FEATURE MAINTENANCE MANAGEMENT
BELOW THE BELT resolving inefficient belt drive
The traditional cure for an inefficient belt drive has been to replace the worn belt. Mark Maher of ERIKS UK argues that repair or replacement of a pulley is far more effective
machine downtime and mechanical failure; noise levels will be kept to a minimum and the amount of raw materials used reduced. Once the correct drive has been chosen
Attention must be paid equally to pulley and belt from initial installation through to regular planned maintenance checks
it must be installed effectively. Alignment is key and there are various ways of testing this from simply holding a taught length of string across the pulley faces in different positions to probably the most effective method: a laser alignment gauge. Similarly, a belt tension indicator can
B
elt drives which operate through friction between belts and pulleys,
are commonly used in many industrial applications ranging from fans, pumps and compressors to conveyors, mills and crushers. However, when a belt drive either appears to be operating well below its intended efficiency or fails completely, quite often the belt is replaced while the pulley condition is overlooked. As many as 50% of new belts are fitted to worn pulleys. A pulley is just as susceptible to wear and tear yet in many cases its condition passes a maintenance manager by. However, determining a pulley’s condition is not a difficult task nor does it require expensive machinery or tools. More often than not a simple tool to
measure the groove gauge such as the Fenner Pulley Groove Gauge is enough to determine whether a pulley needs to be replaced. Simply clean off a section of the pulley and insert the appropriate width gauge profile into the groove and if there is more than 5% wear on the pulley’s pitch-line then it needs to be replaced. Another good rule of thumb is that when the gauge is inserted there should be no visible gap on either side. In addition, if there are any gaps or
movement either side of the gauge it indicates that the belt is not sitting flush with the pulley and therefore unable to produce the optimum amount of friction to operate the drive as efficiently as possible. In reality, replacing a worn belt and then ignoring the condition of the
22 SEPTEMBER 2014 | FACTORY EQUIPMENT
pulley will not only do little to improve the efficiency of a drive but will actually reduce the life of the new belt as one of the most noticeable effects of pulley groove wear is rapid belt deterioration. Poor drive efficiency will impact on
both overall plant production and energy bills. To put it into context: a 37kW electric motor running continuously at an average electricity tariff of £0.08 kWh could cost £28,500 per year to run if fully loaded. Poor pulley groove condition can easily waste 10% of the energy input into the unit, amounting to £2,800 per annum of the energy being absorbed by the worn belt drive rather than being transmitted to the load. In this context replacement pulleys for this system would have a payback period of less than two months.
PREVENTION RATHER THAN CURE While it is inevitable that pulley damage will occur there are actions a maintenance manager can itake to increase operation life. Correct installation is key as 70% of belt friction drives are incorrectly fitted. In the first instance the maintenance
manager must ensure that the most appropriate drive has been chosen. A correctly selected drive uses the fewest number of belts or the minimum belt width required. Doing so will reduce loading on machine bearings which in turn will increase the system’s lifespan and reduce the potential for both
be used to monitor accurate belt tension which can reduce pulley groove wear and prevent belt slippage. By making use of the correct tools available the drive is far more likely to deliver its maximum rated power at its premium efficiency.
AUDITING EFFICIENCY In addition, I would advise conducting regular equipment health inspections. These can be undertaken though a professional belt efficiency audit and assessment or independently by a maintenance manager. If you are looking to conduct regular audits independently the one-off cost to purchase the correct monitoring equipment can easily be offset by the costs of not having to undertake further serious remedial works which are often linked to irregularly checked equipment. I recommend storing a full belt
efficiency kit on site such as one from Fenner which includes a belt tension indicator, drive alignment laser and pulley groove gauge. Keeping up to speed with the condition of your drives and including them within any planned maintenance schedule will ensure process uptime is at a maximum while extending both machine and bearing life. . Attention must be paid equally to
pulley and belt from initial installation - particularly with regard to drive choice and belt alignment – through to regular planned maintenance checks. Only then will you reap the rewards of an optimised and highly efficient belt drive system.
ERIKS UK T: 01452 522265
www.eriks.co.uk
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