Why are scissor lift tables used as goods lifts more expensive than standard lift tables? And why can’t a regular lift table be used for this purpose?
These questions are entirely justified, especially when considering the price difference between a standard lift table and a simplified goods lift. In this article, we explain why a regular lift table is unsuitable for use as a goods lift.
Are there differences in the applicable standard?
No, there is no difference in the applicable standards as long as the lift table only serves two stops. In this case, both standard lift tables and simplified goods lifts fall under the same European standard, EN 1570-1. This standard outlines the safety requirements for lift tables.
However, if the lift table is intended to serve more than two stops or to transport people, other guidelines and standards come into play.
Same standard, but different safety measures?
Even though the same standard is applied when lift tables serve up to two stops, different safety measures are still required. The EN 1570-1 standard accounts for eight different scenarios, each leading to different safety requirements. The necessary safety features are influenced by the following factors:
- Is there more than one landing?
- Is the lift platform in a restricted access area?
- Does the operator have a complete view of the hazard area?
- Do operators ride along on the platform?
- Is the lifting height more than 500 mm or more than 1.6 metres?
- Does the lift operate in dead man's mode or automatic mode?
To better understand how these factors impact the safety requirements, we will illustrate this with two examples:
Example 1: A scissor lift table as a work lift table
A classic example of using a scissor lift table is the work lift table, which is employed in production to improve ergonomics. This type of lift table allows workpieces to be raised and lowered so that the employee can always work at an optimal height.
Since the employee works directly at the scissor lift table, it is ensured that they can monitor the entire danger zone during the lifting and lowering movements.
Another important aspect of work lift tables is the dead man's operation mode. This means that the assembly lift table only raises or lowers as long as the corresponding button is pressed. Once the button is released, the lift table stops immediately.
Installation scenario according to EN 1570-1
When considering the work lift table in the context of the eight installation scenarios according to EN 1570-1, the following insights regarding potential hazards can be derived:
- Is there more than one stop? No, the work lift table has a fixed stop — the fully retracted position. All other lifting positions are flexible and can be adjusted to the needs of the respective employee. There is no fixed transfer position.
- Is the lift table located in a restricted access area? Work lift tables are typically used in industrial production environments that are generally not freely accessible. Outsiders must first gain access to the production area, so it can be considered a restricted access area.
- Can the operator fully observe the danger zone? This question has already been addressed in the previous section. Typically, work lift tables are the size of a Euro pallet, making the entire working area of the scissor lift table easily visible to the operator. However, if a larger scissor lift platform is used, the addition of a release button for two-person operation might be necessary.
- Are operators riding on the platform? No, work lift tables are designed exclusively for lifting workpieces. It is not intended for operators to be lifted on the platform.
- Is the lift height more than 500 mm or more than 1.6 m? The question about a lift height of more than 500 mm is aimed at the potential risk of falling from the platform or from an upper stop. Since neither person transport is allowed nor is there an upper stop, this risk is not relevant here.
For lift heights exceeding 1,600 mm, there is a risk of people getting underneath the scissor lift table. Typically, a work lift table lifts to a final height of about 1,000 to 1,100 mm, so no additional safety measures are required. However, at higher lift heights, an underrun protection might be necessary. - Does the lift operate in dead man's or automatic mode? As mentioned earlier, work lift tables operate in dead man's mode to allow holding at any intermediate position.
What does this mean for the safety measures?
Given the described installation scenario, work lift tables are considered to pose relatively low risks. Therefore, in addition to a stable mechanical design, only the standard safety features are generally required, such as:
- Toe protection saefty strips: To protect against crushing during the lowering movement.
- Pipe rupture safety device: To prevent uncontrolled lowering in the event of a burst or severed hydraulic hose.
- Maintenance supports: To ensure that the lift table remains in the raised position during maintenance work.
- Low control voltage: To ensure safety during operation.
However, it is important to note that these requirements can vary depending on the specific installation situation. For example, an open staircase railing nearby might necessitate additional safety measures. Therefore, it is essential to conduct an individual risk assessment for each scissor lift table to ensure that all potential hazards are appropriately identified and addressed.
Example 2: Scissor lift table as simplified goods lift
Now let's consider a scissor lift table used as a classic goods lift. In this context, "classic" refers to an elevator used exclusively for transporting goods between two floors. While operators are allowed to enter the lift at the stops, riding on it is not permitted.
The lift travels to the selected floors using an automatic control system: The operator simply selects the desired stop, and the lift table then independently moves to the corresponding floor.
Installation scenario according to EN 1570-1
Let’s analyze the simplified goods lift in the context of the eight installation scenarios according to EN 1570-1. The following insights can be derived:
- Is there more than one stop? Yes, our simplified goods lift is assumed to have two stops, allowing the application of EN 1570-1.
- Is the lift table located in a restricted access area? Our simplified goods lift are typically used in production areas or warehouses within industrial facilities. Similar to work lift tables, these areas are considered restricted access zones.
- Can the operator fully observe the danger zone? Since the goods lift is equipped with control stations at both the upper and lower stops, it is unfortunately not possible to fully observe the danger zone. For instance, if the operator is at the upper stop, they cannot see the area beneath the lift platform.
- Are operators riding on the platform? No, our goods lifts are designed exclusively for the transport of goods. Operators are not permitted to ride on the platform.
- Is the lift height more than 500 mm or more than 1.6 m? The lift height for goods lifts typically exceeds 3 meters.
- Does the lift operate in dead man's or automatic mode? To enhance convenience, the hydraulic lift operates in automatic mode. This means the operator does not have to hold the floor selection button throughout the lifting or lowering process.
What does this mean for the safety measures?
Compared to work lift tables, simplified goods lifts present additional hazards that must be mitigated through appropriate safety measures.
- Fall hazard at the upper stop:
One potential danger is the risk of someone falling from the upper stop. To minimize this risk, an enclosure is required at the upper stop. This enclosure must be complemented by an electro-mechanically secured access door. The access door should only be operable when the platform is in the upper position.
Due to the potential fall hazard, particularly high control system requirements are imposed on the safety interlock. For instance, the safety interlock is activated by a dual verification of the upper end position. Additionally, the safety interlock must meet certain technical parameters that exceed mere functional fulfillment. - Safety measures at the lower stop:
An enclosure is also necessary at the lower stop, including an electro-mechanically secured access door. Since the operator at the upper stop cannot see if someone is at the lower stop, these safety measures are essential. - Increased requirements for the hydraulic system:
To further enhance the safety of our simplified goods lifts, we impose stricter demands on the hydraulic systems than those required by the standard. Each goods lift is equipped with electric lock valves and lowering brake valves. These are installed directly at the cylinder connection, without any intermediate pipe segments or hoses. This design ensures a safe operating condition even in the event of leaks (refer to our article Safety devices on a lift table: Hydraulic valves). - Overload protection:
Another potential hazard is overloading. To prevent the goods lift from being overloaded, we install a pressure sensor. This sensor monitors the current operating pressure and compares it with the target pressure. If an overload occurs, the elevator's operation is automatically halted.
Conclusion
The comparison between a work lift table and a simplified goods lift highlights that not all lift tables are the same. For each installation scenario, it is crucial to ensure compliance with applicable standards. Depending on the specific hazards present, different safety measures must be implemented.
This also explains the differences in both equipment and cost between a standard lift table and a lift table specifically designed for transporting goods between multiple levels. The additional requirements for safety and functionality inevitably lead to higher costs but ensure that the lift table meets the specific demands of its intended application.
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