This may be a good time to consider installation of a new internal rubber belt lubricating water spray pipe at the location where it will do the most good. The correct location for this spray is just after the water removal rolls and just before the rubber belt pressure roll. The spray should be aimed so that it makes a glancing contact downward against the rubber belt inner surface just before the pressure roll.
Figure 18
Compressor Unit Profile (Mirror)
Figure 19
Water Spray at Tension Roll
Operating Tips - Temperature
In most cases shrinking machine operators tend to use somewhat higher temperatures on the steam heated rubber belt cylinder than is required or desirable. Even the most difficult fabrics to be processed can usually be pre-shrunk at worthwhile production speed, using no more than 285 deg. F. (140 deg. C). Lighter weight, lower warp shrinkage fabrics can often be pre-shrunk using as little as 220 deg.F (104 deg. C) On the other hand, due to particular cloth finishes, temperatures as great as 300 deg.F (149 deg. C) are used. This will of course result in reduced rubber belt life.
As it has been established that temperature is one of the most important factors in determining rubber belt longevity, we should do everything possible to reduce the effects of exposure of the rubber belts to high temperature.
The condition and adjustment of the felt doctor located just below the rubber belt outside the cooling water sprays is very important. The doctor blade must permit a dam of cooling water to form across the full face of the rubber belt so that an effective thermal exchange or cooling of the belt surface will occur. The spray orifices should be directed at the dam of water and not directly at the face of the rubber belt.
In order to avoid greater than necessary exposure of the rubber belt to the heated cylinder surface, when starting up the shrinking machine, the rubber belt heated cylinder should always be the last cylinder to be heated. When cooling down the machine or for emergency machine stops, the rubber belt heated cylinder should always be the first cylinder to be cooled down.
Anytime it is necessary to stop the shrinking machine for periods longer than 5 minutes, it is recommended that the rubber belt heated cylinder should be cooled down. It is recommended that an emergency cooling water spray pipe be installed directly over the heated cylinder for emergency cooling.
The use of machine entrance and exit fabric scrays can often increase useful rubber belt life by as much as 50%. The scrays eliminate the need for many machine "hot stops" made to obtain samples, to change rolls of fabric, or to verify shrinkage control marks.
Operating Tips - Running Without Fabric
It is very poor operating practice to allow the shrinking machine to operate for long periods of time while awaiting fabric, or for any other reasons. Operating the machine without fabric imposes greatly more severe wear conditions on the rubber belt than operating while processing cloth.
Operating Tips - Belts That Are Too Wide or Narrow
Whenever possible, avoid installing a rubber belt which has a working face greater than 6 to 8 inches wider than the widest fabrics to be pre-shrunk. The use of wider belts to pre-shrink narrower fabrics results in severe wear along the rubber belt exposed edges, requiring more frequent belt resurfacing or grinding.
Rubber belt overall width should be at least 1 inch (25mm) less than the heated cylinder face width.
Rubber belt face width should be at least 6 inches (150mm) wider than the widest fabric to be processed.
Rubber belt width may be reduced by 1 inch (25mm) or more when installed on the shrinking machine, with correct operating belt tension. This width loss will be regained at the rubber belt nip with compression applied to the rubber belt.
Operating Tips - Physical (Nip) Pressure
Physical (nip) pressure is another often neglected or abused factor related to rubber belt longevity. The basic rule is that only enough rubber belt compression should be used to pre- shrink a given fabric the required amount in the warp direction. Over- shrinking at the rubber belt and then pulling out the excess amount of pre-shrinkage by increasing palmer speed (tension) is a very poor practice. This not only results in greatly reduced rubber belt useful life, but also produces a pre-shrunk fabric, which is considerably less stable and prone to tension pull-out.
