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Frequently Asked Questions

Q1: How long do urethane belts last (belt lifespan)?
Q2: Why do Cyclothane belts last longer?
Q3: How can we verify that DuraBelt's belts last longer?
Q4: What effect does high temperature have on urethane belting?
Q5: What effect does low temperature have on urethane belting?
Q6: How can I determine the maximum belt loading tension on a belt?
Q7: Which size of urethane belt should I use?
Q8: What's the difference between overlap welds and butt welds?
Q9: Why do overlap welds eventually pull apart under high tension?
Q10: Will our high tension belts damage bearings?
Q11: Do crowns prevent flat belts from moving sideways (walking), i.e. keep belts centered?
Q12: What is the RAVE technique for tracking sleeve installation?
Q13: How do I prevent tracking sleeves from slipping and moving sideways?
Q14: Where do I find Dura-Belt's part numbers?
Q15: How do I clean, sterilize, disinfect, sanitize and/or washdown urethane or Hytrel belts?
Q16: How much should belts wrap around each pulley?

Q1: How long do urethane belts last (belt life span)?
A: A properly-designed, urethane belt in an ideal environment should last many years, but not all urethane belts are of equal quality. The difference in performance between a high quality belt and an average belt can be huge. For example, in two large postal distribution centers 40,000 of our competitor's belts became limp after only 10 months on powered roller conveyors. They were replaced with our HT (High Tension) Blue Cyclothane-B belts, and ten years later those belts are still going strong. In general the average life-span for most high-quality urethane belts appears to be about four to six years with a typical range of 2 to 12 years. Endless round belts usually last considerably longer than twisted connectable belts. Motorized roller belts usually last longer than lineshaft belts.

There are many factors that determine the life-span of a belt, including operating schedule (shifts per week), duty cycle, belt type, belt length, belt thickness, belt durometer, belt stretch, belt speed, pulley or roller size, pulley or roller material, pulley alignment (angle between pulleys), bearing type (sealed vs. shielded), ambient temperature and humidity, amount and type of dust and dirt in the environment, chemical and UV exposure, box weight, box surface, amount of box accumulation (duration and frequency), motor acceleration/deceleration, conveyor type, conveyor design, conveyor width, and level of maintenance. (Also see Longer Lasting Belts.) If your belts are wearing out too soon, ask our Belt Doctor for assistance.
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Q2: Why do Cyclothane belts last longer?
A: Several factors combine to make Cyclothane belts last longer:

1) Our proprietary process for extruding 100% virgin urethane. Urethane manufacturers typically recommend using regrind to improve extrudability and weldability, plus cut costs by reusing waste. Unfortunately, regrind also makes belts less resilient, so we don't use it, even though we believe everyone else does. We send our waste to hose manufacturers.
2) Our proprietary process for making Super Strong Welds that are practicably unbreakable -- up to 10 times stronger than conventional joining processes.
3) Our ungouged welds do not neck down much when stretched. Necked belts stretch more at the joint which causes them to get limp prematurely.
4) Our proprietary process for cross-linking long-chain molecules makes our HT belts super resilient at 20% stretch.
5) Our proprietary coloring process lets us color belts after we make them, so that the colorant does not dilute or weaken the urethane.
6) Our superior quality control process -- we inspect 102% of our belts (2% are inspected twice). Compliant with ISO 9000, we constantly strive for improvements.
7) Our World's Longest Belt Warranty induces us to make doubly sure that we ship only high quality belts,
8) Our "Belt Doctor" helps customers find and eliminate problems that cause belts to fail prematurely. Also see next question.

Q3: How can we verify that DuraBelt's belts last longer?
A: We are certain that our belts are the most resilient -- so certain that we will send you twenty free belts to test. Put them and our competitors' belts of identical size and durometer on the same conveyor span. After 3 months cut off all the belts and measure their length. Ours should demonstrate their resiliency by being about 1/8" to 1/4" shorter. Conveyor manufacturers often use this test. Now you can too. Greater resilience means more drive, longer life, and less downtime.
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Q4: What effect does high temperature have on urethane belting?
A: Urethane is a thermoplastic, so its physical properties decrease as temperature rises. For example, at 120^oF (49^oC.) its life span as measured by resiliency declines to about 70% of what it is at room temperature; at 150^oF (66^oC) its resiliency drops to about 10%. If you need elastic, high temperature belts try our High Temperature Urethane Belts. They will work up to 230^oF (110^oC).
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. They will retain resiliency as high as 230^oF (110^oC.). See

