Case Study - Potato Supply & Process

Improvements (2010) Client confidentiality precludes naming the client, but the contents are from a real project. This case provides an integrated view of the potato supply chain ……. from the growers through the production process ……

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Background to the Business The ‘potato line’ is part of a wider fresh produce growing business

based across the UK The product range includes:

Freshly prepared salads

Freshly prepared vegetable ingredients.

All produce is either Global GAP or Red Tractor approved as a minimum with organic products approved by the Soil Association

The business has transformed from a traditional grower and packer to one of the leading salad processers in the UK, supplying prestigious names in convenience retail, food service, and food manufacturing

The business has continually improved since 2010 when this project was initiated.

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The Challenges Facing Potato Line (in 2010) A yield variance of between

45%-65% and an operational target yield of 65%. From observing the process, from raw materials inwards to finished products at dispatch, there is a potential overall yield saving of 25% (see breakdown)

On the assumption that there is a £50k profitability saving for every 1% yield loss recouped, the potential saving could be as significant as £1.25m.

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Losses The most significant losses occur

on the dicing line:

Machine downtime of 240 minutes per 12 hour shift

Material loss of 200kg at each changeover (3,600kg per 12 hr shift)

Resource consumed in planning and changeover.

Whilst the dicer is not a bottleneck in the process, it requires significant planning and resourcing to effect changeover.

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Value

Based upon an initial two day investigation of the potato line - from incoming potatoes to packed product ready for despatch - and based on data previously provided, yield losses of between 35-55% were identified

A potential improvement in yield of up to 25% was estimated This potential improvement in yield could result in a 20-28% ‘future

state’ yield loss If the future state average was 24%, this would represent a 21% yield

improvement from the average ‘current state’, which would equate to a £1.05m improvement. This would turn around a £0.5m negative against budget to a £0.55m positive against budget

The reduction in downtime and lost output incurred on the dicing line of 50% equates to a 21% improvement in overall output.

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Supply of Potatoes

4-5 different suppliers and in turn by a number of different growers

Purchased ungraded ranging from 45mm to 150mm.

Supplied by box (10%) or bulk load (90%).

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Grading Completed on site, on arrival 3 types; < 45mm, 45-65mm,

65+mm No inspection process for damaged

stock Damages can vary dependant on

seasonal fluctuations There are no mechanisms on the

grading operation to remove soil and stones

Potatoes can be subject to bruising at the grading process, which will result in yield losses

The grading machine is located outside and grading cannot be done if temperature is too low or in poor weather conditions (the grader will be brought inside in these cases)

In some instances, potatoes are not graded and are used directly on line.

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Sampling A bucket sample of 5-6kg is

taken for each delivery of potatoes

The potatoes are hand-peeled and checked on a quality control attributes check sheet. If the peel test fails a further tonne of the delivery is taken for a factory peel test. If this fails to meet the requirements the delivery is rejected

Rejection rates can vary but on average are 2%.

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Storage Conditions are critical; the ideal storage

range is 8-10°C Potatoes exposed to accelerated

increases or decreases in temperature can give rise to quality problems; too cold can cause frost damage and mould, too hot causes bruising

Supply of potatoes is subject to seasonal conditions and this can affect the length of time that potatoes are stored. There are two distinct time periods:

From July to October potatoes are stored at the supplier for a maximum of one week

From November to June potatoes are kept in cold store at the supplier for up to nine months. Prolonged storage causes dehydration. Potatoes require acclimatisation after cold storage and rapid changes in temperature will lead to problems.

Typically potatoes are stored on site for two or three days in a refrigerated warehouse.

They can be used as soon as they are delivered and can be kept in store for a maximum of two weeks.

FIFO is operated by the FLT drivers to ensure oldest stock is used up first

The ideal storage temperature is 8°C. The temperature in the potato storage area was measured at 7.3°C.

