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Direct Gas Fired Ovens

 

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

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

www.maxoncorp.com

 

LOGO 2014

 

 

 

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      

LOGO 2014

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 

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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.

LOGO 2014

 

How efficient is your oven? – Oven performance

Data from several oven installations shows that the energy usage varies from 0.404 kWh/kg of baked biscuits to 0.492 kWh/kg of baked biscuits. The energy requirement for baking varies with the product. The energy loss depends on the quality of design and construction of the oven.

The energy used by the oven is predominantly from gas or oil fuel. Electricity is rarely used for baking now, due to its high cost. In a gas/oil fired oven the fuel represents around 95-96% of the total energy usage and electricity (for powering the drive, fans and other electrical systems) about 4-5%.

The energy input to the oven is used primarily to bake the biscuit, to achieve the structure, reduce the moisture content by evaporation and to colour the biscuit. Each type of biscuit requires a certain amount of energy to achieve a good quality result.

Energy usage diag

In addition to the energy required to bake a good product, energy is lost in several ways:

  • By extraction of moist air from each oven zone
  • By heat loss through the insulation and outer covers of the oven
  • By the return circuit of the oven band
  • By heat loss from the flues from a heater module or heat exchanger in an Indirect Fired oven
  • By hot air escaping from the oven delivery end

The following is a calculation of heat loss from an actual oven installation (Indirect Radiant oven baking a rotary moulded biscuits at 2000):

 Energy usage

For product                                                      678.4 kWh       56 %

Heat loss from extraction                               220.0               18 %

Heat loss from burner flues                            93.1                 7 %

Heat loss from return band                             87.8                7 %

Est. heat loss of air from oven end                 71.0                 6 %

Est. loss from thro’ metal, fans etc.                30.0                 3%

Heat loss through insulation                           20.1                 2 %

Heat loss from radiation at oven end            17.0                 1 %

Total                                                               1217 kWh       100.0%

 

 Energy usage 2

 

 

 

 

 

 

 

 

The overall oven efficiency is approximately 56%

Of the heat loss through the burner flues, up to 50% can be recovered and used for baking in a Heat Recovery System

HRS oven 2

 

 

 

 

 

 

In this Baker Pacific oven installation the Heat Recovery System reduced the energy requirement by 15%

Read more in the “Baking Process and Engineering” manual at our Training Page

 

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Key components – burners

 

Our key components file lists over 50 key components for biscuit oven construction. These components have all been used and proven and are recommended by Baker Pacific. The file for each component provides a picture, specifications and manufacturer’s details.

  1. Bearings
  2. Burners
  3. Clamping elements, chains, sprockets…….
  4. Control handles
  5. Electrical equipment
  6. Electric cable and trunking
  7. Electric sensor and monitoring equipment
  8. Fans and Blowers
  9. Gas equipment
  10. Insulation and seals
  11. Oven bands
  12. Pneumatic equipment
  13. Painting and coatings
  14. Pressure Switches
  15. PLC equipment
  16. Motors and gearboxes
  17. Motors – DC
  18. Radiant tubes
  19. Refractory
  20. Thermocouples
  21. Temperature controllers
  22. UPS

The complete Key Components file is available for USD 85.00 and may be ordered at our Contacts page.

Our second key component file includes oven burners for Direct Gas Fired ovens and burners for Indirect Fired ovens.

SECTION 2: BURNERS

 

Eratec

MFB burners (metal-fibre burners)

Eratec 1

 

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

 www.era-tec.fr


Flynn Burners

 Flynn 1

 

Flynn Direct Gas Fired Burner installation

 

 

 

Flynn distributor

www.flynnburner.com


 Maxon burners

Maxon

Maxon dual fuel installation

Natural Gas Low Temp Burners

OVENPAK® 400 Series

MAXON’s OVENPAK® 400 Series is the world’s most flexible and reliable industrial burner. The OVENPAK® burns most any fuel gas and requires only low pressure fuel. This natural gas burner provides clean combustion with low NOx levels while providing unmatched turndown.

OVENPAK® Gas Burners provide outstanding performance in ovens and dryers, paint finishing lines, paper and textile machines, food baking ovens, coffee roasters, grain dryers, and fume incinerators.

www.maxoncorp.com

 


Mont Selas

 

Enviro Mont™ Burner

Mont Selas in conjunction with RMR Thermal Solutions have developed an Expanded Nitmesh Tube Firing Burner (patent pending) for use in tunnel baking ovens to replace the old industry standard ribbon burner, to achieve typical gas savings up to 25% *.

  • UP TO 25% GAS SAVINGS*
  • HIGH TURN DOWN
  • EASILY RETROFITTED
  • LOW MAINTENANCE
  • EXCELLENT FLAME STABILITY

Nitmesh is a woven metal fibre and is welded over the slot in the burner tube, it is well proven technology and has excellent flame retention properties and reduces the risk of flash back.

The Expanded Nitmesh burner can be supplied in 1¼”, 1½” and 2” sizes as direct replacements for existing ribbon burners with nominal ratings from 4kW to 44kW.

Burners are designed to work on natural gas or LPG on air blast, high pressure and atmospheric pre-mix systems and will operate with an air turn down ration of up to 8:1 (dependent on flame sensing safeguard limitations).

