Over time riding rings become marred from debris and wore from misalignments.
Because of this resurfacing is a way to recondition the tire. Resurfacing is done with a machine that mounts on the roller housing. The machine has a grinding wheel or abrasive belt, which can be indexed across the tire. The process can take different length depending on the magnitude of resurfacing. Resurfacing can be done while kiln is in operation. The kiln should always be re-aligned after resurfacing.
Maintaining the ring and roller in a smooth condition reduces energy costs and makes it easier to keep the kiln in alignment.
Resurfacing can be done with either cup-stone grinders for small units or belt grinders for larger kilns.
Metso conducts the removal of wear patterns on tire and support rollers both on site and during production. Our custom-built equipment can be sent to the site for fast and economical repairs all over the world.
The resurfacing process
Resurfacing processing using a belt grinding machine
- Machine can be used to grind riding ring and support roller
- Setups are simple and quick
- Material removal rates are high
- Accuracy of setups is excellant
- Shorter grinding period to complete the process
- High speed units can be machine in production
Resurfacing process using cup-stone grinders
- Different machines for both riding rings and support rollers
- Resurfacing on riding rings and support rollers is simultaneous
- Produces excellant surface finishes
- Able to machine radial runout in the riding ring
- Material removal is light so axial thrust of the kiln is stable
Resurfacing concerns from an o.e.m perspective
The resurfacing methods mentioned are the basic systems Metso uses to deal with the various wear patterns that develop on the surfaces of riding rings and support rollers. There are, however, a couple of conditions that exist on rotary equipment that make the resurfacing process difficult. First is the condition of shell runout caused by a "dog-leg" condition or a bend in the shell. The axis of rotation of the shell will not be concentric as a result of the radial runout of the shell in the area of shell damage. The shell damage will create what is referred to as a "wobble" in the riding ring where the surface of the riding will change at the position of contact between the grinding machine and the riding ring. This will make the resurfacing process very difficult and the machinist has to pay close attention to the runout to keep from machining low spots in the riding ring.
What complicates the process even more is creep of the riding ring in relation to the shell, or in other terms, the relative movement of the riding ring.The danger in resurfacing the riding ring is that too much material will be removed from one segment and weaken the beam strength of the riding ring. For example, if the creep of the riding ring is at a rate where it makes one revolution independent of the shell in a twenty four hour period, a machinist working on 8 hour shifts, will be cutting in the same segment of the riding ring every day. If there is any runout in the shell, and there always is some, the high area of runout will cut harder than the low area of runout. This situation will cause an uneven thickness in the riding ring, weakening the beam strength of the riding ring and cause potential failure under high loads. This is especially true on multiple pier kilns where kiln loads are transferred to middle piers by runout from shell distortion.
Another consideration is the material removal on the riding rings and support rollers. The riding ring cross sectional thickness is based on kiln load ratios in the original design. If the kiln loading increases at individual support piers because of shell damage, removing material from the outside diameter of the riding ring may be unwise. With this in mind, Metso’s OEM approach to resurfacing riding rings and support rollers is:
- Perform an inspection of the kiln to determine operating condition
- Evaluate the beam strength of riding rings prior to machining
- Measure the runout of the riding rings at each pier
- Machine only surface wear patterns
- Use machines designed for kiln grinding only
- Make sure riding ring thickness is uniform
More information on rotary kiln technologies - bearing / drive components
See new riding ring options or learn more about riding ring wear patterns