SERVICE IN THE WOOD PANEL INDUSTRY

How to describe a damage properly ?

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.

Belt specific terms and their explanations

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.

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....

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

Cross curvature

The cross curvature describes the flatness of a belt crosswise over the width of a belt.
-  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

Scratch

A visible line in longitudinal direction

That is caused by e.g.
-  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.

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

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

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 longhole patch by the Longhole 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

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.

Thickness deviation

Is the difference between the minimum and the maximum thickness of the whole belt or a specific area

Special terms for the various job categories

Classification and general description of all jobs offered by Berndorf  Band and VFE Service Department.

Dismounting – Mounting

The pulling out of belts respectively the installation of steel belts into the customers machine ( press )

Cutting a belt

The cutting of an endless belt at any point ( preferably ) at the existing cross welding seam , considering that the belt will be welded again to endless condition later.

Tracking a belt

This procedure happens after the belt installation. Herewith all the parts which influence the tracking of the belt ( pulleys, rollers, drums, sheaves and so on ) are to be adjusted in a way that the belt runs in stable / straight running ) conditions

Shot peening

With this method we are able to correct cross curvature deformations of belts in Double Belt Presses during production .
At Single Opening Presses no production is possible during this treatment due to the belt has to run continuously.

Flipping a belt

When a cross curvature has to be removed ( shot peening is not sufficient any more ) the belt will be cut, dismounted , turned around inside to outside , mounted and rewelded again.

Flattening of dents

When dents are to be flattened we try to work this plastic deformation as long as optimum flatness condition is achieved again ( professional hammering )

Leveling

Is the treatment of a belt with heavy cross curvature deformations with the 3 - roll leveling device

Flattening

We understand the correction of the cross curvature or longitudinal oriented deformations by using the flattening device ( 3 – roll leveling device )

Inserting of patches

Many damages can be repaired by inserting patches with round shape only , because of hard deformations or cracks

Regrinding of scratches

Scratches , which are the reason for future cracks are eliminated ( treated ) by local regrinding

Welding of holes

Small cracked areas with missing material ( e.g. holes ) can be repaired by welding using filler wire to close the hole.

Renewing a cross welding seam

It is possible to renew a cross welding seam ( caused by fatigue or overstress ) only with considering the possible tensioning allowance of the press. The old cross welding seam will be cut out ( with approx. 50 – 100 mm belt material ) and the both belt ends rewelded again.

Inserting a belt section

This will be done at large size damages or when the remaining tensioning allowance of the machine is not big enough anymore to cut out the damage and renew the welding seam.

Additional cross welding seam

Is necessary when the damage has to be cut out over the whole belt width and the existing cross welding seam cannot be used ( too far away from the damage )

Inserting of belt edge strips

When the belt edge damages in some areas are so heavily that many cracks appeared then we recommend to cut out the damaged area and insert a belt strip out of the available belt spare material . 

Trimming

Is the removal of a strip on the belt edge over the whole belt length.

This is necessary when extreme damages over the whole length appeared, the tracking behavior is too bad but considering a smaller belt width of the belt after trimming !!

Shrinking

With this method single overstressed areas ( e.g. bubbles ) will be repaired by thermal treatment

Changing of wear plates

We are able to deliver a new wear – or protection plate and to change the old one according to the customers requirements. ( in SOP )

Measurement examples for damages

After explaining some specific terms of damages and repair methods and to be able to describe a occurred damage as exact as possible we want to continue to show and explain how to measure and protocol the damage.

This should be done whenever a
-  damage occurs , whenever
-  you require and need a specialist from outside and
-  to update your belt maintenance
-  and history book for your own planning and safety.

Waviness

The waviness describes periodical appearing of single flatness deviations of a belt by wave height and wave length. The wave height is the distance between the lowest point of the bottom and the highest point of the peak of a wave. The wave length is the distance between two adjacent peaks or bottom points.Waves are zones with bigger length than the surrounding area and can be snapped to the opposite side by hand pressure ( from outside to inner side and vica versa )
Waves can be located on the belt edges as well as in the center of the belt. The size of waves is mainly depending on the tension of a belt, therefore the tension of a belt must be considered in
any case. Waves are caused by thermal or mechanic overload of the belt material.
This can happen e.g. when the belt collides with the framework of the press or the belt is exposed to local overheat. Waves can be repaired only in very few cases

A waviness can be expressed by using the flatness index I.

