Selecting a single-point lubricator
By Scott Batchelor, LubeSite Systems Inc. -- Plant Engineering, 5/15/2008 1:00:00 AM
Lubrication in today’s industrial landscape has changed the way manufacturing equipment is maintained and has undoubtedly lengthened the life cycle of machinery. From complex multiline systems to even more complex air and oil systems for high-speed machine tool spindles, lubrication has never been more advanced. But with every advance, often another segment is adversely affected by the modern ways of doing things. Think about all those Beta users when VHS became the standard. In the case of machinery lubrication, that segment is the small machine tool, or equipment that is just “too small” or lacks the inherent value to justify a centralized lubrication system.
Luckily for manufacturers, a solution exists for this dilemma: single-point lubricators. These small and compact units – also known as SPLs – can be an ideal alternative to complex lubrication systems. While they lack the lubricant volume and some of the precision of centralized systems, they are very effective at delivering lubricant where it is needed.
Three main types of SPLs are available in the marketplace today: spring-powered, electrochemical and electromechanical. They can be used in almost any industrial condition, including those with vibration and high temperatures, and even in corrosive environments. When compared to centralized lubrication systems, the price point is relatively low, depending on the features. However, as with most product line comparisons, each type of SPL has its pros and cons. Before product selection, it is important to look at how the units will be used. Some sample questions to ask include:
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Does machinery run lights-out, 24/7?
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Are maintenance personnel assigned to occasional lubrication spot-checks?
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Are blown bearing seals from lubricators a concern?
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Is price a deterring factor in lubricator selection?
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How soon does the application require the lubricator to start dispensing?
Different designs, different pros and cons
Simple in design but very effective at delivering an “on-demand” amounts of grease to a connected bearing, spring-powered lubricators use different springs to estimate the time it will take to run the unit to empty. The on-demand technology makes it impossible to predict the exact moment that will occur, but clear reservoirs make it easy to visually assess the lubricant level at any time. Once the reservoir is filled and the unit is connected to a bearing, the SPL uses Venturi action to discharge lubricant only when the bearing is in motion (1-5 psi). This benefits manufacturers that will have some planned machine downtime, because the lubricant won’t create a messy pool on the floor or blow bearing seals. Lubricant discharge is immediate when the vacuum is created from the bearing.
Environmentally-minded manufacturers will appreciate the refillable feature of spring-powered SPLs because the unit can remain mounted on a bearing, with just pennies of grease used to top off the reservoir. Spring-powered lubricators also can typically be used with any grease, providing users with flexibility in these applications.
Probably the most recognizable type of SPL is electrochemical, or gas-powered. Available in a variety of reservoir sizes, these units are activated by a gas generator that reacts with a liquid electrolyte contained within the reservoir. This chemical reaction results in increased pressure, which in turn moves the piston, continuously delivering lubrication to the lubrication point. While this can be a positive selling point, it can cause serious issues if the machinery is shut down because lubricant continues to be dispensed regardless of bearing movement.
Other cons of electrochemical SPLs are timing, pressure buildup and disposal. The initial gas reaction of an electrochemical SPL can take up to two weeks to begin moving the piston. Also, while the pressure that is built is usually low enough not to blow out seals, these SPLs can generate from 40 to 100 psi, so they should be watched. Finally, in general, gas units are not refillable and must be disposed of properly, leading to possible environmental concerns.
However, it is not all gloom-and-doom for electrochemical SPLs. Their most attractive feature is that replacement can be included as part of a preventive maintenance schedule. Certain types of gas generators are based on time periods. For example, if a three-month gas generator is used, it will operate for three months before running dry. And with some activators going up to 12 months, these products are perfect for the application where you want to lube it and forget it.
Electromechanical SPLs are driven by batteries and represent the most technological offering among these products. Switching the lubricator on immediately begins the dispensing process, and most units have the ability to set the total discharge time, often in months. Users have the ability to change the discharge time during the discharge cycle, providing the most flexibility of all SPL offerings.
The biggest negative in these units is the cost, since the on-board technology raises the price in comparison to the other SPL units. However, the units are refillable, so there is a potential for savings on lubricant after a few run cycles.
The bottom line is that single point lubricators represent a useful niche in machinery lubrication. With service personnel on the decline, and machinery uptime demands on the rise, an SPL makes a great addition to any manufacturing process.
| SPL Type | Technology level | Refillable reservoir | Pressure range | Cost | Scheduled empty | Lubricant discharge |
| Spring-powered | Basic | Yes | & 5 psi | $ | No | Immediate |
| Electrochemical | Intermediate | Usually no | 40-100 psi | $ $ | Yes | Up to 12 days |
| Electromechanical | High | Yes | 60-100 psi | $ $ $ | Yes | Immediate |
