Timken 3200 A 3300 A Double-Row Angular Contact Ball Bearings

Double-row 3200 A and 3300 A angular contact ball bearings

Timken 3200 A and 3300 A double-row angular contact ball bearings combine two rows of balls in a single bearing with one inner ring and one outer ring. They support radial load and axial load in both directions, and the double-row design resists tilting moments better than a single deep groove bearing of similar size. Timken double-row bearings of the 3200 and 3300 series have a contact angle of 30 degrees.

The compact unit replaces a pair of single-row bearings in a back-to-back arrangement, which simplifies housing design and mounting. Typical uses are pumps, gearboxes, compressors and general industrial machinery where a single bearing position must fix the shaft axially in both directions.

Technical specifications

Sample double-row sizes from the catalog table, with bore d, outside diameter D and width B in mm, and dynamic Cr and static C0r load ratings in kN:

Choosing between double-row and paired single-row bearings

A double-row bearing is the simplest way to locate a shaft in both axial directions in a limited width, and the load ratings in the table already account for the two rows. A pair of single-row 7200 B or 7300 B bearings has a larger contact angle, and so carries higher axial load in one direction, and the set can be adjusted to a chosen clearance or preload.

Compare the axial load share, the speed and the available housing width before choosing. The designation is read as series code, bore code and contact angle; 3206 A is a light-series bearing with a 30 mm bore. Bore codes follow the same rule as the single-row range: from 04 upward the code multiplied by five gives the bore in millimeters.

Closures follow the same options as the single-row range. Shields keep out coarse debris at higher speed, and 2RS contact seals retain grease better at lower speed, so confirm the closure against the speed, temperature and relubrication plan. Shaft and housing fits, axial location and the lubricant fill should be confirmed from the catalog or with Timken before ordering, because they affect the internal clearance and the service life of the bearing in the installed condition.

Key design features

• Two rows in one unit: the two ball rows are arranged so that their contact lines diverge, similar to a back-to-back pair, which gives a stiff support against tilting of the shaft.
• Combined loads: one bearing position can carry radial load together with axial load from either direction, so the bearing is often used as the locating bearing while the opposite end of the shaft is left free to float.
• Shorter shaft and housing: because the double-row bearing is narrower than two single-row bearings side by side, the shaft and housing can be designed more compactly.
• Ready-set internal clearance: the clearance is established at manufacture, so the user does not have to set preload or end play during assembly as with adjustable pairs.
• Sealed and shielded options: lubricated-for-life versions with ZZ shields or 2RS seals remove the need for relubrication in many general applications.

Light series 32 versus medium series 33

For the same bore, a 33 series bearing has a larger outside diameter and width than the 32 series and larger balls, which raises its load ratings. In the sample table, a 30 mm bore increases from 28.60 kN dynamic capacity in the 3206 A to 39.50 kN in the 3306 A, at the cost of a 72 mm instead of 62 mm outside diameter. If the housing allows it, the medium series gives more life at the same load; where space is tight or loads are moderate, the light series is usually sufficient. A bearing life calculation using the actual radial and axial loads and the catalog factors should always confirm the final size.

Mounting and maintenance practice

• Clean the shaft and housing and check fits and shoulders before mounting; incorrect fits change the internal clearance of a double-row bearing.
• Apply mounting force only to the ring being fitted, never through the balls. Use a fitting sleeve or controlled induction heating for interference fits on the shaft.
• Do not wash or relubricate sealed or shielded bearings with solvent; they are delivered pre-greased.
• For open bearings, use the lubricant and relubrication interval recommended for the speed and temperature, and avoid over-greasing, which raises running temperature.
• Monitor temperature, noise and vibration during operation; a rise in any of these is usually the first sign of lubrication or alignment problems.

Use in Oman and GCC conditions

High ambient temperatures, sand and dust are the main challenges for bearings in GCC plants. Fine dust that enters the bearing acts as an abrasive and shortens life, so sealed versions or well-designed housing seals are recommended for pumps, fans and conveyors operating outdoors or in cement, mining and quarry environments. Elevated temperatures also reduce grease life, so relubrication intervals for open bearings may need to be shortened compared with temperate climates. Storage in a dry, temperature-stable warehouse in original packaging protects bearings from corrosion caused by coastal humidity.

What to include in your RFQ

• Full bearing designation including series, bore code, contact angle and closure suffix (for example 3206 A-2RS style designations as listed in the catalog)
• Quantity and whether the bearing is a replacement or for new equipment
• Equipment type, shaft speed and operating temperature
• Any special requirements for clearance, lubricant or packaging
• Old bearing markings or photos if the original designation is unclear

Documents and quotation

The attached Timken catalog contains the full double-row table, nomenclature, tolerances and mounting guidance. See also Electric Motors, Pumps and Turbines. To request a quotation from Seven Star LLC, an independent supplier in Muscat, send the complete designation including any closure suffix and the quantity.