In order to avoid over-compression of the rubber belt, the following practice should be followed: once the compressive shrinking machine is operating a normal speed and the warp shrinkage and cloth width have been verified to be correct, Go to the point between the rubber belt exit and the palmer entrance and look at the pre-shrunk cloth. The cloth should not be running tight between these two points. Actually, it is best if the fabric runs just barely slack, but never tight. If the cloth at this point is tight, very gradually reduce the squeeze (compression) of the rubber belt, until the cloth just starts to become slack. Then, very slightly increase the nip pressure on the rubber belt to avoid the cloth slack from increasing. While it is a good idea to again verify the cloth warp pre-shrinkage, the warp shrinkage should not have changed. The relative speed of the palmer to the rubber belt unit has not changed and this is what determines the amount of cloth pre-shrinkage left in the goods upon leaving the rubber belt.
Rubber belt tension is quite critical. The tension adjustment does not usually have a very great effect on rubber belt useful life, although rubber belt tension can affect the tracking of the rubber belt and this can definitely affect rubber belt life. A poorly tracking belt can suffer irreparable damage or even in the case of light damage to the belt edges due to poor tracking, it may become necessary to trim the width of the belt, which can result in the belt becoming too narrow to process many fabrics. Insufficient tension may result in scuffing and eventual cracking of the belt inner surface.
Operating Tips - If Crack Occur
If cracks should occur on the belt edge, never simply cup out such cracks, as such cups or notches cause severe shock to the belt as the belt edge moves past the limit roller. It is preferable to trim the entire belt edge to remove a crack, or at the very least, make a gradual cut over a long stretch of belt edge to avoid a notch.
Operating Tips - Routine Inspection
It is very important to be sure that the rubber belt unit is set up properly and checked from time to time for proper adjustment. Aiming of the rubber belt limit rollers is very important to avoid damage to the rubber belt. It is especially important that the rubber belt pressure roll be absolutely parallel to the heated cylinder. Uniform and parallel operation of the water removal rolls is likewise very important. Re-setting of the rubber belt nip pressure gauge after installation of a new rubber belt and after each grinding of the belt surface is absolutely necessary. Correct operation of all roll bearings is essential, as is the adjusting of rubber belt tension.
Cleaning of the rubber belt and heated cylinder after a new belt installation, after each surface grinding of the rubber belt and once each day during normal operation of the compressive shrinking machine can greatly help to extend useful rubber belt life.
Operating Tips - Avoiding Cracks
Always avoid use of any sharp cutting instruments around the rubber belt. Attempting to cut fabric under process, as it enters the rubber belt often results in severe damage to the rubber belt.
Never join cloth lengths using knots on selvages. Knots or other similar sized or larger objects passing through the rubber belt nip will almost always result in damage to the rubber belt, which may not be noticed immediately, but which will likely later show up as a crack in the belt.
Selvage clips inadvertently left on the cloth are often the cause of damage to rubber belts.
Operating Tips - Shutting Down
Before stopping the rubber belt unit to shut down , always make sure that the heated cylinder is cool to the touch, the pressure or squeeze of the rubber belt is completely released and the water removal rolls are open. Make sure that the steam supply valve to the heated cylinder is tightly closed and the steam trap by-pass valve is also closed.
Proper training of machine operators to insure that all of the foregoing suggestions are carefully followed can reduce operating costs by thousands of dollars annually and improve the appearance and shrinkage control of processed cloth.
HTRC - Instructions
High temperature release compound is a specially formulated product. Although it is sometimes referred to as wax, technically it is not a wax. It is a chemically formulated product with wax like properties. It contains no petroleum based ingredient which would be harmful to natural rubber, nor does it contain vegetable or bee’s wax.
The elevated melt point of this product permits it’s use on the heated natural rubber belts in a way in which it remains on the belt surface for a prolonged period of time and it is not absorbed into the rubber itself.
High temperature release compound is available in convenient to use cylinders of a size and shape which can be SAFELY and EASILY applied. The hand held cylinders are very economical. They can be used WITHOUT THE DANGER associated with clumsy, smaller wax cakes, which tend to break and crumble during handling. The compound cylinders are uniform in size, 2.25” in diameter and 12” long (57 mm x 305 mm) and weigh 1.5 lbs each (0.680 kg).
APPLICATION – High Temperature Release Compound is applied to the rubber belt outer surface only in the areas beyond the width of the fabric being processed at the time. In other words the compound is applied only to the area of the rubber belt directly exposed to the heated cylinder surface. Normal frequency of application is belt determined by individual experience, however, in most cases application is repeated about every 6 to 8 hours during production. Frequency of application should not exceed every 3 hours even in extreme cases.
