Biscuit Oven Wire Band Interlocking

 Biscuit  Wire band   preventive   maintenance  should include  inerlocking of   wire band with   band brush  movement   as  chances are there  that the operators  stops the  oven band   and let   the   brush run  resulting in severe  damage to oven band or in some cases it even   cuts the oven band through the cross section .

Hence  plant operators  should interlock the  both  such that  the   band brush  runs  only when the oven band  runs

Types of Industrial Biscuit Ovens

Various  types of biscuit ovens  are used in biscuit industry  for production of   varieties of biscuit .  Selection  parameter  for   any biscuit  oven are capacity ( which covers length ,width  and speed ) , products , baking time  and type of fuel  .Normally in bakery parlance  ovens are defined as per  width and no of  baking zones .

Biscuit ovens are mainly  classified  under  following  types

Direct gas fired

 The gas fired  oven is used  for those product  that require  great heating power . They can burn natural gas  or LPG . The gas  is mixed  with air  in a special  mixing pipe  based on  the Venturi tube  principle . In each zone  the heat at  top and bottom  can be  independently set by regulating  the two combustion  air fans which controls  the volume of gas  fed  to the  burners . A bar graph potentiometer  set by operator  can be  used to select the heat ratio between  top and bottom . Each zone is equipped with a suitable humidity  extraction system .


Indirect   radiating  cyclotherm oven

 The Indirect Gas / Diesel fired ovens  also known as  cyclotherm  oven - transfer heat  to the product   by radiation . Each zone consists of  set of tubes  at the top and bottom  of the baking  wire band  through which  the hot air  which has been previously heated  by burner flows .

At the end  of each baking  zone the hot gasses are collected  by a plenum and returned  by blowing  fan to the burner  where they  are heated  up again  to the working  temperature  and sent back  to the tube circuit . The heating  system  is there for  completely  independent  and the products  of combustion   does not  comes in contact with dough being baked . Each zone  has  extraction fan to remove humidity from  baking chambers .

Convection oven 
The convection  oven  is suitable  for baking delicate products  like cookies , wire cut  or sponge . Its baking chamber  is constituted  by a plenum  duct positioned  on the top and bottom  of the baking wire band  where hot air is  gently  blown out of  properly  designed  slats  and comes  in  contact  with the dough . The heat transfer  is mainly by convection . The convection  type of oven can be  direct  or indirect . In those cases  where the available fuel  is natural gas or lpg  and the reduction  of baking time is a necessity the direct convection  is the  correct choice .  In the  In direct   convection type of  oven  the  air is heated  up by passing through  a dedicated  heat exchanger  hence  baking  never comes into contact  with the dough .Humidity  is removed through extraction fans in each zone .

 

Hybrid  Oven

Hybrid ovens are those  ovens which have combination of any of the above types of ovens.  Sections are divided  into different type of heating  systems , depending upon  product and its baking  requirement .
  


Electric  Oven

Electric ovens  are  not so popular with  manufacturers due to low cost of lpg,cng or diesel as compared to  electricity . Oven  consist of electric heater s  which  en capsuled into radiating pipes  . These are then set  for set temperatures by thermostats .

RADIO FREQUENCY - Post baking drying technique

Biscuit manufacturers all across world have following options to increase capacity in existing plant . They have been trying various method to achieve this .

• Increase the oven length hence increasing moulder /cutting speed .Not all ovens has this advantage you have to check whether another zone can be added to existing biscuit oven or not .

• Run plant at maximum speed with increased temperatures in different biscuit oven zones resulting in reduced baking time .This has disadvantage that the quality of biscuit gets affected.

• Using Radio frequency dryers at the delivery end of biscuit ovens ,this helps in reducing moisture further by 10 - 11% hence we can increase the speed of moulder/cutter resulting higher output .

Principle on which radio frequency dryer work s is that as water has As product exiting the baking oven enters the RF post-baking dryer, it passes through an electrode array having an alternating electric field which reverses its polarity at a rate of 40.68 million times per second.
Water is comprised of "polar molecules" which can be likened to each molecule having a north and south pole. When passing through an alternating electric field, polar molecules react similar to the way bar magnets behave in an alternating magnetic field, constantly realigning themselves to face the opposite pole. At a frequency of 40MHz, friction caused by this rapid movement causes the polar molecules of water to quickly heat, wherever moisture is present, throughout the entire thickness of the product.

Nonpolar materials such as fat, oil, and dry ingredients do not react and, therefore, are not directly heated by RF energy. In the case of bakery products, this means an RF dryer will preferentially heat and dry the wettest area of a product without heating the areas already dry. Typically, there is greater moisture in the interior of a product as it exits a conventional oven. Therefore, this moist area will preferentially absorb more of the RF energy.

Developed for high-volume cookie production Post-Baking Dryers quickly and efficiently remove residual moisture trapped within the center of the product, permitting conventional ovens to run at the maximum speed that a product can be produced with the correct loft, crumb structure, and color. These RF dryers are available in different band widths

Advantages of RF heating
Increased Throughput - Up to 30% increase for crackers and often up to 40% for cookies.

Elimination of Checking - By greatly reducing the moisture variation throughout the thickness of the product, checking caused by differential shrinkage is eliminated.

Excellent Control of Final Moisture Content - Final moisture is controlled to approximately +/-0.25%.

Independent Color Control - Since moisture is controlled in the RF dryer, color development in the oven can be done without concern for final moisture content

Refer radiofrequency.com for more details on RF technology