Cost-effective paint and powdercoating: materials management

GG

385

This Good Practice Guide was produced by

Envirowise

Prepared with assistance from:

Enviros Consulting LtdMcLellan and Partners Ltd

Cost-effective paint and powdercoating: materials management

Summary

This Good Practice Guide is one of four complementary guides providing advice on cost-effective paint and powder coating. It is aimed at paintshop and production managerswhose operations use organic solvents, eg in paint, for thinning paints, cleaningequipment or degreasing.

Certain organic solvents, also known as volatile organic compounds (VOCs), can give rise toemissions which contribute to low-level air pollution and directly to global warming.

The Guide explains how a company can reduce its costs and VOC emissions by focusing on itsmaterials and paintshop management.

Paint and solvent consumption can be readily reduced by no-cost and low-cost goodhousekeeping measures, and the implementation of a structured approach to wasteminimisation. Industry examples within this Guide illustrate the savings that can be achievedthrough good housekeeping and other measures.

This Guide highlights ideas that will:

■ save money;

■ save time;

■ use less paint and solvent.

Reducing solvent consumption may help some companies increase capacity, without needing aregulatory permit to operate under Local Authority Integrated Pollution Prevention and Control(LA-IPPC) or Local Air Pollution Prevention and Control (LAPPC). This Guide will also helpcompanies that are regulated to meet their LA-IPPC or LAPPC compliance requirements cost-effectively.

There is an action plan at the end of this Guide to help you focus on the ideas that are mostrelevant to your company.

The other guides in the series cover surface cleaning and preparation, coating materials, andapplication technology. All are available free of charge through the Environment and EnergyHelpline on freephone 0800 585794 or via the Envirowise website (www.envirowise.gov.uk).

This Guide builds upon GG50, first printed in 1997, and contains up-to-date legislation.

Contents

Section Page

1 Introduction 1

2 Solvent use in painting and coating 3

3 What is materials management? 43.1 Defining your aims 4

4 Waste minimisation 64.1 Identifying waste 64.2 Measuring waste 74.3 The cost of waste 84.4 Taking action 84.5 Investigating waste 94.6 Measuring to manage 10

5 Good housekeeping 12

6 Paintshop management 146.1 Paintshop layout 146.2 Paint delivery systems 146.3 Workpiece handling 146.4 Process efficiency 156.5 Scheduling 16

7 Action plan 17

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Introduction

The four complementary guides to cost-effective paint and powder coating in thisseries are:

Cost-effective paint and powder coating: materials management (GG385)

Cost-effective paint and powder coating: coating materials (GG386)

Cost-effective paint and powder coating: application technology (GG387)

Surface cleaning and preparation: choosing the best option (GG354)

These guides and other Envirowise publications mentioned herein are available free of chargethrough the Environment and Energy Helpline on freephone 0800 585794 or via the Envirowisewebsite (www.envirowise.gov.uk).

These guides are intended to help a range of companies, including:

■ metal finishers;

■ fabricators;

■ component and assembly manufacturers for original equipment manufacturers;

■ original equipment manufacturers.

The guides are applicable to companies using paints and powders to coat in:

■ predominantly manual operations, eg hand-spray booths;

■ partially automated operations;

■ fully automated operations.

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An in-house paintshop had a 17% reject level. This meant that up to five workers atany one time were needed to strip or sand parts prior to reworking. An externalconsultant highlighted several problems - all relating to the standard of operationsand housekeeping.

■ Paint quality was not controlled, with no measurement of viscosity ortemperature and, therefore, no proper adjustment of spraying parameters.

■ Plant was not maintained, eg spray guns were not serviced unless they stoppedworking due to a blockage, breakage or the failure of ancillary equipment.

■ The person performing quality control (a quick check for ‘pass’ or ‘fail’) was toobusy to tell the operators when there was a problem. The only feedback wasgiven at the end of each shift.

The consultant analysed the process requirements before setting quality standards,writing operating procedures, training the sprayers and setting up a corrective-action system for communicating quality problems and implementing change.

On the consultant’s recommendation, the company employed an additional person todeal specifically with housekeeping. This person carries out quality control on the paintand plant, maintains equipment, acts as a ‘stand-in’ if necessary and trains new staff.

Reject levels are now less than 2% and still improving. Production levels haveremained constant, but sales have increased by 15.5%. Only one person is nowneeded to prepare rejects for processing and material costs have also fallensignificantly. Profits are, therefore, nearly 30% higher, even after allowing for thesmall increase in staff costs.