METHOD OF APPLICATION - We wish to repeat here that CAUTION should always be taken to avoid personal injury and damage to the rubber belt when working in close proximity with the compressive shrinking machine. With the shrinking machine at normal operating temperature, the compound is applied to the surface of the rubber belt with very light pressure at a point just above the outside water spray pipe. The compound is applied in steps until the entire width of the portion of the rubber belt directly exposed to the heated cylinder surface outside of the cloth width has received the application, on both sides, or edges of the belt. The compound is normally kept in contact with the belt without shifting position, until the rubber belt has made a complete revolution. The cylinder of compound is then shifted sideways, repeating the procedure until the entire desired area has been treated. The same procedure is repeated on both the left and right of the rubber belt.
PURPOSE OF USE – By greatly reducing friction between the rubber belt surface and the heated cylinder surface in the areas where fabric does not protect the rubber belt from direct contact with the heated cylinder surface, several advantages are obtained.
Periods between rubber belt grinding will be extended.
Rubber pick-off or pull-out which may eventually develop into cracking of the rubberbelt in these critical areas is reduced or eliminated.
Erratic jumping or vibration of the rubber belt which, may cause fabric corrugations or a moiré appearance on some fabrics is eliminated.
Erratic jumping of the rubber belt which exposes the rubber to great stress and also in severe cases may even damage shrinking machine parts, is eliminated.
Deposits of rubber or foreign material on the cylinder surface causing excessive wear on the belt surface and sometimes resulting in fabric selvage distortion, are eliminated.
Raising or bubbling of the rubber belt in the center at the pressure roll may be reduced or eliminated.
Compound on the belt edges also makes it easier for the water removal rolls to eliminate excessive water on the belt in this area where excessive water sometimes causes fabric selvage discoloration or wrinkling.
NOTE: High temperature release compound has been found to produce desired results with no negative side effects. Some products which may be similar in color, smell appearance, etc. may be harmful to natural rubber, may cause staining or discoloration of fabrics selvages, or result in other problems depending upon the chemical composition of the product.
This may be a good time to consider installation of a new internal rubber belt lubricating water spray pipe at the location where it will do the most good. The correct location for this spray is just after the water removal rolls and just before the rubber belt pressure roll. The spray should be aimed so that it makes a glancing contact downward against the rubber belt inner surface just before the pressure roll.
Figure 18
Compressor Unit Profile (Mirror)
Figure 19
Water Spray at Tension Roll
Operating Tips - Temperature
In most cases shrinking machine operators tend to use somewhat higher temperatures on the steam heated rubber belt cylinder than is required or desirable. Even the most difficult fabrics to be processed can usually be pre-shrunk at worthwhile production speed, using no more than 285 deg. F. (140 deg. C). Lighter weight, lower warp shrinkage fabrics can often be pre-shrunk using as little as 220 deg.F (104 deg. C) On the other hand, due to particular cloth finishes, temperatures as great as 300 deg.F (149 deg. C) are used. This will of course result in reduced rubber belt life.
As it has been established that temperature is one of the most important factors in determining rubber belt longevity, we should do everything possible to reduce the effects of exposure of the rubber belts to high temperature.
The condition and adjustment of the felt doctor located just below the rubber belt outside the cooling water sprays is very important. The doctor blade must permit a dam of cooling water to form across the full face of the rubber belt so that an effective thermal exchange or cooling of the belt surface will occur. The spray orifices should be directed at the dam of water and not directly at the face of the rubber belt.
In order to avoid greater than necessary exposure of the rubber belt to the heated cylinder surface, when starting up the shrinking machine, the rubber belt heated cylinder should always be the last cylinder to be heated. When cooling down the machine or for emergency machine stops, the rubber belt heated cylinder should always be the first cylinder to be cooled down.
Anytime it is necessary to stop the shrinking machine for periods longer than 5 minutes, it is recommended that the rubber belt heated cylinder should be cooled down. It is recommended that an emergency cooling water spray pipe be installed directly over the heated cylinder for emergency cooling.
