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Reinforced O-ring Belts
(Review of XLD O-ring)

This page reviews Fenner Drives' XLD O-ring belt, comparing Fenner's XLD O-ring to our new V-Conform belt and our HT Blue urethane round belt. It also addresses all Fenner's claims for what, at first, appeared to be a game changing belt. The claims were so impressive that we were eager to distribute their new belts, but after testing them, we found we disagreed with most of Fenner's claims. Consequently, we decided to develop our own V-Conform belt to provide most of the benefits that XLD belt failed to produce. Sadly, our belt will not work on curves. Hutchinson recently announced a similar belt, called ConveyDyn, that will work on curves, so we hope to distribute it when it becomes available in 1 to 1.5 years.
XLD O-ring Belt Comparison
This test was performed using a single zone conveyor with 9 idler rollers and one Itoh Denki PM486-FS-55
Motorized Drive Roller (MDR), running continuously with no load (box) on the zone after two days run-in.
Meter reading XLD O-ring (reinforced with Kevlar) V-Conform Belt (reinforced with stretchy nylon) HT Blue belt (unreinforced polyurethane)
DC AMPS @ 24VDC 1.12 0.61 0.41
MDR RPM (1.91" roller diameter ) 127 204 233
MDR temperature
(hand gripped the motor area)
Hot Warm Warm

Saves Energy?   Fenner's ads claim their new XLD O-ring belt saves energy, yet this test shows that their belt use almost twice as much energy as our V-Conform belt and nearly three times more energy than our HT blue belts, while cutting conveyor speed roughly in half and running hot to the touch with no load on the conveyor!

No Stretch Belt?   Fenner touts this as an advantage, but they don't seem to understand that idler rollers are not precision rollers. Instead, they often WOBBLE a little due to being slightly elliptical and/or slightly bowed and/or having shafts slightly off center. Moreover, belt grooves vary in depth even on the same roller. This means rollers can act like small cams forcing non-stretch belts to put significant strain on motors. Such "cam shock" causes motors to draw excessive electrical current and waste energy with every rotation.

Longer belt life?   Fenner's so-called "D" belts are really "T-top half-round" belts because their little T-top wings conform to fillets on groove edges, preventing the belts from slipping. Fray belt They work well on idlers that have wide grooves, but apparently they were not tested on MDR's narrow groves, where they are pressed upward and stick slightly above the roller's surface. This can cause box rotation and fray T-tops. XLD belts can also fray on curves.

6 times longer life?   Urethane round belt's lifespan can vary widely, depending upon how they are used or abused. In a real world test 40,000 HT Blue belts lasted 9 years in a USPS distribution center, so without actual real world tests, claiming the XLD belts will last 6 times longer is a stretch. However. the problem for non-stretch belts is not the belt's lifespan, but rather the MDR's lifespan. XLD non-stretch belts hammer MDRs with every rotation. You can see the hammering on an oscilloscope and feel how much hotter the MDR is, so it appears that this could significantly reduce the MDR's lifespan. Moreover, non-stretch belts also put excessive stress on bearings. Will they reduce bearing lifespan too? Conversely, 32 years of experience prove that our elastic urethane belts easily stretch and absorb "cam shock", thereby protecting motors and bearings.

Reduces System Costs?   In the event of jams or accumulations where the MDR is not shut down within 4 seconds, XLD belts will keep on moving rollers under boxes until the motor heats up enough to trigger the thermistor inside the MDR and on the PLC. This shuts down the motor to prevent damage. Unfortunately, thermistors have limited lifespans. They only work a fairly short number of times. When the one inside the MDR dies, it cannot be repaired so the next jam or accumulation may destroy the MDR, an expensive loss. Jams and accumulations will cause urethane belts to slip, so they protect the motor. If they fail, they "fail safe" because the cost to replace the belt is minimal compared to the cost of replacing an MDR. Add this to the cost of electricity and the reduced throughput due to slower speed, and it's evident that XLD O-rings probably will not save money.

Eliminates Some MDRs?   Since the XLD O-ring lets an MDR move 30 rollers, theoretically it should let you eliminate two MDRs. Sadly, there are no free lunches. The XLD requires much more energy, while dramatically reducing throughput speed, so a more powerful (and expensive) MDR will probably be required. It is also likely to reduce MDR and bearing lifespan, so it may be more economical to use three MDRs with elastic belts.

Drop in Replacement for urethane belts?   This is true only in areas where human access is prohibited or not possible (like deep inside a diverter). Finger Guards are required by OSHA in areas where people can inadvertently put a finger under a belt that has a pinch point that can damage fingers. Finger Guards EU's EN619 regulations go further specifying that guards are required where the belt will not stretch over a finger with a force of more than 100 newtons (22.5 lbs). Fenner knows this but continues to run many "Drop in Replacement" ads that imply finger guards are not required. They need to run their ads past Michelin's legal department because failing to adequately warn about a known danger is gross negligence, subject to triple damage law suits.

Easy Installation?   Center distances holes between rollers have tolerances, typically +/-.010" On our test conveyor, the 3" center distances meant rollers were typically 2.99", 3.00" and 3.01" apart. Using the rollers as levers, installing belts on the first two center distances was easy, although it required some effort to tension belts the last 1/16". However, one person could do it. Since XLD belts do not stretch, the last 3.01" center distance took two employees to install the belts -- one person had to use both hands to pull the roller in place, while the other person guided the shaft into the hole. Unfortunately, in areas where finger guards are required, installing the belts on rollers is only half the task. The other half requires installation of finger guards, which can take much longer, especially if it involves drilling holes in the frame. Once finger guards have been installed, it is virtually impossible to install or remove belts without first removing the finger guards. In conclusion, first time installation of XLD belts can be difficult, time consuming and expensive.

Bi-modulus Technology?   This is a fancy way of saying reinforced, i.e., composed of two different materials. XLD belts appear to be made from polyurethane reinforced with non-stretch aramid (Kevlar) cord. For years other companies (Volta, Beha, TKF and Fenner) have sold bi-modulus round, vee and/or T-top belts also reinforced with aramid, so "Bi-Modulus Technology" is nothing new. Incidentally, ConveyXonic Poly-V belts are quadra-modulus = 4 different materials. Bi-modulus is prior art, so it alone is not patentable.

For the best in Reinforced O-ring belts, insist on DuraBelt.

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