ABB C360 Product Application Manual

Retort Control in the Food Industry

using the C360

Product Application Guide

AG/RCP–007_2

Fig. 1 Horizontal and Vertical Retorts

1.623

108

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11

.35

C360

Multi-Recipe

Profile Controller

11

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Steam

Steam

C360

Multi-Recipe

Profile Controller

C360

Multi-Recipe

Profile Controller

C360

Multi-Recipe

Profile Controller

Current to
Pressure
Converter

Current to
Pressure
Converter

Current to
Pressure
Converter

Retransmission
Output to
Recorder

Retransmission
Output to
Recorder

Retort Control in the Food Industry using the C360

AG/RCP-007_2

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Why Use the C360?

The C360 ensures high quality retorting and increases productivity. Features making it
ideal for retorts include:

▲

Automatic temperature control for increased production and operational efficiency.

▲

Up to twenty set point profiles, including guaranteed ramp and soak with individual
hysteresis for precise temperature profiles and improved product quality.

▲

Dedicated front panel for Ramp/Soak profile applications.

▲

Retransmission facility for recording purposes as standard.

▲

Fully programmable using PC Configuration software.

▲

Status indicators, a deviation bargraph and three displays showing process
variable, set point and output/segment/program all improve operator efficiency.

▲

Fast startup with self-seeking set point.

▲

Direct-connected RTD and/or thermocouple inputs reduce installation costs.

▲

Easy-clean NEMA4X/IP66 front face.

▲

Front panel profile control keys can be locked out for additional process
security.

Features and Benefits

Comprehensive Ramp/Soak Display

▲

The large, easy-to-read front panel displays of the C360 allow the operator to see
displayed information from a distance. This information includes process variable
in the upper display (red LEDs) and control set point (green LED’s) in the center
display. The lower, multifunctional display provides the following information:
program number and segment running, time remaining in the current segment
and output in %.

▲

The controller also includes status indicators; secret-til-lit LEDs showing the
type of segment being run (ramp-up, hold, ramp-down). Also featured is a
multi-color deviation bar graph which provides the operator with an immediate
representation of the deviation between process value and set point.

PC Configurable

▲

The PC Configuration Editor software (C100/0700) allows very quick and easy
setup of the

C360. Complete configurations can be stored on floppy disk allowing

an unlimited number of different cook cycles to be stored and downloaded when
needed.

▲

Reports can be printed of the controller's configuration for historical records.

Direct Connecting I/O Reduces Installation Costs

▲

With the C360, RTD or thermocouple inputs are connected directly to the
instrument. Linearization and ranging are automatic. This not only simplifies
installation, it also reduces installation costs by eliminating the need for special
termination panels or conversion equipment.

Retort Control in the Food Industry using the C360

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Fig. 2 Loading a Vertical Retort

The Application

Much of the food consumed each year is preserved by packaging it in hermetically­sealed containers in a process known as canning.

One of the most important steps in the canning of foods is 'thermal processing', more
commonly referred to as the retorting operation. In this operation, strict specifications,
concerning both time and temperature, must be adhered to and repeated, batch after
batch, to obtain sterile product and uniform quality.

Processing is done in batches using a cylindrical, pressurized vessel called a retort.
Retorts are classified as either vertical or horizontal, depending on the position of
its long axis. A vertical retort is loaded from the top whereas a horizontal retort is
loaded from one end.

In either retort type, the canned product is cooked by one of two processes:

▲

Steam cooking for product stored in metal containers

▲

Water cooking for product stored in glass jars

Steam cooking is done in a steam atmosphere devoid of air and water cooking is
done in steam heated water.

A

1

A

2

L

R

S

T

M

108

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108

.6

C360

Multi-Recipe

Profile Controller

Current to
Pressure
Converter

Retransmission
Output to
Recorder

Retort Control in the Food Industry using the C360

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C100

Pressure Controller

Steam

Pressure Relief
Control Valv e

C360

Temperature Controller

The Retorting
Process –
Steam Cooking

The cooking sequence is similar in both vertical and horizontal retorts:

• Load retort with canned product

• Lock cover or door

• Vent the retort

• Raise to cooking temperature

• Cook product for a predetermined period of time

• Either cool with water under pressure (normally used for large cans)
or pressure relieve (normally used for small cans)

• Water cool at atmospheric pressure

• Unload retort

Loading, locking the cover or door and unloading are strictly manual functions.

▲

Venting Period

Venting the retort is the first step in the cooking cycle and takes place after the door, or
cover, is screwed down tightly on the loaded retort. Its purpose is to eliminate the air in
the retort. Steam is used to purge the air from the retort in order to obtain a steam-only
atmosphere. It is important to get the air out of the retort before the cooking period
starts because air, due to poor heat conductivity, acts as an insulator preventing the
canned product from being adequately cooked. Proper venting is achieved by purging

for a preset time period and to a desired temperature – there are no shortcuts.

▲

Raise-to-Cook Temperature Period

This period occurs after the completed vent period and is the interim period from the
vent temperature to cook temperature.