The improved efficiency of Nitmesh comes from the extra radiant heat provided by the hot surface of the Nitmesh material which can become incandescent, as opposed to the gas flame on a ribbon burner which provides only a limited amount of radiant heat due to its low emissivity. Most of the heat from a ribbon burner is provided by natural convection heating the oven roof area above the burner which then re-radiates the heat back to the product on the conveyor. For bottom burners the base of the conveyor will be heated by natural convection plus the additional radiant heat provided by the incandescent surface of the Nitmesh.

Burners supplied in varying lengths and sizes to suit your individual requirements.

We can also offer a comprehensive site installation service, and oven profiling, following installation to further improve on the operational efficiency of the oven and reduction of your carbon emissions. For further information and site visit to determine requirements please contact our Chadderton office.

*Subject to operational conditions.

Mont Selas

www.montselas.co.uk

 

 

Weishaupt

Weishaupt

Weishaupt natural gas burner installation on an Indirect Radiant oven

 

  • Exemplary efficiency: The digital combustion management system ensures that only exactly the amount of energy is consumed that is needed at the time.
  • Excellent emission levels: 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
  • Sophisticated technology: All W range burners work fully automatically. Powerful microprocessors continuously control and monitor the combustion process for maximum efficiency.
  • Silent operation: The transversely mounted fan draws air through a sound attenuated inlet.
  • Versatility: The W range offers oil and gas burners in five ratings from 12 kW to 570 kW.
  • Long life: More than 50 years of experience and development work have gone into Weishaupt burner technology. Only the best materials are used in manufacture

www.weishaupt.co.uk


LOGO 2014

 

 

 

Key components – Bearings

Our key components file lists over 50 key components for biscuit oven construction. These components have all been used and proven and are recommended by Baker Pacific. The file for each component provides a picture, specifications and manufacturer’s details.

  1. Bearings
  2. Burners
  3. Clamping elements, chains, sprockets…….
  4. Control handles
  5. Electrical equipment
  6. Electric cable and trunking
  7. Electric sensor and monitoring equipment
  8. Fans and Blowers
  9. Gas equipment
  10. Insulation and seals
  11. Oven bands
  12. Pneumatic equipment
  13. Painting and coatings
  14. Pressure Switches
  15. PLC equipment
  16. Motors and gearboxes
  17. Motors – DC
  18. Radiant tubes
  19. Refractory
  20. Thermocouples
  21. Temperature controllers
  22. UPS

The complete Key Components file is available for USD 85.00 and may be ordered at our Contacts page.

Our first key component file is “Bearings” for high temperature applications and linear bearings for slides for the oven band tension arrangement.

                                                                  

 SECTION 1 – BEARINGS

SKF High temperature bearings for oven band support rollers

SKF bearing

Bearing assembly with SKF bearing type Y – V228 suitable for operating temperatures up to 350oC

SKF heavy duty bearing assembly for oven end drums

Delvy end SKF bearing

 

Delivery end drum SKF bearing assembly

 

Bearing housing                  SKF SNL 522-619

Bearing                                  SKF 22222EK

Adaptor sleeve                     SKF H322

Fixing ring                             SKF FRB 135/200

Seals                                      SKF TSN 522L

High Visc. Grease                SKF LGEV2

Assembly instructions         SKF 4403/III E

www.skf.com


Linear Motion Ball Rail Systems

THK caged ball LM bearings

THK 1+2

THK SHS caged ball bearing linear slide supporting the tension end drum bearing

www.thk.com


Bosch Rexroth

Bosch Rexworth

 

  Bosch Rexroth ball rail system supporting tension end drum bearing

 

 

Bosch linear rail

 

www.boschrexroth.com

 


 NSK / RPH bearings

 Download “The ABC of Bearings” and Catalogue at:

www.nsk.com

www.jp.nsk.com/services/basicknowledge/manual/abc

 

 


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Measuring baking profiles

In order to monitor actual baking temperatures, a thermal data logger is used. These units are slim and will pass through the oven carried on the oven band.

ThermaPro pic

 

 

 

        ThermaPro Data Logger

 

 

Data loggers are available with multi channels, usually 6-8 for biscuit oven applications. Each channel has a thermocouple sensor which is attached to a bar spanning the width of the oven band. In this way the baking temperature is monitored and recorded at multiple positions across the width of the oven.

Data loggers such as the TCK2000, which is made in China, monitor and record baking temperatures. A TCK system comprises the following: the data logger or profiler unit with 3 up to 9 channels within an insulated box, thermocouples with high temperature connections, all accessories, and software to run on a PC. This unit is a convenient way to monitor oven performance, detect problem areas in the oven which may cause poor structure, colour, moisture level, etc.

 

TCK 1-2

 

 

         TCK 9 channel data logger to monitor and record baking temperatures

 

 

Our main baking control in most ovens (direct gas fired, indirect radiant and convection ovens) is by temperature. We set zone temperatures to match the required baking profile and control the heat input from the burners to maintain the set baking temperatures. Monitoring the baking temperatures through the oven and across the width of the oven band is therefore a valuable guide to the performance of the oven and a good starting point for trouble shooting problems such as uneven colour, moisture content…..

More sophisticated data loggers, such as ThermaPro, pictured above, monitor and record heat flux, which indicates heat transfer by radiation, conduction and convection.

For for information and enquiries please request at Contact page