• Siethom's Walk The Belt program provides a specialized crew with the expertise necessary to achieve high operating standards, keeping the system running at maximum productivity. Maintenance tasks can be included in this program and performed either routinely, or upon request.
• Effective upkeep lowers total operation costs. Avoiding unexpected failures saves time and money.
• Specific service requirements will depend on system design, capacity and throughput requirements, desired level of fugitive dust and spillage abatement, and client-approved modifications or upgrades to increase reliability and performance.
• Periodic maintenance inspections, with replacement of equipment prior to failure, will ensure long life and minimum spillage.

A comprehensive survey of the entire plant's material-handling system provides measured levels of respirable and fugitive dust and spillage. The report provides grid-based results, giving the client real information that can be used to prioritize needs, eliminate the risk of spending money in the wrong places, and determine which areas require the most attention.

Installing an idler set between two cradles (or putting each cradle between two idlers) will reduce the drag of the conveyor belt over the bars. This reduces the conveyor’s power consumption. In addition, the heat buildup in the bars will be reduced, giving the bars and belt longer life expectancies.

Idlers should be specified before and after each 1200 millimeter (4 ft) cradle; the number of idler sets required for a given transfer point is the same as the number of cradles required plus one. To ensure uniformity for a stable belt line, all of these idlers should be of the same manufacturer with the same size roller. Impact idlers should be used between cradles under the loading zone; conventional idlers can be used outside the impact area. Track-mounted idlers should be used between cradles to allow for ease of maintenance.

In some impact areas, it may be acceptable to go as far as 2.4 meters (8 ft) between intermediate idlers. These applications might include long loading zones where it is difficult to predict the location of the impact and where rollers might be damaged by point-impact loading. These would also include transfer points under quarry and mine dump hoppers, at pulp and paper mills where logs are dropped onto belts, or at recycling facilities that see heavy objects ranging from car batteries to truck engines dropped on conveyors.

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Typically, the blades of a cleaner do not cover the full width of the belt, because the full width of the belt is not typically used to carry material. Various belt-cleaner manufacturers have their own standard or typical blade coverage. Many manufacturers allow for more than the minimum coverage, but rarely does the blade width need to be equal to or greater than the belt width. For improved cleaning, the carrying width of the material on the belt should be observed or calculated and matched by the cleaner’s width.

In some cases, providing a blade width that is wider than the material load on the belt can lead to undesirable wear patterns. The center section of the blade will wear faster than the portion of the blade on the outside section of the belt, because there is more abrasive cargo material in the center. The outside portion of the cleaning blade will then hold the center section of the blade away from the belt. Carryback can then flow between the belt and the blade, accelerating wear on this center section of the blade.

The material on the belt also provides a lubrication and cooling effect for the blade - therefore, care should be taken to prevent covering too much of the belt. Without this lubrication effect, a buildup of heat on the outside edge can cause the blade to fail and/or damage the belt. Reducing blade coverage on the belt can help alleviate the problem of heat. However, care should be taken when reducing blade coverage, especially on a cupped belt. If the belt curls over the edge of a cleaner blade, it is exposed to the sharp edge of the blade. Some cleaners use a more flexible, nonmetallic blade on their outer edges to avoid this problem. Another solution is to flatten the belt with the use of hold-down rolls.

In some applications, the blade must be as wide as or wider than the belt. A cleaner used as a squeegee to dry a belt may need to be the full width of the belt to catch all the wet areas. Some materials like fly ash tend to spread on the belt or flow horizontally across the belt cleaner. In this case, if the blade does not extend to the full width, material can build up between the belt and the cleaner support shaft, where it can harden and damage the belt.

Belts are troughed to allow the conveyor to carry more material. As the trough angle is increased, more material can be carried. All flat rubber or PVC belts can be formed into a trough by idlers. The type of belt carcass, the thickness of the belt, the width of the belt, and the tension rating of the belt determine the maximum trough angle. On belting manufacturers’ technical data sheets, troughability is typically shown as the minimum belt width allowed for the various trough angles.

Exceeding the maximum trough angle of a particular belt can cause the belt to permanently deform into a cupped position. Cupping can make a belt difficult to seal, difficult to clean, and almost impossible to track. As the cupping increases, the surface contact between the conveyor’s rolling components and the belt is reduced, diminishing the ability of the rolling component to steer the belt properly.

If the belt’s troughability is exceeded, the belt may not form the trough correctly, creating sealing and tracking problems. If a belt is too stiff and will not properly trough, it will not steer (track) properly through the system. This will quickly evolve into spillage off the sides of the conveyor and damage to the edges of the belt.

