By Paul Abelson
Oil changes take vehicles out of service for anywhere from several hours to a full work day. To extend intervals, many fleet managers use bypass filters (more on these later). But operators still have to bring in their vehicles at specified mileages for “dry” preventive maintenance, such as chassis lubrication.
Automatic chassis lubrication
The virtually continuous flow of grease provided by on-board lubrication systems, however, enable preventive maintenance to be scheduled according to oil analysis results instead of mileage.
Traditional — or zerk — lubrication fittings are permanently installed at grease points so technicians can attach grease guns and add grease manually. Automatic greasers consist of a central reservoir, a pressure pump, a manifold to accumulate and distribute grease to hoses, and special fittings that replace the zerk fittings. The systems:
1. Deliver optimal quantities at preset intervals. This eliminates both over-greasing, an environmental and safety hazard, and under-greasing that leaves bearings and wear points unprotected.
2. Distribute grease evenly and completely to all fittings, eliminating the possibility that a technician will inadvertently skip one.
3. Are sealed, so they can't be contaminated.
4. Reduce material costs by up to 25% by reducing waste.
To lengthen the time between changes, the engine's oil must be kept clean. The best way to do this is with bypass filtration.
The term “bypass” describes how the process works. After all the oil goes through the full-flow (primary) filter, a small amount of oil bypasses the engine to go through the bypass (secondary) filter, and returns to the oil sump. The process removes particles smaller than 3 microns (a micron is one-millionth of a meter, or 0.000039 inch) compared to 25 microns with the best full-flow filters.
To keep from blocking this ultrafine system, only 3 to 5% of oil is filtered during each pass through the bypass filter. Engines pump 40 to 70 gallons of oil a minute, so although flow per pass is small, virtually all the oil passes through the bypass filter every few minutes. Once cleaned, it stays clean.
|How to optimize automatic lubrication
Instead of the single layer of media found in most primary filters, bypass filters use depth of material to accomplish their task. Some are made with tightly compressed fibrous waste such as shredded paper, cotton remnants, or sawdust. But vibration opens channels in compressed materials, especially when they're wet with oil, enabling larger particles to migrate through the filter.
The most effective bypass filters use highly tensioned rolls of filter paper instead. They're quite dense and present a great deal of depth for multiple layers of filtering, allowing them to remove even submicron particles.
By using bypass filters and automatic greasers, some fleets have doubled and even tripled the time between preventive maintenance intervals. To determine optimal drain intervals, oil analysis should be done at regular intervals, with results charted to project trends.
— Abelson (email@example.com) is a former director of the Technology and Maintenance Council of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.
For a list of automatic lubrication system and bypass filter suppliers, click here.
Is a 360-degree view on the horizon?
Even the most aerodynamic mirrors disrupt air flow, raising fuel consumption in heavy trucks by more than 5%, and don't cover all blind spots.
Tiny TV cameras, on the other hand, can be enhanced using infrared and low-light technologies to perform better than mirrors. Vision systems employing a camera and dash-mounted screen virtually eliminate aerodynamic drag.
They can also be used to capture images that can be used as evidence if operators are falsely accused of causing crashes.
Other devices, available now, provide lane guidance when coupled with image analysis, reducing the likelihood of incidents that require repairs.
The greatest obstacle to mandating vision systems in light-duty vehicles is the federal government. Motor Vehicle Safety Standard 111 requires trucks to mount external mirrors. Until the standard is amended to require vision systems, no progress related to a driver's range of vision will take place. The motivation to amend the standard may be improved fuel economy.