Better practice leads to improved profits

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Solvent use in painting and coating

Organic solvents are widely used in UK industry for a range of processes. In the metalcoating industry, trichloroethylene can be used for cleaning and a range of organicsolvents including xylene, white spirit and butyl acetate may be part of the paintformulation, or used for thinning.

Trichloroethylene has been reclassified as a category 2 carcinogen (Risk Phrase R45 - may causecancer) and should only be used under contained conditions.

These, and other organic solvents, give rise to volatile organic compound (VOC) vapours. Currently,levels of these VOCs in the atmosphere are a subject of widespread concern and regulation. This isprimarily because of their role in the formation of low-level air pollution affecting human health,crops and natural vegetation, but also because they contribute to global warming.

The EC Solvent Emissions Directive was implemented by the Pollution Prevention and Control(Solvent Emissions Directive) (England and Wales) Direction 2002, which places strict controls onVOC emissions from industry and defines emission limit values for new and existing installations.

The Pollution Prevention and Control Regulations require the operators of prescribed processesto submit a detailed application for a permit to operate to the regulator. Most paint and powderprocesses fall within Part A(2) for Local Authority Integrated Pollution Prevention and Control(LA-IPPC) or Part B for Local Air Pollution Prevention and Control (LAPPC). Detailed requirementsare given in the appropriate LAPPC process guidance note.

There are transitional arrangements for existing installations, authorised under the former LocalAir Pollution Control (LAPC) regime.

Advice about LA-IPPC, LAPPC and other legislation governing your operation is available fromthe Environment and Energy Helpline on 0800 585794.

Even if your company does not use enough solvent to be regulated under the PollutionPrevention and Control Regulations, using good practice will still enable you to achievesignificant cost savings. Companies approaching the relevant threshold may also be able topostpone or avoid registration.

Improving the way in which you manage your material use, as described in this Guide, will help to:

■ reduce costs;

■ reduce VOC emissions;

■ meet LA-IPPC or LAPPC compliance requirements.

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What is materials management?

Materials management is the process of understanding and controlling the use ofmaterials within a company. Although this Guide refers primarily to solvents and solventmanagement, the techniques can be applied to any material used by industry. Thepreparation of a solvent management plan is a requirement under the Solvent EmissionsDirective. The solvent management plan is used to determine the solvent consumption,emissions in waste gases and uncaptured emissions to air. It is a useful tool for improvingmaterials management. The procedure for the calculations is given in the appropriateguidance note.

Good materials management will help your company improve the control of its paint and solventconsumption. Use materials management techniques described in the Guide if your companywants to:

■ reduce paintshop costs and thus increase profits;

■ increase paintshop capacity, while avoiding capital investment;

■ reduce solvent consumption to:

- below the threshold for regulation under LAPPC, thus reducing costs and managementtime spent on non-core business;

- meet LA-IPPC or LAPPC compliance requirements.

It is also important for a company to:

■ reduce employees’ potential exposure to solvent vapours, taking into account, in particular,the reclassification of trichloroethylene as a category 2 carcinogen;

■ reduce the impact of its operations on the local environment.

This Guide describes ways in which you and your company can meet these aims. However,selecting one or more of these ideas may only move your company part of the way towards itsobjectives. To achieve maximum benefit from materials management, your company needs toadopt a systematic approach. This involves:

■ defining your company’s aims in managing its material use;

■ assessing how your company’s performance matches up to these aims;

■ deciding how your company can progress towards meeting these aims.

3.1 Defining your aims

At the beginning of the process of improvement, a company needs to define its aims.

■ Costs are universally important - few companies will turn down the opportunity to savemoney and boost profits. Reducing costs will also help to strengthen the competitiveness ofyour company, particularly during difficult trading conditions.

■ Increasing paintshop or production capacity may be important to a growing company,especially if it is reaching its current capacity.

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■ Avoiding or postponing the need for a permit to operate under LAPPC will enable a companyto save the costs of authorisation. These include not only the application fee and annualcharge, but also the costs involved in collating and submitting solvent inventories, andwriting and implementing upgrade programmes.

■ In some cases, improved solvent management may give the added bonus of allowingincreased capacity without the need for a permit to operate under LAPPC. Small, butgrowing, companies which are currently under the threshold for regulation may want topostpone the need to obtain a permit for as long as possible.

