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Direct Gas Fired Ovens

 

How to build a biscuit oven

Front Cover new

Publishing date to be announced

Description

The book enables a small team to build high quality Direct Gas Fired ovens. The Baker Pacific team of five engineers have manufactured a range of ovens for biscuits, crackers, cookies and cake with local contractors in China, India and Indonesia. Our experience, technical information and drawings are now available for companies who wish to build Direct Gas Fired biscuit ovens.

Our book describes the complete oven building process with photos, assembly drawings and parts lists, together with descriptions of the work in 15 stages.

In addition Baker Pacific can supply a complete set of manufacturing drawings together with all detail technical information and support.

This will allow small teams in biscuit bakeries and contract engineering companies to build ovens locally. The ovens can be built in a low cost environment with minimum shipping cost and requirement for hard currency.

Key features

  • Description of each stage of building and installing the oven with photos
  • All main assembly/layout drawings
  • All parts lists
  • Key component specifications and suppliers
  • Detail oven specifications

Readership

Senior management staff and engineers in contract engineering companies, biscuit manufacturers and companies supplying production and baking equipment in the food industry world – wide.

Author                                                                  

Iain DavidsonPhoto - Iain 1

Iain graduated from the School of Industrial Design (Engineering) at Royal College of Art in London in 1965 and joined Baker
Perkins Ltd. He was Industrial Design Engineer, working in the Technical Department on the design of new biscuit and bakery processing machines until 1975, gaining a thorough technical knowledge of the machines and processes.

In 1975, Iain was appointed Market Development Manager at Baker Perkins, involved in developing the Baker Perkins forward planning for new business, product development and acquisitions. In 1979 Iain became International Sales Manager with responsibility for the business in Asia and Africa.

In 1990 Iain was appointed Regional Manager Asia Pacific for Baker Perkins and re-located to Indonesia and later in 1997 to China. His appointments included Managing Director of Baker Perkins (Hong Kong) Ltd. and Director of Baker Perkins Japan KK.

Iain established a successful manufacturing facility for biscuit ovens in Dalian, China in 1990 for Baker Perkins and subsequently continued a manufacturing capability for Baker Pacific Ltd. in China, India and Indonesia.

Baker Pacific companies

Iain established PT Baker Pacific Mandiri in Indonesia in 2000. As the business outside Indonesia grew, Baker Pacific Ltd was established in Hong Kong in 2004 and is now our principal operating company, providing process technology and machinery for the biscuit, chocolate and candy industries.

Experience in the biscuit industry

  • Engineering design of biscuit process machines including a range of baking ovens
  • Biscuit baking oven manufacture in China, Indonesia and India
  • Sales and marketing in Europe, Asia, North America, Africa
  • Project management and service

 

Price for additional drawings on application to Baker Pacific Ltd.

To order or for more information:

Contact Baker Pacific Ltd. at our Contact Page or by email to: bakerman@bakerpacific.com.hk

