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Supporting oven bands

Baker Pacific successfully use cast iron skid bars to support wire mesh ovens bands, (for example Z47, Z 47R and Ashworth U66-48-1718 PGLW). The skid bars are used on ovens of up to 100m length. Where the products and oven conditions are very dry, some graphite skid bars can be added to reduce friction . Skid bars are trouble free and do not require maintenance, except annual checks and cleaning.

Skid bar pic

 

 

 

 

 

 

 

 

 

Skid bar with access port before oven band installation

Cast iron skid bars are placed inside the baking chamber with a pitch of 0.8 – 1.2m. They are supported in frames and are removable for cleaning. Apart from cleaning, which is infrequent, skid bars do not require any maintenance.

The skid bars are cast from iron with a graphite content which reduces friction. The material and casting are critical to the performance and the skid bars are supplied to suitable specifications, for example International ISO/DIS 185 Grade 200 / 250. The chemical composition, casting process, shape of the mould and cooling rate are important to achieve the optimum low friction and durability of the skid bars in operation.

The surface of the skid bar has a microstructure of a pearlitic matrix with evenly spread type A graphite flakes to ASTM A247 standard with no hard particles. Maximum allowed amount of ferrite is 10%. No ledeburite is allowed. The sliding surface of the skid bar is machined after casting by removing the surface layer (1.0mm), which contains ferrite and would result in scratching of the band. The final surface should have a roughness of Rmax 3.0um

The installation of the skid bars is critical to good band tracking. The bars must be level and at right angles to the direction of band travel. Levelling is best done optically with a laser instrument.

Skid bar supports drg

 

 

 

 

 

 

 

                         Baker Pacific skid bar support with levelling adjustment and access port

Return band supports

On the return below the baking chamber, the band is supported on rollers. A proportion of these, usually one in three, may have spring loaded guide discs. These are very effective in keeping the band in its central position.

 

Return roller

 

 

 

 

 

 

 

 

 

 

 

Baker Pacific spring loaded return band support roller

Heavy mesh band supports

Heavy mesh bands are supported on rollers, which will carry heavy bands with low friction. The design of the supports and adjustment for levelling and the specification of the bearings are critical as the rollers operate at baking temperatures. If the rollers seize, they will quickly cause wear to the oven band. The ends of the rollers are therefore exposed for inspection and high temperature bearings must be used. The bearings are mounted outside the baking chamber and are insulated from the chamber.

Band support roller 2

SKF bearing

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

More information may be found in our Baking Process and Engineering Manual

Oven band cleaning

Wire mesh oven band cleaning

Oven band cleaning is critical to the quality of the biscuit and the oven performance. We strongly recommend a band cleaner which operates all the time during baking, ensuring that there is no build-up of carbon, which is difficult to remove.

The Baker Pacific oven band cleaner consists of two independent driven wire brushes for cleaning both sides of the band. The unit is designed for a continuous, gentle cleaning action to maintain the band in good condition.  The top wire brush, driven by a fixed speed motor gearbox cleans the inside of the oven band. The lower wire brush unit cleans the outside of the oven band. It is mounted on a trolley for removal to the side of the oven. Guide rails are provided for the trolley with stops and locking handle. The brush is raised or lowered to the working position by a lever and the brush pressure is adjustable.

Band cleaner

Baker Pacific oven band cleaner manufactured in China

Maintaining a clean band is important, particularly when baking products with sugar toppings, and preventing contamination is vital. When baking products with toppings a good system of recovery for surplus toppings is essential to prevent toppings dropping on the oven band. A long wire-mesh panning conveyor is recommended with a level transfer of the dough pieces to the oven band.  The panning web should an open mesh band (enrober wire-mesh) and be around 2 – 3m long. The end transfer roller or nosepiece is of small diameter to allow a level transfer of dough pieces to the oven band.

For wire mesh bands which have become dirty, some hard carbon deposits may be removed by heating the band to 400oC, when the hard carbon deposits will break and can be removed by the brushes. It is important that the band is heated evenly and only sufficient temperature to carbonise the debris is used. Uneven or excess heating will distort the band.

Soft deposits may removed by steam cleaning with an industrial cleaning fluid. Suitable drainage is required. After cleaning, the band should be dried and oil (soybean oil / coconut oil) applied to prevent rusting.

LOGO 2014