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STEEL BELT SERVICE

Service History

 

 

 

HOW TO DESRIBE DAMAGE

To get a service inquiry started it is very important to describe as exact as possible the kind of damage which occurred.

The following chapter will help you to explain with the right terms what damage you are confronted with and it makes it much more easier for us to get a first exact overview about the problem.

1.1.       Belt specific terms and their explanations
1.1.1.    Dent : Is a local “ plastic deformation “ , a flatness deviation which either goes inside or outside of the belt surface. To describe a dent the geometric extensions ( the length and the width ) , the height or depth and the direction ( towards the inside or outside ) have to be mentioned. The reasons for a dent are external forces which work from the outside ( glue balls in the mat, mat forming problems ) or inside ( something came between belt and drum ) onto the belt and deform the surface of the belt.
1.1.2.    Bubble : Are deformations with an extension on the belt of more than 200 mm in diameter. To describe that kind of damage we need the exact measured location from one belt edge ( always seen in production direction , from the infeed ) The reason are various : from overlapping of chains or rods, to mat double forming or bigger layers stick on the drum, and so on....
1.1.3.    Waviness or Wave : These are zones of bigger length as the adjacent
( surrounding ) areas and are snapping most likely to the other side ( from the inside to the outside or otherwise around ) by manual pressure. This shape describes the periodical appearing irregularity in the longitudinal direction with the length and height of the wave.

The waviness is mainly depending on the belt tension
1.1.4.    Cross curvature.  The cross curvature describes the flatness of a belt crosswise over the width of a belt. This shape is either

·         concave ( troughing shape ) , or

·         convex ( roof share ) , or

·         sometimes a mixture of both 

The reasons for this kind of damage are sometimes 

·         roll- and slide frictions , or

·         lines of scratches e.g. on the underside of the belt are causing a troughing shape

·         production of different products with different widths

1.1.5.    Scratch : A visible line in longitudinal direction. That is caused e.g. by

·         blocking of supporting rollers

·         the upper – and lower belt are running with different speed without product

·         foreign material is sticking on scraper

·         machine breakage

·         the cleaning is not professional

This “ finest “ kind of damage can cause big problems due to this notche always a crack is the next kind of damage or and further more when the scratches are multiplying a  cross curvature is occurring.
1.1.6.    Crack : A more or less heavy “ opening “ of the belt surface which has to be welded out. Most important for the description of a crack is

·         when and why the crack happened

·         the length

·         the depth

·         if visible on both sides of the belt

·        other damages ( deformations ) nearby the crack

The reasons for cracks are e.g. 

·         the belt edge touches the machine frame >> edge cracks

·         foreign particles  came in between both belts or between belt and drum

·         material defect

·         bad welding repair

·        material fatigue

Single cracks are welded out,  

Belt edge cracks are repaired by cutting out the damaged area and a trapezoide-shaped belt piece is inserted. 

Many cracks in a specific area or star shaped cracks are repaired by cutting out this damaged area  and a round shaped patch is inserted either.

·         by hand ( in emergency cases )

·         and/or later replaced by a patch automated welded and finished by the Berndorf Band Patching Tool PT 2001

1.1.7.    Sharp belt edge or other belt edge deformation : The belt edge is not in the round shape and condition as delivered Sharp belt edges always causes soon or later belt edge cracks and as a result  Edge waves are caused by touching some parts at the press  >> a production stop <<
The reasons are e.g.

         belt edges are touching machine parts ( edge waves )

·         if the belt edge has a troughing shape it will get damaged at the supporting rollers

·         belt is over stretched at one edge caused by hydraulic defect at the tensioning drum

·         drum layers are in bad conditions

·         the edge sensors are not working properly

·        the belt tracking system is not working properly

Sharp belt edges can be reshaped with the Berndorf Band BERMT tool 

Belt edge cracks must be welded out immediately 

Many cracks in a certain area only should be repairs by inserting a belt piece ( strip ) over the damaged length by hand 

or a patch by the PT 2001  or a long hole patch by the Long Hole Patching Tool. Inserting a belt piece over the whole belt width. Trimming the whole belt length. Belt edge waves can be shrinked by very skilled technicians

1.2.             Flatness- and Thickness deviation
1.2.1.    Flatness deviation : Describes the difference of a certain area of a belt ( e.g. the peak or the valley of a dent or wave ) in relation to the surrounding optimal flat area of the belt.

1.2.2.    Thickness deviation : Is the difference between the minimum and the maximum thickness of the whole belt or a specific area

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