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Asked on 24.02.2021.
Changing the type of belt in tunnel ovens

As a former product manager and now consultant for tunnel oven belts I would be interested to ask for your experience in changing the principal type of belt used in your tunnel oven and for what reason.

Did you change from solid steel belt to mesh belt or (multiple spiral) CB5-belt to Z-belt (rolled baking oven belt)? Or was it vice versa?

Or are there intention and thoughts to do something like this?

Looking forward to your comments and replies.

Thanks

Peter Otten

Accepted answer
Answered on 26.02.2021.

Well, I guess, this is a question, easy to answer as: "Depends on".

Honestly, all our contacts, so far, doesn´t involved us into the reasons, why they wanted to do this. I guess, very often, they had a very expensive belt on and are looking for a cheaper and more easy solution to handle.

But it depends more to the function, than to the price, I guess. 

Which kind of product should be transported through the oven?

Will it be directly at the belt or in trays? 

Which condition will the product be? Hard or soft dough.

Will it be allowed, that there will be marks from the belt to the product?

What´s about the temperature dividing? Does the belt will have a big influence to the product, if it keeps the heat in the belt in a regulating procedure? Or will it be better to have a more open belt to let the heat flow easier inside the oven?

Can the belt bring too much heat outside the oven, when it is running back outside? Than it would be better to have as less as possible volume of steel material inside the belt.

And mostly forgotten. How and how often the belt needs to be cleaned.

Finally, It depends on the local process, which belt will be the best. It doesn´t need to be the most expensive one always. Sometimes it will be even a bad choice. It needs to be focussed to the local situation and local processing.

This is the theory. In praxis, I guess, the price will be a very common driver for the decission to change.


Answered on 05.03.2021.

Dear Peter,

I'm not a baking expert nor very knowledgeable about biscuits but since 1988 I’ve picked up a few things about steel belts and how to make the most efficient use of them. The first bake oven band, made of steel, was installed in 1925-ish.

I started to work for Sandvik 1979 and later 2017 the belt department of Sandvik became IPCO. Since 2021 I'm an independent consultant., running my company BandAid-AB.

Steel Belts for Bake Ovens

Historically one can say that the choice of baking band type is end-product driven. Bake ovens have over time been transformed from mesh to solid steel belts or to perforated steel belts which could be a perfect solution when having different end-products with different characteristics and different content. A perforated steel belt delivers most of the mesh properties but also the solid band advantages.

A solid steel bake oven belt is normally lighter than a mesh belt. A perforated belt is up to 35% lighter than a solid one. From an energy usage point of view, this means less steel to heat and less steel to pull.

Solid and perforated bake oven belts are easy to clean and maintain. Normally they deliver a safe and problem-free operation for many years. The end product is normally very easy to discharge from the belt surface after the oven.

Some people think that a fatty product is better to bake on a solid belt and that the moisture remains within the biscuit shell instead of ending up at the bottom of the oven, where it easily can cause a fire. Here is also a lot of taste, crustiness, and brittleness in focus.

The wire marks on the bottom of some crackers or snacks are often also "trademarks" for the actual brand and an argument for not transforming belt type.

End-product quality is what most of the main companies will underline when it comes to explaining why steel belts. 

We have over time meet cultural aspects as well when talking to end customers about their choice of baking band. For instance, are “Marie Biscuits” baked on mesh as well as on solid steel belts but also on perforated steel belts. Quality-wise the last example is to prefer. It all depends on what quality means for the customer.

When thinking about changing belt type in an oven one need to consider a few basics:

The product to be baked of course. 

Normally if trays are considered a solid or perforated belt is not needed. But if you want to use the belt surface as well for baking you have a different situation or an opportunity one can say.

A mesh oven does normally not need as big radius end-drums as a steel belt one.

For a steel belt oven, the formula is: Belt thickness in mm X 1000 = gives a theoretical unlimited lifetime of the steel belt. Normally factor 0.8 is multiplied to get a good enough bending stress environment. ( IE a 1.2 mm thick solid or perforated steel band requires 960 mm diameter end-drums)

With this said one can state that it is not a really big deal to transform from mesh to solid or the opposite. But you need to change most of the belt support items. Tracking systems, guide rollers, support rollers or skid bars are of different designs and compositions so some engineering support is normally required during the entire process of transformation.

Feel free to contact me for more sharing of conveyor belt topics.

All the best and good luck/Staffan

Answered on 01.03.2021.

Dear Mr Peter,

Changing the belt in the tunnel oven is not a simple job and it requires lot of plan and skill to do in defined time and run it without any tracking and damage.   

So changing the belt from mesh belt (of any design as you mentioned) to steel band or vice versa is to be decided on the variety you are running.

low fat (from 8% to 20%) fat level it is better to bake in mesh belt.  If the variety is like high fat variety, or danish cookies, or cookies dropped directly on the belt (like HAAS Meineke machine, Rhino machine, or comas machine you preferred steel belts.  ( double colour, or double colour with single liquid filling etc,,)--These variants also much depends on the heat circulation system you are having in the oven.  High radiation heat or direct bottom heat will spoil high fat and premium type cookies.

Before you plan to change better brainstorm on the requirement and do the change over as Soft dough with comparatively low fat (glucose, milk), hard dough, fermented dough, crackers needs mesh type belts for quick heat transfer and low baking time where your cost of operations are very important when you arrive final cost of the product






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