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4/11/2014 Auto Dish & Glass Washing Reprint of our 5 part series from the Arpal Group Blog. All comments and feedback welcome. Contact Us www.thearpalgroupblog.com

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In a series of five articles published on the Arpal Group blog between September and October 2014, we provided ‘best practice’ advice to our customers and partners covering Auto Dish and Glass Washing. All five articles are reproduced here in a free to download e-book.

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Page 1: Auto Dish & Glass Washing eBook

4/11/2014

Auto Dish & Glass Washing Reprint of our 5 part series from the Arpal Group Blog. All comments and feedback welcome. Contact Us

www.thearpalgroupblog.com

Page 2: Auto Dish & Glass Washing eBook

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INTRODUCTION

Efficient and effective dish and glass washing is critical to many of our customers. Professional cleaning chemical suppliers play an important role in ensuring that the wash process results in hygienically clean and dry crockery, cutlery and glassware delivered in a prompt, reliable, efficient and professional way.

In a series of five articles published on the Arpal Group blog between September and October 2014, we provided ‘best practice’ advice to our customers and partners covering Auto Dish and Glass Washing. All five articles are reproduced here in a free to download e-book.

We hope that our customers, distributors and end-users will find the advice provided to be very useful in ensuring that proper dish and glass washing procedures are followed.

Please do not hesitate to Contact Us immediately if you require further clarification on any of the points raised in the series of articles. We will be only too happy to share our experience and expertise in this area.

Arpal Group www.thearpalgroupblog.com

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Auto Dish & Glass Washing

Introduction

1. Introduction

2. Machine Types

3. Temperature & Water Conditions

4. Top 10 Best Practises

5. Chemicals & Dosing

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1. Introduction

The first reliable hand-powered dishwasher was invented in 1887 by Josephine

Cochrane (US) and unveiled at the 1893 Chicago World’s Fair.

The Cochrane’s had a busy social life, and in 1870 when they moved into a large home,

ideal for entertaining, they regularly entertained guests using heirloom fine china.

After one event, when servants carelessly chipped some delicate dishes whilst washing

up, Mrs. Cochrane was furious and refused to allow the servants to handle the china

again.

The result was that, after every subsequent dinner party, she begrudgingly endured

dishpan hands wondering why someone had not invented a machine that could clean

dirty dishes, when machines had already been invented to sew clothes and cut grass.

Consumed by the challenge of inventing an automatic dish washer, she developed the

idea of securing the dishes in a rack whilst applying high pressure water to clean them.

Her husband William Cochran, who was a rising star in the Democratic Party, died in

1883 leaving a significant amount of debt, so the development of the dishwasher

escalated from a project of convenience to a project for survival. Her first creation had

wire compartments for plates, cups and saucers which were put inside a wheel that

lay flat inside a copper boiler. A motor turned the wheel, pumping hot soapy water

from the bottom of the boiler over the dishes, but it didn’t really work too well, so she

got help with the design from mechanic George Butters, and the first patent on the

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refined design of the Garis-Cochran Dish-Washing Machine was issued on 28th

December, 1886.

It was much later, in 1924, when William Howard Livens (UK) invented a small

dishwasher that was actually suitable for domestic use. This was the first modern

dishwasher, and incorporated most of the design elements that feature in the models

of today – a front door for loading, a wire rack to hold the dirty crockery and a rotating

sprayer. Drying elements were added to his design in 1940. It was the first machine

suitable for domestic use, and it came at a time when permanent plumbing and

running water was becoming increasingly common in residential properties.

Although there have been many improvements in design and components over the

years, the basic functions of a dishwasher are essentially the same as before. A dish or

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glass washer is simply a machine designed to clean and disinfect plates, cups, glasses,

cutlery, utensils, and trays by spraying a detergent solution to clean and a rinse

additive to aid drying. By rinsing at high temperature (71*C for 7 seconds), items are

also disinfected, so a commercial ware washing machine is now a time-saving

necessity and valued capital asset for any commercial food and beverage operation. Although large commercial dish washers look daunting and complex, they can be

regarded simply as large stainless steel boxes that can wash and rinse items in water

that is hotter than can be used safely by hand.

