Vertical conveyors (vertical transport)
- What is a vertical conveyor (vertical transport)
- Why should you use a vertical conveyor?
- Different vertical conveyors
- What to watch when choosing a vertical conveyor
What is a vertical conveyor (vertical transport)
A Vertical Conveyor is a machine that is specifically designed for efficient material handling processes. Vertical Conveyors are used to automate the process of moving products or materials from one level to another. Making it a crucial component of intralogistics (internal logistics). However, it’s important to note that a vertical conveyor is not the same as a product elevator or lift. It is integrated into a material handling system or conveyor system and is solely used for transporting materials or products. You can only speak of a Vertical Conveyor when it is integrated in a material handling system or a conveyor system.
In the past, traditional conveying methods like incline or declining roller or belt conveyors were commonly used in industries. However, these methods require a significant amount of floor space, which can limit the usefulness of a facility. It might work in big facilities when there is enough floorspace to place such conveyors. Inclining and declining conveyors have a big disadvantage because it takes up a lot of floor space which could be used for more useful purposes. Nowadays, more and more companies are seeking space-saving solutions, and the vertical conveyor is a popular choice because it maximizes the use of existing floor space. If you’re looking for an efficient way to move materials or products vertically within your facility, a vertical conveyor is the perfect solution.
Why should you use a vertical conveyor
If you’re looking to optimize your production area or warehouse, a vertical conveyor is a great option to consider. Space is sparse and at a premium, making vertical transport essential to upgrade most production lines. Whether products need to be supplied at a different height, or floor space needs to be freed up for other machines or to give forklifts/trucks and people access, an automated vertical transport system is crucial.
In warehouses, maximizing cubic feet as well as square feet is essential for efficient activities like order picking. Multi-floor transport systems need to be able to move products up and down quickly and frequently throughout the day. Distribution centers are increasingly making use of fully automated storage and order picking systems, which require a conveyor system with the characteristics of a production line.
When selecting a vertical conveyor system, there are many options available on the market. However, the system you choose will depend entirely on your unique situation. After all, production and logistics processes are different in every company. Considerations like the frequency and speed of product supply, the infeed and outfeed levels or positions, and whether the product flow is in one or both directions, all need to be taken into account. Additionally, the amount of available space will be a crucial factor.
To select the best vertical conveyor system for your company, there are five key aspects that must be addressed in the selection process. Later in this text, we’ll explain these five aspects in detail, but first, we’ll describe the different types of vertical conveyors available on the market.
Different vertical conveyors
There are different vertical conveyors with each its own pro’s and con’s. We will explain the biggest difference between the following vertical conveyor solutions
– Inclined belt conveyor
– Discontinuous vertical conveyor
– Continuous vertical conveyor (paternoster conveyor)
– Platform (lift) conveyor
– Spiral conveyor
Inclined belt conveyor
The simplest way to transport products up or down is to use a traditional (inclined) conveyor belt. Capacity is generally not a problem for inclined belt conveyors. After all, similar to a normal belt conveyor, products can be placed one after the other on the inclined belt conveyor. It should be noted that a more powerful gear motor is needed to drive an inclined belt conveyor. Operational speed will often be slower than with horizontal transport. In addition, outfeed and infeed direction are identical, unless a bend is fitted in the configuration as with horizontal transport systems.
The main disadvantage of an inclined belt conveyor is the enormous space that is required for this system. The reason for the big floor space that is needed is entirely the cause of the slope of an inclined belt conveyor. In order to prevent products from falling over backwards or sliding down, the maximum slope angle – depending on shape, dimensions and weight – is usually somewhere between 15 and 30 degrees. An inclined belt conveyor at a slope angle of 30 degrees must be no less than 6.0 feet long to bridge a height of 3.0 feet. With an angle of 15 degrees this increases to over 11.5 feet. Needless to say, the distance travelled and transport time for goods will increase too.
Discontinuous vertical conveyor
The most simple vertical conveyor is the so-called discontinuous vertical conveyor: a single product carrier that can move up and down. The product carrier is suspended in a steel column and is usually hoisted using chains or belts. A discontinuous vertical conveyor has a small footprint because the only space that it occupies is the steel column with lifting platform that must be slightly larger than the maximum size of the products.
The discontinuous vertical conveyor has the advantage that one machine can serve multiple infeed and outfeed levels and transports products both up and down.