■ Companies regulated under LAPPC will want to use the most cost-effective route tocompliance with upgrade plans and other conditions.

Some companies may have other aims. These aims need to be thought about, discussed, agreedby company management and recorded. Having defined its aims and obtained managementcommitment, the company should then consider how to achieve them. One of the best ways ofachieving a reduction in material use is to apply the ‘waste minimisation’ techniques describedin the following section.

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Waste minimisation

Waste minimisation is a systematic approach to minimising the production of waste atsource. In this sense, ‘waste’ is not just discarded solid materials, but includes wastedtime, off-grade product, loss of materials to air and drain, and excessive use of energyand water. All of these cost money. Rather than creating waste, and then perhapshaving to pay for it to be taken away, why not aim to stop producing it altogether?

In practice, it is not always possible to stop generating waste completely. However, it may bepossible to reduce the amount of waste a company produces. Alternatively, there may be waysof putting waste to good use through re-use or recycling (in-house or externally). Finally, acompany may have to consider treating its waste to make it less harmful to people and theenvironment.

Fig 1 summarises this ‘waste hierarchy’.

The following Good Practice Guides published by Envirowise may help your company organiseand implement a waste minimisation programme:

Saving money through waste minimisation: raw material use (GG25)

Saving money through waste minimisation: reducing water use (GG26)

Saving money through waste minimisation: teams and champions (GG27)

4.1 Identifying waste

Waste minimisation requires a company to take a systematic look at all the waste its operationsgenerate - not just solvent use, although this may be a good starting point. The first thing to dois to identify all the forms of waste generated within the company.

5

Material

Dispose

4Recycle

3Re-use

2Reduce

1Eliminate

Product

Avoid producingwaste in the

first place

Minimisethe amount

of waste youdo produce Use items as

many times aspossible Recycle what

you can onlyafter you

have re-used itDispose of

what’s left in a responsible way

Start here

WASTEONLY

Fig 1 The waste hierarchy

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The list might include obvious wastes such as:

■ waste paint;

■ waste gunwash solvent;

■ waste cleaning solvent;

■ waste paint containers;

■ dry wastes, eg rags, wipes and abrasives.

The list can also include less obvious wastes, such as:

■ gunwash solvent lost to the extraction system during gunwashing;

■ paint lost due to overspray;

■ solvent lost from paint during paint application;

■ time lost due to poor finish quality (rectification/rework).

These wastes need to be identified. Some are easy to find, eg in skips, bins, or drums full ofwaste. Others are more difficult to pinpoint.

Having identified all possible sources of waste from an operation, the next stage in minimisingwaste involves identifying opportunities to eliminate or reduce different waste streams. Theseopportunities should be ranked in order of importance, eg safety, cost, environmental benefits.The highest priority opportunities can then be implemented in order and the benefits realised.

Prioritising action to eliminate or reduce waste is not always easy. While it may seem obvious totackle the largest waste stream first, companies should consider their aims. Is the priority thehighest cost or the largest volume of wasted material?

This type of structured approach to waste minimisation is best carried out by teams, as thisspreads the workload and helps to keep a balanced view. Having team members from differentfunctions and departments within the company helps to ensure that:

■ all possible sources of waste are identified;

■ the best solutions to problems are generated.

If possible, team members should be selected from all levels in the company, ie from the shopfloor to senior management. In manufacturing industry, experience has shown that teams aremost effective if they include employees from:

■ engineering/utilities/site services functions, who are responsible for the design, installation,maintenance and operation of plant and equipment;

■ production management responsible for scheduling and line management;

■ operatives who actually perform the day-to-day production tasks and who usually know mostabout the activities that cause waste.

Saving money through waste minimisation: teams and champions (GG27) gives advice tocompanies organising a team approach to waste minimisation.

4.2 Measuring waste

The next stage in minimising waste is to quantify the wastes that have been identified.

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Some wastes are easily measured. Wastes in skips and bins (eg paint cans or waste solvents) canbe counted or weighed.

Other wastes, such as rework or wasted time, are not as easy to measure. Timesheets,production logs and batch records are good sources of information about rework rates. However,these sources of information may be of poor quality and you may need to set up systems tocollect good quality, reliable data.

Estimating the amount of paint and solvent used each year and comparing these figures withyour waste disposal records can sometimes highlight areas of significant waste. If your companyhas a permit to operate under LA-IPPC or LAPPC, you will need to prepare a solvent managementplan each year and submit records to your local authority under your permit to operate.

