available equipment at the university was inquired about and a list of equipment that the company would need to bring therefore was complied

Secondly, following an email from our lead engineer asking about valves, it was discussed what valves we would need and where in the rig they should place them

Next different types of valves were researched and 3 were selected to be included in the rig- global needle valve, pneumatic valve and a gate valve

Lastly the flow chart was updated with the new valves in place

EES Minutes: Further Residential Preparations and Research 12/12/13

The university was asked if they had a vacuum pump with an air flow greater than 25m3/h

The flow chart was updated, so that the vacuum pump was placed at the end of the system, rather than placed at the start in response to an email from the Engineer saying that vacuums suck

The ways to measure oil in the air researched - the theory is called flushing, it includes using solvents and a 3 port valve

The “ Bourdon Pressure Gauge” was researched and a word document was produced explaining how it works

A diagram for the oil measuring device was created

EES Minutes: Recommendations for the Rig 16/01/14

Recommendations on how the rig could be improved in the future were discussed

Laskin Nozzles were researched in order to find a way to challenge the filter The project report was started Other filter companies were emailed about specific regulators Other company correction factors were researched

EES Minutes: Further Recommendations for the Rig 23/01/14

Recommendations for the test rig were discussed and clarified Replies were accessed from the other companies for specific regulators

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A particle detector, to be inserted into the new rig, was researched The report structure was considered and the information for it was collated

EES Minutes: Working on the Report 30/1/14

The front cover page was designed for the report The appendices was arranged for the report The website addresses were compiled into the bibliography

EES Minutes: Report Work 13/02/14

Emails were sent to the engineer, Dr. Simon Bartram to show the final design for the test rig.

Roles for the report were organised. The methodology was written.

EES Minutes: Continuation of Report 27/02/14

Aspects of the report that individuals had produced were checked by the whole team and added to the report.

The results and analysis of them were completed.

EES Minutes: The Report was Continued 06/3/14

The discussion was started The background for Walker Filtration was created Improved the results, writing them up and adding a graph Introduction was started The improvements were discussed 

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Appendix D: Photographs

Prototype of Test Rig

Air Flow Measuring Device

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A

digital humidity measurer, a digital thermometer and two barometer (from left to right)

The Bourdon Pressure Gauge

Acknowledgements

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There are many people we would like to thank for their help in completing our project.

Firstly we would like to thank Dr. Simon Bartram our assigned engineer from Walker Filtration, who contributed a substantial amount of time and effort to our project, his knowledge and experience was highly valued by the team, and we thoroughly enjoyed working with him.

In addition we would like to express our gratitude towards Walker Filtration, for the invaluable opportunity and equipment they gave to us in particular Jen MacEwan and Lianne Walker, as they were particularly enthusiastic and supportive.

Next we would like to thank Bowman Bradley our mentor for his all-round knowledge and advice on how to tackle the report.

Moreover, we would like to express our appreciation Mr. Morton and Mr Ivison for allowing us to use the labs and constant encouragement, support and good humour.

Furthermore, we would like to thank Newcastle University for allowing us to use their laboratories, equipment and providing us with technicians, in particular Mr Iain Strong, who never failed to meet our many requests.

Finally we would like to thank the Engineering Development Trust for organizing the Engineering Education Scheme, in particular Charity Watkins for her dedication and enthusiasm to the event.

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