Another problem that may occur if the belt’s troughing capability is exceeded is damage to the top and bottom covers and to the carcass in the idler-junction area. In addition, if the belt’s troughability is not compatible with the troughing idlers, it might take more power to operate the conveyor than originally designed.

The distance required for a belt’s transition varies with the amount of troughing required, the belt thickness, the construction of the belt, the type of carcass (steel cable or fabric) and the rated tension of the belt. A transition distance must be selected to provide at least the minimum distance for the belt selected.

The heavier the belt carcass, the more it will resist being placed in a troughed configuration and the longer the required transition distance. This is easy to understand if one remembers that a string stretched down the center of the conveyor will be shorter than the string placed on the outside edge of the idlers. The outer edges of the belt must travel farther than the middle of the belt. The higher the trough angle, the more the edges are stretched and the greater the distance required to reach that angle.

The transition distance required is a function of the construction of a belt. When engineering a new conveyor, the belting should be selected to match the material load and conveyance length characteristics of the conveyor. The transition distance of the system would then be designed to match the requirements of the selected belting. However, a more likely scenario is that, due to space constraints and cost considerations, the belting will be selected to match the transition distance engineered into the steel conveyor structure. Either way, however, the belting manufacturer should be consulted when determining the recommended transition distance.

In the case of replacement belting for existing conveyors, the belt should be selected to match the transition distance provided in the conveyor structure. In no case should a belt be placed on a conveyor where the transition distance is too short for the belt.

It is highly recommended that the supplier of the belt be contacted to ensure that the transition distance of the existing structure is compatible with the belt. Charts identifying the recommended transition distance as a function of the rated belt tension for both fabric and steel cord belts at the various trough angles are published in manufacturers’ literature and by CEMA in Belt Conveyors for Bulk Materials, Sixth Edition.

A cleaner, safer operation is normally a more productive operation in the long run. Safety issues normally correspond to unsafe operating conditions, which are also detrimental to the equipment. Airborne dust can find its way into lungs and bearings; material can accumulate under and on walkways and conveyors, leading to trip, slip and fall hazards. These unsafe operating conditions are not only hazards to health, but also to the condition of the conveyor equipment. When equipment is shut down for unscheduled repairs, it cannot be productive.

Cost Effective

The total cost of ownership, including the cost per kilogram (per pound) of dealing with fugitive material releases, should be considered in making design and purchasing decisions. Unfortunately, the lowest-bid process discussed earlier, which considers only initial purchase price, has slowed the evolution of clean, safe and productive designs. While initial purchase price may be lower for a system with no adjustment capabilities and no consideration for future wear-component replacement, the higher costs required to properly install and maintain components, clean up fugitive materials and cover additional equipment downtime will far exceed the costs of a system which takes these factors into consideration in the initial design.

Utilizing standard components where possible in the design may make economic sense, because some economy of purchase may be realized. With some forethought and some slight design changes, standard components (structure, cradles, skirting, etc.) can often be adapted to these new design principles. Use of standard components can provide for ease of installation and replacement due to standardization across the plant. Designing the system for ease of upgradability, by making components track mounted and service-friendly, can reduce down time and control fugitive materials.

Upgradeable

Designers routinely consider capacity upgrades, but they rarely include provisions for component upgrades. A track-mount system provides flexibility for quickly installing different problem-solving components. The use of a pre-engineered mounting hole pattern in the structure around the conveyor's transfer point allows for the installation of a new or improved system quickly and easily. A uniform-hole pattern for accessory mounting will encourage component suppliers to adapt modular, bolt-on or clamp-on designs for easy retrofits. Utilizing structural platform designs - which incorporate tracks, modularity and easy retrofitability - will encourage designers to continue to modernize the way bulk materials are handled today and in the future.

Where a belt is loaded at more than one point along the conveyor’s length, care must be used in the positioning of the skirtboard at the loading points. The skirtboard at the subsequent load points must be designed to allow the previously loaded material to pass freely, without being "plowed" off the belt by the skirtboard or chute steel of the following loading point.

Because it is impossible to rely on material being loaded evenly and centrally onto a conveyor with multiple load points, a certain amount of plowing and spillage of the material is probably inevitable. This fugitive material contributes to higher operating and cleanup costs as well as premature equipment failures. Therefore, it is a sound practice to incorporate continuous skirtboards.