The use of machine entrance and exit fabric scrays can often increase useful rubber belt life by as much as 50%. The scrays eliminate the need for many machine "hot stops" made to obtain samples, to change rolls of fabric, or to verify shrinkage control marks.
It is very poor operating practice to allow the shrinking machine to operate for long periods of time while awaiting fabric, or for any other reasons. Operating the machine without fabric imposes greatly more severe wear conditions on the rubber belt than operating while processing cloth.
Operating Tips - Belts That Are Too Wide or Narrow
Whenever possible, avoid installing a rubber belt which has a working face greater than 6 to 8 inches wider than the widest fabrics to be pre-shrunk. The use of wider belts to pre-shrink narrower fabrics results in severe wear along the rubber belt exposed edges, requiring more frequent belt resurfacing or grinding.
Rubber belt overall width should be at least 1 inch (25mm) less than the heated cylinder face width.
Rubber belt face width should be at least 6 inches (150mm) wider than the widest fabric to be processed.
Rubber belt width may be reduced by 1 inch (25mm) or more when installed on the shrinking machine, with correct operating belt tension. This width loss will be regained at the rubber belt nip with compression applied to the rubber belt.
High temperature release compound is a specially formulated product. Although it is sometimes referred to as wax, technically it is not a wax. It is a chemically formulated product with wax like properties. It contains no petroleum based ingredient which would be harmful to natural rubber, nor does it contain vegetable or bee’s wax.
The elevated melt point of this product permits it’s use on the heated natural rubber belts in a way in which it remains on the belt surface for a prolonged period of time and it is not absorbed into the rubber itself.
High temperature release compound is available in convenient to use cylinders of a size and shape which can be SAFELY and EASILY applied. The hand held cylinders are very economical. They can be used WITHOUT THE DANGER associated with clumsy, smaller wax cakes, which tend to break and crumble during handling. The compound cylinders are uniform in size, 2.25” in diameter and 12” long (57 mm x 305 mm) and weigh 1.5 lbs each (0.680 kg).
APPLICATION – High Temperature Release Compound is applied to the rubber belt outer surface only in the areas beyond the width of the fabric being processed at the time. In other words the compound is applied only to the area of the rubber belt directly exposed to the heated cylinder surface. Normal frequency of application is belt determined by individual experience, however, in most cases application is repeated about every 6 to 8 hours during production. Frequency of application should not exceed every 3 hours even in extreme cases.
METHOD OF APPLICATION - We wish to repeat here that CAUTION should always be taken to avoid personal injury and damage to the rubber belt when working in close proximity with the compressive shrinking machine. With the shrinking machine at normal operating temperature, the compound is applied to the surface of the rubber belt with very light pressure at a point just above the outside water spray pipe. The compound is applied in steps until the entire width of the portion of the rubber belt directly exposed to the heated cylinder surface outside of the cloth width has received the application, on both sides, or edges of the belt. The compound is normally kept in contact with the belt without shifting position, until the rubber belt has made a complete revolution. The cylinder of compound is then shifted sideways, repeating the procedure until the entire desired area has been treated. The same procedure is repeated on both the left and right of the rubber belt.
PURPOSE OF USE – By greatly reducing friction between the rubber belt surface and the heated cylinder surface in the areas where fabric does not protect the rubber belt from direct contact with the heated cylinder surface, several advantages are obtained.
Periods between rubber belt grinding will be extended.
Rubber pick-off or pull-out which may eventually develop into cracking of the rubberbelt in these critical areas is reduced or eliminated.
Erratic jumping or vibration of the rubber belt which, may cause fabric corrugations or a moiré appearance on some fabrics is eliminated.
Erratic jumping of the rubber belt which exposes the rubber to great stress and also in severe cases may even damage shrinking machine parts, is eliminated.
Deposits of rubber or foreign material on the cylinder surface causing excessive wear on the belt surface and sometimes resulting in fabric selvage distortion, are eliminated.
Raising or bubbling of the rubber belt in the center at the pressure roll may be reduced or eliminated.
