HeavyWeight Training CD Details

Introduction

The two key words used in this training module are Tracking and Training.

"Tracking" is a description of how a conveyor belt runs laterally relative to the center line of the conveyor structure. If the belt "Tracks" well, it follows the centerline of the structure very well. "Tracking" poorly can mean almost anything from a belt which runs very erratically to both sides of the conveyor, to the belt running off-center and into structure or some other obstruction at one particular point.

If the belt "Tracks" poorly at the loading point, there is a high probability of having material spillage which can create tremendous housekeeping problems and safety hazards.

But more importantly, a belt which contacts structure at any location in the system is in danger of being damaged. Since the belt is the most costly component of the conveyor and can sometime be up to 50% of the conveyor cost, "Tracking" is extremely important.

"Training" the belt is a process of aligning structure, adjusting idlers, pulleys and loading conditions in a manner that will correct any tendency of the belt to run other than centrally. This module will discuss "Tracking" problems as well as "Training" devices and proper "Training" procedures.

Training Procedures

• Before running the belt, make sure the structure is centered, square and level . All pulleys and idlers should also be checked for square and level. Even if the conveyor is not new, it is important to start every training exercise from a known square position. Every belt is different and adjustments will need to be made even if the old belt was running well. Pre-start-up check list.
  
  
• Always start training an empty belt.
  
  
• On a new conveyor or an existing conveyor with a new belt, position people at critical locations around the belt prior to initially starting up. Critical points include head and tail pulleys, drives, take-up and any point where the belt could contact structure. On long conveyors, people should be positioned at intermediate points along the structure. All observers should be able to signal the conveyor to stop if the belt is contacting structure.
  
  
• Jog the belt for several revolutions. Initial movement of the belt will indicate where corrections are required to prevent the belt from being damaged. If the belt cannot be run at all without contacting something, install Side Guide Rolls to prevent damaging the belt before continuing. Once it is determined that the belt is not contacting structure anywhere, let the belt continue to run empty. After several revolutions of contact free running, the crew can be reduced to the actual training force and a sequence of training operations can be followed.
  
  
• Before making any adjustments, a general review of the entire conveyor should be made to find tracking patterns. This requires an observer to watch at least 2 complete revolution at critical points such as pulleys as well as a couple representative points along the conveyor length. If the belt appears to be running off center at any locations, at least one revolution should be observed at that location. It is very important to identify tracking patterns before making any adjustments as required adjustments will differ depending on the pattern observed.
  
  
• Start at the discharge pulley and work along the return side toward the tail pulley making adjustments to the idlers as you go. Begin shifting idlers 4 to 6 idlers before the point of belt runout. Always make small idler adjustments to multiple idlers rather large adjustments to a single idler. Tracking correction may not occur immediately, therefore wait for several minutes between adjustments to make sure the affect of the previous adjustment has occurred. At this point, no pulley adjustments should be made.
  
  
• Always follow the direction of belt travel while making adjustments.
  
  
• When the return is complete and the belt is centered on the tail pulley, begin moving towards the head making adjustments to the idlers on the carry side.
  
  
• If the belt can not be properly trained by adjusting idlers only, adjustments to the pulleys can be considered. However, pulley adjustments should not be done unless absolutely necessary.
  
  
• When the belt is tracking properly empty, begin loading the belt lightly while continuing to observe belt movements. Make sure the loading chute is placing the material on the middle of the belt and the load is symmetric. Gradually increase the load to full capacity.
  
  
• As the belt runs between empty and loaded, the take-up will move to adjust to belt length changes. The take-up carriage has a strong influence on the running of the belt at that point due to carriage movement. Therefore the take-up should be watched very closely during the initial loading sequence. A new belt will generally continue to stretch for 4-8 weeks after startup and therefore belt tracking at the take-up should be watched until permanent stretch has stopped.
  
  
• A new belt can sometimes be difficult to train properly due to built in tension distributions , improper storage, ect and may "break in" or run better over time. It is sometimes recommended that a "rough" alignment be performed immediately and final alignment be done after 4-8 weeks of normal running with a load. This time period will vary depending on the belt carcass with all nylon (low modulus/high stretch) fabric belts breaking in quickly and polyester (high modulus/low stretch) belts taking much longer. In the case of steel cord carcass belts, the modulus is so high and the stretch so low, they will seldom change their tracking behavior over time.

Reasons for Poor Belt Tracking