Making the best of an "in-situation"

FLSmidth is well-known for our service and maintenance programs, and for our own OEM equipment. But many people don’t know that for many products, we can support and service other manufacturers’ equipment as well.

 Rotary dryer illustration showing area of supports and rollers

Rotary dryer illustration showing area of supports and rollers

Once everything has been installed and is up and running, it's important to monitor and maintain the equipment to ensure that it's working in optimal condition. For a rotary dryer, even normal wear and tear can cause alignment issues throwing off calibration and creating problems that lead to unexpected shutdowns and repairs. 

A recent example takes us to one of the mineral plants located in the western part of India. This plant, run by GHCL Limited, houses several rotary dryers originating from another manufacturer. One of the dryers faced serious production hindrances which caused unscheduled stoppages.

In this particular case, problems were evident due to the following conditions:

  •     High vibrations at the supports 
  •     High load on the thrust rollers
  •     Excessive load on the bearings, which reduced their life 
  •     Abnormal contours developed due to uneven wear of tyres and rollers' working faces

With the operation of the rotary dryer worsening, GHCL contacted their local service unit to ask how to resolve the performance issues. An expert from FLSmidth’s plant service maintenance team was sent to carefully inspect the situation and provide recommendations.
After careful evaluation, FLSmidth was awarded the contract to do as it recommended and carry out a procedure known as in-situ grinding of the tyres and supporting rollers of the dryer. This would then be followed by a cold alignment activity of the rotary calciner. 

 Demonstration of tyre grinding machine

Demonstration of tyre grinding machine

In-situ grinding

Various wear patterns develop over time on the tyres and rollers of the rotary dryer, causing vibration at the supports that, when not addressed, can quickly lead to failure of the rotating components. Utilizing specialized equipment, in-situ grinding may be carried out during operation without any production loss. This activity grinds the surfaces of the tyres and rollers and returns them to a cylindrical shape for smoother operation. 

FLSmidth has developed separate grinding machines for correcting the surfaces of the tyres and the rollers. The tyre machine operates on the centerless grinding principle in which a cup grinding stone is firmly indexed on a fixed arc guided by the tyre surface itself. A flat surface and a true cylinder can be cut back on the tyre even though the tyre rotates without a true center.

The separate support roller mechanism simultaneously grinds the support rollers. Doing this at the same time prevents damage to each of the components and allows for a more uniform mating of the roller to the surface of the tyre. The cylindricality of the tyre and the rollers is ensured by using an electronic diameter-counting instrument.

 Cold alignment of dryer

Cold alignment of dryer

Cold alignment

After the completion of the grinding activity, a cold alignment of the dryer is implemented to distribute the load evenly over the support rollers. By using an automatic level and electronic total station, the skew and slope of the support rollers are corrected to retain the proper surface contact and alignment with the tyres. Finally, skew correction was carried out to reduce axial load on the support roller bearings, thus optimizing the dryer float.

These specialized maintenance activities, when performed correctly and periodically will return the dryer to reliable operation and help prevent such failures and problems from happening in the future. 

Benefits bring satisfaction

Upon completion of the in-situ maintenance and alignment procedures, GHCL management was satisfied with FLSmidth's ability to correct the problems within the deadline.

"We are very happy with their services," said R. D. Badgujar, Deputy General Manager, GHCL. "After completion of the maintenance activities, we have observed reduced vibration levels of the equipment and improved performance of the calciner.” 

In December 2015, FLSmidth’s India team received a letter of appreciation from GHCL that listed the benefits gained by the maintenance that was carried out. 

  1. Vibration completely reduced at the supports
  2. Bearings life considerably increased
  3. Reduced load on the thrust rollers
  4. Reduction in breakdown and maintenance costs, thus achieving the maximum availability of the equipment
  5. Now able to meet the plant’s production targets

A similar in-situ grinding and cold alignment maintenance activity was carried out recently for a plant owned by Mangalore Chemicals & Fertilizers Limited (MCF) in the southwestern part of India. Their experience with our FLSmidth team was also reflected in a letter:
“The entire job was completed in the stipulated time and in a safe manner," said Mr. Neeraj Shetty, Deputy Manager – Machinery Department, MCF. "We appreciate the fact that FLSmidth responded promptly and immediately took-up our job… The dryer and granulator are running smoothly, and the axial float is in ideal condition.” 

 Images shown are actual customer appreciation letters

Images shown are actual customer appreciation letters

The FLSmidth maintenance team is always ready to answer any specific queries related to the rotary dryer. Their experience can help improve the balance life of all rotary equipment, and the team continues to help plants run at optimal performance. 

CONTACT: Patthi Kalyan