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Manually greasing a bearing is an act that, at least on the surface, appears to be purely physical. One grabs the grease gun, pumps it full of grease or installs a cartridge, goes to the machine, attaches the gun to the grease fitting and pumps the lever to deliver grease - right? Regrettably, this is too often the case.
When the act of greasing a bearing is viewed as a purely physical task, the plant has little chance of developing a world-class machinery lubrication program that delivers machine reliability, profits and competitive advantage. Today’s technology is paving the way to a more precise and cerebral approach to the seemingly simple act of greasing a bearing.
The lever-action style grease gun has changed little since it was first developed in the early 1920s. Apart from adding pneumatic or electric power to some models, changes to the original design have been only modest in scope and impact. Well, that’s changing - and at a rapid pace.
While the grease gun itself is not undergoing major changes, we are starting to bolt on various instruments and devices that materially alter the appearance and the function of the grease gun, which can increase the cost of the device from about $50 to more than $2,000!
If used correctly, however, grease guns equipped with the right technologies can yield many multiples of return on investment (ROI) by eliminating machine failure that is linked to chronic mistakes in machinery lubrication.
Let’s briefly review some of these new technologies and discuss the impact they can have on machinery lubrication.
When a bearing needs to be greased, it produces a detectable acoustic signal. Properly equipped sonic and ultrasonic monitoring devices can detect when the bearing needs to be lubricated. Such a device may be used to drive condition-based regreasing schedules, or to confirm or optimize the validity of scheduled regreasing intervals.
Whether the interval is condition-based or schedule-based, these devices can also be used in conjunction with a grease gun to ensure that the proper volume of grease is applied. Once grease is applied to a running bearing, the bearing “quiets.” When the lube tech has filled the bearing’s internal reservoirs, adding more grease will result in overlubrication. An ultrasonic listening device produces an audible signal from the friction caused by churning.
This signal cues the technician to discontinue adding more lubricant, thus reducing or eliminating the chances of overlubrication. Some of these devices attach to the grease gun. Others are stand-alone accessories. While some use visual meters, others modulate the signal to an audible frequency so that the lube tech can listen to the bearing as it is being greased.
Some ultrasonic listening devices offer both visual and audio feedback options. All can be made to work. The key is that these ultrasonic devices can help optimize both the regrease interval and the volume of lubricant applied.
A flow meter, when attached to the grease gun, enables the lube tech to apply the prescribed amount of grease if a calculated approach is employed, or to record the volume of grease required to lubricate if the sonic/ultrasonic approach is employed. This can be useful in troubleshooting for seal problems, caking of expired thickener and a host of other conditions.
When a formula is used to calculate the amount of grease to apply to a bearing, we have historically translated this into the number of shots required, and this estimate gets worked into the preventive maintenance (PM) work order. The volume of grease delivered per shot varies from one grease gun to the next.
So if a new grease gun is purchased, and the new gun delivers more or less grease per shot than the previous model, overgreasing or undergreasing will occur unless the work order is modified to reflect the change. A grease gun-mounted flow meter eliminates the guesswork. Simply define the volume required to relubricate the bearing then deliver that volume, thus eliminating the variability.
The grease fitting, orifices and bearing create resistance to flow that can be measured with a pressure gauge. If the pathway to the bearing is obstructed, a change in the normal pressure can be measured and recorded. Often, if the pathway to the bearing or its reservoir forms a cavity or is blocked, grease will bypass the bearing and exit through the relief plug, if one is present, or through the shaft seals.
By measuring pressure, the technician can often avoid the scenario whereby the bearing fails due to lubricant starvation even though grease is being routinely applied.
While it is not a grease gun-mounted modification per se, newly developed “smart” grease fittings equipped with integral thermocouple and/or piezo electric vibration sensors are entering the market place (Figure 1).
These fittings operate like a conventional grease fitting, but enable the lube tech to acquire temperature and vibration readings with a data collector while greasing the bearing.
Other innovations will no doubt enter the marketplace in droves, each offering a new twist to the grease gun. The most powerful approach is a combination. When pressure, flow, ultrasonic/sonic, temperature, vibration and other measurements and observations are evaluated collectively, a powerful analytical synergy is formed.
By integrating the information from numerous grease gun-mounted sensors (and those integral with the grease fitting) into a preprogrammed data collector, the $50 grease gun is transformed into a smart and powerful precision maintenance tool. What was once the leading source of bearing failures and motor rebuilds becomes arguably the most powerful tool in the reliability technician’s arsenal.
I expect that more innovations will be forthcoming. Employing the muscle between the ears to effectively grease bearings is a reliability home run!
Smith, A., Smith, C. and Bernard, T. U.S. Patent No. 5,691,707. November 25, 1997.