July 1, 2013
…and other tips for keeping your portable plant chassis well maintained.
By Dave Anderson
In the aggregates industry, portable crushing and screening plants are more popular than ever. While the heart and soul of a wheeled plant is the crusher and/or screen mounted on the plant, it’s important to pay attention to the maintenance of the “supporting cast” — the portable chassis and conveyors — on any portable plant.
Read and understand the original equipment manufacturer’s (OEM’s) Operations & Maintenance manual of your plant. Every crusher or screen manufacturer has specific maintenance procedures to cover its brand of machine, so always consult that manufacturers Operations & Maintenance manuals for care of its equipment. When maintaining the chassis portion of the plant, however, there are some basics that can be applied across the board.
Put safety first
First, safety is always job #1. Before performing plant maintenance, follow these guidelines:
• Make sure the plant power is shut off and proper lockout/tagout procedures have been performed.
• Familiarize yourself with all danger, caution, and warning emblems on the plants. Take some time each month to make sure all of the OEM-supplied safety and caution emblems are in place and legible throughout the entire plant. Any plant manufacturer should be able to supply you with a drawing to show which safety emblems were on the plant when it was new, and where they were located.
• Check the grounds around the plant for any trip hazards. Make sure all electrical cables and wires are safely arranged and out of the traffic pattern around the plant.
• Check all access ladders and walkways for any broken or bent components that could lead to an accident. Keep open mesh walkways clean of rocks or spillage.
• Make sure that all electrical equipment is properly grounded. Be aware of and remove any wet spots near electrical components that could create a potential shock hazard. Most plants have a grounding lug on the plant, so make sure the ground cable is securely attached to the lug and the grounding rod is sunk into the ground to meet local code requirements.
• Check all drive guards. Make sure they are in place with the attaching hardware all tightened to correct torque specs. Make sure the guards do not interfere with the drive belts, drive lines, or any other part of the drive mechanism when the drives are operating.
Plant maintenance tips
Once you have confirmed that all safety aspects of the plant and grounds around it are in good order, check for things that could negatively affect the plant’s efficient operation.
• Check to be sure the plant is level in all directions. You should have bubble levels on every side of the plant chassis to make this an easy task. A plant that is not level may experience production problems that can shorten the life of the structural steel on the plant, as well as the crushing and screening components.
• Check that the plant is cribbed correctly, and the cribbing is solid. Ensure any optional jack footpads are on a level, firm surface. All weight should be off the suspension during plant operation. Follow manufacturer guidelines and the crib point decals on the plant for correct cribbing instructions.
• Make sure all shipping braces are removed. Most manufacturers use shipping braces of various types during plant transport, and they paint them a different color than the machine. Your company also probably uses these when transporting the plant. Operating vibratory or crushing equipment with these braces in place can cause serious damage to the equipment.
• Make sure the tires are off the ground for plant operation. This protects the tires and ensures there are no unwanted vibrations in the plant due to tire bounce or ground conditions.
• Check the tire pressures.
• Check for and clean out any material build-up around conveyor pulleys, bearings, and component intake and discharge chutes. Be especially aware of build-up under the vibratory component of a plant. Excess build-up will cause interference between the vibratory unit and the stationary chutes or support structure. This can cause serious damage to the vibratory unit. In many cases, solid evidence of excess build-up around vibratory units can void a manufacturer’s new equipment warranty.
• Prior to starting up the plant, check all drive belts for correct tensioning. Always use the factory-recommended belt tensioner gauge or one supplied by your local v-belt supplier.
• While you are checking the drive belts, check the drive sheaves for any wear between the grooves that could contribute to drive belt failures. Your local drive belt supplier should be able to supply a tool for checking the condition of the grooves in any drive sheave on your plant.
• Look over all of the conveyors on the plant. Make sure they are clear of any loose material before starting up.
• Check the conveyor belt for correct tension and look for any signs of tearing that may be starting. Check the sides of the belt to look for evidence that the belt may be running to one side rather than centered. If the belt is not aligned correctly, follow your Operations & Maintenance manual for directions on centering a conveyor belt.
• Inspect the skirt board rubber and hopper rubber/liners for wear or leak points. Replace any defective rubber so aggregate fines don’t leak onto other conveyor components.
• Look under the conveyor belt for signs of any rollers or returns that show excessive wear or may be locked and not rolling with the belt. Catching a locked or worn roller before it totally fails may save the conveyor belt from serious damage.
• Check the belt scraper blade for wear, and make sure it is adjusted correctly to clean the belt.
• Inspect the conveyor pulleys for signs of wear. This is especially important on self-relieving wing type pulleys to make sure the “wings” are in good shape. A bent or broken wing pulley can affect belt alignment and cause belt damage.
• While looking at the pulleys, periodically check the bushings that mount the pulley to the shaft to ensure they are tight. Your manufacturer’s Operations & Maintenance manual should give you a torque spec on the bushing hardware. Catching a loose bushing early could save a major failure if the pulley were to come loose on the shaft during operation.
Lubrication is a major factor in the longevity of all aggregate crushing and screening equipment. A comprehensive lubrication procedure, carried out on a daily basis, is critical to any successful plant operation. Consult your Operations & Maintenance manual for details on the types and quantity of factory-recommended lubricants required for each component on your plant and follow it closely for best results. A common component on portable plants is the flanged or pillow block bearings on the conveyors, and these all use lip seals to protect from contamination. Take care to NOT over grease these as you can blow out most lip seals in this manner. Of course, a blown lip seal will not protect the bearing and will a premature failure will occur. Always keep an up-to-date, accurate log of all lubrication work performed.
One final note involves safety when taking the portable plant down the road. Always do a complete cleaning of all conveyor belts, take ups, hoppers, fenders, and any ledges that could hold loose aggregate material.
Working through a comprehensive maintenance plan for a portable plant may seem a bit overwhelming, but it is an important process for any plant operation. The old adage that “an ounce of prevention is worth a pound of cure” could’ve been written about the equipment that powers the aggregates industry. A good maintenance program is the best way to ensure the continued, profitable operation of any aggregate producing site. AM
Dave Anderson is the service manager of Terex Minerals Processing Systems. He can be reached at firstname.lastname@example.org or 800-821-5600.