A disadvantage of the discontinuous vertical conveyor – sometimes called discontinuous product lift or start/stop lift – is the limited speed and capacity. A discontinuous vertical conveyor can only transport another product after the product that is on the carrier has been deposited and the empty product carrier has returned to the starting position. The capacity is thus determined not only by the upward but also by the downward movement. Another drawback is the restriction on the possible infeed and outfeed directions. The product carrier usually consists of a roller conveyor or a belt conveyor. Products can only be fed out in the same or exactly opposite direction as they are fed in. There is no other option
Continuous vertical conveyor (paternoster conveyor)
In addition to a discontinuous vertical conveyor, there is also a continuous vertical conveyor that works according to the paternoster principle. A continuous vertical conveyor working according to the paternoster principle has the benefit of giving the user the option to add multiple product carriers to the vertical conveyor. The product carriers travel in a loop just like the platform (lift) conveyor.
There is one important difference: all product carriers remain horizontally positioned during the entire trip from infeed to outfeed, this gives the benefit that a product can remain on the carrier for the duration of the cycle. Another benefit is that the paternoster lift allows users to add multiple infeed and outfeed positions in one vertical conveyor. Moreover, the paternoster lift is the only vertical transport system which can lift and lower multiple products simultaneously. A paternoster lift does require a little more space than a discontinuous vertical conveyor and a platform (lift) conveyor, but not nearly as much as an inclined belt conveyor or a spiral conveyor.
In terms of capacity, this system is similar to an platform (lift) conveyor and a much larger capacity than a discontinuous vertical conveyor, but it really competes with an inclined belt conveyor or spiral conveyor. It is possible to expand the capacity – to some degree – by adding more product carriers or placing multiple products on a carrier without having to increase the speed of the system. Similar to the platform (lift) conveyor, the paternoster lift also needs a supply rate controller. Accurate synchronization between the feed belt and lift is not ne- cessary, thanks to the specific design of the product carriers. This makes a paternoster lift a lot easier to integrate than a platform (lift) conveyor in terms of control
Platform (lift) conveyor
The main difference between a vertical conveyor and a platform (lift) conveyor is the direction of movement of the product carrier. With a vertical conveyor the product carrier goes up and down, whereas with a continuous product lift such as the platform (lift) conveyor the product carrier describes a loop.
Once a product is transported to another level, the product carrier returns via a different route to the starting position. This makes it possible to install multiple product carriers and therefore transport multiple products per cycle. The capacity of a continuous vertical conveyor is therefore much greater than that of a discontinuous vertical conveyor. The product carrier of the platform (lift) conveyor consists of a flexible, pliable mat. It is hoisted up using four chains or hoisting belts. Once the product reaches the right height and is deposited on a belt conveyor or roller conveyor, the mat makes its way back down. The advantage of the platform (lift) conveyor is its limited use of space. Furthermore, the necessary shielding can also be integrated into the lift. It is also relatively easy to transport longer or heavier products. The process here does not change whether the products are small or big and light or heavy.
Most platform (lift) conveyors are only suitable for situations with a fixed infeed and outfeed height. Combining ascending and descending movements in a single platform (lift) conveyor is difficult. Moreover, as with a discontinuous vertical conveyor, the number of possible infeed and outfeed configurations is limited. Products can only be fed in or out in the same or opposite direction. An additional drawback is that not only the rate of supply of products needs to be controlled but the feed belt and conveyor (mat) must also be precisely synchronized. If the mat is a little too early or too late then the product will drop into the platform (lift) conveyor. As you can imagine, that will cause some problems and impact the daily operations of a facility. In the event of such an issue the chance of product damage or product contamination is high, because the product is always located inside the lift while it is being transported up or down.
A spiral conveyor is nothing more than a belt conveyor that runs up or down in a spiral.
The main advantage of a spiral conveyor is its capacity. As with an inclined belt conveyor, products can be fed continuously one after the other, keeping in mind that a certain gap must be observed between the products in connection with the ascent angle and the radius. It is possible to fill the entire spiral with products, so this solution is also suitable as a buffer system. Another advantage is the flexibility with regard to infeed and outfeed direction and infeed and outfeed height. In principle it is possible to feed products in and out at any angle and at any height, simply by connecting a horizontal belt conveyor or roller conveyor to the spiral conveyor at those points.
