Of all the tools that the modern arborist uses, the chipper is often the largest, loudest and most complicated. Brush chippers need to operate long hours with little to no downtime. Unless you are an extravagantly well-equipped crew, you rarely have an extra to use in a pinch.
To be effective, efficient and safe, chippers must be maintained and cared for on a regular basis. This article will break down chipper maintenance into manageable chunks (pun intended) and help establish regular checks, adjustments and repairs. Like all complex jobs, chipper maintenance should be a routine series of tasks performed in a routine way.
There are numerous brands of chippers on the market today, and manufacturers strive to make machines that are productive, safe and affordable. There are a number of ways to achieve these goals, and infinite variations on them. As such, all chippers have characteristics in common, but no two brands are exactly the same. We will explore some overall strategies and tips, but in no way can we cover every detail of the chipper you use daily.
For that, you must refer to the bible of chipper maintenance and operation, the owner’s manual. If you bought it new, your chipper comes with one by law. If you bought it used, you are required to get one. Either way, OSHA/ANSI require one on the machine during use. The OM has all the details you need to check and adjust your machine per the original specifications.
For our purposes, we will break the chipper down into three sections. First is the chassis. Most chippers are towed behind another vehicle. The chassis allows it to move safely from one job to the next. Think of it as the trailer your machine sits on. The next part is the power plant. This is the engine that powers the knives and spits the chips out the chute. Finally comes the core, or everything in between the power plant and the in-feed chute. These three areas have separate concerns deserving separate consideration.
Just latching on and going down the road is no way to tow anything. Before hooking up, go over the chassis systematically from front to back. Starting at the front of the chipper, inspect the hitch, chains and electrical hookup. Look for broken, bent or missing pieces, weld cracks, excessive rust and excessive wear. What defines excessive? Always refer to the OM for specific metrics, but don’t forget the little voice in your head. If it looks wrong, err on the side of caution. Avoid the tragedy of losing your trailer while going to the job by never allowing the condition of you chassis to deteriorate. For efficiency and safety’s sake, the jack stand should be operational and the correct size.
Moving to the rear of the vehicle, make sure any traffic cones, toolboxes, fenders, mud flaps or other things attached to the chipper are secure. Also make sure an appropriate, serviceable fire extinguisher is present and operational. Take a close look at the decals provided by the manufacturer. Make sure all the warning and operational ones are present and legible. These serve as valuable reminders to the crew.
Check the tires for proper tread depth and air pressure. If the chipper is equipped with a braking system, check for proper functioning as per the OM. If any of the frame surfaces are used as steps or footholds, make sure they are covered in anti-slip tape and are oil and dirt free. Check all lights and assure proper functioning. As with all chipper maintenance, a checklist is vital to ensure items are checked in a routine manner.
Regular engine service is critical for safe operation. Most likely your chipper has a separate OM for the engine. Follow it for service intervals, lubrication types and replacement part guidance. However, a daily inspection is also necessary. Be sure to look for fluid leaks, missing bolts, loose belts and excessive debris nestled up close to the engine block. Maintain the proper fluid levels and replace the filters as stated in the OM. Keep the radiator cleaned to avoid overheating. Regularly clean the air filter. Chipping brush and wood is dusty business. Use a high-quality fuel source and additives as needed for climatic conditions.
The core is what makes a chipper a chipper. Any accident can be boiled down to a root cause, and chipper accidents are no exception. Any chipper manufacturer will tell you that improper maintenance and operator error are the root cause of the majority of chipper incidents. Poor maintenance leads to improper equipment function. Poor function leads to anger and frustration. This, in turn, leads to bad judgment and rushed actions.
The core of chipper maintenance is safety through properly operating machines. Adopt an attitude of safety as the basis for chipper use and upkeep. Well-running machines are easier to use, last longer, generate more revenue and are prone to fewer accidents. You can’t expect your crews to safely operate a poorly working machine.
Before any maintenance or adjustment begins, the chipper needs to be shut down, with no parts in motion. Manufacturers install a number of safety devices to ensure that access to rotating belts, disks, knives and drums is restricted if in motion. Make sure these are all operational. As a further check, attach any keys to locked areas or panels of the chipper to the machine’s ignition key. Doing this means the machine must be turned off with the keys removed from the ignition before maintenance can begin. The keys should then reside on the person who is performing the work. This is a basic lock-out, tag-out procedure and should be used as a minimum precaution. Expand it as your equipment and work environment demands. Also, never check for hydraulic leaks without eye protection and covered hands. High-pressure hydraulic fluid can penetrate the skin or eyes and cause serious injury. Even with the machine off, latent pressure can still be high.
Chippers notoriously shake, rattle and roll when processing material. This constant vibration leads to cracks, breaks and fatigue on all parts of the system. Bouncing down the road on the way to the job can also cause breakage. Look for signs of wear and tear at weld seams. Scan for loose or missing bolts, nuts and/or rubber mounts. Check the hydraulic hoses for chafe marks, loose fittings and leaks.
Vibration stress can rear its ugly head in any number of ways. It is particularly tough on rusted areas of the machine. The weakness of the metal oxidation is further stressed by vibration, torsion or other shock loading. Address rusted areas before they get out of hand. By far, the best way to prevent vibration stress is to prevent vibration. That leads us to our next topic.
Keep it sharp
The leading cause of excessive chipper vibration is dull knives and worn anvils. These cutting surfaces wear through use and must be constantly maintained. Dull knives start a cascading effect on the whole system. Not only does vibration increase, but the drive belts, clutch and bearings are stressed. This, in turn, makes the engine work harder to chip the same amount of material and causes a decrease in the workload, which can lead to frustration and bad choices. Even a properly used chipper that is fed only the cleanest material will dull. Check the knives frequently and rotate to sharp surfaces when necessary. Check your OM for the minimum knife width and never use knives that are less than this. As a knife is sharpened it becomes narrower across the long axis. This increases the space between the anvil and the cutting edge of the knife. If this distance gets too large, then even a sharp knife cannot cut material and instead tears it. Imagine a sharp pair of scissors with a loose pivot bolt. Also check the knives for cracks or other irregularities. Replace knives as needed.
The anvil is the second piece of the cutting equation. Anchored to the body of the chipper, it adjusts in relation to the knives on the disk or drum. While not sharp, the anvil must have a clean, square, smooth edge to process material properly. Think of the unsharpened side of a set of scissors. Anvils wear more slowly than knives, but still need periodic examination and adjustment. Refer to your OM for the specifics. Conditions, materials and operator habits will dictate how often the anvil needs to be serviced.
No single article can discuss all the possible scenarios and maintenance issues for every chipper in use today. However, there are many similarities and procedures that can, and should, be implemented by all brush chipper users to ensure safe, productive operation of any machine. Use what we have discussed as a starting point, expand on it as necessary. Follow your OM. Keep the safety devices operational. Keep the cutting surfaces sharp. Implement and follow sound operating and maintenance procedures and processes routinely, and your brush chipper will work as long and hard as you and your crew.
Editor’s note: This article was originally published in February 2011 and has been updated for accuracy and comprehensiveness.