Lift tables are used in a wide variety of applications – whether in extremely cold environments, such as cold storage, or in very hot environments, like steel plants. However, these extreme temperature ranges present specific challenges for the technology. In this article, we will take a closer look at what needs to be considered when using lift tables under extreme temperature conditions.
When it gets cold: Challenges in low temperatures
The following considerations apply not only to the use of lift tables in cold storage but also to lift tables used outdoors. Especially in winter, when temperatures drop significantly, lift tables must operate reliably. To ensure this, several important factors need to be taken into account.
Hydraulic oil: Optimal choice for different temperature ranges
When installing lift tables indoors, most lift table manufacturers typically use the hydraulic oil HLP32. This oil is designed for a temperature range of -10 °C to 40 °C.
For outdoor lift table applications, where temperatures often drop lower, we rely on thinner hydraulic oil. In these cases, we usually use ISO VG 22 oils, which are suitable for temperatures as low as -20 °C.
Even when temperatures drop below this range, the operation of a hydraulic lift table is still possible. One solution is the installation of a tank heater that maintains the hydraulic oil at a sufficient operating temperature. Generally, simple heating systems with a two-point control are installed, making both installation and operation relatively straightforward.
Other important factors in low temperatures
While hydraulic oil is a crucial factor for the operation of a lift table in low temperatures, there are other aspects that must be considered during the design process.
Choosing the right steel grade
Not only do hydraulic oils have temperature-dependent behavior, but steel also exhibits different properties depending on the operating temperature. At low temperatures, impact toughness plays a critical role. Impact toughness is a measure of resistance to sudden impacts. As temperatures drop, the impact toughness decreases. Therefore, the steel grade must be carefully selected and adapted to the specific operating conditions to ensure safe and long-lasting use of the lift table.
Lubrication
Another important factor is the lubrication of the lift table. In extremely low temperatures, the grease used may become thick or even solidify, leading to insufficient lubrication and potential damage to the bearings. To prevent this, it is important to choose a grease with the right viscosity that retains its lubricating properties even in cold conditions. This ensures that the lift table's mechanics continue to operate smoothly.
When it gets hot: Challenges in high temperatures
It's not just low temperatures that pose challenges for the design of a scissor lift table – high temperatures also bring important aspects that must be considered.
Hydraulic oil and power unit
As previously mentioned, hydraulic oils have not only a minimum but also a maximum operating temperature. In high temperatures, the hydraulic oil can overheat, leading to issues with the hydraulic pump. The maximum recommended oil temperature is typically around 80 °C. If this value is exceeded, the system's performance can be severely compromised. To ensure operational safety, it is essential to provide adequate cooling for the hydraulic oil.
In addition to hydraulic oil, the selection of the hydraulic power unit also plays a crucial role. In our article Compact power unit or submerged power unit? we have already highlighted the benefits of submerged power units. However, they have a significant disadvantage in high-temperature environments: The electric motor transfers its heat directly to the hydraulic oil, further heating the pressure medium.
For this reason, we use compact power units in extremely high ambient temperatures, as they minimize this heat transfer and are therefore better suited for operation in hot environments.
Other important aspects in high temperatures
The bearings
Standard plastic sliding bearings are suitable only up to a maximum operating temperature of 100 °C. For applications in higher temperature ranges, high-temperature bearings capable of withstanding up to 160 °C are recommended.
Lubrication
High temperatures also impose special requirements on the lubrication of the bearings. Similar to low temperatures, it is essential to choose the appropriate viscosity grade for the grease. At very high temperatures, grease-free bearings can be a viable alternative.
Surface coating
For conventional paints, temperatures above 180 °C are considered critical. However, they can begin to lose their structural integrity at lower temperatures, failing to provide adequate protection under load. Since lift tables are designed for lifting heavy loads, a durable surface coating is essential.
An alternative to traditional painting is hot-dip galvanizing, which can withstand temperatures up to 315 °C. Another option is to forgo surface coating entirely by using stainless steel as the material.
The steel
At very high temperatures, steel loses a significant amount of its strength, which can compromise the stability of the entire steel structure. Therefore, it is important to choose a type of steel that retains sufficient strength even under very high temperatures.
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