I = H? / L? x 250.000 ( H = wave height , L = wave length , in mm )

(See 6.4.1. Service Handbook for table page 2 and 3)

The maximum allowed waviness of a new Berndorf belt (according to Berndorf - Standard Specification) can be found
in following table:

for the welding area is valid: 

The cross curvature describes the size and the direction of the flatness of a belt in the cross direction.

The direction can be a concave ( troughing shape ) , a convex ( roof shape ) , or a mixed one.

It is influenced by the internal stress condition of the belt and by the geometry of the supporting .

The reason for the increase of the cross curvature of a belt in comparison to the original condition when delivered , are mainly changes of the internal stress.

This is caused mainly by roll and friction stress in the customers machine

or by scratches in the belt surface.

By this, compression stresses are induced into the belt surface which change the cross curvature condition.

At the measuring position the belt must show a free sag and should be between two adjacent rollers

It must be checked prior to the measurement if the cross curvature is uniform all over the length of the belt.

If not the worst deformation area must be found , measured and protocolized.

The measuring ruler is placed parallel to the belt over the whole width of it and the weight of the ruler should not influence the measuring result by deforming the belt shape.

Every 100 mm , over the whole width , starting at one belt edge , the distance between the ruler and the belt surface will be taken ( measured ) and these values are noted in the appropriate column of the measuring protocol.

If the measurement of the cross curvature is to be done within the scope of a repair ( shot peening or flattening the belt ) it is necessary to measure the deformed belt shape before and after the repair .

Please find below a correct filled out cross – curvature protocol.

(6.4.2., page 3 – Service Handbook )

Straight Running Deviation

The straight running deviation describes the amount of the sideward movement  of a belt edge of a well – tracked belt during one revolution in relation to a fix point of the press construction ( or drum edge )

Mark the measuring points on the belt in an interval of 10 meters over the whole length of the belt , starting with the cross welding seam.

Take a fix point ( preferable e.g. the edge of the drum where you are positioned or a point at the frame of the press ) and measure the distance of the belt edges to that fix point.

The difference between the minimum and the maximum value is the :

Maximum straight running deviation : = ( 2 / 10.000 ) x L ( = belt length )

And should not exceed 20 mm ( Berndorf Band Standard Specification )

CHECKLIST  FOR  SERVICE  JOBS

Preparatory works to be executed by the customer before a Berndorf Band

or Vienna Far East belt specialist is arriving on site

The necessary Berndorf Band welding equipment is always sent from the VFE Service Department in time to the customer before a job is getting started.

If a crane or a forklift is available on site , it should be possible to use it at short notice if necessary.

All required dismounting works e.g. for the new belt installation and for placing our clamping device must be concluded prior to the beginning of the works with the belt.

Platforms for e.g. mounting the Berndorf Band clamping device or installing the Berndorf Band High Power Shot Peener and working areas for the technicians must be established , already.

For the installation of a new belt a motorized uncoiling device with a brake and an electrical winch with a sufficient long cable , must be available.

Furthermore the Installationbar for pulling the belts into the press and to the appropriate place has to be prepared according to the attached sketch .

As auxiliary staff 2 to 4 persons , if possible already experienced people in working on steel belts should be permanently present.

Always consider the need of in electricity ( 220 V AC / 16 A and / or 380 V AC / 32 A ) for welding procedure and grinding works to be carried out

And the need in compressed air of 6 to 8 bars ermanently support with water separator for very dry air in case of a shot peening work or plasma cutting and cooling water , approx. 20 – 30 liter / min, max. 20 degrees and clean . ( ?? pf >> to ask Berndorf )

For welding works a bottle of protective gas , at least one 20 liter bottle Argon gas with 4 m? pure Argon , quality 5.0 or purity of at least 99,999 % , has to be available by the customer. With this gas bottle a argon gas regulator should be provided, too.

For security reasons it is not allowed to bring a gas bottle over the border of a country.

For the welding of Carbo 13 belts ( belt installation or belt repairs ) an autogenous welding battery has to be available.

This battery consists of 2 filled gas bottles one with Oxygen and the other with Acetylene as well as both pressure reducers with gas hoses ( with a length of at least 5 meters )

The ecessary torches are provided by the service specialist.

The belt material or inserting whole belt pieces or patches are provided by the customer. If there is a need for spare belt pieces kindly contact Berndorf Band or VFE directly.

In order to handle a job as fast as possible it must be possible to run the belt to the appropriate position backwards and forwards.