Table of Contents

1. Why build a biscuit oven?                                Page 1

1.1 Growing world-wide market for biscuits

1.2 Limited number of suppliers

1.3 Biscuit oven manufacture

1.4 Biscuit baking process

1.5 What is required?

2. What type of oven?                                                      7

3. Heat transfer and heat ratings                              10

3.1 Heat transfer

3.2 Radiation

3.3 Conduction

3.4 Convection

3.5 Oven designs

3.6 Heat rating

3.6.1 Crackers

3.6.2 Short doughs

3.7 Multi-purpose ovens

4. Direct Gas Fired Oven specifications                 18

4.1 Oven output

4.2 Calculation of oven zone lengths

4.3 Calculating the number and type of burners

4.4 Recommended burners

4.5 Technical specification for a multi-purpose oven

4.5.1 Oven feed end

4.5.2 Direct Gas Fired Oven 89.9m long, 7 zones

4.5.3 Direct Gas Fired burners and gas system

4.5.4 Automatic temperature control

4.5.5 Oven band

4.5.6 Oven band cleaner

4.5.7 Delivery end section

4.5.8 Emergency drive

4.5.9 Oven end extraction hood

4.5.10 Control panels

4.6 Oven safety systems

4.6.1 Oven band

4.6.2 Ignition

4.6.3 Purge system

4.6.4 Over temperature

4.6.5 Power failure

4.7 Electrical installation

4.8 Components

4.9 Finishes

4.10 Spare parts

5. Selecting the oven conveyor band                    28

5.1 Products

5.1.1 Crackers

5.1.2 Semi-sweet biscuits and short doughs

5.1.3 Cookies

5.2 Open wire mesh bands

5.3 Compound balanced weave belts (heavy mesh)

5.4 Steel bands

6. Purchasing and Shipping                                      33

6.1 Purchasing

6.1.1 Contractors for fabrication

6.1.2 Purchase of specialist components

6.2 Shipping

7. Manufacturing drawings                                    41

7.1 Design layout drawings

7.2 Oven construction

7.2.1 Modular construction and build on site

7.2.2 Manufacture and installation of the oven

7.3 Drawing numbers

7.4 Parts lists

7.5 Electrical drawings

7.6 Control panel fascias

8. Construction of the Direct Gas Fired Oven     52

8.1 Stage 1: Oven base structure

8.2 Stage 3: Baking chamber slides

8.3 Stage 4: Baking chambers

8.4 Stage 5: Crown sheets, explosion panels, extraction

8.4.1 Explosion panels

8.4.2 Extraction ducts

8.5 Stage 6: Frames for outer covers and fan supports

8.6 Stage 7: Clean out and inspection doors, wall sheets

8.6.1 Clean out doors

8.6.2 Inspection doors

8.6.3 Oven insulation

8.7 Stage 8: Extraction fans and dampers

8.8 Stage 9: Air header pipes

8.9 Stage 10: Gas header pipes

8.10 Stage 11: Outer covers for control side

8.10.1 Outer covers

8.11 Stage 12: Gas burners

8.11.1 Eratec MFB burners installation

8.11.2 Burner specification

8.11.3 Flynn burners and gas system

8.12 Stage 13: oven roof sheets

8.13 Stage 14: Outer covers on non-burner side

8.14 Stage 15: Oven extensions

9. Oven conveyor construction: feed/tension end  102

9.1 Oven band circuit

9.2 Conveyor feed / tension end

9.3 Feed end unit: Final assembly

9.4 Oven end drum and shaft assembly

9.5 Drum bearing and mount assembly

9.6 Oven feed end frame assembly

9.7 Pneumatic tension assembly

9.8 Plough assembly

9.9 Drum scraper assembly

9.10 Oven band tracking: band wander warning

9.11 Oven feed/tension end covers

10. Oven conveyor construction: delivery/drive end  125

10.1 Delivery/drive end arrangement

10.2 Drive end frame

10.3 Delivery end drum

10.4 Bearings, sprockets and drive train

10.5 Motor and gearbox

10.6 UPS Uninterruptible Power Supply

10.7 Stripping knife

10.8 Stripping conveyor

10.9 Drum scraper

10.10 Drive end band wander warning

10.11 Delivery end outer covers

10.12 Oven end hood design

10.13 Calculations for oven band drive

10.13.1 Calculation of oven band tension

10.13.2 Calculations of torque required for drive

11. Conveyor construction: oven bands                   159

11.1 Wire mesh bands

11.1.1 Skid bar supports

11.1.2 Return band supports

11.1.3 Wire mesh oven band cleaning

11.1.4 Wire mesh oven band tracking

11.1.5 Joining wire mesh bands

11.2 Compound balanced weave belts (heavy mesh)

11.2.1 Band support rollers

11.2.2 Heavy mesh band tracking

11.3 Steel bands

11.3.1 Steel band supports

11.3.2 Steel band tracking

12. Key Components                                                   180

12.1 Bearings

12.2 Burners

12.3 Clamping elements, chains, sprockets….