When a dish washing machine is first switched on, a solenoid valve (an electrically

operated tap) is opened to allow fresh mains water to flow into the “Wash Tank”

where electric elements heat the water to between 55ºC – 65ºC. As the wash tank is

filling, an initial charge (amount) of chemical detergent is dosed at the appropriate

level. We will look at the subject of chemical dosing in a later post within this series.

The initial charge is the amount of detergent that is added to the water in the wash

tank to achieve a detergent concentration that will clean effectively at optimum levels.

The detergent is dosed by a small electric pump and the amount dosed is programmed

depending on the site water conditions and other factors (see later post on the impacts

of hard water and lime-scale on wash performance). Once the correct amount of water

and detergent is in the tank, and the rack of soiled dishes has been placed into the

machine, the washing process begins.

In the wash process, the hot detergent/water solution is pumped from the wash tank

through washing arms, fitted with spray nozzles, mounted above and below the racks

of dishes. The pressure of the water jets causes the wash arms to rotate and disperse

the spray on to the items being cleaned. In a well-maintained machine, the pressure

of the spray is high and the mechanical action of the water striking the soiled surfaces,

combined with the chemical action from the detergent, allows effective cleaning. The

soiling is either completely emulsified by the hot detergent solution or flushed from

the surfaces to be collected on scrap trays situated within the machine for later

removal.

When the washing stage is complete, the items in the dishwasher are rinsed with

clean, hot water. During the rinse cycle a specialised chemical called a rinse aid is

dosed into a small boiler in the dishwasher that heats the water to 820C – 880C and

the hot solution is sprayed onto the items in the racks to flush away any detergent

residues and to assist streak free drying.

The chemical rinse aid simply speeds up the drying of the items by allowing the hot

water to be shed from the surface efficiently without runs or water marks. In later

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posts we will examine the importance of consistent temperatures and the removal of

lime scale in achieving maximum cleaning results.

Acknowledgements: http://forgottennewsmakers.com/2010/04/20/josephine-

cochrane-1839-1913-invented-the-dishwasher/

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2. Machine Types

Following the brief overview of the origins and history of the dishwasher presented

in Part 1, this post describes the most common types of dish and glass washer

machines available to commercial food and beverage operations. We have posted

some machine manufacturer links at the end of the post. It is important to note that although machinery and chemical companies are closely

linked, they invariably don’t work closely enough together. Problems with wash results

are routinely directed towards the chemical supplier in the first instance because, in

most cases, they will visit the site free of charge, whereas the machinery company will

routinely charge for the visit. R.P. Adam collaborates with all machinery suppliers to

work in the best interests of their mutual clients.

New dish and glass washers can range from £1,000 to £25,000+ so with this significant

capital outlay it makes sense to have a preventative maintenance programme set up

from the outset. Pumps need maintained, peristaltic tubes need changed and heating

elements will degrade and fail over time. Likewise, essential parts such as wash jets,

rinse jets and door seals should be maintained and replaced as required.

Commercial Under-Counter Dish & Glass Washers (Front Loaders)

Also referred to as a front loader type machines, these are perfect for the licensed

trade, small retail catering outlets where space restrictions apply and are commonly

used on hospital wards. They are built to accommodate different interchangeable

plastic racks which come in various sizes and capacities. The relative performance of

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the machine models is normally measured by the number of plates or pint glasses

washed per hour.

Hood Type Dish Washers

The single tank, single cycle pass-through dish washer is one of the most common

machine types used today. They are usually configured as a straight through or corner

style model and fitted with custom stainless steel tabling for sliding the dishwashing

racks directly into and out of the machine.

They use different interchangeable plastic racks and the capacity of the machine is

measured by the number of plates washed per hour. There is often a sink and

overhead pre-spray system fitted alongside these machines to pre-spray loose food

debris prior to entry into the machine.

Conveyor Type Dish Washers (Rack Conveyors)

Also referred to as rack conveyors, they are designed to “pull” the wash racks through

the wash cycle on a chain conveyor. Usually found in larger catering departments such

as university refectories, large cafeterias and hospital main catering departments

serving between 250 to 1500 meals during peak hours per day. Although the washing

capacity depends upon the length of the machine, they usually wash up to 400 racks

per hour.

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Flight Type Dish Washers

Also referred to as “rack-less”, “belt conveyor” or “tunnel” machines, they do not use

wash racks because the wash items are placed directly onto the conveyor belt. Most

flight type dish washers are individually designed and custom-built for the

requirements of each operation and are commonly found in mass catering/banqueting

areas, airline catering operations and large hospital main catering departments. The

largest machines are capable of washing tens of thousands of dishes per hour.