It should be noted that due to the spiral shape it is not possible to freely select both infeed and outfeed directions and infeed and outfeed heights. Another disadvantage is the amount of space that is required for a spiral conveyor. Because the products follow a spiral with a certain radius the space occupied by a spiral conveyor is several times larger than that of a vertical conveyor or platform (lift) conveyor. The longer and wider the product, the greater the radius and space needed and the more expensive the spiral conveyor. The spiral movement also ensures that products must travel a relatively long distance, resulting in a long drive system that requires extra power (energy consumption) and maintenance. There are spiral conveyors on the market that can simultaneously transport products both up and down. Actually, these would be spiral conveyors with two belts: one on the inside and one on the outside. A disadvantage is that the products on the outer belt have to travel very long distances, making it often more convenient to install two spiral conveyors with one belt conveyor. rather than one spiral conveyor with two belts. The main reason for that is because of a spiral conveyor with a double belt conveyor not only requires a double drive but also a larger diameter and thus more floor space
What to consider when choosing a vertical conveyor
There are actually only two basic techniques for transporting products up or down. The first basic technique makes use of conveyor belts and the second of an elevator system. Every vertical transport system on the market today makes use of one of these two basic techniques. If conveyor belts are used it is not necessary to integrate a start/stop function into the system. After all, products go straight from the infeed belt to the conveyor belt, after which they are finally sent to the discharge belt. In an elevator system the rate of supply of products must always be controlled. Elevator systems do however travel the shortest vertical distance, meaning their use of space (footprint) is minimal.
1. Use of space
A vertical transport system is primarily intended to free up valuable floor space. Space which, as stated before, m2 is scarce and is becoming increasingly expensive. It is therefore important that a vertical transport system not take up a large portion of this valuable space. And some vertical conveyors are simply more
compact than others.
2. Infeed and outfeed directions
In the simplest situation the product will continue in the same direction after bridging a difference in height. However, there are situations where it is desirable for a product to be directed to a different or even opposite direction.
Many vertical transport systems make it possible to combine change in outfeed direction with bridging differences in height. There are even systems where product orientation can be changed. This increases the number of logistics solutions and prevents the need to install a bend in the belt conveyor or roller conveyor immediately after the system. However, the number of possible infeed and outfeed directions varies per vertical transport system.
3. Infeed and outfeed heights
In some situations it is desirable to be able to pick up products from different heights and deposit them at variousoutfeed heights. This is frequently the case in warehouses, which often contain several mezzanines and where products must be circulated between all of these floors. Not all vertical transport systems can serve multiple infeed and/or outfeed heights.
4. Ascending and descending
Especially in warehouses it may be necessary to alternate between ascending and descending products. Consider, for example, order picking across different floors. Products must not only be transported to the different floors but also be returned again at some point. A vertical transport system that can transport products both up and down eliminates the need for two different systems for these two movements.
The capacity of a vertical conveyor mainly depends on the achievable speed of a viertcal conveyor. The faster a vertical transport system is, the more products it can handle per hour. Another factor is the number of products that can be processed simultaneously. The height of a vertical conveyor can influence the capacity as well.
The minimum capacity required in any situation is almost always determined by the structure of the overall process. A vertical transport system should never be the bottleneck in a production line. The vertical transport systems available on the market today can vary considerably in terms of the above aspects. Some vertical conveyor systems are faster, more compact and more versatile than others. Of course, prices also vary widely by system. The goal is to select the system that best fits your situation in terms of price, performance and your specific needs.
Pros and Cons of each Vertical conveyor
|Type of vertical conveyor machine
|Continuous vertical conveyor
|Disontinuous vertical conveyor
|Inclined belt conveyor
|Use of space
|Multiple infeed and outfeed directions
|Multi infeed and outfeed options (multi product flows)
|Ascending and descending product flows
This table provides an overview of the advantages and disadvantages of the various vertical conveyor solutions
The cost of purchasing, running and maintaining a vertical conveyor
The manner in which a vertical transport system can be integrated into a production line or logistics process is not the only important factor. Other factors such as initial costs, installation, maintenance and energy consumption play an equally important role in choosing the right vertical transport system and the right supplier.
• Initial costs
Many companies look first and foremost at the initial costs. These can vary considerably from system to system. In general, an inclined belt conveyor is the cheapest solution, followed – in ascending order – by a discontinuous vertical conveyor, a paternoster, a platform (lift) conveyor and finally a spiral conveyor.
One important factor to determine the price of a vertical conveyor is the height that must be bridged. The larger the difference in height, the greater the differences between for example a paternoster and a spiral conveyor price is. For each additional feet or meter, the framework of the spiral conveyor but also of the belt conveyor must be extended. You will probably need an additional or at least a stronger gear motor with the appropriate frequency inverter to make it possible to lift the additional feet(s)/ or meter(s) of the belt conveyor and products that are moved on the conveyors.
In other words, a spiral conveyor that is twice as high is also about twice as expensive. With a lift this is different, whether it is a discontinuous vertical conveyor, platform lift or continuous vertical conveyor. In these systems, only the length of the steel construction and the length of the hoisting cables or chains needs to be extended. After all, the number of moving parts, product carriers and drive motors remains the same. A discontinuous product lift of 30 feet is therefore only slightly more expensive than a lift of 15 feet.
