Operating conditions and special requests

The following information relates to pivoting operations or slow rotations. Of course, rothe erde^® slewing bearings can also be used with rotational speeds which result in a higher circumferential speed. For these requirements, it is, however, necessary to separately check both the raceway and the gearing and, where necessary, draw up operating conditions accordingly. For such applications, we kindly ask you to state your operating conditions and requirements. Without exception, we will carry out a test for any usage with horizontal axes.

Operating temperature

The standard version slewing bearings are suited to operating temperatures of 253 K (-20°C) to 333 K (+60°C). A lubricant suited to the respective operating temperature is to be used (see also Installation, lubrication and maintenance).

For higher or lower operating temperatures and/or differences in temperature between outer and inner rings, kindly pass on the conditions to us for review. Here, requirements related to the mechanic properties of the ring material are to be considered. This is why, for low temperatures, for example, a minimum absorbed impact energy level is required.

Classification/special conditions

A range of applications, for example, offshore systems and deck cranes, need to be classified in accordance with the operating conditions. For this purpose, a catalogue of requirements is determined by the relevant classification societies and the approval of bearings is stipulated in accordance with this document. So that the specifications can be taken into consideration when we are suggesting a bearing, we must be provided with a detailed list of requirements.

Seals

The seals at the bearing gaps are meant to prevent the dust and small foreign bodies from entering directly and maintain fresh lubricant in the bearing gap. They have been tried and tested under normal operating conditions in this capacity for decades. Their function is enabled by evenly spread grease collars on the circumference, which ensures sufficient re-lubrication. Appropriate covers for the companion structure must be provided in cases of marked dirt accumulation.

Since the sealing materials are susceptible to wear caused by various environmental influences, the seals must undergo maintenance. Depending on the condition determined, the seal may need to be replaced. A check is required every six months.

For applications in particularly dusty environments, for example, handling machinery for coal and ore, special seals are necessary. In these cases, for example, additional steel mazes and seals can be provided which have proven effective in opencast mining. The steel maze protects the seal from mechanical damage and can be segmentally screwed off so that the greasy area can be cleaned.

The bearings in deck and floating cranes can be sprayed and splashed with water. Here, we insert a special seal, as shown in the image on the right above. If such seals are necessary, there may be an increase in height. For these operating conditions, bearings with interior gearing are preferred because the gearing is then protected by the enclosing structure.

Raceways

Plastic spacers can be found between the raceways’ rolling elements. By default, the bearings are greased for delivery. Please request special designs directly from thyssenkrupp rothe erde. Aggressive media penetrating the raceway is to be avoided at all costs. Aggressive media modify the lubrication properties, lead to the corrosion of the raceways and damage the plastic spacers.

Special designs

In addition to the range of bearings shown, we manufacture bearings which are tailored to specific operational conditions in terms of their dimensions, running accuracy, bearing clearances and materials. We also manufacture wire race bearings. For this bearing system, it is possible to use rings made of non-ferrous metals and, thus, fulfil wishes with regard to minimum weight or corrosion resistance, among others.

Packaging

Normally, the slewing bearings are wrapped in film or similar materials. The outer surfaces of the bearings are protected against corrosion by Tectyl 502 C (oily) and the raceway area filled with lithium grease. Depending on the transport route, different packaging is provided (for example, pallets or boxes).

The normal packaging guarantees sufficient protection for a storage period of up to around one year in a closed, temperate space. Upon request and after consultation, other preserving agents and different packaging can be used for long storage periods (for example, long-life packaging for five years).