Pot & Pan Washers

Pot and pan washers utilise much higher water pressure and longer wash cycle times

to remove baked-on food from large pots, pans, baking sheets and food preparation

vessels. These are found in food processing factories like commercial bakeries and

airline catering operations where there is a requirement for industrial scale cleaning

of larger heavily soiled items.

Although not an exhaustive list the following machine manufacturers’ provide good

quality equipment for all types of operations:

Hobart (http://www.hobartuk.com/warewashing)

Meiko (http://www.meiko-uk.co.uk/products/warewashing/)

Winterhalter (http://www.winterhalter.co.uk/)

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3. Temperature & Water Conditions

In this post we look at two critical factors that affect wash performance in any dish or

glass washer operation – maintaining correct wash and rinse temperatures and

knowing the hardness of the water coming into the machine.

Maintaining the correct temperatures is critical in achieving clean dishes or glasses.

Optimum WASH temperature: Failure to achieve the correct wash temperature

will lead to poor cleaning performance, poor removal of protein residues and

possible foaming on an industrial scale!

Optimum RINSE temperature: Failure to maintain the correct rinse temperature

will result in wet crockery and cutlery, streaking and spotting.

For Commercial Dish Washers:

Pre-Wash Tank: 50-55°C

Main-Wash Tank: 60-65°C

Rinse Boiler Tank: 82-88°C

Final Rinse: 88-90°C

For Commercial Glass Washers:

Main-Wash Tank: 50-60°C

Rinse Boiler Tank: 82-88°C

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It is critical that these temperature thresholds are adhered to. A reputable chemical

company offering regular field service visits will record the wash and rinse

temperatures and notify the customer if the temperatures are incorrect. The chemical

supplier has no authority to tamper with the dish washer itself, so it is important that

the machine manufacturer is contacted to rectify below par temperature settings and

delivery.

Operators should be aware that every item that enters into a dish or glass washer is

colder than the wash water in the tank, therefore the temperature of the wash water

will drop slightly after each cycle. If the machine is used continuously without a

recovery period to allow the water to be re-heated, cleaning performance is likely to

become progressively worse.

Note: Some machines have dedicated wash programmes (like laundry machines) that

wash at either lower or higher temperatures than those stated above because of

specific requirements – for example, there may be a dedicated washing programme

for polycarbonate glass.

Combatting the Effects of Lime-Scale

If you live in a hard water area (please see the hard water maps of the UK and UAE

below) and look inside your kettle, you will notice a tough, stony, off-white crust

inside, particularly surrounding the heating element. This is lime-scale, a mineral

deposit left behind when hard water is heated or boiled.

Rainwater is naturally ‘soft’, containing few impurities and if it runs over/through less

permeable rocks like granite or slate, it remains as such. However if rain water runs

through soft, spongy rocks, like lime stone or chalk, it absorbs minerals from them.

These dissolved minerals, often calcium or magnesium carbonate, are what makes the

water “hard”. Where acid rain precipitates, especially over metropolitan and industrial

areas, this process is speeded up considerably.

Quite simply it is more difficult to wash in hard water. If you have tried to use soap or

shampoo in central London, for example, you may have noticed that the soap does not

lather readily and you may have to use more to get the desired effect. In the same

way, if the chemicals used are not the right formulations for the water quality, they

will be less effective and more will be required.

Some of the minerals found in hard water possess a chemical property called “inverse

solubility”, meaning that they dissolve more easily in cold water than in hot. So as the

temperature increases, the dissolved salts start toun-dissolve and deposit on surfaces.

This is why you normally see the heaviest deposits around the heating element, the

hottest part, in a domestic kettle (or dish washer).

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In commercial dish and glass washing, a bigger problem arises if the untreated hard

water is heated above 55°C or left to stand. The dissolved minerals within the water

will dry out and solidify onto wash jets and metals surfaces as the water evaporates.

This solidified mineral coating is lime-scale and is the cause of many problems in both

domestic and commercial premises.

On an industrial level, the presence of lime-scale makes the machines less energy-

efficient. According to British Water, a 1.6mm coating of lime scale on a heating

element can make it up to 12% less effective.