12.4 Electrical equipment

12.5 Electrical cable and trunking

12.6 Electric sensor and monitoring equipment

12.7 Fans and blowers

12.8 Gas equipment

12.9 Insulation and seals

12.10 Oven bands

12.11 Pneumatic equipment

12.12 Painting and coatings

12.13 Pressure switches

12.14 PLC equipment

12.15 Motors and gearboxes

12.16 Motors – DC

12.17 Thermocouples

12.18 Temperature controllers

12.19 UPS

13. Oven installation                                                    204

13.1 Factory layout drawings

13.2 Oven installation equipment

13.2.1 List of equipment required for the installation

13.2.2 Centre line

13.3 Oven installation

13.3.1 Installation stages

13.3.2 Stage 1: Oven support structure

13.3.3 Stage 3: Bottom oven sheets and slides

13.4 Stage 4: Baking chambers

13.4.1 Welding of the baking chambers

13.4.2 Installation of oven band supports

13.5 Crown sheets, explosion panels, extraction ducts

13.6 Frames for covers

13.7 Clean out doors, inspection doors

13.8 Extraction fans and dampers

13.9 Air header pipes

13.10 Gas header pipes

13.11 Outer covers, insulation, main air pipe

13.12 Gas burners and equipment

13.13 Roof sheets

13.14 Outer covers

13.15 Electrical installation

13.16 Oven band installation

13.16.1 Oven band tracking

13.16.2 Joining wire mesh oven bands

13.16.3 Joining compound balanced weave bands

13.16 4 Joining steel bands

13.16.5 Oven band cleaner

14. Disclaimer                                                                229

 APPENDIX: Operations and Maintenance Manual

_________________________________________________________________

 For more information:

Contact Baker Pacific Ltd. at our Contact Page or by email to: bakerman@bakerpacific.com.hk

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Biscuit Baking Technology

PUBLISHED BY ACADEMIC PRESS 2016 An imprint of Elsevier

DESCRIPTION

Biscuit Baking Technology, Second Edition, is a reference book for senior managers and staff involved in industrial scale biscuit baking. It covers the biscuit industry process, ingredients, formulations, besides design, manufacture, installation, operation and maintenance of the baking ovens.

Written by an expert on the biscuit baking industry, the book is a complete manual guide that will help engineering, production and purchasing managers and staff in the biscuit industry to make the best decisions on oven efficiency purchasing.

CONTENTS

  1. The Biscuits
  2. Baking process
  3. Biscuit design and output
  4. Heat transfer
  5. Oven designs
  6. Oven specifications: hybrid ovens
  7. Oven construction: Direct Gas Fired Ovens
  8. Oven construction: Indirect Fired Ovens
  9. Heat Recovery System
  10. Oven conveyor bands
  11. Oven conveyor design
  12. Process control systems
  13. Oven safety monitoring and alarm
  14. Oven operation: Direct Gas Fired Oven
  15. Oven operation: Indirect radiant Oven
  16. Oven efficiency
  17. Oven inspection and audit

APPENDICES

  1. Ingredients for biscuits
  2. Maintenance
  3. Combustion data
  4. Oven manufacturers
  5. Oven band manufacturers

 

 

 

For more information contact Baker Pacific at bakerman@bakerpacific.com.hk

 

Burners for infrared baking

BURNERS FOR DIRECT GAS FIRED OVENS

DGF oven burners use a “zero pressure” gas system. The burners ignite and burn a gas/air mixture. The gas is supplied to the gas/air mixer unit at nominally zero pressure. The air is supplied at a positive, controlled pressure. An increase in air pressure increases the flame and the heat input to the baking chamber. The gas may be natural gas, town gas (manufactured from coal), or LPG (liquid petroleum gas).

Gas train

Mains gas is supplied from a factory system to the oven where it is regulated by a “gas train”. This consists of the following equipment:

  • Manual shut off valve
  • Two – automatic shut off valves for safety the system
  • Gas filter
  • Zero pressure gas governor
  • Gas pressure high/low detection
  • Gas pressure gauges (2) at gas inlet and outlet of gas train
  • Gas valve tightness proving facility (to check for a leakage of gas)
  • Main gas pipes and gas distribution system

The gas is fed to header pipes running along each zone of the oven at the top and bottom. The headers are connected to each burner by flexible hoses and via a solenoid valve and gas/air mixer.