When loading points are relatively close together, it is usually better to provide a continuous skirtboard between the two loading points and a deeper trough angle than would be normally used rather than use individual skirtboards at each loading point.

Another excellent approach for situations with multiple load zones would be the installation of an air supported conveyor. Airsupported conveyors are uniquely suited for multiple load zones, as they require only a centered load, rather than conventional skirtboard or skirt seals.

When specifying a skirt-sealing system, it is wise to consider its mechanism for adjusting and replacing the wearable rubber. As the conveyor runs, the heat generated by the friction of the belt against the skirting seal combines with the abrasive nature of the material fines to erode the sealing strip. To counter this wear, the sealing strip must periodically be adjusted down against the belt.

Applying too much downward pressure to the sealing system leads to additional power requirements to move the belt - it also leads to extra wear in both the belt and the seal.
If the procedures for the service of skirting rubber are cumbersome or complicated, three detrimental consequences are likely:

A. No adjustment:
Adjustment does not happen at all, so the skirting sealing strips wear, gaps open, and leakage resumes.

B. Infrequent adjustment:
Adjustment is made too infrequently, so spillage occurs intermittently.

C. Over-adjustment:
The maintenance person or conveyor operator, to compensate for not making regular adjustments, will over-adjust the seal. Applying too much force down onto the belt risks damaging the belt or catching a splice and ripping out the entire section of sealing strip.

To prevent these problems, skirtboard seal maintenance procedures should be as free of complications, tools, and downtime as possible.

Sealing systems that rest gently on the belt, using little more than the pressure of their own weight or the tension built into the design, can minimize the need for maintenance adjustment.
Some multiple-layer sealing systems provide a self-adjusting function, as the elastomeric memory maintains the sealing pressure. As the legs of the secondary strip wear, the natural resilience of the elastomer strip keeps it down on the belt, maintaining seal effectiveness.

Far Forward:
To minimize the release of carryback into the plant, belt cleaning should take place as far forward on the conveyor’s return run as possible. Typically, at least one cleaner is installed at a point where the belt is still in contact with the head pulley. Normally, this cleaner is installed on the face of the head pulley, just below the point where the material leaves the belt. This position, called the primary position, provides a significant advantage in that the carryback is immediately returned to the main material flow. This reduces the potential for release onto rolling components and into the plant environment. With the cleaners tensioned against the belt and the belt still against the head pulley, control of the blade-to-belt pressure is more precise. The head pulley provides a firm surface against which to mount the cleaner.

Utilizing the space available and mounting the first cleaner in what is considered the primary position creates more space available for the installation of one or more cleaners in the secondary and tertiary positions. As with the primary cleaner, the farther forward each added cleaner is installed, the less chance there is for carryback to escape and the less need there is for devices like dribble chutes or scavenger conveyors to return recovered material to the flow.

Out of the Material Flow:
It is important that cleaners are installed out of the flow of the material and that the material cleaned from the belt does not adhere and build up on the blades or structure.

A cleaner installed in the trajectory of the material may experience premature wear on the support frame and the back of the blades, making it necessary to change the blades before the cleaning edge is worn out. Preferred placement of a cleaner in the primary position involves installing the cleaner so the blade tip is below the horizontal centerline of the pulley.

A cleaner installed outside the material trajectory can still acquire a buildup of material that adheres to its outside surfaces. Cleaners should be designed to minimize the chance for material adhesion. This is accomplished by avoiding flat surfaces and pockets that can capture material and by utilizing non-stick materials for cleaner construction. In the proper environment, water sprayed on the surface of the belt - or on the cleaners - assists in softening the material and minimizing material buildup.

With Minimal Risk to the Belt:
An essential consideration in the selection of a belt-cleaning device is minimizing any risk that the cleaner could damage the belt or a splice, the very systems it was installed to protect. Belt-cleaning systems must be designed so the blade is capable of moving away from the belt when a splice, damaged section of belt or other obstruction moves past the cleaner with the belt. The cleaner’s tensioning systems, particularly on the primary cleaner where the angle of attack is more acute, should include a mechanism to provide relief from the shock of the splice impact.

An aggressive primary cleaner with a lot of cleaning pressure will have a tendency to more quickly wear away the top cover of the belt. These cleaners inherently provide an increased risk of catching on a protruding splice or flap of belt.

Care should be taken in choosing an appropriate material to put in contact with the belt. Materials such as strips of used belting should never be applied as a belt-cleaning or sealing material, because they may include steel cables or abrasive fines. These embedded materials cause excessive wear of the belt’s top cover.