By Colin Foreman
Over the summer, a number of major projects around the region ground to a halt as they waited for cement deliveries. One company trying to help cement plants boost their reliability and productivity is SKF.
Cement plant performance|~|51 tech body.jpg|~||~|Lost production and excessive maintenance costs were making management’s life difficult at two separate cement mills. The introduction of reliability systems overcame the problems and stopped the financial losses.Early and unexpected failure on eight critical fans was repeatedly bringing kiln production to a stop. On average a failure occurred every month so mill output was seriously affected and costs were running into thousands of dollars.
Looking for a permanent solution to this problem the company brought in SKF Reliability Systems.The company recommended that a complete Machine Reliability Assessment (MRA) be carried out on the fan system using the technologies and processes required to improve reliability. This meant that: the complete fan system including bearings and lubrication were assessed and key performance indicators be used to define or measure the results. The results taken included: fan mean time between failure (MTBF); kiln running time; maintenance costs; mill uptime; and profit.
A customised solution was then built around technologies, processes and cultural needs to improve fan MTBF. The technologies used were: new bearing and lubrication technologies; improved installation processes with precision techniques; and different monitoring and maintenance systems.
The first benefit experienced by the mill management was a complete absence of all fan failures with a corresponding increase in MTBF. After twelve months, mill uptime had increased and the management had US $450 000 more product to sell (which translated into US $80 000 more profit).Maintenance cost savings totalled $150 000, so the total impact on profits was $230 000.
Machine reliability and maintenance issues are frequently complex—and the solutions require special tools and expertise that are not always available on-site. SKF offers service packages designed to help keep this critical element in the production process running more efficiently. Backed by decades of experience with OEMs and machine applications in every industry, SKF Reliability Specialists are trained to use the most up to date practices and specifications whenever applicable.
The MRA process is well defined to produce results. A team of Reliability Specialists reviews the entire machine, examining both operational and engineering aspects of the system to develop a complete solution. Some of the activities include: Operating deflection shape analysis; lubrication analysis and recommendations; advance vibration analysis; precision maintenance; bearing maintenance; bearing mounting and installation and seal application review.
At the second cement mill, the management was very anxious to improve the operation and maintenance of their critical equipment. To measure performance they used two key performance indicators: Total delays on production equipment and maintenance costs per units produced.Because the mill was being run seven days a week and 24 hours a day, with customers ready to buy all the cement produced, both these indicators had a direct impact on the mill’s profit.
The client’s challenge was how to improve both indicators in an effective manner that would provide a significant return on investment. Lower total delays on production equipment equals $5000 per hour in increased product profits. Lower maintenance costs resulted in increased profits by dropping the savings right to the bottom line for increased mill profitability.
This company aksi decided to bring in SKF Reliability Systems, which recommended that the mill should introduce a Proactive Reliability Maintenance (PRM) programme using a number of technologies and processes to improve plant reliability. The solution process included: Assessing the operational reliability and maintenance processes of the entire mill; apply critical component mechanical and advanced condition monitoring expertise to pinpoint failure-causing points; and use the PRM process to maintain reliability improvements and eliminate unplanned downtime.
The customer realised real success by reducing the total delays on production equipment by 56 hours. The maintenance budget was reduced by $70 000. The impact to maintenance costs per units produced is still being evaluated, but should be positive. The total impact to the mill so far is $323 700 of increased profit and the figure is still rising. The return on investment for the first six months of this program is greater than 35%.
Most traditional forms of predictive maintenance will form a sustained maintenance loop, whereas the PRM programme forms a continuous improvement loop. Each of the following four steps builds on one another to prevent repetitive failures or problems. The first step is to design a predictive maintenance (PdM) system specifically for the plant, based on information using information gathered by a detailed assessment which provides an understanding of the parameters that affect plant and equipment effectiveness. The PdM system includes activities such as: vibration analysis and bearing monitoring; thermography; and lubrication analysis.
The PRM process may also highlight the need for additional activities during maintenance, such as geometric alignment, precision balancing, lubrication, filtration and sealing improvement. For the second step engineers diagnose the root cause of problems and determine corrective maintenance actions, such as machine realignment, changing the lubricant, or replacing a damaged component.
Detailed machine diagnostics can be conducted on site, or at a remote diagnostics facility. Physical analysis on the damaged components may also be required to determine the root cause of the failure. This information is used to prevent the same type of failure from recurring. For the third step, the key performance indicators are measured.
These figures act as performance improvement targets and may cover a wide range of factors, from bearing performance to plant availability. Where possible, once a KPI is achieved, a new target is set to facilitate continuous improvement. The operations of the mill are reviewed under the fourth step. A periodic review of the improvement programme is important to monitor KPI achievement. Results are documented and presented at performance review meetings. Operational review meetings are held to continually refine the PRM process to achieve the best balance of plant asset performance with the PRM process activity cost.
The implementation of a well-managed PRM process will ensure the best possible return on plant assets by managing potential risk. A consultant is able to guide a company in establishing its own PRM process or design, implement and manage the process. This can apply to the entire plant or any area of it. A full management program will include all the hardware, software, and the technical resources needed to ensure measurable improvements.||**||