A critical task for maintenance professionals revolves around lubricating rotating machinery. Timely, effective lubrication reduces component wear, minimizes lubricant consumption and sustains equipment performance and reliability. With the goal to deliver the proper lubricant precisely when and where needed, workers more often than not will have their hands full. Manual user-friendly lubrication tools (such as grease guns, packers, pumps and meters) provide a big assist, but some applications present even bigger challenges, especially when time and labor are at a premium.
In some cases, handling the sheer number of lubrication points — sometimes hard-to-access — can consume countless hours. As examples, there can be upwards of 7,500 individual lubrication points in a paper mill, 5,500 in an automotive assembly plant, 4,000 in a steel mill, 3,500 in a refinery, 2,000 in a cement mill and 1,500 in a plastics plant. Each requires service and vigilance, while adding to the potential risk and problems associated with over- or under-lubricating, ill-timed or sporadic application and the introduction of harmful contaminants.
Technology has responded with an array of automatic lubricators and centralized lubrication systems engineered to provide reliable time- and labor-saving alternatives to manual lubrication.
Set and forget automatic lubricators
Figure 1. Single-point lubricators allow users to “set and forget” for a predetermined period, typically one to 12 months.
Automatic single- or multipoint lubricators offer around-the-clock lubrication service with minimal maintenance staff involvement. Single-point automatic lubricators for bearings (Figure 1) typically feature flexible time-setting periods ranging from one to 12 months and enable users to “fit and forget” about the lubrication procedure until some predetermined date. Transparent one-piece lubricant containers (usually polyamide) allow visual inspection of the dispense rate and the container material reduces gas diffusion. Hermetic sealing safeguards against ingress of dirt or foreign matter. Such lubricators can be filled before they reach the plant and ready-to-use, supplied with the proper grease, which removes guesswork, mistakes and effort.
Multipoint automatic lubricators for bearings and machinery can be configured for as many as 20 lubrication points. These flexible systems benefit from electronically-controlled programming options and alarm functions to signal when feed lines are blocked or cartridges or containers are empty. Advanced versions use a high-pressure pump and progressive feeder to dispense the same amount of lubricant for each designated lubrication point.
Automatic lubricators can be complemented with additional technologies to make life easier for maintenance staff. For example, relubrication calculation software accurately determines correct interval settings. After entering the criteria and specified grease, the program pinpoints the correct settings for optimized lubrication and timing.
Another device automatically adjusts oil lubrication levels inside a bearing housing, gearbox, crankcase or similar oil-bath application. These oil levelers adjust the level in real time (eliminating potential equipment downtime) and compensate for leakage.
Centralized systems can service any machine
Figure 2. Circulating systems offer the opportunity to remove wear particles and contaminants.
Any standard or specialized machine can be serviced by a centralized lubrication system. Applications encompass equipment used in automotive, machine tool, metals, printing, paper, food and beverage, mining, chemical, plastics, hydrocarbon processing, refinery and wind energy, among many others.
With centralized lubrication, every bearing receives the proper dose of lubricant. Problems associated with excessive lubrication can vanish. Lubricant consumption can fall over time (in some applications by as much as 50% compared with inexact manual methods) and maintenance time, energy and costs can diminish. The only manual requirements are to refill the lubrication reservoir and occasionally inspect the connected lubrication points.
Centralized lubrication technology generally falls under two umbrella categories: total-loss and circulating oil systems. In total-loss systems, friction points are always supplied with fresh lubricant (oil, fluid grease or grease) at specific intervals (time or machine-cycle dependent) during the lubricating cycle (such as pump run time). The lubricant is supplied in the proper quantity to buildup an adequate lubricant film during the subsequent idle period.
In circulating-oil lubrication systems (Figure 2), the lubricant flows back to a reservoir for reuse after passing through the friction points. In this way, the lubricant, without human intervention, removes abrasion particles from friction points, stabilizes the friction point temperature (cooling or heating), prevents corrosion, and removes condensate and process water.