Ball bearing swivels in general are roller thrust bearings for supporting axial loads. Some models (typically larger swivels) also incorporate roller alignment bearings for better side load capacity. Ball bearing swivels are used in different industries/applications such as:
- Underground pulling operation such as directional pulling, pull back of cable, wire rope or conduits
- Utility industry use for overhead pulling application of tension stringing of wire and cable
- Crane/Hoist operation use of eye to eye swivels for load handling and control of a lift
In all applications, a ball bearing swivel’s main function is to provide a rotating link that releases the rotational torque on the pull (cable, wire rope, conduit, etc.) by keeping the pull in the neutral position so to eliminate the twisting of the pull.
There are different types of ball bearing swivel made:
Sealed – Typically used in overhead pulling application where chance of exposure to contaminant such as mud or dirt is minimal. These swivels are greased and permanently sealed at the factory. They never need to be internally greased again.
Sealed Greasable – Used in underground pulling application where exposure to contaminant such as bentonite, mud and dirt is maximum. These grips typically are equipped with a grease zerk that can be used to purge the old grease (which gets rid of the contaminants) and fill the swivel with new grease. Make sure the grease zerk has a recessed design so it is protected during the pull.
Non-Sealed – The non-sealed (a.k.a. unsealed or regular) swivels were originally designed for basic in conduit cable pulls as chances of swivel’s exposure to contaminant were lower. These lower cost swivels provided an affordable alternative to sealed ball bearing swivels. The non-sealed swivels should not be used in pull back operations as they have no seal to prevent ball bearing damage resulting from the contaminants.
Ball bearing swivels are remarkably robust and should give great service and performance, if you take care of them. They typically should be made from high-grade, pre-stressed steel for best performance and long life. However, little things like a bit of mud or bentonite mud, grit or exposure to salt water and other corrosive chemicals could affect their performance and shorten their life. Overloading them and using them in improper manner could create very small cracks or damage them to the point of creating a hazardous condition that could lead to serious injury or even loss of life.
Another consideration when buying your swivel is their connection point. Typically, you have option of ordering your swivel with pins that are screwdriver or Allen wrench removable. For pullback operation and attachment to back reamer bits, it is recommended to pick bentonite-resistant pins and hardware.
Swivels in the overall cost of operation are relatively inexpensive but accidents are not. The following are some general guidelines in maintenance and operation of ball bearing swivels to help with safety of your operation and health of your gear.
- Always inspect the swivels carefully before and after each use. This applies to all swivel types including sealed, sealed greasable, and non-sealed swivels.
- Check for any cracks around the throat on both ends of the swivel, and on the body of the swivel. If any cracks are apparent discard the swivel immediately.
- Check the pins of the swivel. They should not be bent, deformed, worn, cracked and their threads should not be stripped, worn or misshaped. If there are any abnormalities on the pins the swivel should be removed from service and discarded.
- A healthy swivel should rotate smoothly and freely. Make sure the swivel rotates freely without any binding.
- The swivel’s stem should not be loose, with no up and down or lateral movements. Swivel sections should be snugly fitted together with no sloppiness in the operation. Any such sloppiness would indicate a damaged swivel which should be discarded.
- Before making a pull, make sure swivel pins are tightened all the way and mate up properly. If pins have stripped threads, replace immediately. Usually pins are available with standard slot grooves or with Allen wrench fittings so make sure to use the proper tool to tighten them.
Do not exceed the workload (WL) of the swivel. Usually a swivel’s workload is stenciled on the ball bearing swivels, read and follow the work load. If the work load is in question, please consult the manufacturer of the swivel. If for any reason the stenciled work load is not legible, the swivel should be removed from service.
- If you anticipate your pull to be within 10 percent of the work load at any time during the pull, a larger swivel should be considered, especially if any shock loading might occur during the pull.
- Do not pull any swivel around a bull wheel that has a diameter that is smaller than the overall length of the swivel. Doing so exposes the swivel to a side load and can permanently damage the swivel.
- If you know a ball bearing swivel has been exposed to an unqualified side load, the swivel should be removed from service and replaced.
- Clean the swivels before and after each use. Make sure there is no debris in the swivel gap (the area where rotation occurs between the swivel body and the eye). Even a sealed swivels needs cleaning.
- Lubricate all greasable swivels (sealed greasable and non-sealed). Purge the old grease completely. Make sure the swivel gap is free of debris. The only substance that should be in the swivel gap is the fresh grease that has been used to purge the swivel of contaminants. Use a high-grade. water-resistant/waterproof grease.
- Do not expose the swivel to long durations of harsh and corrosive environments. After each use, remove the swivel, clean and store it in a dry and protected location so that the swivel is not exposed to harsh environments such as offshore drilling platforms or other salty, corrosive environments.