Publishing date to be announced
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.
- 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
Senior management staff and engineers in contract engineering companies, biscuit manufacturers and companies supplying production and baking equipment in the food industry world – wide.
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: email@example.com
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
3.5 Oven designs
3.6 Heat rating
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
4.6.3 Purge system
4.6.4 Over temperature
4.6.5 Power failure
4.7 Electrical installation
4.10 Spare parts
5. Selecting the oven conveyor band 28
5.1.2 Semi-sweet biscuits and short doughs
5.2 Open wire mesh bands
5.3 Compound balanced weave belts (heavy mesh)
5.4 Steel bands
6. Purchasing and Shipping 33
6.1.1 Contractors for fabrication
6.1.2 Purchase of specialist components
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
12.3 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
12.18 Temperature controllers
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: firstname.lastname@example.org
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.
- Baking oven design and manufacture
- Management of engineering and maintenance
- Oven up-grades
- Introduction of heat recovery system
- Making and procuring spare parts
- Improved operation and maintenance
- Oven efficiencies / reduced production cost
- Improved reliability / less downtime
- 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
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
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
Baking process and engineering – baking by infrared
Individual company programs
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
Baker Pacific oven installations baking by infrared radiation
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:
500 Power Point presentation slides
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 email@example.com
Successful crackers from Europe, USA and Asia………………..
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
Baker Pacific Direct Gas Fired Oven for cracker baking
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.
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.
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.
“Baked not fried” has become an established healthy, low fat choice for consumers in many markets. Potato snacks and crackers are baked with infrared radiation on Direct Gas Fired ovens or hybrid DGF/Indirect Radiant ovens.
Baker Pacific Direct Gas Fired / Indirect Radiant oven
The production process for potato snacks follows that for crackers and wheat based snacks quite closely. With some modification, cracker lines can produce baked potato snacks in addition to potato crackers.
Potato crackers from Khong Guan, Indonesia Potato snacks from Walkers, UK
The ingredients for baked potato snacks may be mixed on continuous mixers or on horizontal high speed mixers with suitable modifications or on plough share type mixers with bottom discharge. All the dry ingredients are blended, fat is added and finally water is added. Horizontal high speed mixers require a steam jacket and suitable modifications to the bearings and seals. The dough is heated during mixing to gelatinise the starches.
APV Baker High Speed Mixer
The dough is sheeted and gauged to produce a dough sheet of approximately 0.75mm thickness. Potato doughs are tough and require heavy duty forming equipment. The robustness and accuracy of the gauging equipment is critical as variations in thickness of the snacks will cause variations in colour after baking. Achieving the minimum variation in thickness requires large diameter gauge rolls, 400mm diameter and these may be of solid construction to minimise deflection.
Heavy duty gauge rolls from Baker Perkins
Ripple snacks are formed on a final gauge roll unit, which has grooved rolls, which intermesh to form the ripple in the dough sheet. By using one plain and one grooved roll, other forms such as hollow flutes can be made. These rolls only form the dough sheet and do not alter the thickness. When making plain products the ripple roll gap is opened to allow the product to pass through without ripples.
After gauging, the snacks are cut by a rotary cutter. The scrap dough is lifted and may be milled before returning to the mixer. Cracker doughs which have a strong, extensible dough sheet may be returned to the sheeter.
Potato snacks are baked on pre-heated Z47 type wire mesh or heavy mesh oven bands, such as Ashworth CB5. The ovens require high radiant heat and may be either a Direct Gas Fired (DGF) oven or hybrid DGF / Indirect Radiant oven. Convection ovens are unsuitable as the convective air will disturb the very light snacks on the band and will cause snacks to be blown off the band. Baking times are of the order of 4 minutes and the output of a 1.0m x 40m oven will typically be around 500kgs / hour.
Baker Pacific Radiant oven baking by infrared radiation
The snacks are conveyed directly to the oil spray and flavour applicator. The flavours may be added to the oil and the slurry pumped through the oil spray. This method has the disadvantage of possible blockages and increased cleaning time, particularly where more than one flavour is applied on the same line. The alternative is to use a flavour applicator after the oil spray machine. The flavour is metered on to the snacks while they are agitated in a rotating drum. After flavouring the snacks are cooled and conveyed to packaging.
Storeveyor for potato chips from Gough Engineering
Packaging is usually a vertical Form fill seal pack, but may also be a block bottomed bag or a bag in a box.
