Autolube systems: Dispelling the myths

‘Fit and forget’ auto lubricators help balance the requirements of sensitive and complex modern machinery with making best use of lubrication engineers’ time – as well as keeping up with production demands. However, as their operation can be hampered by any number of factors, forgetting an autolube can result in over or under lubrication of expensive parts. 

Drip-feed bottles are the simplest model available and use gravity to dispense lubricant. Those with a wick provide a constant, steady stream, while modern needle valve varieties can more closely control the feed and are adjustable for different temperatures and viscosities. Autolubes depending on gravity for discharge suffer from a clear drawback – oil will continue to dispense even when machinery is idle. Engineers must therefore manually shut off and restart drip-feed bottles, especially on lines which shut down periodically – which instantly dispels the myth of ‘fit and forget’.

Additionally, drip-feed autolubes are configured to a set operating temperature and cannot adjust automatically to atmospheric changes. Any alterations must be made manually, which is particularly important in facilities where a variety of products are manufactured at differing temperatures, or for outdoor machinery which is affected by external weather conditions. Even when ambient temperatures are not expected to fluctuate, machinery can experience changes in temperature due to malfunction, vibration or friction. Drip-feed autolubes should therefore be regularly inspected and adjusted where necessary, especially as temperature changes affect the viscosity of the lubricant which reduces effectiveness.

Gas-powered autolubes rely on gases created by a controlled chemical reaction taking place inside a hermetically-sealed chamber. As gas is released it forces the chamber to expand, releasing the lubricant at a pre-determined flow rate. Similar to drip-feed lubricators, temperature changes will negatively affect the rate of reaction and therefore the discharge rate, meaning manual adjustments must be made as necessary (and if possible) rather than fitting and forgetting. 

Most gas-powered auto lubricators feature a pressure relief valve to counteract blockages in the bearing or lube line which may be caused by resistance to lubricant flow or any deviations from the recommended PSI level. While this prevents over-pressurisation, it usually means lubricant is released from the autolube before it reaches the bearing or component – potentially damaging the equipment and resulting in contamination or replacement. Each device should therefore be inspected for changes in pressure and potential blockages before the pressure relief valve needs to open. Looking for potential autolube blockages before the valve releases lubricant helps to reduce the costly downtime associated with replacing bearings. 

Battery-operated autolubes are a useful option for a faster flow rate. They allow closer control over the device, as flow rates can be set based on a number of contributing factors including runtime hours or machine cycles. Multi-point battery operated systems can also be created, where one device lubricates many components due to a series of internal pistons which provide progressive distribution. While this reduces the number of autolubes required, it can pose a risk to a greater number of bearings as, if there is a blockage at any point, the whole device will cease operation. Here again, regular visual inspection is essential to identify blockages, while periodic maintenance can help prevent them forming. 

Best practice

When installing an autolube device, the following should therefore be taken into consideration:

•  Fit the device where it can be viewed and monitored easily

•  Ensure discharge frequencies are calculated correctly and applied on installation

•  Make sure that installation pipework used does not exceed the maximum recommended length, as too great a pressure drop will prevent functioning

•  Never fit an autolube unit in a position where it could be affected by vibration

•  Ensure staff do not adjust without consulting lubrication engineers

•  Set the correct schedules for regular inspection of the device, as well as replacement at the required intervals

An efficient lubrication programme is essential to all production facilities and auto lubricating devices can play a useful role. However, the assumption that they will take care of themselves could prove costly. Regular monitoring and maintenance of each device is the only way to ensure a continuous and correct flow of lubricant, and should be undertaken as part of an overall conditional-based monitoring and maintenance programme.