Preventing Belt Side Tracking vs. Correcting Misalignment
Though belt misalignment is a common problem in bulk material handling, it can have a variety of causes, it may not be easily solved and definitely cannot be ignored.
Conveyor belting can track off-center for many reasons. The Conveyor Equipment Manufacturers Association (CEMA), in thei 7th edition of Belt Conveyors for Bulk Materials, notes several factors that influence belt tracking. They list recommendations to avoid mistracking and, starting with the basics, a number of conditions that need to be in order for a belt to remain in the correct path.
According to CEMA, the fundamentals of proper tracking include a conveyor structure frame that is aligned and leveled, and the tail and head pulleys of the conveyor need to be square and aligned on the conveyor frame. In addition, the belting must be straight and splices must be square, belting should be in good contact with troughing rolls, all troughing and return idlers should be square with the conveyor frame, belting must be properly tensioned, and material should be loaded centrally on the belt.
In real world applications meeting these ideal conditions can be a daunting task. Yet, even when these requirements are checked off as well as can realistically be accomplished, the problem of off-center tracking may remain.
Traditional ways to correct this problem
There are a number of traditional methods in use that attempt to correct this problem. These include conventional training idlers that come in a variety of designs. All of these designs have a common denominator in that they include some kind of reactive moving component like pivots or swivels that are engaged when belt misalignment occurs. The intent is to move the belting back to the correct path of travel.
Scott Smith, Applications Engineer at Richwood in West Virginia, USA, explains, “Sometimes these methods are helpful, but in other applications they are found to be ineffective. Products that use edge guide rollers can actually damage belting, leading to premature belt replacement. Pivots and swivel bearings can eventually seize, rendering them infective and creating additional risk of damage to belting.”
Permitting the belt to walk back and forth not only damages belt edging, but the conveyor frame itself can be damaged, creating an unnecessary safety hazard. Conventional training idlers are designed to react to changes in the path of travel of the belt. In each case, the training idler responds by skewing or pivoting an idler to steer the belt back to the center.
In order to get the trainer to respond, the belt must have already misaligned. The training idler then compensates, pushing the belt in the opposite direction where it often over-travels and the process repeats itself. The result is a belt that continually walks from side to side.
Smith continues, “Traditional designs work by reacting to a belt once it begins to travel off-center, then pushing the belt in the opposite direction—either by pivoting or on edge rollers, and then repeating that process continuously. We do not believe that this is an ideal situation.”
A modern solution
In response to the need for a solution that eliminates these negatives, Richwood has developed the ON-Track® Return Belt Tracking Idler. This new alternative does not use edge guides or pivot, nor does it allow the belt to travel back and forth.
Smith says, “What makes the ON-Track® different is the fact that it does not need to respond to belt misalignment because it keeps it from ever going off-track to begin with by applying tension to both sides of the belt. The belt’s own tendency to find equilibrium keeps it in the right place.”
He continues, “Should the belt attempt to misalign, the gentle tension differential created by the ON-Track® unit keeps the belt in place in the center of the conveyor structure. The ON-Track® uses a multiple roll design that creates a smooth arc, which helps guide the conveyor as tension gets progressively greater toward the edges. This system works by safely controlling where a belt travels instead of reacting to belt misalignment.”
When faced with a persistent problem of belt misalignment, rethinking the traditional strategies may be in order. This alternative has demonstrated reliable success in the field.
Case Study #1- One of the Largest Coal Mining Complexes in the World
72” belt width / 6000 tph / 1200 fpm
A surface mine in Wyoming was experiencing severe belt tracking issues. Their first experience with ON-Track® was on a 72” belt running 6000 TPH and moving at 1200 FPM.
Jeremiah Hinds, the Richwood representative who was directly involved with this project, provides the details. “One of the biggest problems was with the belt going off-track through the tail section. It was running under the seal and ruining their skirt rubber, not to mention creating a constant mess.”
The initial survey showed the belt traveling 8 to 9” back and forth on the tail pulley even though they were using a traditional belt trainer. Once the ON-Track® was installed, and the old trainer removed, this issue was resolved. They are very pleased with the results and no longer deal with belt mis-tracking.
Case Study #2- Facility in Southern United States
48” belt width / Pep Coke and Sulfur / 2500 tph / 650 fpm
In a busy facility in the southern United States, the end users were looking for a solution to a serious tracking problem. Local Richwood representative Scott Baisden was invited to take a look at the application.
According to Baisden, upon review of the site, several issues were noted. He states, “The belt had multiple problems; the tail pulley had no lagging, there were peaks and valleys worn into it causing the belt to run off when loaded, and the age of the belt was causing it to break down from the inside, seriously affecting belt tracking. The loading conditions were also a factor due to the weight of the material. The severity of the problem was even more clearly seen in the amount of spillage they were experiencing and for this reason the belt was constantly being stopped, taking a serious toll on productivity.”
Baisden continues, “A vac truck was needed frequently, costing $700 per day plus man power, not to mention the cost of material loss.”
Richwood recommended installation of the ON-Track® to solve this severe belt tracking problem. Once installed and with the conveyor running in its typical conditions, the company no longer experienced mis-tracking or material spillage. They have decided to install an additional unit on another conveyor with tracking issues.
Baisden sums it up, “Under variable loading conditions, testing confirmed the path of the return belt was positively controlled at all times. There have been no other belt trainers required or belt tracking issues since installation of the unit.”
A proven benefit
In a wide variety of applications the ON-Track® Belt Tracking Idler has proven to be the reliable solution to this common problem.
The new technology found in the system design focuses on the prevention of belt side tracking and misalignment rather than correcting misalignment after it occurs. When you are attempting to guide the conveyor back into its path, you have likely already lost the battle.
The belt’s tendency is to find the place of lowest tension, or equilibrium so it stays centered on the structure. Should the belt attempt to misalign, the gentle tension differential created by the ON-Track® unit keeps the belt in place in the center of the conveyor structure. It may sound simple, but even more interesting than the design, are the immediate results end users are experiencing in the field.
When faced with an application where conventional methods of belt training are not working, consider the solution that comes from a new point of view. Instead of fighting belt misalignment with repeated attempts at belt training, simply keep your belts ON-Track® with Richwood’s proven performance.