The store next door used for onion storage is controlled at 3°C, however the door is not always kept closed

Observed potatoes being stored outside ready for taking to the line, as the storage area does not facilitate use of FIFO. The outside temperature can vary throughout the year -3°C to 30°C

FIFO – First In First Out; FLT – Fork Lift Truck

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De-stoning and Washing Potatoes are loaded onto the box

tipper by FLT

The box tipper inverts the potatoes into the bulk hopper

Potatoes are fed along a conveyor (the feed rate is determined by a sensor) to two de-stoners and a washing process to remove stones and soil

The potatoes are fed through a spiral conveyor.

(NB – In 2015 - De-stoning often takes place at the harvesting point earlier in the process).

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Peeling

The potatoes then enter a four step peeling process

Each peeler is set to vibrate for a pre-set time

Abrasive peeler settings (see Table)

These settings are in the heads of the Team Leaders and not clearly defined or written down

The settings used are not recorded in any product data records.

Good quality

Medium quality

Poor quality

1 22s 27s 28s

2 20s 25s 26s

3 18s 23s 24s

4 18s 23s 24s

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Steam Peeling Potatoes are diverted at the

washing step/de-stoner into an in-feed scroll that transports along to a steam peeler.

The steam peeler can be loaded with 60 kg of potatoes per load; the steam peeler is a five step process that can be split into time intervals (see Table)

Only the product unloading time can be altered. This is the time it takes for the steam vessel to return to its position ready for reloading having unloaded the potatoes.

Loading Time 5 seconds

Peeling Time 2 seconds

Resting Time 2 seconds

Unloading Time 5 seconds

Product Unloading time 15 seconds

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Speed Settings for Peelers The settings for both peeling processes

can vary. In general they are set at:

Steam Peeling 13 seconds

Abrasive Peeling 22-24 seconds One of the constraints on steam peeling

is that large Piper potatoes jam in the in-feed scroll if the speed is too fast

Outputs can vary between steam and abrasive peeling.

Large Piper abrasive peeling can achieve output of eight dolavs an hour (2,800 kg per hour)

Steam peeling can produce six dolavs (2,100kg per hour)

These outputs were quoted by the Team Leaders but contradict the outputs stated in the ‘Production Master data’

The peeled potatoes are the transported by a dip elevator to the main line.

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The Main Line The potatoes are fed via a vibro-

feeder and agro-selector onto a sorting table

A camera (Select and Analyse) is on line to:

detect potatoes with blemishes identify the potatoes by size and

separate them onto the sorting conveyor

Yield losses occur at the drop onto the sorting table

The Camera unit is has not worked for eight months.

The non-functional camera means that no potato sorting is taking place and additional labour is required on the line to manually sort.

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Sorting Table

Two or three packers pick potatoes for a specific customer order (i.e. product with no blemishes for Customer ‘A’) and are placed on a separate conveyor

The expected yield when product goes for dicing is greater, due to less inspection at the sorting table.

Lane 1 40-60mm

Lane 2 45-65mm

Lane 3 45mm + mids

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Sorting & Defects/Damage

Badly damaged or blemished potatoes are picked from the sorting table and placed in a dolav for waste.

Badly damaged potatoes can vary in quantity but the quantity is not recorded

Approximately one tonne per day is put down to damage, but this can be more depending on potato supply quality. This damaged product can be claimed back from the supplier.

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The Dicing Line The dicing line runs from 10am

until 10pm Potatoes are fed along the end of

the conveyor and into the cutting machine

Three different machines are used for dicing different specifications of potato:

The flexi-pump The 25 ml dicer The 20 ml dicer

The 25 mm dicer is used on other lines for other products and is not always available when required

This piece of kit does not appear to be factored into the planning process

Dicer Changeover:

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Flexi-Pump Dicer The flexi-pump dicer is capable of

doing a range of different sizes by using different blades

There does not appear to be a standard operating procedure for changeover and there is no visual identification of change parts required.

There are observed yield losses as a result of changeover

There do not appear to be any line clearance procedures

There is little evidence of a quality check following changeover

The hopper that collects diced potatoes is of small surface area, and diced potato impacts hard against the hopper resulting in potential spillage and waste.

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Drop Screw Changeover Every four dolavs (1,600kg) or

approximately every 40 minutes, the drop screw on the dicing line has to be taken out in order to replace the water/preserve solution.