Q5: What effect does low temperature have on urethane belting?
A: Urethane becomes more brittle as temperature decreases. Belts that are allowed to sit overnight in low temperature environments can take a set that is difficult to overcome at start up. This can cause even Super Strong welds to shear apart. Although urethane manufacturers often claim that regular urethane will work down to -10°F, we do not recommend using Cyclothane-A below 30°F (0°C). Our low temperature Cyclothane-E will work down to -10°F (-23°C), but for temperatures below zero F (-18°C) we recommend Hytrel ®. It will work down to -40°F (-40°C) and is especially well suited for ice cream plants. Since Hytrel is not as resilient as urethane, it should not be stretched beyond 7%. Care must be taken not to overstretch it during installation.
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Q6: How can I determine the maximum belt loading tension on a belt?
A: See instructions under the BELT SIZER pull down menu.
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Q7: Which size of urethane belt should I use?
A: See instructions under the BELT SIZER pull down menu.
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Q8: What's the difference between overlap welds and butt welds on reinforced urethane belts?
A: You can easily see the difference between an overlap weld and a butt weld. An overlap weld usually has a big 2" long bump at the joint where the reinforcing cords are overlapped, whereas a butt weld is just a thin line circling the belt. Overlap splices can last a little longer than butt welds if they are perfectly made, but it is hard to make perfect overlaps. A thick layer of urethane must surround each cord. If the two cords touch each other, or if one cord is too close to the surface, the cord pulls out and the belt stretches prematurely. Trying to make perfect overlap welds often produces quite a few rejects, so the price must be higher than for butt welds. (see next question).
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Q9: Why do overlap welds eventually pull apart in high tension applications?
A: Since the reinforced cord is not endless or tied, high tension applications will eventually cause the reinforcement to disbond and slide through the urethane.
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Q10: Will our high tension belts damage bearings?
A: No, because most bearings will take loads considerably larger than our belts can exert. For example, our 3/16" HT Blue belt exerts an initial force of about 25 lbs (12kg), but typical 1.9" (50mm) diameter conveyor rollers will handle a maximum load of 250 lbs (100kg), which is 10 times larger. Moreover, urethane belt tension declines quickly at first. Five minutes after installation, it drops 30%, and after a week the tension levels off at about 14 lbs (30kg). Our idler pulleys use the 6203 bearing, rated at 600 lbs (270 kg) at typical conveyor speeds, so the chances of bearing damage are slim or none. Nevertheless, make sure that your belt tension does not exceed the rating of your application. Our tension calculator lets you calculate the force exerted by our belts.
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Q11: Do crowns prevent flat belts from moving sideways (walking), i.e. keep belts centered?
A: Yes, a crown on a pulley will prevent "walking or wandering". All flat belts have a tendency to “walk”, "wander" or move sideways on flat surfaces. Therefore, uncrowned, flanged pulleys are not recommended because the belt will either rub against the flange and abrade, or stretch and walk up over the flanges. To hold the belt in the center of the pulley, the pulley must be crowned, i.e., larger at the center than on the sides. (See drawing below). All our flat idler pulleys have round crowns of .016” to .020” See crowns on flat idler pulleys. This means that the center diameters are .032” to .040” greater than the diameters at the outside edges of the pulleys.

Our tracking sleeves provide a quick way to add a rectangular crown to a pulley or roller. For elastic belts the sleeve thickness should be about 2% of belt width and about 20% to 40% as wide as the belt. Our standard 1/32” (0.8mm) thick x 1/2” (12.5mm) wide tracking sleeve is stretched 7.5%, but thicker and wider sleeves should be stretched only 2%, otherwise they will be too difficult to install. Our standard sleeves will stay in place by their own tension. For larger sleeves you may wish to put a drop of super glue under them to ensure they will not move.

These are rules of thumb, that may need to be changed, depending upon how parallel your rollers/pulleys are and/or how square the belt is, so you may need to experiment.

Note that crowns may not work on belts that frequently reverse direction, because it usually takes about three pulley revolutions before flat belts center themselves on crowns. In such cases you may need to use a flat belt with a V-guide (i.e., a small V-belt welded to the bottom of the flat belt) and flat pulleys with a V-groove in the center. For information on the physics of crowns see flat belt crown. The next two questions provide tips on tracking belt installation and prevention of slipping.

Flat Belt Pulley Crowns

Q12: What is the RAVE technique for tracking sleeve installation?
A: Installing sleeves (or spool flanges) on rollers is difficult because the sleeve diameter is less than the roller diameter. If you spray RAVE Ultra-Hold hair spray (or the equivalent sticky hair spray) on the end of the roller, the surface remains very slippery while the RAVE is wet, so sleeves will slide on much easier. In about 90 seconds RAVE will dry and act like a glue that prevents the sleeve from moving. Usually the sleeves are so tight, they will not move easily, but hair spray provides added holding power. You can purchase RAVE hair spray at CVS Pharmacy.

