SKF DryLube Bearings

SKF DryLube bearings are designed to reduce machine operating costs, extend maintenance intervals and provide a high degree of operational reliability over a wide temperature range. SKF DryLube bearings are filled with a dry lubricant, based on graphite or molybdenum disulfide (MoS2) and a resin binder. The dry lubricant is injected into the free space of the bearing and cured until it solidifies (fig and fig). The dry lubricant can protect the rolling elements and raceways from damage caused by solid contaminants.

During operation, the dry lubricant maintains a very thin film on the raceways and rolling elements to avoid metal-to-metal contact. After a while, small fragments of solid lubricant may break free and temporarily increase noise and vibration levels. This does not reduce the performance or service life of the bearing.

SKF DryLube bearings provide the following benefits:

• effective lubrication for extreme temperature applications
• low start-up torque at any temperature and low frictional moment during operation
• higher speed capabilites than bearings for extreme temperatures with a graphite cage
• lubricated for the life of the bearing
• minimal lubricant loss
• suitable for extremly slow rotating speeds and oscillating movements
• improved worker safety and environmentally friendly compared to many oils and greases

Typical applications where SKF DryLube bearings are used include:

• metal industry (rolls in bloom and billet casters, cooling and roll out tables, guide rolls in bar mills, reheating furnaces rolls)
• industrial ovens (kiln truck wheel bearings and chain bearings for hardening and annealing ovens)
• food and beverage industry (ovens, smokehouse conveyor lines, wafer machines, sterilization equipment)
• paint lines for automotive and powder coating
• paper industry (paper converting lines, rope sheaves)
• vacuum and space applications
• oil and gas (applications with aggressive media)

Assortment Most SKF rolling bearings and bearing units can be supplied as SKF DryLube bearings provided the bearing is fitted with a sheet metal cage and is available with internal clearance greater than Normal.

The assortment of SKF DryLube bearings mentioned in this catalogue includes:

• deep groove ball bearings
• Y-bearings
• angular contact ball bearings
• cylindrical roller bearings
• tapered roller bearings
• spherical roller bearings
• thrust ball bearings
• spherical roller thrust bearings

For self-aligning ball bearings or customized units filled with dry lubricant, contact the SKF application engineering service.

For the assortment of deep groove ball bearings and Y-bearings with dry lubricant or high-temperature lubricants, not described here, refer to the section Bearings for extreme temperatures.

For detailed information about the assortment of SKF DryLube bearings please contact the SKF application engineering service.

Designs and variants SKF DryLube bearings are available in four main variants to deliver excellent performance, based on the operating conditions of the application which are shown in the table. The bearings are filled with a dry lubricant based on graphite or molybdenum disulfide. To further reduce friction, increase speed capabilities or extend bearing service life, nano particles and lowfriction additives are also available (table).

For some variants, the surfaces of the bearing rings, rolling elements and cages are manganese phosphated to enhance adhesion of the dry lubricant to the metal and provide additional protection against corrosion (fig).

Selection of bearing size The requisite bearing size for rotating bearings can be determined based on the basic dynamic load rating C.

The corresponding standard bearing should have a C value = the requisite value.

However, the basic static load rating C0 is used when the bearings are to:

• rotate at very slow speeds (n < 10 r/min)
• perform very slow oscillating movements
• be stationary under load for extended periods

The corresponding standard bearing should have a C0 value = the requisite value.

Calculating the requisite basic dynamic load rating Creq = Sreq P/fT

For calculating P, refer to the product chapter of the relevant standard bearing.

P = Fr when P < Fr

For deep groove ball bearings, Fa should not exceed 0,15 C0

Calculating the requisite basic static load rating C0 req = 2 P0/fT

For calculating P0, refer to the product chapter of the relevant standard bearing.

P0 = Fr when P0 < Fr

For deep groove ball bearings, Fa should not exceed 0,15 C0

Symbols

Creq = requisite basic dynamic load rating [kN]

C0req = requisite basic static load rating [kN]

Fa = axial load [kN]

Fr = radial load [kN]

fT = temperature factor (table)

P = equivalent dynamic bearing load [kN]

P0 = equivalent static bearing load [kN]

Sreq = guideline value for dynamic load safety factor (table)

Temperature limits The graphite-based lubricant in SKF DryLube bearings is effective at temperatures up to 500 �C (930 �F). At temperatures above 250 �C (480 �F), the resin binder begins to degrade, but the dry lubricant continues to lubricate. Therefore, for continuous operation at temperatures above 250 �C (480 �F), SKF recommends using bearings with a shield on both sides (designation suffix 2Z), or bearing arrangements with Nilos rings to keep the lubricant in the bearing. Bearings with dry lubricant only between the inner ring (or the shaft washer) and cage (Bearing data) may work at elevated temperatures without shields.

The recommended temperature limits are listed in the table.

Speed limits The limiting speed for the different variants of SKF DryLube bearings can be calculated using the formulas listed in the table.

The diagram provides estimated values.

If the bearing clearance is greater than C3, the limiting speed should be reduced according to the relevant diagram (diagram, diagram or diagram).

Design of bearing arrangements

SKF DryLube bearings for extreme temperatures can be mounted with a loose or an interference fit on the shaft and in the housing. However, either the inner or outer ring should be mounted with an interference fit, to locate the shaft and provide satisfactory support (table).

For additional information, refer to the section Bearing arrangements.

Mounting Mounting with mechanical force might crack the dry lubricant. Therefore, SKF DryLube bearings should always be hot mounted to reduce the mounting force.

For additional information, refer to the section Mounting, dismounting and bearing care, or the product chapter of the relevant standard bearing.

Maintenance SKF DryLube bearings do not have a relubrication facility as they are lubricated for the life of the bearing.

Designation system Refer to “Designation system” in the relevant product chapter of the standard bearing.

The designation suffixes used to identify SKF DryLube bearings are part of group 4.6 (fig) in the designation system. They are explained in the following.

The following additional suffixes used with SKF DryLube bearings are part of group 4.4 in the designation system. They are explained in the following.