Slewing ring bearing use conditions and typical application

Typical Application

“Typical application” of Xuzhou Wanda Slewing Bearing Ring will exhibit the conditions listed below. Special consideration must be given to bearing selection and features whenever the application conditions differ from those considered “typical”. Those typical application conditions are:

· Vertical axis of rotation. Essentially, the bearing mounted “flat”.

· Compressive thrust and moment loads being predominant compared to tension loading.

· Radial load limited to less than 10% of the thrust load.

· For single row bearings, intermittent rotation (not continuous) should not exceed a pitch-line velocity of 500 feet/minute.

· Operating temperature between -40ºF to +140ºF.

· Mounting surface geometry and installation procedures to assure roundness and flatness of both races. An example approach would be to apply a centered thrust load while tightening the bolts using the alternating star pattern method.

· Periodic checking of mounting bolts to verify proper tension is provided for.

· Periodic lubrication is provided for.

Load Capability

XZWD Slewing Ring Bearings are designed to accommodate significant radial, thrust and moment loads as shown below:

This is accomplished in most cases by the unique four point contact raceway geometry, which is similar in concept to XZWD X-Type Thin Section bearings. This allows a single bearing to accommodate all three loading scenarios noted above, either individually or a combination thereof.

For more detailed information on Xuzhou Wanda Slewing Bearing Ring load capabilities consult the load curves charts.

Speed

XZWD Slewing Ring Bearings are used most commonly where rotation is slow, oscillating, and/or intermittent. For speed limit calculations please contact XZWD Engineering. 

Accuracy

XZWD Slewing Ring Bearings are not typically provided with diameter tolerances. Some slewing ring applications require a higher degree of accuracy. For engineering and design support on special applications please contact XZWD Engineering.

Environment

XZWD Slewing Ring Bearings are often used indoors, and outdoors where exposure to moisture and significant contamination is possible. Normal temperature ranges -40°F to +140°F (-40°C to +60°C) are standard. Slewing rings designed to operate in harsher environments are available from XZWD, contact a XZWD Engineer early in your design process to identify the best bearing system solution for extreme environments. Such as if you want to use it in this slewing bearing for crane, you could contact us. 

Mounting – Tension versus Compression

As mentioned earlier, it is best to mount the bearings in “compression” as shown below. This ensures that the load is carried by the balls, which is represented in the load curve provided. Tension mounting has significantly less capacity, as then the bolt strength becomes the primary consideration for capacity.

Mounting

Mounting surfaces need to be machined accurately for proper function of the bearing. Where standard bolt patterns cannot be accommodated, contact XZWD Engineering for alternative options. Consideration must be given to mounting in tension or compression. In tension, BOLT strength becomes the limiting load consideration, the load curve no longer applies, and special considerations must be made. See additional guidelines below.

Minimum Mounting Structure Guidelines

Generally, this rule of thumb will provide adequate structural integrity.

Lubrication

Grease is the most common lubricant used in slewing ring bearings and gear applications. Regular lubrication through provided grease fittings or grease holes is required for proper operation on standard slewing rings. For special lubrication options, contact Xuzhou Wanda slewing bearing.

Friction Moment(Rotation Torque)

The Friction Moment can be estimated for a slewing ring bearing using the formula noted below. The resulting values assume that the bearing is mounted according to the guidelines outlined in this catalog. This estimate only applies when load is applied to the bearing, and does not reflect starting torque in an unloaded condition. Also not considered are frictional torque generated by the lubricant, seals and weight of the components. This does however provide a starting point, and with additional experience adjustments can be made in the assembly to accommodate for additional torque.

Securing Bearing to the Mounting Surface

When installing the bearing , it is important to ensure that the bearing is as round as possible. This will optimize load distribution and promote the smoothest operation. The following procedures are recommended as an aid.

Use hardened round flat steel washers in accordance with ASTM F436 under the head of the bolt, and also the nut. Lockwashers, and locking compounds on the thread, are not recommended.

Install the washers, nuts and bolts in the bearing and supporting structure and hand tighten. Do not distort the bearing in order to install bolts. Apply a moderate centered thrust load to the bearing. Tighten the bolts to the equipment designer’s specifications. A common approach is to use a star pattern to tighten the bolts, sequences as shown in the diagram below. The pattern is usually done in 3 steps at approximately 30%, 80% and 100% of the final bolt torque or tension level specified by the equipment designer.

Loss of proper tension can lead to premature bolt failure, failure of the bearing and structure, damage to components, and fatality or injury to anyone in the vicinity. The bolts require frequent inspection for proper tension, which is commonly accomplished by measuring torque of the bolt.