If more hold is needed, read the next question below. If you need to reposition the sleeve, you can unlock the glue by sliding a small screw driver under it. If you don't have hair spray, soapy water can be substituted. Heating the sleeves in hot water will temporarily expand them so they slide on easier.
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Q13: How do I prevent tracking sleeves from slipping and moving sideways?
A: Do the following:

Rollers are often covered with a thin coat of oil (e.g. cutting fluid) or grease to prevent rust. This can cause sleeves to slip sideways when side pressure is put on the belts. Before installing sleeves, wipe rollers with acetone to remove any oil or grease.
Some installers use two hooks to stretch sleeves over rollers. If sleeves are stretched more than 40%, they may deform because the urethane has been stretched beyond its elastic limit. This will reduce sleeves' holding tension. Therefore, do not over stretch sleeves during installation.
We recommend using women's "ultra-hold" hair spray (e.g. RAVE) to facilitate installation. It is slippery when wet and glues the sleeve to the roller when it dries. See previous question above.
If a sleeve has already slipped, clean the roller with acetone and move the sleeve back to its original position. Then use a small screw driver to lift the edge of the sleeve while putting a dab of contact cement (e.g. DAP Weldwood) at 0, 90, 180, and 270 degrees around its circumference under both edges. You do not have to let each surface dry before bringing the surfaces together. However, let the cement dry for an hour before restarting the conveyor.
If the sleeve still slips, clean the roller with acetone on each side of the sleeve. Then make a barrier on each side of the sleeve by winding 3 or 4 layers of aluminum foil tape around the roller. (We recommend Nashau aluminum foil tape because its adhesive binds so tightly that it is almost impossible to pull apart. If you want to remove it, you have to cut it off with a razor. The adhesive on 3M aluminum tape seems to become gummy and slip after a while, so do not use it.) If the barrier is about one third as thick as the sleeve, the sleeve will be locked in position.
If none of this works, then try a shorter sleeve.
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Q14: Where do I find Dura-Belt's part numbers?
A: Theoretically we have an infinite number of part numbers because we can make belts of any length. To date we have over 10,000 part numbers. That is why it is not practical to show them. Just tell us the description and we'll tell you the part number.

Actually all are part numbers are "smart", meaning they describe the belt. The first two digits are the thickness in inches without the decimal point. The next letter is a code for the durometer (a = 83A, 85A or 88A, r = 90A, 92A or 95A). The next 5 digits are the cut length in inches. The words describe special attributes, like Rough Green, Orange, HT Blue, Super Red, Static Dissipative, etc. No words means it is standard clear urethane.

For example, our popular 3/16" (.187") x 9.5" HT Blue belt's part number is 18a09.50 HT Blue
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Q15: How do I clean, sterilize, disinfect, sanitize and/or washdown urethane or Hytrel belts?
A: Food processing plants often disinfect their conveyors by washing down with a 20% bleach solution. Bleach attacks urethane, causing it to crack and lose its elasticity, so bleach should not be used to sanitize urethane belts. Food processors that wash down with bleach should use Hytrel belts. (Make sure Hytrel belts are not overstretched during installation, as Hytrel does not “bounce back” like urethane.)

In our laboratory tests we found that Oxine (Chlorine Dioxide), a biocide disinfectant and sanitizer, has minimal effect on urethane, when used at Bio-Cide's recommended 100 ppm concentration in solution with room temperature water for short exposure times. Moreover, Oxine appears to have virtually no effect on Hytrel belts, even up to 500ppm with prolonged exposure at room temperature.

Urethane belts can also be cleaned by washing them in lukewarm water (120°F, 50°C or less) with dishwashing soap like Palmolive or Joy.

Occasional washing of Cyclothane-A urethane will probably not harm the belt, but since it is hygroscopic, frequent washing can slowly damage it, especially if the water is hot. Cyclothane-E belts are not hygroscopic, so frequent washing should not affect them.

Isopropyl alcohol (rubbing alcohol) can be used to clean the surface of urethane, as it evaporates quickly, but prolonged immersion in alcohol will damage urethane.

Steam is not recommended for cleaning any thermoplastic belt because high temperatures reduce belt life. However, steam may cool down substantially by the time it contacts the belts, so flashing them with “cool” steam (150°F, 70°C or less) may not significantly harm Hytrel or Cyclothane-E.

When in doubt, test a few belts before applying any substance to all belts. We recommend immersing a belt in a bottle of the chemical and letting it sit for a week at the belt’s operating temperature. If there is any change in the surface or tensile strength, then the chemical is harming the belt.
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Q16: How much should belts wrap around each pulley?
A: Most applications are designed so that belts wrap between 120 and 240 degrees around their pulleys. If the force needed to turn a pulley is very small, then you may not need more than 90 degrees of wrap. However, tension in urethane belts declines over time, so what is acceptable today might not work in two years. Therefore, if in doubt, increase the belt wrap as much as possible by moving the pulleys further apart and/or by adding an idler pulley that forces the belts to wrap more about the drive and driven pulleys. The more wrap you have, the less the belt will tend to slip, and the more force will be exerted on the other pulley. If you have enough surface contact (i.e., a lot of wrap), then there may be enough friction between surfaces so that everything continues to work, even after the belt becomes limp.
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