 

 

Gas train

Gas train

Combustion air

In each zone the air is fed to the air header pipes from an air blower mounted on top of the oven. The air is drawn from the bakery and is filtered. The air pressure for the burner system is controlled by motorized valves which are regulated by the automatic temperature control system or by a variable speed inverter drive for the fan.

Moro air blower for combustion air

Moro air blower for combustion air

ERATEC MFB BURNERS

FIG_7-1.28

FIG_7-1.29

 Eratec high rate infra-red ribbon burners for Direct Gas Fired Ovens

  • Direct heat transfer by radiation (without contact and air movement)
  • High radiant power density 100 – 1000KW/m2
  • Precise control and power modulation
  • Energy consumption savings compared to conventional Direct Gas Fired Burners (up to 20% saving depending on the oven and number of burners)
  • Low pollution (up to 80% less CO and NOX)
  • Safe for people and equipment (no burn back)
  • Low maintenance

 

Infra-red baking

Baker Pacific Direct Gas Fired oven zones with Eratec MFB burners

www.era-tec.fr

FLYNN BURNER CORPORATION

Flynn pipe gas burner

Flynn pipe gas burner

 

 

Stainless steel corrugated  burner strip

Stainless steel corrugated burner strip

 

Flynn distributor burner for multi-flame control

Flynn distributor burner for multi-flame control

FIG_7-1.26

 

Baker Pacific Direct Gas Fired oven with Flynn burners

Baker Pacific Direct Gas Fired oven with Flynn burners

 

www.flynnburner.com

 

BURNERS FOR INDIRECT FIRED OVENS

Each oven zone has one burner firing into a burner tube connected to a heat exchanger system. The hot air and burnt gas circulates in the heat exchanger and does not enter the baking chamber. Fuel may be gas or diesel oil. Burners may be specifies for either fuel or dual fuel.

MAX WEISHAUPT GMBH

Weishaupt burner on an Indirect Radiant oven

Technical description

The Weishaupt WG burner is a forced draught gas burner. For biscuit oven applications, the burner should always be a fully modulating type. The burner comprises the following features:

Combustion manager

  • Microprocessor control and monitoring of all burner functions
  • LCD display
  • Keypad operation
  • Data bus connection
  • Integrated valve proving of the solenoid valves
  • Flame sensor: Monitors the flame during operation. If a problem occurs, a safety lockout will operate
  • Double solenoid valve
  • Gas pressure governor. Controlled pressure is set by an adjusting screw
  • Air/gas ratio control provides optimization over control range
  • 2 solenoid (Class A) valves
  • Gas filter
  • Low gas pressure switch
  • Gas pressure switch for automatic valve proving
  • Air pressure switch: Loss of combustion air pressure activates a safety shut down
Weishaupt WG burner

Weishaupt WG burner

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Picture courtesy of Max Weishaupt GmbH

 

Weishaupt gas train

Weishaupt gas train

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Specification: Weishaupt burner WG30N/1-C ZM LN

(for 1.25m wide Indirect Radiant Oven) Version: modulating via 3 term switching and Buyer’s PID controller

  • Fuel: natural gas
  • Gas pressure: 30mbar
  • Rating capacity: 40-350kW
  • Electro motor: 1ph, 0.42kW, 230V, 50Hz
  • Combustion manager: Siemens Type W-FM20
  • Flame monitor
  • Continuous running fan
  • Gas valve train size 1”
  • Double Magnetic Valve (DMV)
  • Gas pressure switch
  • Gas pressure regulator assembly with safety valve
  • Gas pressure inlet: (max.) 2.5 bar
  • Gas pressure outlet: 20 mbar
  • Gas filter
  • Gas ball valve

Weishaupt burners- features:

