How long should a rubber belt last?

Most rubber belts are not taken out of service because they no longer perform. Many rubber belts removed from machines because they have reached a certain thickness such as 50 mm or 45 mm, are often capable of performing perfectly if rubber belt tension is increased.

Most rubber belts are removed from service because of damage to the rubber belt resulting from accidents, poor machine operator practices, poor maintenance, etc.

Good quality rubber belts used to pre-shrink 14-3/4 oz. (500 gr/m2) denim, if properly maintained by well trained shrinking machine operators, should last between 11 and 14 million yards (10 and 13 million meters). Some users have even reported 10% greater useful life.

Rubber belts used for lightweight goods or cotton blends, as well as belts used to improve cloth hand only, may last between 20 and 25 million yards (18.3 and 22.9 million meters).

Unfortunately, many users of good quality rubber belts who shrink heavy weight denim fabric regularly obtain only 7 to 9 million yards (6.4 to 8.2 million meters) of useful life. This is due to poor operator skills, poor preparation of cloth to be pre-shrunk, and poor rubber belt and shrinking machine maintenance.

Why am I experiencing wavy selvages?

Wavy selvages normally appear only after the cloth has conditioned for several hours or even days after having been pre-shrunk.

In most cases, the problem is caused by moisture differential between the cloth edges and the body of the cloth. A typical reason for this differential moisture is excessive moisture pick up by the cloth edges due to over spray during dampening of the goods prior to entry into the rubber belt. The cloth edges may pick up extra moisture from skyer rolls if spray pattern is too wide for the cloth.

Under spray can also cause this problem if cloth edges are dryer, relative to the body of the cloth when it enters the rubber belt unit.

Sometimes, when belt tension has not been increased during belt grinding, excessive curl of the belt edges will result in the edges being ground thinner than the body of the rubber belt. Thin belt edges will carry more rubber belt cooling water, which will be absorbed by the cloth edges.

Improperly adjusted, or poorly operating water removal rolls may also allow more cooling water to remain on the belt edges and can result in wavy selvages.

Rubber belts that are too narrow for the cloth being processed may develop wavy selvages. The rubber belt ideally should be 8 inches (200 mm) wider than the widest cloth to be processed.

Using insufficient temperature of the steam heated rubber belt cylinder can sometimes result in wavy selvages.

Insufficient palmer cylinder temperature can result in cloth edges leaving the palmer with more moisture than the body of the cloth Occasionally a wavy selvage on only one side or on both sides of the cloth can sometimes be traced to a worn or improperly operating pad used prior to dry cans in the process prior to compressive pre-shrinking.

There is occasionally a tendency for liquid squeezed from the cloth at the pad to follow the diagonal twill pattern to one side of the goods resulting in that side of the goods retaining greater moisture. Even after partial drying on heated cans, moisture on the one side may be higher.

Rolls of heavyweight denim taken from the pad/dry can finishing range with 7% or more residual moisture, if not passed through the compressive shrinking machine within 4 hours or less may sometimes have dryer edges at the time the goods is being pre-shrunk and this can result in wavy selvages.

Standing rolls of pre-shrunk goods on end will often result in wavy selvages.

Why do I have roughness throughout the interior of my rubber belt?

Most rubber belt shrinking machines have the internal water spray installed in the wrong location. The internal water spray is used to lubricate the belt interior. Lubrication is important so that as the rubber belt elongates and becomes wider as it is squeezed at the nip point, it must slip easily against the surface of the pressure roll, otherwise elongation of the belt will be restrained and the capacity of the rubber belt to recoil and compact the cloth will be reduced. Severe abrasion to the rubber belt interior may also occur.

Therefore, the internal water spray should be located just below the pressure roll and after the water removal roll. Water sprays located at the back side of the rubber belt are very much less effective, since most water applied to the belt inner surface at this location, will be removed by the wiping action of the belt idler roll and the water removal roll (s), by the time it arrives at the pressure roll.

When my belts get reduced to 2 inches (50mm) or less, why can I no longer get the required warp shrinkage and the cloth is corrugated?

When rubber belts reach a thickness of 2 inches (51 mm) or for rubber belts ordered at 2 inches (51 mm) thick, the amount of lengthwise tension required to insure best performance is ½ inch (13 mm) of stretch of the 12 inch (305 mm) marks placed on the belt edge. Failure to apply sufficient lengthwise tension to a rubber belt will often greatly reduce the capacity of the belt to shrink, cause generalized light corrugations in some shrunk fabrics and may result in the occurrence of cracks on the belt interior.

Why do I frequently get wrinkles on the cloth edges which look like crows feet?

1. Insufficient lengthwise Tension on fabric entering rubber belt causing overfeeding or uneven lengthwise tension of fabric. This caused the edges of the fabric to become creased.
2. Over moisturization on edges of cylinder thus causing too much moisture on edges of fabric.
3. Differential moisture across fabric. (i.e., uneven moisture applied).

When I process certain dark colored fabrics why do I get a loud whistling sound?

It is not always possible to eliminate this high pitched sound. In some cases increasing the temperature of the steam heated cylinder or pre-heating the cloth using the hated can located between the fabric skyer and the rubber belt unit will reduce or eliminate the noise. Increasing rubber belt heated cylinder temperature will also reduce rubber belt useful life

Some success has been reported in eliminating the noise by hanging a heavy cotton cloth over the emergency cooling water spray pipe and allowing the cloth to just drape onto the top of the steam heated cylinder. Water from the emergency cooling spray is allowed to lightly drip onto the cloth so that very light moisture wicks down the cloth and onto the heated cylinder. This reportedly sometimes solves the problem.

Cloth shrinkage coming off the shrinkage machine appears to be perfect based on shrinkage measurement marks measured at the machine exit, but when the cloth is re-checked before shipment to the customer.

This is usually a problem of cloth elongation after shrinking. The cause may be insufficient moisture in the cloth being pre-shrunk or too much or too little moisture in the cloth coming from the palmer. Cotton fabrics usually require about 1% of moisture for each one ounce per square yard of cloth weight for stable cloth shrinkage. Too little moisture in the cloth being pre-shrunk does not permit the cloth to take on a stable new dimensional memory. Yarns may tend to pus out or elongate and the cloth will again shrink when washed.

Too much or too little moisture in pre-shrunk cloth coming from the palmer will also result in elongation of the cloth during relaxation. Ideally cloth coming from the palmer should have 4% residual moisture content. Less than 4% moisture content will usually result in relax elongation of the cloth, while more than 4% residual moisture content will result in less stable cloth which can be stretched with slight tension such as is normal during inspection and rolling of the cloth.

Cloth between the belt unit and the palmer is often slack on one side and causes wrinkles going into the palmer.

Parallel of the pressure roll to the steam heated rubber belt cylinder is extremely important. If this adjustment is not made precisely, fabric shrinkage will vary from side to side causing a slack selvage on one side of the cloth coming out of the rubber belt. This may also cause the rubber belt to track forcibly to one side, resulting in belt edge cracks.