Crinklys potato snacks from Jacobs and Walkers Baked from UK
We are concerned not only to bake high quality biscuits, but also to achieve the lowest cost per kg of baked product. We need therefore to consider the amount of energy required by the oven. As energy costs increase in almost every country, the efficiency of the oven is of growing importance. In certain countries such as India, fuel is very expensive and represents an important element of the total production cost.
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. In the example we will use, a typical rotary moulded product requires 0.2120 KWh (182 kcal) of energy per kg of baked product.
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 heater module or heat exchanger
In order to minimise the heat loss, (wasted energy), we need to pay attention to the extraction system to achieve the final moisture content required, without excessive waste of heat from the burners, insulate the baking chamber adequately and also insulate the return band, particularly where the band temperature is high, for example when baking crackers.
In the following energy calculations, we will just consider the energy from the gas or oil fuel.
The following calculations of the energy balance of an oven are taken from an actual installation. Details of the product and the oven are given below, so that different data for other ovens can be substituted to make calculations of energy use accordingly.
Rotary moulded biscuit
Dimensions: 58 x 37mm
Weight: 5.1 gms
Baking time: 3.8 mins
Baking chamber: 1.25 x 100m
Zones: 8 (7 burners)
Oven band: 8.25 kgs/m2
Extraction fans: 34 m3/min (maximum)
Oven output: 3,200 kgs/hr
Data from independent test results
Total energy used by the oven: 0.4043 KWh/kg of baked biscuits
Of this, the energy required to bake the product to the required quality:
0.2120 KWh/kg of baked biscuits
Waste energy: 0.1923 KWh/kg of baked biscuits
The total energy requirement to bake the product is 0.2120 KWh/kg of baked biscuit
This gives a total energy usage (gas) to bake the biscuit of:
3200 x 0.2120 = 678.4 KWh per hour
This is the energy utilised to bake the biscuit, form the structure, remove the moisture and colour the biscuit.
Latent heat of evaporation
An important element in energy use is providing the latent heat of evaporation. In order to evaporate the moisture in the dough (14 % by dough weight) to a final moisture content of 3.0% latent heat is required. The latent heat energy required to evaporate the water from the product is 539 cal/gm of water.
Moisture to be removed to reach final moisture content of 3.0%: 0.135 kg per kg of biscuits
Moisture to be removed: 0.135 x 3200kgs = 432 kgs per hour
Latent heat required to evaporate 432 kgs of water:
432,000 gm x 539 cal = 232848 kcal = 270.75 KWh per hour
Heat loss from extraction system from baking chambers
Volume of air extracted from each zone
34m3/min x 60mins x 8 zones = 16320 m3/hour (maximum)
Estimated average extraction damper setting: 40%
Actual volume of air extracted from baking chamber = 6528m3/hour
The air extracted has been heated from ambient temperature over the oven (55oC) to an average baking temperature (200oC). This requires an energy input as follows:
Weight of the air extracted = 6528 x 0.746 kg = 4870 kgs
The energy required to raise the temperature of this air in the oven from 55oC to 200oC (145oC) is:
145 x 1.009 KJ/kg x 4870 kg = 712505 KJ = 198 KWh perhour
Energy required to raise the temperature of the water vapour from 100oC to 200oC
1.996 x 432 x 100 = 86227 kJ = 23.97 KWh perhour
Heat loss from extraction system per hour = 222 KWH
Specific heat of water vapour: 1.996 kJ/kgK
Density of water vapour at 100oC = 0.958
1 KJ = 0.000278 KWH
Heat loss from return band
Oven band drum centres: 111m
Band width 1.25m
