Energy Conservation in Belts and Drives

This article showcases the case studies of few industry segments, where one can find the energy loss in the power transmission from the motor to machine by the belts and pulley drives. S Ashok, K S Subramanian

The industry is facing energy losses in each of its machine in the motor-to-machine power transmission. This is happening due to oversized pulleys meant for V belts, existed in the decades-old running machine. Now, since the energy efficiency route is taking over the energy conservation route, it is time to think of reducing the weight of rotating component and increase the size of conducting component in a system. While talking of energy conservation in the industry now, material conservation is the first thing to tried by the OEM in its new and old products supplied long years back; and to be tried by the user industry to achieve energy conservation in its decade-old running machines, as they are paying excess energy bills.

Any industry segment will have this system of motor-coupled-to-machine by belts in majority of its machines. Here, the machine OEMs in each segment do take extra care of its product safety first and then only focused its running cost. That is why the government suggested going for 5-Star rated products with the slogan ‘More the Stars, More the Energy savings in that product’. This article showcases the case studies of few industry segments, where one can find the energy loss in the power transmission from the motor to machine by the belts and pulley drives. Especially, the pulley drives are not replaced by the industry for its total machine life. These dished out pulleys increase the energy loss in power transmission. Also pulley needs to be undersized to match to the new compact and power saving belts and here raw cogged
belts now.

These heavy weight pulleys consume 10 per cent more power when transferring from the motor to machine in some of our case studies and this is an eye-opener. The loss percentage may vary, but it needs to be focused now, immediately. So, the user industry is suggested to revisit today to study energy breakup analysis of his motor–to-machine power transmission, generically, and horizontally deploy this instantly applicable exercise to all his other machines.

Instead of investing on industry’s proposed swap from his decade old standard motor to the latest IE3 motor now, first one must try to find the ways to reduce energy demanded by the machine and links from the motor end. And by implementing this immediately, the user can reduce energy loss from today and this paves way for more productivity from each of its machines at less power consumption, and the simple payback period is in the order of few weeks to months now. After energy demand reduction achieved first in the motor only, then the user has to replace with the optimum-sized IE3 motor.

Existing Energy Losses Existed in Old Pulley Drives

The symptoms of energy losses can be seen in belts due to the looseness, worn-out belts, that is visibly observed, but what is not noticed, is that the worn-out pulley which is ignored by the user. Because he assumes that the pulley is part of the equipment meant to serve for the lifetime of the machine. The existing running pulley grooves look with glossy finish in most of grooves. They need to have rough surface with matt finish. Rough surfaced grooves only can grip the belt better and they were over-designed till date. Grooves inside pulley have been dished out of differential driving of belts over grooves. Over five years of 24×7 hours of usage, that pulley had gripped many old and new belts, hence this pulley is a consumable based on its condition.

The user has to have a mindset to change his pulley costing few thousand rupees after few years. This is the need of the hour now because, when switching over to REC belts from V belts, the pulley can be undersized in size and weight due to reduction in groove numbers says three grooves in new pulley instead of six grooves in the old multi-groove pulley.

Energy Efficiency Improved Due to REC Belts & Pulleys Now

Thanks to old energy efficient concepts in belts and the industry conveniently switched over to raw edged cogged REC belts in the past decade. We suggest swapping for cogged belts now, due to the additional factors of correction power rating, speed ratio, belt length correction factor, and arc of contact correction factor. These factors aid in optimising the pulley drive for cogged belts. This REC belt swap is taken because of its superiority over V belts as mentioned under:

  • The cogged belts by design, is having 30 per cent power carrying capacity for the same classical V belt weight now.
  • The cogged belts run cooler, run say, 50 per cent more longer hours, and occupy less space in pulley.
  • The narrow and cogged belts operate higher speed ratios using smaller diameter pulleys.
  • Hence, this needs the existing pulley to be replaced with say 20 per cent around, less-dimensioned pulley.
  • Being cogged on the pulley side the belt has a better grip with the pulley, to sustain the RPM drop better.
  • Better grip and higher coefficient of friction reduces slippage to near negligible and improves its efficiency.
  • Cogs on the inner surface of the belt increase air flow and facilitate cool running.

