Bulk material handlers depend on the conveyor belt and idlers as foundational to daily operations. The performance of that vital component in turn greatly relies on other sometimes less-heralded parts that support and preserve its function.
During a typical day, a conveyor belt will transfer tons of bulk material, much of which can land on the belt with a relentless impact. The belt’s operating environment also can involve large amounts of dirt, dust, and humidity, as well as extremely high or low temperatures.
These conditions can result in excessive wear and tear on the conveyor belt over time. When the belt begins to deteriorate, it will often affect other areas throughout the load zone. In addition to complicating daily production, the related chain of glitches can result in safety hazards and costly downtime and maintenance.
A few common problems with the conveyor belt can include:
- Mistracking when the conveyor belt slips to a side, shifting the entire system out of its proper path. Beyond throwing the system out of whack, mistracking can cause uneven belt wear that further compromises steady production.
- Slipping when the belt has too much or too little tension. In particular, if the head pulley wears or breaks down, there won’t be enough tension to prevent the belt from slipping around. This can cause the belt to become overly stretched and strained.
- Carryback from material build-up on the conveyor belt. Many bulk materials leave residue while being conveyed. As the residue accumulates, it can begin to interfere with rollers and pulleys. Carryback can often lead to safety hazards, excessive equipment wear, and costly material loss.
- Spillage, which can typically be anticipated with conveyor belt systems. Most materials will accidentally slide or spill from the belt as it transfers massive amounts. Problems will arise when excess spillage can develop into safety risks, production obstructions, and wasted material.
- Sag when the weight of bulk material makes the conveyor belt dip in unsupported areas. Even very small widths of sag can allow gaps to form between the secondary skirting and the conveyor belt, causing material emission.
Unsung Hero: The Conveyor Belt Idler
The conveyor belt alone cannot endure its operational conditions without the right supporting parts. Conveyor belt idlers play a crucial role in helping to prevent problems with the conveyor belt system.
Conveyor belt idlers are rollers used with certain spacing beneath both the carrying and return sides of the belt. As bulk material is loaded onto the belt, the idlers support it along its full length to keep it from stretching, sagging, and eventually failing. In doing so, the idlers allow bulk material to be transferred more evenly from one point to another. This contributes to longer, more-consistent belt performance while limiting premature wear.
Many idlers are made from uniformly machined cast iron or heavy steel tubes that are mounted on antifriction bearings over a fixed steel spindle.
Primary Conveyor Belt Idler Components
- Housing: the complete inner body or bearing chamber inside the roller. It creates an air-tight seal for guarding the idler’s inner components out to the head. Optimal housing will ensure perfect concentricity to achieve desired performance and prolong roller life.
- Bearings: the resistance to radial and axial loads. Bearings made with 2RS ball bearings will support high performance with little to no maintenance or regreasing.
- Shafts: premium cold-rolled steel slotted to secure the idler to the frame. Idlers’ shaft sizes will differ according to their CEMA class.
- Seals: durable rubber that protects the bearing and shaft from dust, moisture, and other fines and contaminants
- Snap rings: for locking seals and bearings in a stationary position to reduce wear
Different idler types can include carrying idlers, return idlers, impact idlers, and troughing idlers.
What Are the Benefits of Troughing Idlers?
Troughing idlers aid the belt in forming a trough for conveying loaded material. The trough helps prevent material spillage while also increasing the belt’s load-bearing capacity.
Installed along the length of the belt’s carrying side, troughing idlers are used to transition from an impact area or load zone. They also can be used to transition from a flat pulley area to or picking to feeding area
Each troughing idler includes a central idler roll with a fixed width and two or more wing idlers on each side of the central idler roll. The depth of the trough can be modified by adjusting the wing idlers up or down.
A troughing training idler frame will further maintain the conveyor belt’s configuration and tracking by adjusting automatically to a detected belt misalignment in the troughing section. This also ensures an even cross-sectional area for material transport.
