Housing plain bearings

The Zollern housing plain bearings are designed according to different DIN and ISO specifications for a wide range of heavy duty applications (electrical machines, fans and blowers, turbines and test rigs). The modular system applies for the different types of bearings, i.e. the combination of different modules of this modular system is always possible. This has resulted in simple assembly and elimination of mistakes during installation, commissioning and maintenance procedures due to the positioning of screws and pins.

The ZOLLERN housing plain bearings are marketed under the name of Z-bearings. The different types of this Z-bearings are:

  • pedestal bearings
  • end flange bearings and
  • centre flange bearings

Beside this standard Z-bearings ZOLLERN offers the ZT-line for hight thrust loads up to 2.500 kN or special design bearings.

The bearing housings are finned and manufactured from grey cast iron EN-GJL-300 (GG30) or nodular cast iron EN-GJS-400-15 (GGG 40) giving high strength and best heat dissipation. The spherical seat in the housing ensures easy alignment during assembly and the loads are steady induced to the lower part of the housing. Therefore these bearings are designed for highest stress. Thread holes for the fitting of thermosensors in the journal bush and oilsump as well as for oil inlet and outlet pipes are provided on both sides of the housings as a standard. Water cooling tubes and vibration probes can be easily fitted by small amendments of the housings.

Bearing shells
The shell is supplied in halves and spherically seated in the housing ensuring easy alignment during assembly. The material is low carbon steel lined with high tin based white metal. This construction allows easy assembly and long life cycle. Bearing shells with plain cylindrical bore and loose oil ring are used in most cases, but other shapes of bore are possible. Optional water coolers are avilable and the bearing can be connected to an oil circulation. Where the spe cific load on start-up is too high, or for slow speed applications a hydrostatic jacking system can be incorporated. Zollern will give recommendations for the oil supply pressure and the required flow rate. Bearing shells without thrust capability, or with plain white metal lined shoulders (small, temporary thrust loads) with oil grooves, or taper land faces (medium thrust loads) for one or both sense of rotation can be selected depending on the level of the thrust load. The bearing shells are equipped with tilting thrust pads for highest thrust loads.

Oil supply
Fully self contained lubrication is achieved from a loose oil ring. Alternatively, where bearings are lubricated by an external oil circulation system, this loose oil ring can be used to permit emergency shutdown without damage if a system failure occurs. Z-bearings can be used for marine applications by using an oil ring guide to cater for vessel motions.

The seals are selected for the different operation conditions and for the requested protection level. The standard arrangement is the floating labyrinth seal (IP 44) made of high heat resistant, fibre-reinforced synthetic material. Bearings for high oil throughput are equipped with ad justable rigid seals (IP 44) made of aluminium alloy. Both types of seals can be equiped with bolt-on baffles (IP 55) or dust flingers (IP 54) if the bearing is operating in a dusty or a wet environment or if rotating parts (clutches, couplings, fans etc.) are fitted close to the bearing. Special seals offering higher protection, or pressurized seals etc. can be supplied for special applications. Details upon request. An end cover is used while the end of the shaft is inside the bearing.

Electrical insulation
To prevent stray currents conducted by the shaft Z-bearings can be supplied electrically insulated as an option. In this case the spherical seat of the housing is coated with a wear-resistant and temperature-resistant synthetic material.

Selection of oil
It is recommended that any branded mineral oil (preferably inhibited against foaming, ageing and oxidation) is used as the lubricant. The viscosity for every application is selected by the Zollern bearing design computer program. The output resulting is provided with every quotation.

Temperature control
Provisions for the fitting of thermosensors in the journal bush and oil sump are provided as standard. Which type of sensor is used depends on the type of reading (direct reading, centralized control system, recording instrument). It is
possible to fit two different and independant thermosensors.