■ Ask your solvent supplier for details of your solvent purchases and for advice on how to workout your solvent losses.

■ Ask your paint supplier for details of paint purchases and how much solvent your rawmaterials contain.

■ Ask the waste disposal companies you use to confirm your waste disposal records.

Cost-effective solvent management (GG13) describes how to keep track of solvent use.

4.3 The cost of waste

Does your company know exactly how much its waste is costing? Experience has shown thatmost companies significantly underestimate this cost.

As wastes are measured, so costs can be assigned to them. It is important to know the costs of:

■ waste disposal;

■ useful material that is being thrown away in error or wasted through rework.

Information about material costs is usually known by someone within a company, but not oftenby everyone. For example, if sprayers are made aware of the cost of paints and solvents, thenthey will be more aware of the cost of any wastage.

Rework costs should also be determined. These include:

■ the cost of the additional coating materials;

■ the cost of the materials to clean the job for rework;

■ the cost of the labour required to do the rework.

At the end of this exercise, your company should have a reasonable idea of which wastes arecosting the most.

This is the point at which you can take action to reduce waste.

4.4 Taking action

Some ways to reduce waste will be obvious. Some of the ideas from this and other guidesproduced by Envirowise may be useful, eg Good housekeeping measures for solvents (GG28),and Finding hidden profit - 200 tips for reducing waste (EN30). You may want to develop yourown ideas, particularly those specific to your company’s operations.

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However, it is important to ensure that any action taken to reduce or eliminate waste is cost-effective.

For example, your company may decide that one priority is to reduce the disposal costs for wastesolvent. One possibility is to buy a solvent distillation machine and recover solvent in-house. Thepayback period on the investment can be easily calculated by dividing the purchase cost by theannual savings. The savings include the money saved by not sending the solvent waste fordisposal plus the money saved on solvent purchases, less the annual operating costs.

Projects with a payback period of less than a year will be self-financing as they can be carriedout without affecting your budget. In addition to cost savings, waste minimisation opportunitiescan also often provide:

■ improved quality;

■ increased plant capacity;

■ improved health and safety;

■ lower environmental emissions.

Agreeing the actions to take in other priority areas may be more difficult. You may haveidentified the problem but you don’t know what’s causing it. In such cases, investigations will beneeded to identify possible causes. However, action to discover the reason for waste should betaken only if the waste in question is significant.

For example, a company may decide that the cost of purchasing and disposing of the solventused for spray gun washing is a priority area for waste minimisation. The problem is that nobodyknows where all the solvent goes. The obvious solution is to find out how the gunwash solventis used and where it might be wasted.

Saving money through waste minimisation: raw material use (GG25) describes how to gather allthe data and information needed to identify opportunities for reducing waste and how toprioritise these ideas.

4.5 Investigating waste

There are a number of practical ways of identifying waste and its causes (also see the industryexample in section 5). For example, you can:

■ observe how people operate and use materials;

■ compare the different ways people operate;

■ ask people where they think materials could be saved.

In larger plant, it may be necessary to compare the performance of machines or production linesagainst each other and against their specifications.

When talking to people about waste, it is important to explain the aim of the waste minimisationprogramme. Stress that the company is trying to save money, not trying to find out whose faultthe waste is.

Consider instituting a ‘no-blame’ system or at least be aware that instilling a ‘blame culture’ candrive waste and rework underground. This benefits nobody.

It is also important to remember that there is often more than one correct way to do a job - butthere will always be one way that is more efficient, ie lower cost, than the rest.

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It may prove more difficult to identify the cause of a particular waste. This is where a techniqueknown as ‘measuring to manage’ can help.

4.6 Measuring to manage

To reduce material use or costs, a company needs to be in control of the job in hand. But acompany cannot manage something if it is not being measured in the first place. Measuring tomanage is all about gaining and keeping control over the use of solvent, paint, energy, etc, bymeasuring it and then comparing that measurement against how it was used.

For example, when filling a car with petrol, many people keep a note of their car’s mileage andhow much petrol was needed to refill the tank. They can then calculate the distance travelledagainst the fuel consumed, and work out the kms/litre and check it is what they would normallyexpect.

You learn through experience that when the fuel consumption goes up the car probably needsa service. If the fuel consumption changes suddenly, then you are alerted that there is somethingwrong with the car and can investigate the problem. Seeing whether the fuel consumptionreturns to normal is one way of checking you have found the right solution.