  • The digital combustion management system ensures that only exactly the amount of energy is consumed that is needed at the time.
  • Weishaupt Low NOx technology (standard for gas burners, optional for oil burners) is exemplary in reducing emissions with special mixing assemblies for intensive flue gas recirculation
  • All W range burners work fully automatically. Powerful microprocessors continuously control and monitor the combustion process for maximum efficiency.
  • The transversely mounted fan draws air through a sound attenuated inlet.
  • The W range offers oil and gas burners in five ratings from 12 kW to 570 kW.
  • More than 50 years of experience and development work have gone into Weishaupt burner technology. Only the best materials are used.
Baker Pacific Indirect Radiant oven with Weishaupt burners

Baker Pacific Indirect Radiant oven with Weishaupt burners

www.weishaupt.co.uk      www.weishaupt.de

 

MAXON BURNERS

FIG_7-2.25

 

Maxon 5155SP dual fuel burner

Maxon 5155SP dual fuel burner

 

 

 

Specification for a 1.2m wide Indirect Radiant oven: Maxon OVENPAK 515 gas/oil burner

  • Maximum heat release: 1,250,000 Btu/hr (366kW)
  • Minimum heat release: 77,000 Btu/hr (22.5kW)
  • Oil pressure required: 60 psig (4.13 bar)
  • Natural gas pressure: 0 bar (to be reduced to 0.005 bar)
  • Compressed air required: 60 psig (4.13 bar)

Each burner is complete with:

  • Pilot adjustable orifice
  • UV sensor device
  • Dual type nozzle for oil/gas operation
  • Integral combustion air blower
  • Servo motor
  • Ignition transformer
  • Air pressure switch

Maxon Gas Trains

  • Gas strainer
  • Gas cock
  • Main gas regulator, size 1 ¼”
  • Pressure gauge for up stream (0-30psig)
  • Pressure gauge for down stream (0-15″ WG)
  • Low pressure switch (.5 – 4″ WG)
  • High pressure switch (5 – 28″ WG)
  • Maxon solenoid valve series 5000
  • Solenoid valve

Pilot gas train

  • Pilot regulator: high pressure regulator
  • Pilot solenoid: general purpose type
  • Pressure switch for pilot
  • Outlet pressure gauge
  • Locking ball valve

Oil pipe train

  • Oil filter, size 3/8″
  • Oil pressure regulator, size 3/8″
  • Low pressure switch
  • High pressure switch
  • Solenoid valve for burner
  • Locking ball valve
  • Fuel: diesel oil

Compressed air train

  • Air filter
  • Air pressure regulator
  • Air pressure switch for low air pressure
  • Solenoid valve for burner

???????????????????????????????

                     Baker Pacific Indirect Radiant oven: 1.2m x 100m with Maxon dual fuel burners and Heat Recovery System

www.maxoncorp.com

 

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Biscuit Baking Technology, 2nd Edition

Biscuit process and engineering manual – now available for Pre-Order at www.store.elsevier.com/9780128042113

For author’s 30% discount use code: ATR30

Cover 281015

 

 

Author: Iain Davidson

Expected release: 01 February 2016

Imprint: Academic Press

Print book ISBN: 9780128042113

Pages: 384

Dimensions: 229 x 152

Print Book: GBP 106.25

Paperback: GBP 125.00

 

 

 

 

 

A manual for designers and operators on the biscuit oven – baking technology

Table of Contents

INTRODUCTION

1 THE BISCUITS

2 BAKING PROCESS

3 BISCUIT DESIGN AND OUTPUT

4 HEAT TRANSFER

5 OVEN DESIGNS

6 OVEN SPECIFICATIONS: hybrid ovens

7-1 CONSTRUCTION: Direct Gas Fired Ovens

7-2 OVEN CONSTRUCTION: Indirect Fired Ovens

7-3 HEAT RECOVERY SYSTEM

8 OVEN CONVEYOR BANDS

9 OVEN CONVEYOR DESIGN

10 PROCESS CONTROL SYSTEMS

11 OVEN SAFETY MONITORING AND ALARM

12-1 OVEN OPERATION: Direct Gas Fired Oven

12-2 OVEN OPERATION: Indirect radiant Oven

13 OVEN EFFICIENCY

14 OVEN INSPECTION AND AUDIT

APPENDIX 1 Ingredients for biscuits

APPENDIX 2 Oven maintenance

APPENDIX 3 Oven manufacturers

APPENDIX 4 Oven band manufacturers

Pre-order at  www.store.elsevier.com/9780128042113 

For 30% author’s discount use code: ATR30

 

Baker Pacific Ltd. 3905 Two Exchange Square, 8 Connaught Place, Hong Kong

Tel. +852 2522 1114       email: bakerman@dircon.co.uk      

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Baking Process and Engineering Manual

A technical manual for senior technicians in the biscuit industry

 

282 pages including over 200 illustrations. Published in hard copy and e copy by Baker Pacific Ltd.