200kg is lost each time there is a change over (3,600kg per 12 hour shift assuming 40 minutes between changeovers)

It takes 20 minutes to carry out a changeover (240 minutes lost time each 12 hr shift)

Losses also occur on the slots of the conveyor where potatoes gets caught

The framework of the elevator causes some loss

There is an amount of give-away on the (10kg) finished bags of diced potato.

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Planning Process The planning process works as follows:

Three weeks of sales data by date are taken by SKU and by volume per line.

An average figure is calculated from the previous three weeks’ volume for that day

This is then adjusted based on local knowledge, forecast promotions, trends and orders coming in early

Materials required are potatoes of different grades, bags (purchased) and labels (produced in-house).

The availability of potatoes is rarely an issue as normally there is one or two days worth of stock in the store.

NB - If production running hours were 3pm until 3am, a production plan could be issued to the line that could reflect the best running order and would not require changes

Planning Issues:•Planning requirements are put on an Excel spreadsheet•The production line loading is based on the KPI information supplied by production i.e. set up times, run rates, labour etc.•95% of potato production is planned to run down the steam peeling process as this gives a better yield output (In reality 90% runs down the abrasive peelers)•The daily production plan is issued at 3.30pm (this is the cut off time for receiving daily orders)•The production plan is ordered in dispatch times and does not reflect the most suitable running order for production to maximise yield, effective use of equipment etc.•The plan is reworked by the production shift manager to accommodate the above and the final running order is dictated by production and issue of production labels•There was little evidence of a production plan on the line•There is no shop floor data capture that helps advise and drive the plan•Production downtime and production output are not accurately recorded on the line•Schedule adherence to the production plan is not measured, but if so would be low due to the constant reworking.

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Production Master Data

Line Number

Machine Capacity per day

Average M/C output

kg/day

Average labour

requiredProcess

Average M/C output

kgs/hr

Average Labour

loading / day / hr

Std Labour loading / day / hr

M/C Capacity hrs/ day

M/C Std breaks hrs

/ day

M/C Std C/Over hrs

/ day

Average C/Over

lost tonnage

4 14.5 35265 4 Potato Abrasive peeling 2432 4.1 58 16 1 0.5 0.69

18 13.5 44550 7 Potato Steam peeling 3300 0.0 95 16 1 1.5 4.95

9 13 35693 5 Potato dicing 2746 47.2 65 16 1 2.0 5.49

3 14.5 19938 2 Potato dipping 1375 16.9 29 16 1 0.5 0.69

19 14.5 1450 2 Potato salad 1/2 100 0.0 29 16 1 0.5 0.05

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Summary Observations & Areas for Improvement (2012) – ‘A general lack of control in all areas’

• Settings for the abrasive peelers are not defined anywhere • There does not appear to be a defined process or maintenance

schedule for the changing of the abrasive rollers• Rollers are changed by maintenance on the request of team

leaders. This can vary from one month to three months• When settings are made there does not appear to be a record of

what those settings were and why • The use of the steam peeling facility is not controlled; there is a

preference to use abrasive cleaning. Steam cleaning was used 10% of the observed time

• There is no visible running order for production• There is little evidence of support functions • There do not appear to be clearly defined quality standards• Longer peeling times may be used to ensure that no customer

complaints occur as a result of blemishes etc.

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Summary Observations & Areas for Improvement (2012) – ‘A general lack of control in all areas’• Additional peeling time is used for poorer quality potatoes

• Poorer quality potatoes tend to be older potatoes• There are no visual standards for the picking operation• Quality control stipulates that steam peeling cannot be used for

some products.• On the grading of incoming potatoes, there is no inspection to

check for damaged potatoes.• Damaged potatoes may be in region of 2% yield loss• On the dicing line, the digital Ph tester was missing and there was

confusion to the frequency of checking and changing the preservative levels in the water

• The quality control records for dicing line preservative water were filled out, but the test carried out was using the Ph paper.

• The water temperature used for the washing process is cold. This is used for a whole 12 hour shift and changed at the end of the shift by the hygiene team. Does performance improve or decline as the water gets older?

• A production meeting is held on a daily basis involving Team Leaders, technical and engineering.