Similar techniques can be used in industry. By measuring the quantity of material (solvent orpaint) or energy used and comparing this figure with a measure of work, you can start to get afeel for what the average use is and how much it varies. Possible measures of work include:

■ items coated;

■ area of paint applied;

■ number of spray guns cleaned.

Weekly measurement and comparison are recommended. Taking measurements every day istime-consuming, while with monthly measurement, people tend to forget what happenedearlier in the month, making it difficult to achieve control.

It is often useful when measuring to manage to record the ratio of consumption to production.Examples of the many possibilities include:

■ volume of gunwash used in a week/number of spray guns washed;

■ volume of gunwash used in a week/number of jobs coated;

■ volume of gunwash used in a week/area of paint applied;

■ quantity of paint used/area of paint applied;

■ quantity of paint used/number of items coated.

A good way of presenting this information is to draw a graph. Pictures can often tell you farmore than numbers on a page.

4.6.1 Presenting data

You can use your data to plot a scatter graph (sometimes known as a ‘cost driver chart’), suchas the one shown in Fig 2.

The line of ‘best fit’ represents the average amount of solvent used each week to wash a givennumber of guns. You can use this line to predict how much solvent you might need forgunwashing. You can also use the line to identify weeks when you have done better or worse

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than standard (or average). Points above the line are worse, points below are better. Minorvariations in material use are to be expected and should be tolerated.

You can now start to work towards improved use of materials by finding out how or why youdo better or worse than standard each week. As you find out the answers, you must take actionto prevent repeating events that cause worse performance. You must also ensure that betterperformance is encouraged and repeated.

If you identify and eliminate the causes of waste, you will see, with time, all your measurementsfalling below the line. You will also start to see costs falling.

Saving money through waste minimisation: raw material use (GG25) gives more practical adviceon taking measurements, drawing graphs and presenting information.

Measuring to manage can also help companies to monitor medium-term and long-term trendsin material use. This enhances business control, planning and predictability.

Solv

ent

use

d p

er w

eek

(lit

res)

Number of guns washed per week

The line of 'best fit'

Worse than average

Better than average

Fig 2 Example scatter graph of measured performance

Remember:If you don’t measure it, you can’t manage it.

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Good housekeeping

One easy and low-cost way of reducing waste is to improve your company’shousekeeping. This means stopping the casual waste of materials and energy, whichoccurs through bad habits, poor practices and use of unsuitable equipment.

It is estimated that UK industry wastes up to 10% of materials through poor housekeeping.

Good housekeeping measures, which often cost nothing to implement, include:

■ putting caps back on solvent cans and drums;

■ putting lids on paint cans;

■ storing paint cans and solvent cans/drums so they cannot get knocked over;

■ closing tank lids and keeping them closed;

■ ensuring that cans are fully emptied into the solvent waste before throwing them into a solidwaste skip;

■ setting up stock rotation systems to ensure that paints do not go out of date;

■ enclosing paint mixing scales in sealed plastic bags to prevent spillages from causingweighing inaccuracies and potential damage;

■ only mixing or measuring out sufficient paint for the job;

■ in larger installations, fixing leaks in solvent and paint distribution pipework immediately.

Your company can also set housekeeping standards. It is important to:

■ write down a list of rules that are expected to be kept (an example is shown in Fig 3);

■ make sure everyone in the company knows what these rules are and understands the reasonsfor them.

Put caps back on solvent cans and drums

Put lids on paint cans

Store paint and solvent cans and drums so they cannot get knocked over

Close tank lids and keepthem closed

Make sure cans are fully emptied into the solvent waste before throwing them into a solid waste skip

Remember stock rotation

Only mix sufficient paint for the job

Green & Keen Ltd Housekeeping Standards

Fig 3 Good housekeeping rules

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To reinforce the rules, carry out regular - perhaps weekly - housekeeping reviews by walkingaround the factory or paintshop, looking at how clean and tidy things are.

■ Look for spills, tops off cans, solvent rags left lying around, etc.

■ Ask people to correct faults straight away.

■ Congratulate people who are doing things correctly or when the factory/paintshop is cleanand tidy.

■ Explain to people that keeping high standards of housekeeping will improve workingconditions and reduce costs.