Engineering

  • Baking oven design and manufacture
  • Management of engineering and maintenance
  • Oven up-grades
  • Introduction of heat recovery system
  • Making and procuring spare parts

Production

  • Improved operation and maintenance
  • Oven efficiencies / reduced production cost
  •  Improved reliability / less downtime

Purchasing

  • Smart buying: oven designs, specifications, controls
  • Contracts: performance guarantees
  • Purchasing of spare parts and  components
  • Directory of  suppliers, including Asian manufacturers

A comprehensive manual that supports the principal activities of

purchasing, production and engineering, providing the basis for training

programs for all levels of management and staff

CONTENTS                                      Pic 1

1  The Biscuits

2  Baking Process

3  Biscuit Design and Output

4  Heat transfer

5  Oven designs

6 Oven specifications: hybrid ovens

7.1 Oven construction: Direct Gas Fired Ovens

7.2 Oven construction: Indirect Fired Ovens     Pic 2

8  Oven conveyor bands                      

9  Oven conveyor design

10 Oven control systems

11.1 Oven operation: Direct Gas Fired Oven

11.2 Oven operation: Indirect radiant Oven

12 Oven maintenance

13 Oven inspection and audit

14 Oven efficiency

APPENDIX 1: Combustion data

APPENDIX 2: Oven manufacturers

APPENDIX 3: Oven band manufacturers

APPENDIX 4: Key components

 

 

 

 

 

 baking by infrared

 

To order for the special price of USD 199.00 please request at our contact page

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Training courses

Baking process and engineering – baking by infrared

  Individual company programs 

Button    The training programs are designed to suit each company’s requirements. Especially valuable for production management, engineering, maintenance staff  and oven operators.

Button    The programs include class work with Power Point presentations, discussion and  questionnaires. The training may also includes on-site training by our senior engineer. This can cover trouble shooting, oven operation, maintenance, planning oven up-grades and efficiency improvements

Button    Normally 2 – 3 modules are presented each day and the complete course is delivered in a 5 day week

Button    Each of our technicians has over 35 years experience as engineers in the biscuit industry in factories in Europe, Asia, North and South America

Post fig 1

 

 

 

 

 

Baker Pacific oven installations baking by infrared radiation

Training Modules

Complete course in one week

Day 1   Introduction / the biscuits / baking process / biscuit design and output

Day 2   Heat transfer / oven designs and specifications

Day 3   Oven bands and conveyor design

Day 4   Oven control / safety systems / oven operation

Day 5   Oven maintenance / inspection and audit / oven efficiency / heat recovery

 

Our training program has exclusive information on:

Button   All types of oven designs / direct and indirect fired / radiant / convection / re-circ ovens

Button   Specifying ovens for different applications for biscuits, cookies and crackers

Button   Setting standards and guarantees for suppliers

Button   Oven bands: types, tracking, cleaning, supporting on skids and rollers

Button   Oven efficiencies with actual data from trials

Button   Energy usage and energy loss

Button   Heat recovery system to save capital and operating costs

Button   Oven operation and maintenance

Button   Oven inspections and audits

 500 Power Point presentation slides

Post fig 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Complete course given by a senior Baker Pacific engineer USD 4,500.00

(excluding travel and living expenses)

Alternative: complete course materials for in-house presentations USD 240.00

To order please contact Baker Pacific at bakerman@dircon.co.uk

 

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Crackers………………………..

Successful crackers from Europe, USA and Asia………………..