Band weight: 8.20kgs/m2
Specific heat of carbon steel: 0.12kcal/kgoC
Band temperature at delivery end: 140oC
Return band temperature at feed end: 105oC
Weight of band (on return circuit): 111 x 1.25 x 8.20 = 1137.75
Temperature loss: 140 – 105 = 35oC
Heat loss: 0.12 x 1137.75 x 35 = 4778.55 kcal (5.56 KWh) per revolution of the band
Bake time: 3.8 mins
Heat loss per hour: 5.56 KWh x 60/3.8 = 87.8 KWh
Heat loss from the insulation and outer covers of the oven:
Oven baking chamber: 1.25m x 100m
Width over covers: 2.3m
Height of covers 1.23m
Average bake temperature: 200oC
Average temp in heater modules: 350oC
Ave. outer side cover temperature: 55oC
Ave. outer top cover temperature: 55oC
Rockwool insulation thickness (s): 200mm sides and 250mm top
Rockwool thermal conductivity (k): 0.066 W/m.oC
Heat loss from sides and top of the oven through the insulation
Heat loss = k A dT / s
Total area of oven sides: 100m x 2m x 2 = 400m2
This includes 7 heater modules and baking chamber sides
Area of heater modules on burner side: 13m2 x 7 = 91m2
Area of heater modules on non burner side: 2m2 x 7 = 14m2
Total area of heater modules = 105m2
Total area of oven sides (less heater modules) = 295m2
Heat loss from sides of baking chamber sections:
0.066 x 295m2 x (200 – 55oC) / 0.2 = 14116 W
Heat loss from heater modules:
0.066 x 105m2 x (350 – 55oC)/ 0.2 = 10222 W
Heat loss from top of oven:
0.066 x 100m x 2.3m x (200 – 55oC) / 0.25 = 8804 W
Total heat loss through the insulation of oven sides and top: 33.1 KW
Heat loss from radiation from oven delivery end:
Area of oven delivery end covers 6m2
Area of oven end hood: 14m2
Total area 34m2
Heat loss = ∑ σ (Th4 – Tc4) A
∑ = emissivity
σ = 5.6703 10-8 (W m2 k 4) (Stefan Boltzmann constant)
T = absolute temp. (Kelvin)
A = Area m2
0.5 x 5.6703 x 10-8 x (298 x 108 ) x 34m2 = 28725 W
Heat loss from radiation at the delivery end: 28.7 KW
Heat loss from burner flues
Total energy used: 0.4043 kWh x 3200kgs = 1294 KWh/hour
7 burners: average energy used per hour per burner = 1294/7 = 185 kWh
Gas consumption: 185/9.8 kWh/m3 = 18.9 m3 / hour per burner (average)
Gas/air volume required per burner: 18.9m3 gas + 301m3 air = 319.9m3
Estimated average temperature of flue gases: 200oC
Gas / air weight at 200oC per burner = 319.9 x 0.746 kg/m3 = 239 kgs/hour/burner
Estimated energy in flue gases: 239kgs x 200 x 1.026 KJ = 49043 KJ
= 13.6 kWh /hour/burner
Estimated water vapour content of flue gases: 119.5 kgs /burner/hour
Energy required to raise the temperature of the water vapour from 100oC to 200oC
1.996 x 119.5 x 100 = 23852 KJ = 6.6 kWh /hour/burner
Total heat energy in flue gases: 7 x (13.6 + 6.6) kWh = 141.4 kWh per hour
Of this 50% can be used in the Heat Recovery System
Specific heat of water vapour: 1.996 kJ/kgK
Specific heat of air: 1.026 kJ/kgK
Density of water vapour at 100oC = 0.958
Density of air at 2000C = 0.746 kg/m3
1 KJ = 0.000278 KWH
Combustion process: CH4 + 3O2 = Heat + 2H20 + CO2 + O2 (see Appendix 3)
Note 1: For complete combustion 10% excess air is required (this amount can vary considerably depending on the burner and heat exchanger design)
Note 2: air contains 20.9% oxygen
From calculations above, the energy consumption of the oven per hour:
For product: 678.4 kWh 50.6 %
Heat loss from extraction 222.0 16.6 %
Heat loss from burner flues2 141.4 10.5 %
Heat loss from return band: 87.8 6.5 %
Est. heat loss of air from oven end: 75.0 5.6 %
Est. loss from thro’ metal, fans etc. 75.0 5.6 %
Heat loss through insulation: 33.1 2.5 %
Heat loss from radiation: 28.7 2.1 %
Total 1341.4 kWh 100.0%
Note 1: estimated accuracy in the assumptions and base data is +/- 5%
Note 2: the heat loss can be considerably larger than given depending on the design of the heat exchanger and flue. Please see Appendix 3, “Combustion Analysis”.