Imagine the impact on a multiple-chain of restaurants, hotels or bars, whose estate is

primarily located in hard water areas, incurring a 12% increase in energy costs because

of poor machine maintenance/failure to combat lime-scale?

Softening Water Reduces the Negative Impacts of Lime-Scale

Water softening is the most common method of treating hard water. It works by a

fairly simple chemical process – swapping the calcium which forms lime-scale for

sodium, which is more likely to stay dissolved. In simple terms this is how a commercial

water softener works:

1. As water enters the system it passes through an ion exchange column filled with

thousands of tiny beads of resin.

2. This resin has charged sodium attached to its surface and it swaps this for the

more reactive calcium and magnesium as water flows over it.

3. The resin can continue to do this indefinitely as long as it is washed through with

salt water every so often to wash off the calcium and magnesium and replace

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the sodium. Most modern columns will automatically rinse themselves if

regularly provided with salt.

Most dish washers have either a built-in softener or a separate water softening

dispenser which removes hardness from water and prevents the formation of a white

film on glassware or crockery. It is vital that staff are aware of the importance of this

piece of equipment and know how to replenish the softener.

To find out whether your business premises are in a hard water area, please see the

maps below:

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If there is a lime-scale build-up within your dish or glass washer, this can be removed

by using an acidic liquid descaler as follows:

(http://www.rpadam.co.uk/products/product-items/descaler-2x5lt/)

1. Switch off the electronic wall mounted dosing equipment (if applicable).

2. Dilute the descaler with up to 20 parts water depending on the degree of scale

build up and add directly into the wash tank.

3. For best results, heat up the water to working temperature and circulate until

all scale is removed.

4. Drain solution, refill and rinse thoroughly with clean water.

5. Drain again and refill with clean water.

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4. Top 10 Best Practises

Many of the negative impacts affecting dish and glass washing results can easily be

overcome by adhering to some very basic rules like thorough pre-scrapping, pre-

rinsing (above photo) and effective racking and stacking. Here are some key issues to

address:

1. Scrape all food debris from plates and ensure all heavily soiled items are pre-

rinsed prior to entering the machine. Always remove solid debris like cocktail

sticks, fruit peel, pips, paper etc. from glasses and plates. They can block the

wash jets and impair performance.

2. Rack items of the same size together so none are hidden from wash jets. Fill the

racks evenly but not too tightly making sure items are well-spaced so that the

wash solution gets an even coverage.

3. When loading glassware always ensure that the baskets are filled to capacity to

minimise breakages and place cups and glasses upside down to allow the wash

water to spray in from below. Always stand glasses on drip mats to dry.

4. Allow crockery to air dry – never use a tea towel as it can harbour bacteria and

may contaminate the items which have already been thermally disinfected.

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5. Always mix different types of cutlery in baskets to avoid items sticking together

and ensure that they are stacked in baskets with the handles down – eating end

up.

6. All pots and pans and larger utensils should be washed by hand unless there is

a dedicated pan washer for larger items.

7. Remember to “dump” the wash water after each session and refill with fresh

water, otherwise the machine will be re-circulating dirty water.

8. Ensure that the filter trays within the machine are checked and cleaned so that

larger items of debris do not re-circulate and impede the wash performance.

9. Ensure that the machine wash and rinse jets are cleaned on a weekly basis and

are free of food debris, broken glass and lime-scale. If these jets are blocked the

wash water will not make effective contact with the items to be washed.

10. In hard water areas where lime-scale is a problem, ensure that the machine is

descaled once a week with a liquid phosphoric acid descaler. Lime-scale build

up will significantly reduce the efficiency of the machine and will consume far

more energy than normally required.

The dish and glass washer needs cleaned like any other piece of catering equipment

or surface, so ensure you clean thoroughly the inside of the machine after each

session:

1. Shut off machine at the mains supply and not just on the machine.

2. Open the drain plugs to empty the machine completely.

3. Remove the curtains and clean with a degreaser/sanitiser.

4. Remove both wash and rinse arms and clean out all debris.

5. Remove scrap trays and clean out all debris.

6. Thoroughly clean out the inside of the machine with a degreaser/sanitiser and

rinse thoroughly.

7. Replace scrap trays, wash and rinse arms and curtains.

8. Shut doors and switch on and allow machine to heat up to correct working

temperature.