• Integration costs
Inclined belt conveyor and spiral conveyors are relatively easy and cheap to install. Of course, these vertical transport systems require a relatively large amount of space that needs to be made available, once the space has been found they can be installed pretty easily. The products flow onto the inclined belt conveyor or spiral conveyor is a non-stop flow when being transported to the level. Both machines still require some control software. However, this is only necessary for the engines. Spiral conveyors also need slack-chain protection software that prevents problems caused by slack chains over time.
A vertical conveyor lift requires a bit more work. The main reason being is that the supply of products and movements of the product carrier must be geared to one another. A product can only enter the lift once an empty product carrier has arrived. With a platform (lift) conveyor, unlike a paternoster lift, both movements actually need to be accurately synchronized. This requires a bit of control software, which is fed with data from sensors. For the programmers who already have to code the control system for an entire production line or transport system those few extra sensors won’t really pose much of a problem.
• Energy costs
There are costs that extend beyond the commissioning of your vertical transport system. First, there is the cost of running the system, the energy costs. The advantage of vertical conveyors, platform (lift) conveyor and paternoster lifts is that with these machines the products always take the shortest route, i.e. straight up.
With inclined belt conveyors and spiral conveyors the distance is multiplied, resulting in higher energy costs. The greater the differences in height, the greater the difference in energy consumption between elevator systems and spiral conveyors. An increasing amount of energy is required to the make longer belt conveyor move including the products on them.
In an elevator system the relationship between differences in height and energy costs is less strong. The paternoster lift is a real exception when it comes to energy costs. With a paternoster lift the ascending and descending carriers balance each other out. This means that energy is only needed to transport the products up, not for the product carriers themselves. In most situations an engine with an output of 0.37 kW is therefore sufficient.
• Maintenance costs
When it comes to maintenance costs, the differences are great. The solutions with belt conveyors (inclined belt conveyor, spiral conveyor) often have a very large total length. A belt must be kept running and has to be replaced in its entirety if the weakest point fails. In most spiral conveyors the belt conveyor consists of a long chain covered with overlapping slats. Dirt and dust can fall from the products through the slats and directly into the drive system. In addition, products can be turned by the overlapping moving slats and end up getting caught between the side guides, which can cause extensive damage.
A vertical conveyor is easy to maintain and has few critical points. With platform (lift) conveyor (depending on the manufacturer) the delicate drive system often consists of a very expensive rubber chain. Possible replacement of the chain can be very costly. And if a product falls it could result in damaging the drive system. Just like the discontinuous vertical conveyor, the continuous vertical conveyor is easy to maintain. The drive system consists of an extra strong standard steel chain that is cheap and readily available around the globe. The forks are product-specific, but very quickly interchangeable. Its control system protects it from jamming.
• Total Cost of Ownership
Initial costs, integration costs, energy costs and maintenance costs: these are all part of the total cost of ownership (TCO) of a vertical transport system. The table below compares the cost of the five different systems. And yet it is not wise to look only at the total cost of ownership of a single system. It is more relevant to look at the TCO of the total production line or logistics system that was installed. No matter how good the vertical transport system is, if elsewhere in the overall system something is wrong the company still has a problem. Besides cost, reliability is also important. Irrespective of the price of the vertical transport system, if it stops working an entire production line will often stop working too, resulting in considerable expenses and perhaps even lost turnover.
• Optimal price / performance ratio
Choosing a vertical transport system is a process that involves many different solutions with both strengths and weaknesses. First, the system must fit perfectly in the layout of the production line or warehouse. A production line will generally involve a steady stream of identical products that need to be transported no more than a few feet up or down and often only in one direction.
Capacity, reliability and maintenance friendliness are important factors. Flow diagrams are much more complex. Products must not only be transported upwards but downwards as well, which will often involve multiple levels. The number of products that need to go up or down can change from minute to minute. A vertical transport system will thus soon become a vertical sorting system. Flexibility and versatility are important in such situations, where capacity should be large enough to avoid creating a bottleneck.
In a world where costs play no role, inclined belt conveyors or spiral conveyors would be the preferred method of transport if very high capacities are required. In the opposite case, if required capacity is low and complexity minimal, you would be better off with a vertical conveyor. But unfortunately in the real world cost does play a role.
Ultimately, choosing a vertical transport system is choosing the optimal price/performance ratio. In the comparison between the different systems the continuous vertical conveyor scores the highest on both price and performance. This paternoster concept – revived by Qimarox – really has no weaknesses. The paternoster is flexible when it comes to the amount of product ccarriers, the number of infeed and outfeed directions and levels. This vertical conveyor fits into almost every operation. Above all, the continuous vertical conveyor also has undeniable advantages in terms of maintenance. No wonder the continuous vertical conveyor has gained so much market share in recent years compared to other vertical transport systems