For any industry application of motor to machine belt transmission, here, one can find the motor OEM sizes his motor to suit the machine demanded load. The machine OEM manufactures his efficient machine taking utmost care to reduce his manufacturing cost and as well he sees to it, that his machine consumes optimum energy as running cost.

Here, for the sake of not losing RPM, we are implementing the timing belt and matched pulley. This increases the power of transmission here. Take ambient at 40C, if the belts are hotter by 20C above the ambient, say at 60C and above, then the belt life reduces by 50 per cent that is noticeable. This hotter belt in turn reduces the pulley life and dishes out pulley more, but not noticed by us. Soft belt also by continuous rubbing the hard pulley, can elongate the pulley inside dimensions.

While discussing about the motor to machine transmission, the machine OEM wants to play it safe to go in for stronger belt (at least for him, his belt must not fail during his warranty period prematurely). So, to accommodate his strong belt, he plans for stronger pulley to withstand the belt, and the tangential stress from the motor to machine. By this, he makes his pulley size that of a flywheel and that acts as heavy tare load to the motor, consuming more of Tare KW, during idle loading.

The industry conveniently ignored the swap of old to new pulley as that involved more of additional labour in erection and alignment of new pulley in place of old pulley. Here, the industry needs to understand only one concept that energy saving is fully possible and achievable in a healthy power transmission system by fine tuning and optimisation. If the same system is unhealthy by way of old oversized worn-out pulleys, then this will result in mismatch of new belts in old pulleys and energy savings is achieved meager, compared to better energy savings achievable.

Replacing Existing Worn-out Oversized Pulley

V belts are designed for motor at full load rating and in 7 out of 10 cases, over belting is designed. The motor and blower pulley are heavy mass when designed and this adds more to Tare-load consumption of motor, belt and pulley upto the load, thus, increasing unproductive load on the motor power. Because of overweighing belting, the pulley sizes, belt width and the number of belts go up to increase power demand to motor. The motor is always not running to the designed full power ratings. It is ideal to use the actual running KW as the motor load now applied to the belt as the transmission power.

One has changed his or her motor starting from Harsh DOL, Star Delta starting to smooth VFD starting now and so now his belt and pulley also need to undersized to withstand only slow and soft ramp of VFD starting current. The origin of inefficiency is due to the overdesign of belt and pulley drive transmission starts from the OEM at the design maximum only.

The industry needs to be aware that pulley (also due to this cyclic belt movement under harsh conditions) needs to be replaced around five years duration based on the loading nature and thermal imager inputs on pulley. Now, we always demand the industry after our energy audit to replace belts and pulleys, and optimise power in their pulley. After thermal imaging and measuring the slippage losses, we the Energy Auditors now suggest to the user to replace both belts and pulley from V belt to cogged belt now. Citing the above factors, let the user first resize the pulley, discuss with the belt and machine OEM to achieve the same RPM or the desired RPM after reduced slip, possible now due to this cogged belt.


Material conservation is the first thing to be tried by the OEM to achieve energy conservation in their products. Motor OEM is reducing the overall weight, but improves the material composition and in its MOC (Material of Construction). In the load ends like pump or fan or compressor, the OEMs are innovating to reduce the weight of rotating wetted parts inside the housing. So here too, the user industry is suggested to follow, what the OEM is doing now to improve their machine efficiency.

It is necessary for OEM to revisit to the power transmission areas in decades-old machines and analyse what is the cup-to-lip energy losses happening in between due to the rotation of the heavy bulk weight of the pulleys especially now, since he is replacing the belts only routinely till date. He needs to consult belt and pulley specialist or the machine OEM today and ask him what can be done now to reduce the energy losses in there.

S Ashok,
BEE Accredited Energy
Auditor, Coimbatore

K S Subramanian,
Specialist, Belts & Pulley
Drives, Coimbatorez


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