Moreover it must be possible to operate the tension of a belt in order to judge the flatness of the welding seam.

Furthermore it must be possible to test run the belt in order to measure the straight running deviation. For that several revolutions are necessary.

In case of emergency repairs , when the belts are heated up and the press is hot an appropriate cooling time or heat isolation must be provided, so that the working area reaches a temperature which enables a careful and concentrate working.

If this requirement is not met we cannot guarantee the success of the work.

For some works a plasma cutter is necessary and has to be provided by the customer.

In case there is no plasma cutter available the service department has to be informed.

VFE has all necessary tools available in Bangkok.

Acetone , a cleaning detergent has to be provided from the customers site , this cleaning solvent cannot be taken with us ( e.g. in a plane ) and this cleaner is the best solution for cleaning the belt before welding !!

A color penetration test  ( white – and red color - spray for testing the penetration of a welding seam ) has to be provided by the customer ;

it is not allowed to take this test with us ( e.g. in a plane ).

You can find and buy this kind of test in every good welding shop.

In case no Berndorf Band Repair Tooling Box is on site it is always very helpful due to their weight  if the customer can provide us with his own copper plates for welding. ( 3 pieces with a groove  of 10 mm width exactly in the middle of each copper plate ; dimension preferable : 300 l x 100 w x 10 mm thickness )

The best preparation for a service intervention is always to check the listed items mentioned before and if not yet done

to ordera Berndorf Band Repair Set ( small or big )

to be prepared for all upcoming damages and repairs and to save a lot of time

in sending our tooling box to the customer.

Whenever an emergency call has to be done to the VFE Service Department the only time needed is to coordinate the working scope and the travel schedule and our technicians are on site in the shortest possible time.

CHECK LIST

To describe damages properly

Date

Customer

Name
Address
Telephone
Mobile
Fax
E-mail
Responsible Person

Press Datas

Belt Datas
-  belt number
-  date of belt installation
-  top belt or bottom belt
-  material          mill finished                one side / both sides ground
-  length              width                        thickness
-  surface : inside          outside
-  longitudinal welding seam : no / yes : one or two
-  belt tension
-  remaining detensioning allowance in mm
-  maximum product width
-  belt speed

Belt tracking system
-  none
-  mechanic
-  hydraulic
-  pneumatic
-  others

Which kind of repairs have been already executed on the damaged belt
-  1
-  2
-  3
-  none
-  by yourself
-  by technician from outside
-  when
-  why the previous damage (s )  occurred

What kind of damage happened

The questionnaire below if for the exact description of  scratches (s) ,

cracks ( c ) , dents ( d ) , bubbles ( b ) , and waves ( w )

s – c – d – b – w  :   quantity, length, width, direction, location :
-  distance to CWS
-  distance from left / right belt edge

direction

-  longitudinal
-  cross
-  diagonal

visibility

-  inside
-  outside
-  both

Was the damaged area already repaired before

Probable cause of damage

Best possible drawing of the damages : s – c – d – b – w  

PREVENTIVE MAINTENANCE – Keep A Protocol ( KAP )

Belt edge inspection for cracks and damages –  always when shut down KAP

measures:

crack welding,
grinding the damaged edge by hand,
edge rerounding by filing,
using the Berndorf Band  BERMT to prevent all these kind of damages

Belt shape observation – always when shut down - KAP

measures

measurement of the belt shape, always when shut down
shot peening
flipping the belt

Surface inspection for scratches, dents, or cracks – always when shut down - KAP

measures

inspection always when regular shut down
grinding off the scratches
hammering or leveling the dents
welding out the cracks

Inspection of the belt inner side for pitting, wear off or scratches - always when shut down - KAP

measures

find the reasons or inform VFE immediately
repair accordingly

Inspection of the belt edge sensors for the belt guiding system
 – always when shut down – KAP

measures

correct adjustment To check and to avoid that foreign material can come between belt and drum or between both belts – always , even during production – KAP

measures

magnets
scrapers

Inspection of the belt cleaning devices – always , even during production – KAP

measures

replacement
cleaning
correct adjustment

Suitable lubrication in quality and quantity – always – KAP

measures

regular control

Inspection of the drum linings for wear , lift – off or excessive dirt
– always , whenever possible – KAP

measures

repair
call specialist

Inspection of the belt supporting rollers for even contact and easy movability
 – always - KAP

measures

correct adjustment

Check movability of the rollers and chains in the press – whenever possible – KAP

correct adjustment