9. Machine is now ready to operate.

10. Ensure no broken parts (like missing wash & rinse jets for example).

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5. Chemicals & Dosing

In this post we look at chemicals and chemical dosing. For best results, commercial

dish washers are normally fitted with electronic dosing pumps to dispense the

chemicals. Electronic chemical dosing pumps are programmed to allow dish washer

detergent and rinse additive to be metered precisely and consistently into the correct

wash cycle.

There are two methods of pumping detergent and rinse aid into a dish or glass washer:

1. Via pumps located within the design of the washing machine itself – this is called

“integral feed” and these are usually found on smaller capacity machines like

cabinet glass washers. The pumps are pre-set by the machine manufacturer to

try to accommodate most liquid chemicals available on the market. This often

means that the pumps dose more chemical than required for optimum cleaning.

The chemical manufacturer therefore only supplies the chemical and has no real

input into dose levels.

2. Via external dosing pumps which are usually provided Free-On-Loan by a

reputable chemical manufacturer who will fit the dosing unit and set the dose

rates for their specific chemicals and tailored to site requirements.

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There are different types of electronic dosing systems available but most chemical

suppliers use timed (or cyclic) dosing to get their products into the wash tanks in a

controlled manner. Calculated chemical dose levels are pre-set by the chemical

manufacturer to ensure the optimum concentration of chemical is used in each wash

cycle, taking into account the amount of water in the wash tank and the volume of

water added in the rinse cycle. The pumps are then calibrated and dose levels are

programmed into the memory of the dosing unit to ensure that the correct amount of

chemical detergent and rinse aid is added every time.

In future posts we will examine the pros and cons of timed dosing versus probe based

dosing. In simple terms this type of dosing is based on the premise that a probe

(located in the wash tank) detects the concentration of chemical available. If the

concentration is too low, it “asks for more” and the pumps dose additional detergent

to the required level. If the probe’s detection sensitivity is compromised (by being

scaled up or enveloped in debris) it will falsely ask for more detergent when it is not

required, meaning the machine asks for more than is required.

Although not an exhaustive list the following dosing unit manufacturers provide good

quality equipment for all types of operations:

Brightwell Dispensers (http://www.brightwell.co.uk/dishwash)

Dema (http://www.demaeng.com/kitchen-food-service/warewashing-

dishwashing/)

Knight (http://www.knightequip.com/kitchen.html)

Seko (http://www.sekousa.com/category.php?c=Warewashing)

It is also worth considering setting up a preventative maintenance schedule with your

chemical supplier, who will check, service and maintain chemical dosing units on a

regular basis. A reputable chemical manufacturer will have an experienced team of

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service personnel who will routinely change pump heads and peristaltic tubing to

ensure consistent dosing and will have access to qualified electrical engineers to fit

and repair sophisticated dosing equipment.

The supplier should regularly conduct titration tests of the wash tank solution to

ensure the correct chemical concentration levels are being maintained. They should

also conduct temperature tests so that clients have hygienically clean and dry

crockery, cutlery and glassware.

Wasted time is wasted money; therefore a prompt, reliable, efficient and professional

engineering function from your chemical supplier is essential to maintain the

operational efficiency of a commercial dishwashing operation. Customers need to

know that if a breakdown is reported it is dealt with in a prompt and efficient manner

to ensure as little downtime as possible for the operator.

For further information on the types of chemicals available for automatic dish and

glass washing click here (http://www.rpadam.co.uk/products/dish-glass-washing/)

Both RP Adam and Arpal Gulf (following the completion of a new account installation)

operate systems whereby a schedule of on-going service calls is automatically

generated, thus offering customers unrivalled engineering support. Our technicians’

vehicles are well stocked with a wide variety of equipment, spares and tools, ensuring

that work can be completed at the first visit. Our objective is always the same –

complete the work first time, every time.

It should be noted that the automatic dish, glass and pot wash detergents that are

automatically dosed into machines are almost all corrosive to the eyes and skin, so

great care should be taken when handling these types of products and the appropriate

eye and skin protection used. Please see our recent Golden Rules of COSHH post

(http://www.thearpalgroupblog.com/chemicals-in-tea/)

As safety is our primary focus at all times, we will shortly be unveiling a brand new

“Ultra-Safe” liquid dish and glass washing system…watch this space.