To keep everyone involved, you could consider posting a housekeeping review report on anotice-board so that everyone in the company knows how they are doing. This approach canalso be useful in instilling a spirit of competition between departments or shifts.

Good housekeeping measures for solvents (GG28) describes practical and affordable measuresfor reducing solvent and paint losses, together with ways of reducing the risk of pollution fromhandling and storing such materials.

A number of problem areas were highlighted when a company operating anautomatic powder plant with manual touch-in took stock of its operations. Forexample, it found that:

■ colour changes were slow due to a lack of procedures and the wide range ofcolours used;

■ the right powder was never available when needed;

■ half of the staff stood around at the beginning and end of the day waiting forcomponents to be pretreated or unloaded after stoving;

■ the plant was dirty, leading to contamination of finished components;

■ quality standards varied due to the lack of information given to operators.

Significant increases in productivity, sales and profits were achieved by introducinggood housekeeping measures, including:

■ a person employed to keep the factory clean and to perform general duties, suchas fetching powder and disposing of old boxes;

■ a production system that includes a card stipulating requirements, which followsthe job around the plant;

■ a planned production schedule based on colour, ease of colour change, customerdelivery time and plant hour requirements;

■ training of operators and the introduction of written procedures to reducedowntime, particularly on colour change.

Production has increased by 6%, while profits have increased by over 10%.Downtime is 4 - 6 hours/week less, quality standards have improved due to the newproduction system and the cleaner, more organised environment has improvedemployee motivation.

The rewards of good housekeeping

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Paintshop management

Paintshop design and layout can have a marked effect on both the efficiency andcapacity of your paintshop operation.

6.1 Paintshop layout

Paintshop layout depends on:

■ the space available;

■ the location of the paint store in relation to spraying operations.

Each stage of a painting/coating process should be examined to determine its layout requirements.

Due to the flammable nature of solvent-based paints, paint stores are usually located away fromthe main production building, often in prefabricated sheds with little or no space heating.

Paint becomes more viscous when cold. This can lead to too much thinner being added toproduce the desired spraying viscosity, which in turn leads to a dilute coating being applied.

The use of paint lockers containing small amounts of paint located next to spraying areas allowsgreater control of paint temperature and more even application throughout the year. Storing theday’s materials at hand also saves time.

6.2 Paint delivery systems

Using pumped or pressurised paint pots also improves the efficiency of paint handling. Suchpaint pots can hold and deliver larger amounts of paint than a standard spray cup, thus savingtime on refilling. However, they are really useful only when single colours are being sprayed.

In contrast to pressurised systems, pumped systems can be quickly topped up to prime thesystem once spraying has begun.

Paint pots can, if necessary, be stored in a temperature-controlled environment to provide evengreater control over viscosity.

Pumped ring mains, where paint is distributed from a paint store to numerous spray guns, areone of the more sophisticated paint delivery systems available to medium-to-high volume users.Some systems have built-in paint heating to control viscosity, while others allow different coloursor paint types (primer, basecoat, clearcoat, etc) to circulate separately within the system at thesame time. The latter have spray guns equipped for quick changeovers.

6.3 Workpiece handling

Workpiece handling should also be considered when designing a paintshop.

Cleaning requirements should be taken into account in jig design. For example, the useful life ofjigs can be prolonged by:

■ having a minimal surface area to prevent build-up of overspray;

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■ fitting caps to cover unused hangers.

6.3.1 Smaller operations

The use of hooks to hang workpieces from when spraying, or a wheeled A-frame for largerworkpieces, enables a sprayer to reach all sides easily. This allows spraying to be carried out inone operation. The next workpieces can then be loaded onto a second frame, while thosealready coated are flashing off.

6.3.2 Larger operations

The use of a conveyorised transport system using jigs or flight bars should be considered whenlarge numbers of workpieces are passing through a painting process.

Where jigs are used with electrostatic application systems, it is important to ensure that the partsare adequately earthed, so that:

■ spraying efficiency is maintained;

■ an electrostatic charge does not accumulate and pose a fire risk.

Connection to earth can be achieved by:

■ designing the jig to be self-seating, ie the component always rests on the same point(s), thuspreventing these points being insulated by the applied coating;

■ ensuring that the jig is in contact with a part of the component which does not get coated.

Where jigs are used for dipping components, they should be designed to reduce paint drag-outto a minimum to reduce losses.

