Split Bearing

BEARING TYPES

ZWA bearings are commonly supplied in two forms: the Fixed Type (`GR7`) and Expansion Type (`EX`) as described below. Where conditions are unsuitable for these standard types other configurations are possible, some of which are described on pages 472 to 474.

Fixed Type Bearings (GR)

The outer race of the fixed (GR) bearing has shoulders integral with the roller track, while the inner race assembly has shoulders formed by hardened lips on the clamping rings or similar integral shoulders.

This type of bearing provides axial location to the rotating portions of machinery and can sustain both radial and axial loading.

The inner race halves are accurately aligned by means of fitted clamping rings.

Expansion Type Bearings (EX)

The expansion (EX) bearing has a plain outer race roller track. This bearing takes radial load only.

The inner race is clamped to the shaft, and moves axially with it when expansion or contraction occurs.

The ZWA expansion bearing offers virtually no resistance to axial movement as the rollers spiral through the outer race.

 Here are some of the alternative configurations we are able to supply where the EX and GR types, shown on the previous page, are unsuitable. If you wish to specify one of these alternative types, contact our technical department. Please supply details of your application, so we can ensure the most suitable solution is provided.

Comparison of Series

For most shaft sizes ZWA offers a range of three standard series:

01 Series for medium duties

02 Series for heavy duties

03 Series far extra heavy duties

In the range 45mm to 105mm the 01 Series is superseded by the 01E Series of increased capacity，but with matching envelope dimensions.

For certain bore sizes in the range 75mm to l50mm ZWA also offer the 100 Series This has slightly lower capacity than 01 Series but is more compact and capable of higher speed operation.

The 04 Series is a specialised range of high speed bearings available in a restricted range of bore sizes from 6 inches to l550mm.

Bearing references contain the series identification as the prefix numbers in the designation, e.g.:

01 8 120M EX

02 B l20M EX

are bearings of 01 & 02 Series respectively.

This catalogue is laid out with 100, 01/01E, 02 and 03 Series listed together by bore size. This allows you to compare the capacity and speed capabilities, in order to select the most appropriate series.

Generally, if conditions allow and a satisfactory life is theoretically achieved by 01/01 E bearings, this series of bearings is the most economical series to select The 02 and 03 Series are also more expensive in terms of first cost. If high speeds and/or restricted envelope dimensions preclude the use of 01/01E Series, the 100 Series should be selected if other conditions allow.

In the case of an existing bearing being replaced, there may have been other factors than just load capacity involved in the selection of the original bearing. It is often unnecessary to match load capacities of existing bearings to achieve satisfactory bearing life. Wherever possible, the loads on existing bearings should be assessed. This will ensure the most appropriate and economical selection of ZWA bearings to replace them ZWA can assist with this selection.

Bearings

The following pages list standard bearings of series 100, 01, 02 and 03, alongside compatible standard cartridges and pedestals. Principles of bearing selection are explained on pages 478 to 484.

Large bore bearings and 04 Series bearings are listed separately elsewhere in this catalogue.

Cartridges and Seals

Most ZWA split roller bearings are mounted in a ‘cartridge’．This is a spherically- machined inner housing that can be fitted into a number of outer housings including pedestals, flanges, rod-ends, take-up units and custom housings either supplied by ZIWA or manufactured by the customer.

The cartridge houses the bearing and seals. For any given size of bearing there are two main types of cartridge. Except for in North America the standard cartridge, up to 300mm/12" shaft size, features a groove in each end bore that can accommodate felt seals (supplied as standard with the cartridge), high temperature packing, or a rubber lip seal. Above 300mm/12" shaft size the standard cartridge features grease groove seals.

The standard cartridge in North America, but available worldwide, is the `triple labyrinth`(TL) type, which accommodates either an aluminium triple labyrinth (ATL )seal or, on some sizes only, a neoprene triple labyrinth (NTL). ATL and NTL seals are not supplied with the cartridge and must be ordered separately.

Cartridges to accommodate other types of seal, such as lip seals for submerged conditions, and combinations of seals, may require special machining. They may also have a different length on shaft to the standard types listed.

Cartridges for expansion (EX) and fixed (GR) bearings differ, so care must be taken to order the correct version and ensure that EX and GR bearings are fitted in the correct cartridges during assembly.

Cartridges for GR bearings feature drillings for `side screws` that locate the outer race against one side of the seating, while cartridges for EX bearings may include additional internal machining.

Pedestals

Pedestals (also known as Pillow Blocks) are the most common method of mounting ZWA split roller bearings (in cartridges as explained above).

ZWA standard pedestals are shown on the following pages. Pedestals with height-to-centre and bolt hole configurations to match industry standard SN, SD and SAF pillow blocks are listed separately in this catalogue.

Pedestals are common between expansion (EX) and fixed (GR) units.

Loads and Mounting

The maximum safe radial load for a pedestal is based on the static rating (Cor) of the corresponding size of roller bearing. The full static rating can be applied if the angle of the load falls within the shaded area of the sketch.

If the radial load falls outside the shaded area, if the radial load exceeds Cor, or if the axial loads exceed 50% of the axial rating (Ca) of the corresponding roller bearing please consult our technical department. For 100 Series bearings, the maximum axial load is reduced to 35% Ca.

Pedestals should be fully supported on a flat, rigid surface to avoid distortion of the pedestal or deflection under load.

For loads within 45°of the horizontal, the base should be chocked or dowelled.

Standard ZWA pedestals are manufactured from grey iron. Ductile iron and steel pedestals are also available and should be considered for shock or pulsating loads. Particulars of pedestals in alternative materials are available from our technical department.