slew ring bearing condition monitoring to ensure safe crane operation

Large diameter slew ring bearings are critical components in many applications.  These slew ring bearings allow the crane to rotate 360 degrees, while sustaining the load of the crane and associated weights, including the payload and counterbalance. A failure of the slew ring bearing would result in an operational breakdown that could end in catastrophe. One of the methods of preventing these potential failures is condition monitoring. This article will introduce slew ring bearing condition monitoring to ensure safe crane operation.

Here are the main points of the article:

• Applications of slew ring bearing in the crane

• What is condition monitoring of the slew ring bearing

• Slew ring bearing condition monitoring to ensure safe crane operation

1. Applications of slew ring bearing in the crane

There are several vital design components of a crane, including slew ring bearings. These slew ring bearings allow the crane to rotate 360 degrees, while sustaining the load of the crane and associated weights, including the payload and counterbalance. A failure of the slew ring bearing would result in an operational breakdown that could end in catastrophe.Other potential outcomes of crane failures include increased replacement and maintenance costs for your business. Luckily, there are several ways in which you can assess and prevent potential failures from occurring. One of those methods is condition monitoring.In lifting equipment, the large diameter bearing serves as a joint between the upper structure and the undercarriage, providing a means of 360-degree rotation. Lifting devices typically have a complex load spectrum: the slew ring bearing can simultaneously handle all combinations of thrust, radial, and tilting moment loading. The use of a slew ring bearing provides yet another benefit: its shaftless design eliminates the need for a spindle or kingpost. The center of the bearing remains open to allow passage of various hydraulic and control components.

2. What is condition monitoring of the slew ring bearing

Condition monitoring is a testing method that allows a company to uncover how the specific bearings being tested are performing while the machine is in operation. As a result, potential equipment failures can be detected early on and remedied well in advance. For slew ring bearings, purged grease is analyzed.

Carefully thought out and documented sampling techniques are a must for condition monitoring to be successful. Inadequate condition monitoring procedures can provide companies with a false sense of security that can land said companies in a dangerous position down the line. Proper sampling of used grease will not only compliment your other monitoring strategies, but also shed light on the actual condition of your bearings.

Since the bearing is so critical, careful maintenance is necessary. More than 96% of slew ring bearing failures are due to surface-originated lubrication problems, contamination, overloading, and improper installation and mounting fits. These surface failures occur much earlier than classical fatigue failures and are less predictable.

3. Slew ring bearing condition monitoring to ensure safe crane operation

Slew ring bearing life is calculated assuming infinitely rigid and flat mounting structures. A structure that distorts significantly under load, and/or one that is out-of-flat, applies loads to localized areas rather than evenly distributing them. This causes permanent deformation in the local area, leading to early failure. The unique design of slew ring bearings allows for combination loads to be handled quite efficiently. However, whenever a load is applied that exceeds the bearing capacity, permanent deformation could occur, again leading to a premature failure.

Safety is the primary concern in detecting turntable bearing problems. Excessive bearing clearance due to accelerated wear results in less overall stiffness in the entire system. This lack of stiffness is magnified tremendously at the bucket, causing a potential problem for the operator. Another safety concern relates to uneven work distribution.This is especially common among excavators where most of the work is done in the same general area. Poor work distribution leads to an uneven wear pattern usually causing excessive play. The potential costs associated with a worn slew ring bearing can be significant if the problem is not detected in a timely manner. A severely worn bearing can damage other components, such as the drive pinion and gear box.

While maintenance is critical to lengthening the life of large slew ring bearings, the severity of use of heavy equipment means that eventually, any large slew ring bearing will become worn. Detection of bearing wear makes repair a less costly alternative to replacement. If you practice proper maintenance and watch for common warning signs, a worn bearing is likely to be deemed repairable.It is recommended that companies test six to eight sampling locations per bearing. The results should then be trended. Your company will be able to see an accurate visual representation of your specific bearing’s performance and pivot if necessary. If deterioration is present, it will be shown through the trend report.

Visual inspections should be utilized as well. Generally, if you can see a crack or other defect, you’re already in need of a repair, but it’s good to cover your bases regardless. You can never have too much monitoring, especially if it prevents catastrophes from happening.

Do you have a condition monitoring plan of slew ring bearing for your cranes or other heavy machinery? If you need a slew ring bearing ,please contact us .