6.4 Process efficiency

Conveyorised systems require sequential ordering of the process. Where processes have beenextended in an ad hoc manner, double handling of components can often be reduced bymodifications to the plant layout. This will:

■ save time;

■ minimise damage due to mishandling;

■ reduce production bottlenecks.

Remember, output rates are dictated by the slowest stage of the production process. Bottlenecksneed to be identified and eliminated. For example, if stoving is the slowest part of the process,installing a bank of infrared driers prior to an existing oven could enable the entire line to runmore quickly, thus increasing effective capacity.

Jig or flight bar design also affects the plant’s capacity. For example, if a conveyor is moving at4 metres/minute, then 4 metres of conveyor space are available every minute. However, theeffective width of the spray operation dictates the area available for spraying. This is the limitingfactor, not the conveyor speed. The greater the density of workpieces on the line, the greaterthe output.

If, for example, you are coating small workpieces using hangers set 1 metre apart, then usingsecondary hangers holding several workpieces will enable you to increase capacity. It could alsomean that the line can be loaded and unloaded more quickly.

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Process set-up is often time-consuming and reduces coating plant capacity, eg colour changesmay require guns, lines and paint vessels to be cleaned. Anything which reduces the time takento set up a process will speed up the changeover process and increase output.

Preparatory tasks that can be carried out while the plant is operating will also reduce changeovertimes.

6.5 Scheduling

Scheduling of workloads can significantly reduce the amount of time and materials used forsetting up and cleaning equipment.

Scheduling light-to-dark production every day or shift could enable guns and paint pots to beused without being cleaned as the darker colours may mask the lighter ones. Although thequality of the final finish may be paramount, there are cases where this technique hasadvantages.

Where various different finishes are used, scheduling large batches of similarly coated objectstogether - rather than interspersing them - reduces time and material losses due to cleaning andset-up. The people in charge of scheduling should be aware of these technical issues and bearthem in mind, rather than just dealing with the needs of customers.

By discussing these technical issues with schedulers and customers, it may be possible to producelarger batches of goods less frequently. Some of the cost saving could be passed on to thecustomer. ‘Just-in-time’ production requirements may, however, preclude this option.

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Action plan

IF YOU WANT TOREDUCE PAINT AND SOLVENT CONSUMPTION:

■ Use materials management to control your paint and solvent use.

■ Follow a structured approach to waste minimisation:

- identify and quantify wastes;

- work out how much waste is costing your company;

- investigate significant sources of waste;

- take action to reduce waste according to your company’s priorities.

■ Control materials and energy use by measuring to manage.

■ Implement a good housekeeping programme.

■ Consider your paintshop management:

- optimise paintshop design and layout;

- improve paint handling and process efficiency;

- consider workload scheduling when handling large numbers of workpieces.

■ Contact the Environment and Energy Helpline on freephone 0800 585794 to obtain freecopies of the Envirowise publications mentioned in this Guide or visit the Envirowise website(www.envirowise.gov.uk).

Don’t forget to ask for the three other guides in the series on cost-effective paint and powdercoating, if they relate to your operation:

Cost-effective paint and powder coating: coating materials (GG386)

Cost-effective paint and powder coating: application technology (GG387)

Surface cleaning and preparation: choosing the best option (GG354)

Envirowise - Practical Environmental Advice for Business - is a Government programmethat offers free, independent and practical advice to UK businesses to reduce waste atsource and increase profits. It is managed by Momenta, an operating division of AEATechnology plc, and Technology Transfer and Innovation Ltd.

Envirowise offers a range of free services including:

Free advice from Envirowise experts through the Environment and EnergyHelpline.

A variety of publications that provide up-to-date information on wasteminimisation issues, methods and successes.

Free, on-site waste reviews from Envirowise advisors, called FastTrack visits, thathelp businesses identify and realise savings.

Guidance on waste minimisation clubs across the UK that provide a chance forlocal companies to meet regularly and share best practices in waste minimisation.

Best practice seminars and practical workshops that offer an ideal way toexamine waste minimisation issues and discuss opportunities and methodologies.

For further informationplease contact the

Environmentand EnergyHelpline0800 585794© Crown copyright. First printed September 2003. Printed on paper containing a minimum of 75% post-consumer waste.

This material may be freely reproduced in its original form except for sale or advertising purposes.

Harwell International Business Centre | Didcot | Oxfordshire | OX11 0QJE-mail: helpline@envirowise.gov.uk Internet: www.envirowise.gov.uk

Practical Environmental Advice for Business