Fig. 3 Loading a Horizontal Retort

Retort Control in the Food Industry using the C360

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▲

The Cook Period

This period is essential in order to cook the product thoroughly, thereby destroying any
organisms that could later spoil it. These organisms, called spores, are able to withstand
several hours of atmospheric boiling water temperature, but are destroyed in a short

time at a temperature of 116 to 121°C (240 to 250°F).

The correct temperature and the duration of the cook period are equally important in
achieving the desired objectives. Overcooking not only increases costs, it also causes
loss of taste or appearance of the finished product.

Fig. 4 Sparge Tubes

▲

Pressure Relief Period

The retort pressure, attained as a result of cooking at high temperature in a closed
vessel, must be relieved before the product can be removed safely. If the retort has
been filled with small cans, the pressure can be reduced to atmospheric immediately
in a process known as blowdown.

However, if the retort contains large cans, it is necessary to lower their internal
pressure before blowdown takes place to prevent them from exploding or distorting.
The reduction of internal can pressure is obtained by circulating cooling water through
the retort whilst maintaining retort pressure at the value attained during cooking by
introducing pressurizing air. When can internal pressure has dropped to a safe
value, indicated by the temperature of the cooling water leaving the retort dropping
to a desired value, blowdown can take place without the threat of can damage.

▲

Water Cooling Period

In order to increase retort production, small cans are removed from the retort immediately
after blowdown and immersed in a cooling canal prior to labeling. Larger cans, after
cooling in the retort, may require further cooling in the same manner. The determining
factor is the temperature of the product at the time it is packed in cases. This temperature
is critical because cans that are too cool may rust externally, while those that are too
warm prior to being cased and closely stacked in storage will cool too slowly and be
damaged by 'stack burn', or spoiled by creating conditions that encourage the growth
of thermophile bacteria.

The cooling canal is a rectangular-shaped, cold-water filled channel near the retort
through which the can-filled baskets are pulled after they are unloaded from the
retort. The length of the canal, the temperature of the water and the speed of the
conveyor determines the final can temperature. When a cooling canal is used instead
of the retort for final cooling, the reduced retort-time cycle increases production.

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The Retort Process –
Water Cooking

Product in glass jars is processed in a water-filled retort that is heated with steam. The
topmost jars must be covered by 100 to 150mm (4 to 6in.) of water throughout the
cycle and the water must be agitated to provide uniform cooking. Good agitation of the
heated water is attained by introducing air into the steam supply line to create a bubbling
action.

To ensure that the jar lids remain tightly sealed, the retort pressure is maintained slightly
higher than internal jar pressure. Pressurizing the retort also means that cooking

temperatures in excess of 100°C (212°F) can be achieved.

Cooling Water

Manual By-pass
Hand Valv e

108

.6

C360

Multi-Recipe

Profile Controller

Fig. 5 Ancilliary Control Capability

Retort Control in the Food Industry using the C360

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Preheat Period

During the first cycle, the vertical retort is filled with water prior to loading the jars. On
subsequent cycles, the water used to cool down the last batch remains in the retort.
The temperature of this water is too low for the next batch of hot-product filled jars –

glass cannot withstand a thermal shock of more than 28°C (50°F).

The water must therefore be heated with steam to a predetermined temperature before
the jars are immersed. This operation is called preheat. The preheat water temperature

must not be more than 8°C (15°F) above product temperature to avoid raising the

internal jar pressure which would cause the jar lids to open.

Preheating in a horizontal retort is not possible because the jars must be loaded and
the door closed before water can be added. The water used to fill the retort must be
preheated externally.

Raise to Cook Temperature Period

The period in which the water is heated from initial temperature to cook temperature is
referred to as the 'raise to cook' period and should be kept to a minimum to prevent
overcooking.

The Cook Period

Both temperature and time are critical for the same reasons as outlined in steam cook.

The Pressure Cool Period

The internal jar pressure must be lowered sufficiently to prevent it from forcing the jar
lids open after cooking. To do this, retort pressure is maintained above jar internal
pressure as cooling water is circulated through the retort to cool the product and
reduce the pressure in the jar. Temperature reduction is done quickly to stop the
cooking of the product.

Pressure Relief Period

After the jars have been cooled sufficiently, the retort pressure may be reduced to
atmospheric (blown down) without danger to the containers.

Atmospheric Cooling Period

After blowdown, and with the retort cover or door open, cooling water can be circulated
through the retort in order to continue the product cooling process. Alternatively, the
jars can be removed and submerged in a cooling canal before labeling.

AG/RCP–007 Issue 2

ABB Limited

Howard Road, St Neots
Cambridgeshire
PE19 8EU
UK
Tel: [phone]
Fax: [phone]

ABB Inc.

125 E. County Line Road
Warminster
PA 18974
USA
Tel: [phone]
Fax: [phone]

ABB has Sales & Customer Support
expertise in over 100 countries worldwide

www.abb.com

The Company’s policy is one of continuous product
improvement and the right is reserved to modify the

information contained herein without notice.

Printed in UK (12.03)

© ABB 2003