Credit: Roy Gambrell
Rust jacking occurs when brake shoes corrode under the linings.
With concrete producers under greater pressure to squeeze longer life out of each piece of equipment, preventive maintenance (PM), the functions necessary to prevent ready-mix trucks or light-duty vehicles from breaking down, takes on greater importance.
PM is built around oil and filter changes and, where still needed, chassis greasing. It also involves inspecting components on a regular basis to prevent failures of wear items like fan belts.
A good PM program requires downtime for the vehicle while it is in the shop, and it also includes recordkeeping. The benefits of a PM program go far beyond just preventing breakdowns. Done properly, it can lower maintenance costs and extend vehicle life. A comprehensive approach to maintenance also can improve safety and minimize legal liability.
When vehicles are in the shop, they can’t do their specific tasks, so you will want to minimize the time they spend there as much as possible. One way is to schedule more tightly. If you know from experience that full PM on a particular piece of equipment will take two hours and 45 minutes, schedule a truck every three hours instead of in the morning or afternoon.
If you do oil analysis and chart dynamic results, you can safely extend PM intervals by predicting when oil should be changed. By extending intervals, you can reduce shop time and increase vehicle utilization.
When a vehicle undergoes maintenance, inspect it for corrosion damage. In northern climates, the effects of snow-fighting chemicals are well-documented. But even in warm weather states, saltwater and humidity cause corrosion, especially when dissimilar metals are in contact.
When aluminum bodies, boxes, or brackets are mounted to steel chassis and bodies, they are often separated by rubber gaskets or RTV compound. Overtightening can distort the materials, allowing condensation or spray to come in contact with the metals. That can set up corrosion often out of sight of normal inspections. By the time warm weather corrosion is discovered, it may already have weakened support structures, necessitating fabrication of replacements.
In the Snowbelt, where more highly corrosive snow-fighting chemicals are used, chemically-induced damage is usually more severe. Every time you drive on roads that have been treated, your tires kick up a fine spray of liquid or salt dust that gets into the tiniest crevices. About a dozen years ago, a new term entered truckers’ vocabulary: rustjacking. This occurs when brake shoes corrode under the linings. The increase in volume stresses the brake lining until the lining, riveted in place, cracks to relieve the stress caused by the rust jacking up the linings.
A cursory inspection may not reveal this condition. After driving on snow removal chemicals, the undercarriage should be hosed down with copious amounts of water. But even if that is done daily, brake shoes must be inspected for cracks.
Corrosion attacks more than just brake shoes. Every part of the truck where bare metal is exposed to spray is vulnerable. Even with the most modern powder coat paint systems, road debris, sand, and gravel can abrade surfaces, presenting a path for salts to act on metal. Trucks’ hangers and brackets, hose connections, springs, hinges, and body mounts are especially vulnerable. Inspection may not prevent corrosion, but it will allow you to identify it in time to take remedial action.
Your inspection program and maintenance operations should include more than just checking for problems. While your drivers and operators stay close to home and are not required to complete log books, drivers should have a procedure to report vehicle defects. Also, you need procedures to address defects as they are brought to your attention.
Not all may require immediate attention. But anything involving safety, especially concerning steering, braking, vision, and vehicle stability, should be addressed immediately. Keep records from the moment a defect is noticed until the time it is resolved and the vehicle is cleared to resume operations. This is not only for your maintenance operation, but for liability protection as well.
Let’s assume a driver brings a ready-mix truck to the plant and he comments that the vehicle pulls to one side under braking. You already have a full schedule of trucks in for service and are short-handed. You make a note to check the brakes when you get time. After all, the driver brought the truck in without too much difficulty and he wasn’t complaining too loudly.
The next day, he takes the truck out and comes back without incident, but he comments again about the brakes. You can imagine the rest of this hypothetical problem. After the inevitable crash, what is your company’s liability? If you are a defendant in a lawsuit, can you defend yourself and your company with documentation? To minimize exposure, you should have a proper maintenance program, which includes comprehensive records keeping.