When you compare our products with those of our competitors, you will quickly notice that we generally rely on submerged units, while other lift table manufacturers prefer compact units. In this article, we will outline the advantages and disadvantages of both types of units, so you can make the best decision for your needs.
What are the differences between the two types of units?
The main difference lies in the positioning of the electric motor. In a submerged unit, the motor is directly integrated into the hydraulic tank, whereas in a compact unit, it is mounted externally. Apart from this, the operation and the other components of both designs are largely identical.
In both cases, the electric motor drives a gear pump that provides the flow rate for the hydraulic cylinders. Additionally, both variants feature a valve block that holds the lift table in position using a check valve and allows for controlled lowering of the lift table through a lowering valve.
External dimensions
Due to the integration of the electric motor into the hydraulic tank, submerged units have a more compact design compared to compact units. This design is particularly advantageous when space is limited. While compact units are often installed externally, submerged units can be installed directly within the scissor lift table, saving valuable space.
Noise emission
Both types of units exhibit similar sound pressure levels between 70 and 95 dB(A). However, the hydraulic oil in the tank effectively filters the high frequencies produced by the electric motor. This results in a more pleasant noise profile for submerged units, as the high-pitched "whine" of the electric motors is not audible. This is particularly advantageous when the scissor lift platform is used as a work lift table, where an employee is working in close proximity.
Duty cycle
Since the electric motor in submerged units is directly immersed in hydraulic oil, the motor’s heat is immediately transferred to the oil. This can lead to overheating during extended operating periods. If the critical temperature limit of around 80 °C is exceeded, there is a risk of damaging the gear pump. In such cases, it is advisable to increase the oil volume or install an additional cooler.
Compact units, on the other hand, use the surrounding air for cooling, allowing them to achieve a duty cycle of up to 100%. This makes them ideal for high performance lift tables that need to handle high cycle rates.
Which type of unit do we use?
Most of our lift tables are equipped with submerged units. Why? In applications such as goods lifts or dock lift tables, the maximum duty cycle of 15% is rarely reached. The submerged unit is only activated during the lifting process. During loading and unloading phases, as well as during lowering, the unit remains off. This provides enough time for the hydraulic oil to cool down.
However, in specific cases, such as with high performance lift tables, we rely on compact units. High performance lift tables are characterized by very high lifting frequency and long operating times. Sixty lifts per hour in a three-shift operation are not uncommon. Due to these requirements, a submerged unit would not be suitable here.
Finding the right type of unit for your application
How can you find the ideal type of unit for your lift table? It's simple: Provide us with as much detailed information as possible about the intended application of the lift table. Discuss with us the load requirements, the required lift cycles and the location of use. Based on this information, we will ensure that you receive the optimal lift table.
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