Designing an Optimal Pallet Monorail System

Bastian Solutions | 1 December 2021

When it comes to pallet transport, pallet monorail systems offer a solution that can be significantly less expensive than an equivalent roller conveyor system. Accommodating various applications and adjustable for performance levels, once you’ve determined that a pallet monorail system is the right transportation solution for your application, the next step is putting together an initial concept design.

Despite having two primary types of pallet monorails to choose from, design adjustments need to be made for system flow which helps to determine track curves, load stability, load weight and more. The following guide will help you get off on the right foot towards this effort.

Different types of pallet monorail

The first major decision is deciding how the track system shall be supported. The track system can be either hanging or inverted:

Hanging monorail is the most common type. This type might also be referred to as “Overhead Electrified Monorail”. Floor conditions could be a key factor driving towards hanging monorail, in case the quality of the floor is poor, there are inclines / declines, or areas that require frequent cleaning.

Inverted monorail is simply one where the track system is directly mounted on the floor. These are more easily implemented, as they don’t require a structural framework for mounting the track overhead.

Design Guidelines

As a starting point, we want to define all of the sources and destinations for your system. The first step is to summarize the total system flow into a flow matrix. As an example, let’s say we have a system with three different process steps A, B, and C. We want to summarize all of the pallet flow between each step in terms of pallets-per-hour (PPH). For our example, we have 100PPH coming from A and going to B. After this step, 80PPH return back to A, and 20PPH go to C. For the 80PPH that returned back to A, they eventually go to C as well. This example is summarized into the flow matrix below. For this scenario, this system would have a flow of 280 transfers per hour total.

The next step would be estimating the travel distance between each of the stops. For our example we’ll simply state the distance between all steps is 300 feet. The diagram below summarizes what we have so far and shows the distance relationship between each of the stations. As you can see in the diagram, the flow is almost balanced between each process step. We have assumed that trolleys arriving with loads at step B will be able to receive a new load at B to take to either A or C (trolleys would not be traveling from B while empty). However, it is shown that we will have empty trolleys returning from C to A.

Trolleys can typically travel anywhere from 350 FPM to 400 FPM. We’ll use 350 FPM for the purposes of the example. The final detail to incorporate is how long trolleys would dwell at each process step. If we assume it takes 15 seconds to transfer a pallet load from the static conveyor onto a trolley, and another 15 seconds to transfer a pallet off the trolley, our typical dwell time at most process steps would be 30 seconds (0.5 mins). We can put everything together, include 80% safety factor to account for inefficiencies and an extra trolley (as a spare) and we’d need 11 trolleys total.

There are many additional variables that come into play when determining how quickly trolleys can move pallets between process steps. For example:

• Curves in the track where the trolley might need to slow down
• Load stability (e.g. non-stretch wrapped pallets of cartons)
• Load weight
• Recirculation paths & track switches

These variables will all effect the velocity and acceleration of the trolley, and the design should always be validated via simulation to determine the exact number of trolleys required.

Reviewing Your Specific Application

These systems can be very complex, and some applications require a bit of customization. However, the above guide should help you get a rough concept together. An optimal design for your specific application means improved throughput and efficiency.  Our experts are always standing by and ready to assist with an evaluation of your application.

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Image credits:

• Blog images provided by Pentanova.
• Tables and charts by Bastian Solutions.  

Author: Bastian Solutions