Compound on the belt edges also makes it easier for the water removal rolls to eliminate excessive water on the belt in this area where excessive water sometimes causes fabric selvage discoloration or wrinkling.
NOTE: High temperature release compound has been found to produce desired results with no negative side effects. Some products which may be similar in color, smell appearance, etc. may be harmful to natural rubber, may cause staining or discoloration of fabrics selvages, or result in other problems depending upon the chemical composition of the product.
Physical (nip) pressure is another often neglected or abused factor related to rubber belt longevity. The basic rule is that only enough rubber belt compression should be used to pre- shrink a given fabric the required amount in the warp direction. Over- shrinking at the rubber belt and then pulling out the excess amount of pre-shrinkage by increasing palmer speed (tension) is a very poor practice. This not only results in greatly reduced rubber belt useful life, but also produces a pre-shrunk fabric, which is considerably less stable and prone to tension pull-out.
In order to avoid over-compression of the rubber belt, the following practice should be followed: once the compressive shrinking machine is operating a normal speed and the warp shrinkage and cloth width have been verified to be correct, Go to the point between the rubber belt exit and the palmer entrance and look at the pre-shrunk cloth. The cloth should not be running tight between these two points. Actually, it is best if the fabric runs just barely slack, but never tight. If the cloth at this point is tight, very gradually reduce the squeeze (compression) of the rubber belt, until the cloth just starts to become slack. Then, very slightly increase the nip pressure on the rubber belt to avoid the cloth slack from increasing. While it is a good idea to again verify the cloth warp pre-shrinkage, the warp shrinkage should not have changed. The relative speed of the palmer to the rubber belt unit has not changed and this is what determines the amount of cloth pre-shrinkage left in the goods upon leaving the rubber belt.
Rubber belt tension is quite critical. The tension adjustment does not usually have a very great effect on rubber belt useful life, although rubber belt tension can affect the tracking of the rubber belt and this can definitely affect rubber belt life. A poorly tracking belt can suffer irreparable damage or even in the case of light damage to the belt edges due to poor tracking, it may become necessary to trim the width of the belt, which can result in the belt becoming too narrow to process many fabrics. Insufficient tension may result in scuffing and eventual cracking of the belt inner surface.
If cracks should occur on the belt edge, never simply cup out such cracks, as such cups or notches cause severe shock to the belt as the belt edge moves past the limit roller. It is preferable to trim the entire belt edge to remove a crack, or at the very least, make a gradual cut over a long stretch of belt edge to avoid a notch.
It is very important to be sure that the rubber belt unit is set up properly and checked from time to time for proper adjustment. Aiming of the rubber belt limit rollers is very important to avoid damage to the rubber belt. It is especially important that the rubber belt pressure roll be absolutely parallel to the heated cylinder. Uniform and parallel operation of the water removal rolls is likewise very important. Re-setting of the rubber belt nip pressure gauge after installation of a new rubber belt and after each grinding of the belt surface is absolutely necessary. Correct operation of all roll bearings is essential, as is the adjusting of rubber belt tension.
Cleaning of the rubber belt and heated cylinder after a new belt installation, after each surface grinding of the rubber belt and once each day during normal operation of the compressive shrinking machine can greatly help to extend useful rubber belt life.
Always avoid use of any sharp cutting instruments around the rubber belt. Attempting to cut fabric under process, as it enters the rubber belt often results in severe damage to the rubber belt.
Never join cloth lengths using knots on selvages. Knots or other similar sized or larger objects passing through the rubber belt nip will almost always result in damage to the rubber belt, which may not be noticed immediately, but which will likely later show up as a crack in the belt.
Selvage clips inadvertently left on the cloth are often the cause of damage to rubber belts.
Before stopping the rubber belt unit to shut down , always make sure that the heated cylinder is cool to the touch, the pressure or squeeze of the rubber belt is completely released and the water removal rolls are open. Make sure that the steam supply valve to the heated cylinder is tightly closed and the steam trap by-pass valve is also closed.
Proper training of machine operators to insure that all of the foregoing suggestions are carefully followed can reduce operating costs by thousands of dollars annually and improve the appearance and shrinkage control of processed cloth.
