Tubular drag conveying is a common method of moving loose bulk materials between processes in industrial plants. Chain-type tubular drag conveyors fall into two basic categories: those that use round-link chains and those that use engineered chains. Each chain type features a unique design philosophy and construction, so there is some variation between them in terms of operation and reliability.
The round-link variety employs a mass-produced chain made from material that is cut, formed into loops, and welded together at the ends. If all of the proper operating conditions exist, these chains may be sufficient for extremely low-duty, low-risk applications.
For the majority of industrial environments, however, engineered chains are the way to go because they are specially designed for use in heavy-duty material handling equipment. Overall, the performance and serviceability of engineered chains are significantly superior, resulting in a much lower longer-term cost of owning, operating and maintaining a conveyor that uses them instead of round-link chains.
Here are five reasons why round-link chains are insufficient for most industrial applications:
1: Round-link chains require dramatically longer start-up time.
Round-link chains are impossible to install without inadvertently introducing a significant amount of unwanted twist. Consequently, the start-up procedure for a conveyor with a round-link chain requires close monitoring of the inevitable accumulation of twisted chain. When that occurs, plant personnel must stop the conveyor, locate the master link, part the chain and untwist it. This procedure must be repeated several times, and depending on the length of the conveyor, can take several days before twisting no longer accumulates.
While too much twist is problematic, especially with round-link chains, some twist is often desirable and even necessary for certain conveyor routings to work. Engineered chains are designed with this capability in mind. It is exceedingly easier to control them and prevent undesired twisting during chain installation, which dramatically shortens start-up time while eliminating monitoring and the associated labor costs.
2: Round-link chains are more likely to fail and cause other maintenance-related headaches.
Round-link chain construction inherently includes a welded seam that is the most common point of failure in a chain that’s not very robust to begin with. Operators must also bump the conveyor or go searching for a master link when round-link chains require maintenance.
The design and construction of an engineered chain eliminate this troublesome seam. They also allow each link to be individually parted and serviced wherever it is most convenient.
3: Round-link chains operate less efficiently and cause excessive spillage.
Conveyors that use round-link chains are notorious for spilling material from one flight to the next due to flight tipping. Plants often install wiper flights in an attempt to counter this phenomenon, but this is merely a stopgap measure.
Due to their longer pitch, engineered chains naturally hold flights more firmly and keep them perpendicular to the carry surface. This allows a conveyor to operate more efficiently and retain more material.
4: Round-link chains require the “over use” of roller turns.
If a configuration calls for bends or any kind of conveying length, roller turns are required in the corners to reduce the load on a round-link chain. Unfortunately, they can allow material to flow through the mechanical assembly, where it can damage the material, cause excessive wear on the assembly or create material build-up, which is difficult to remove.
Engineered chains are strong enough to withstand the loads in corners and do not require mechanical turn sections. This effectively prevents material from entering the conveyor’s mechanical assembly.
5: Round-link chains are prone to performance problems if any slack develops.
Compared to engineered chains, round-link chains have a much shorter and narrower target, which can compromise the equipment’s positive engagement and ability to wear evenly. Also, conveyors with round-link chains usually include a spring-loaded chain tensioning mechanism. These devices are necessary to keep short-pitch chains engaged with the sprockets that drive them, but if any slack develops, derailment often occurs.
An engineered chain does not require a tensioning mechanism, and its drive sprocket teeth can be wider and longer for more positive engagement and even wear distribution by virtue of having more contact surface. Greater engagement also makes the conveyor more slack-tolerant and allows the use of a simple jack-screw-type take-up mechanism.
While both varieties of chain-type tubular drag conveyors often compete for the same work, clearly they shouldn’t. A thorough examination and comparison of the two chain types reveals a different design mentality and vastly disparate calibers of equipment—and not all conveyor manufacturers offer the engineered-chain option. Hapman offers both, and you can be confident that we will steer you in the right direction when selecting the correct chain type for your tubular drag conveyor.
Read our white paper to read a more detailed comparison of round-link and engineered chains.