In addition to reinforcing belt stability, tracking, and carrying capacity, troughing idlers, and troughing training idlers reduce material spillage.
Load Rating: Choosing the Right Idler
The bulk material application, the conveyor belt speed, and the operating conditions are factors in determining the proper idlers to use.
Idlers also must be the correct size for the conveyor belt’s width and trough angle. The size is determined by the idler’s load rating, which is the specified load that the idler can carry at any point.
The CEMA system categorizes idlers according to their load-carrying capacity (load ratings). The CEMA tables are generally selected based on bearing L1O life of 30,000 or 60,000 hours (dependent on series), with the idler roll rotating at 500rpm.
CEMA provides the standard load ratings that any CEMA B, CEMA C, CEMA D, and CEMA E should handle. The following variables factor into a conveyor belt’s load rating.
- Mounting length: mounting on the conveyor where bolts will be set in
- Roll diameter: measurement of the circle at its largest point across
- Idler height: total height for ensuring the idler does not sit too high on the belt and that no other structure will interfere
- Belt width length: dimension measurement that ensures the idler’s troughing angle has not compromised the belt’s ability to fit within the idlers
- Backing height: equal distance needed from the bottom of the base pad to the top of the center roll to keep the belt height uniform
- Footstrap slot width: typically 5/8” or .63” for making sure the bolts being mounted onto the conveyor will fit
- Roll length: combined with slot placement to ensure the roll will fit within the center/ end brackets
- Minimum footstrap width: minimum dimension for making sure the bolt spacing on the conveyor structure will bolt within the given distance
- Maximum footstrap width: maximum dimension for ensuring the bolt spacing on the conveyor structure will bolt within the given distance
Correctly sized idlers will allow the conveyor belt to perform at its highest levels for heavy-duty applications even in extreme environments. The idlers also should be able to be replaced easily and efficiently as needed, particularly at high-impact loading points.
The spacing between idlers will have a major impact on how they help support and shape the conveyor belt. Idlers with too much distance between them will not correctly support the belt, nor will they maintain the needed belt profile. Idlers that are too close will enhance belt support and profile, but they will also often increase the cost of conveyor construction and require the conveyor to use more power.
Factors that will determine idler spacing include:
- Belt Weight
- Material Weight
- Idler Load Rating
- Belt Sag
- Idler Life
- Belt Rating
- Belt Tension
- Vertical-Curve Radius
Idlers are typically spaced closely enough to support a belt with a full load so the belt will not sag between the idlers. For example, carrying idler spacing for material with a bulk density of 100 lbs. per cubic foot might often be 48”. Spacing for the return idlers for the same bulk density might be 120”.
Should you ever need more information concerning proper idler spacing, a Benetech specialist can assist you.
Benetech Conveyor Belt Idlers
Accurately made, precisely installed and well-maintained idlers are vital for the efficient and enduring operation of a conveyor belt. As a global leader in bulk material handling solutions, Benetech offers engineered conveyor components including idlers for industries ranging from underground mines to steel mills to cement plants.
- Exceed CEMA standard load ratings
- Available with standard or wide-base frames
- Come in any belt width and troughing angle
- Utilize impact or steel rolls
Some of Our Belt Support & Alignment Solutions Include:
- Steel & Return Rollers
- Simple Slide Idlers
- Troughing Idlers
- Drop and Slide Idlers
- Impact Troughing Idlers
- Warrior Impact Bed
- Troughing Training Idlers
- Training Idlers
- Return Idlers
- Reversible Training Idlers
Benetech: Your Ally in Bulk Material Handling
Here at Benetech, we dedicate ourselves to the most important details of daily operations at a bulk material handling facility. We welcome each opportunity to answer your questions about greater productivity in the load zone. If you would ever like to discuss the right idlers for your conveyor belt, contact us at (630) 844-1300 to speak with a specialist.