Cracker baking

A wide range of products characterised by crispy, open texture and savoury flavours. Crackers include soda and saltine crackers, cream crackers, snack crackers, water biscuits, puff biscuits, maltkist (sugar topped cracker), “TUC” type, “Ritz” type, vegetable crackers.

In general crackers may have some of the following features which influence the baking process:

  • Doughs which are leavened and fermented with ingredients such as yeast, ammonia and sodium bicarbonate
  • Doughs generally have a high water content (15 – 25%)
  • Cracker doughs are laminated, (the dough sheet is made up from multiple thin layers)
  • Cracker doughs spring or lift in the first part of the oven to achieve the open, flaky texture. This requires humidity and high heat input.
  • Some crackers are baked in strips or complete sheets and broken into individual products after baking
  • Some crackers require a colour contrast between dark blisters and a pale background colour
  • Traditional English crackers such as cream crackers and water biscuits are normally baked on light wire-mesh bands
  • Traditional American crackers, such as soda or saltine are baked on heavy mesh oven bands which are pre-heated to transfer heat rapidly by conduction into the dough pieces
  • Crackers are baked to low moisture contents (1.5% – 2.5%), which requires a high energy input

 

DGF oven

 

Baker Pacific Direct Gas Fired Oven for cracker baking 

Logo 2015

Heat Recovery System

The Heat Recovery System (HRS) uses the waste heat from the burner flues. This may be used to heat one or two final zones of the oven. These zones would not require burners, giving a saving in capital and running costs.

All gas burners draw in a large amount of air for combustion. 1.0m3 of gas requires 3.0m3 of oxygen, (approximately 15m3 of air) for complete combustion. This air is exhausted through the extraction system of a direct gas fired oven and through the natural draught burner flue of an indirect oven. The hot air and burnt gas in the burner flues of an Indirect Radiant oven are at a high temperature, typically up to 200oC in the first zones and this hot air can be recovered and used for baking in a Heat Recovery System.

A proportion of the hot gases in the burner flues are diverted to an HRS collection pipe which runs along the top of the oven. Hot gases are collected from each zone with a burner. The hot gases are drawn along the collection pipe by a fan and blown into radiant ducts in the final oven zone.

 

HRS oven 2

 

The HRS zone is constructed with radiant ducts above and below the oven band. The hot gases recovered from the burner flues are fed by the fan to the ducts. The fan is located on top of the oven at the end of the collection pipe.

Oven efficiency with Heat Recovery System

Independent tests were carried out on 3 ovens in the same factory producing identical rotary moulded biscuits with the same baking time. The tests measured the oven efficiency by calculating the energy usage (gas) in kWh (kilowatt hours) to produce one kilo of baked biscuit.

 

Oven efficiency table

 

The Baker Pacific Indirect Radiant oven was 18% more efficient than the DGF/cyclotherm oven and 6% more efficient than the DGF/convection oven. The savings in gas consumption per 8 hour shift (23 tonnes of biscuits) are approximately 212 m3 of gas compared to the DGF/cyclo and 62 m3 compared to the DGF/convection ovens.

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How efficient is your oven? – The products

Each product takes an amount of energy for baking for achieve the correct structure, moisture content and colour. The energy required varies with each type of biscuit, crackers, short dough biscuits and cookies. Each individual biscuit also varies depending on the formulation and quality of the ingredients and the final structure, moisture content and colour required.

Biscuits

Energy is required to bake biscuits as follows:

  1. The dry ingredients must be raised in temperature from ambient to baking temperature
  2. The water in the dough must be raised in temperature from ambient to 100oC
  3. Energy must be provided for the latent heat of evaporation
  4. The water vapour must be raised from 100oC to the baking temperature

The following is a guide to the approximate energy required for different categories of biscuits.

Rotary moulded biscuits:        0.17 – 0.20 kWh/kg of baked biscuits

Hard sweet biscuits:                0.25 – 0.27 kWh/kg of baked biscuits

Crackers:                                 0.30 – 0.33 kWh/kg of baked biscuits

Note: These are theoretical calculations and this is an approximate guide only. Calculations should be made for each formulation and baking profile.

 Read more with “Baking Process and Engineering” manual.