- The overall oven efficiency is 50%
- Of the heat loss through the burner flues, up to 50% can be recovered and used for baking in a Heat Recovery System
- In this Baker Pacific oven installation (picture below), the Heat Recovery System reduced the energy requirement by 15% (as calculated by an independent test)
Indirect Radiant Oven with Heat Recovery System
Comparison of Oven Efficiencies
Comparison of oven efficiency for different oven types
|Product||Oven type||Oven size||KWH/kg of biscuits|
|Snack cracker||DGF/conv||1.2m x 90m||0.477|
|Rotary moulded||DGF/conv||1.5m x 100m||0.441|
|Rotary moulded||DGF/conv||1.2m x 60m||0.430|
|Rotary moulded||DGF/cyclo||1.2m x 60m||0.492|
|Rotary moulded||IR (cyclo) + HRS||1.2m x 100m||0.404|
|Rotary moulded||IR (cyclo)||1.2m x 100m||0.475|
Armstrong Group, “Specific Heat – Specific Gravity”, www.armstrong-intl.com
J.S. Alakali and others: “Specific Heat Capacity of Palm Oil”; Dept. of Biosource Engineering, McGill Univ. Canada, Dept of Food Science, Unive of Agriculture, Makurdi, Nigeria
Y.S. Kim and others: “ Physical, Chemical and Thermal Characterisation of Wheat Flour Products”; Dept. of Bio. and Agriculture Eng. Kansas State Univ., USA
Sugar Engineers, “Specific Heat Capacity”, www.sugartech.co.za
Testo Inc: “Combustion Analysis”: www.testo.com
“kW and kWh explained” www.energylens.com
“Thermal Conductivity” www.quats.com
“Thermal properties for water” www.engineeringtoolbax.com
“Thermal properties for air” www.engineeringtoolbax.com
“Food and Foodstuff” www.engineeringtoolbox.com
Three modes of heat transfer are used in baking biscuits: radiation, conduction and convection.
1. Direct Gas Fired / Indirect Radiant oven 2. Conduction from steel band 3. Convection oven
All objects above a temperature of absolute zero radiate energy to their surroundings. This energy or radiation is emitted as electromagnetic waves which travel at the speed of light. The waves may travel through a vacuum or other medium. When they impact an object, they are partially absorbed and partially reflected. Good emitters are also good absorbers of thermal radiation.
Infra-red radiation is in the wavelength band of 0.7-300 microns (above visible light). Higher temperatures produce shorter wave lengths. Typical wavelengths in a radiant oven are around 4.6 – 6.4 microns, which provides good heat penetration of the dough pieces. Infrared radiation for baking is emitted principally by the DGF burner flames and by the radiant tubes in an Indirect Radiant oven.
Radiant tubes in an Indirect Oven High rate direct gas fired burners
The most important mode of heat transfer for baking is infrared radiation, which has the following advantages:
- Penetrative heat transfer: Infrared radiation penetrates biscuit doughs by approximately 4mm, (depending on wavelength and moisture content). It is the only heat transfer mode to truly bake the product from the centre. This is the key advantage of baking by infrared radiation
- Biscuit structure: because radiation penetrates the dough pieces, it is essential to achieving good structure with optimum volume and texture and is always the main mode of heat transfer in the first part of the baking process
- Even moisture content: radiant baking ensures a low moisture gradient from centre to the outer surface of the biscuit. It is the best heat transfer mode to avoid “checking” (cracks appearing in the biscuit after baking)
- Efficiency: heating of the surrounding air in the baking chamber is not necessary, which lowers energy consumption
- Colouring: radiation enables highlighted colour contrasts for crackers and rotary moulded products, whereas convection gives an overall, bland, even colour
- Versatile: infrared baking is suitable for all types of biscuit
Conduction transfers heat from the oven band directly to the base of the dough pieces. The heat transfer is dependent on the temperature and heat mass of the oven band and the surface area of the band in contact with the dough piece. With steel bands and heavy mesh bands this approximates to full contact and is very effective.
Ovens with band pre-heat can quickly transfer heat into the base of the dough pieces and achieve rapid development of the biscuit structure and texture; this is particularly valuable for cracker baking.
Convection baking uses hot air jets which impinge directly on the top of the dough pieces and the underside of the oven band. This system effectively dries and colours the surface of the dough pieces. However it produces a hard, dry skin on the dough pieces and will prevent good expansion and “lift” of the product if used at the start of the baking process. Also it is a cause of a moisture gradient between the surface (very dry) and the centre of the biscuit (more moist). This may result in “checking”, (cracking of biscuits after baking), unless the moisture gradient is reduced after baking.
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.
- Clamping elements, chains, sprockets…….
- Control handles
- Electrical equipment
- Electric cable and trunking
- Electric sensor and monitoring equipment
- Fans and Blowers
- Gas equipment
- Insulation and seals
- Oven bands
- Pneumatic equipment
- Painting and coatings
- Pressure Switches
- PLC equipment
- Motors and gearboxes
- Motors – DC
- Radiant tubes
- Temperature controllers
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
MFB burners (metal-fibre burners)
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
Flynn Direct Gas Fired Burner installation
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.
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.
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