Balancing system pays for itself in six months

Since installation of the Lord Corporation's balancing system, Castle Cement estimates a savings of more than 200 hours per year increased production through the reduction of downtime.

When your company is responsible for supplying 25% of the cement used in the UK, a smoothly running production process is critical to success.

That is why having to go offline for about 200 hours each year for unscheduled kiln shutdowns is disastrous in terms of lost production, not to mention the cost of labor and materials.

Such was the case for the Ketton Works plant of Castle Cement in Lincolnshire.

Open since 1929, the plant now has an annual production capacity of 1.3 million tonnes of clinker per year or 4200 tonnes per day.

Despite the high demand, the kiln preheater ID fan suffered from a continual build-up problem resulting from dust and particulate exiting the preheater with the hot gases that are then drawn through the fan.

This particulate would stick to the fan rotor, causing it to become unbalanced - especially when large chunks of the build-up break off.

In 2005, the build-up became so prevalent that the fan reached excessive vibration levels on multiple occasions, resulting in unscheduled shutdowns about once a month to grit-blast and clean the scale build-up.

The downtime totalled more than 200 hours that year alone.

By the time the team at Castle Cement would reheat the kiln and restart operations after the cleaning process, countless hours of production were lost, in addition to the expense of labour and materials.

Also, the refractory lining that protects the steel structure of the kiln was subject to failure due to the repeated heating and cooling from these unplanned fan shutdowns.

"Shutting down is a serious process that typically takes several hours to allow the kiln to cool off, and another couple of hours to conduct the cleaning process", said Mike Hart, Mechanical Engineer for Castle Cement.

"But, our only other option was running the fan at reduced speed, which also greatly decreased our production capacity".

"Regardless of the solution, the staff was often taken away from regular duties to troubleshoot vibration problems".

Although Castle Cement began looking for a balancing solution in 2000, there simply weren't many products on the market.

By the time Operations Manager Mark Cox joined Castle Cement in 2003, the problem was seriously impacting production.

Fortunately, Cox remembered reading an article about a technology offered by Lord Corporation - a leader in the management of vibration, motion and noise - that might help solve the problem.

Castle Cement contacted Lord Corporation and Andy Winzenz, Lord Sales Manager, with its UK distributor, TEVA, visited the cement plant in early 2005 to help confirm the diagnosis.

According to Winzenz, the main problem was in fact the product build-up in the kiln ID fan, which sends the fan out of balance.

"The cement manufacturing process is dependent on the performance of the ID fans and the ability to maintain process air flow", said Winzenz.

"As such, when the fan was thrown out of balance because of build-up, the result was untimely and expensive shutdowns".

"Our goal was to implement a solution to keep the fan running smoothly and reduce kiln downtime".

After analysing the problem and the fan specifications, the recommendation was to install Lord Corporation's balancing system - a permanently mounted device that continuously monitors fan vibration levels and corrects for unbalance while the fan is running.

Although Lord Corporation has a variety of vibration control products, the balancing system was recommended because of its ability to make rapid balance corrections and withstand the harsh environment surrounding the ID fan.

The system is set up to monitor fan bearing vibration levels and the vibration phase angle in order to automatically correct for unbalanced conditions.

This is done while the fan is running at operating speed, eliminating costly downtime to clean and manually balance the fan.

Once levels reach a preset high trip point, the system switches on, commanding balance mass inside the shaft mounted system to adjust as needed to counteract the unbalance and reduce the vibration.

The balancing ring of the system mounts directly to the fan shaft and houses counterweight masses that can be repositioned to offset the unbalance detected in the fan rotor.

Using vibration sensors, the system monitors the fan bearing vibration.

Vibration signals are received and processed by an "Adaptive Influence Coefficient" control system, which then determines the balance adjustments that are required.

The controller relocates the counterweight masses to the desired position to minimise the vibration levels.

This process continues until the controller senses that balance has been restored.

Typical balance cycle times range from 30 to 120 seconds, depending on operating speed.

Lord Corporation developed and patented the actuator coil assembly used in their balancing system.

The actuator coil is traditionally mounted to support brackets located on the bearing pedestal.

The noncontact power supply used in the actuator coil eliminates the need for maintenance, sending power across an air gap between the stationary actuator coil and the rotating balancer ring.

According to Hart, Castle Cement opted to install the balancing system during a regularly scheduled shut-down in February 2006.

The two-plane balancing system was installed on Castle Cement's 8 Kiln ID Fan (Solyvent Fan), which is part of a 3000 tonne per day process.

The installation, performed in concert with Lord Corporation's UK distributor TEVA, involved moving the motor out of the way, pulling the coupling and bearings off the fan shaft, installing of the balance ring, reassembly of the bearings and coupling, and then reinstalling and aligning the motor.

Other work, such as running conduit and cables between the balancer and the controller and mounting the controller in a dustproof, waterproof box near the fan, was completed in advance of the shutdown.

According to John Hall, Business Development Manager for TEVA, although Castle Cement was confident that the balancing system would counteract the vibration problem, nobody was sure how long it would be before sandblasting was necessary.

As such, Cox and his staff watched the build-up rate carefully.

Fortunately, the balancing system proved so effective in correcting the unbalance that the maintenance team experienced no unscheduled shutdowns during the first six months of operation.

"Building on this success", said Hall, "we are in the midst of installing and commissioning a single plane balancing system on Castle Cement's 7 Kiln ID Fan (FL Smidth Fan), which is part of a 1200 tonne per day process".

According to Hart, this process improvement has added up to big savings and the Lord Balancing System paid for itself in six months.

Not only is Castle Cement able to run the kiln with no production interruptions, they are also extending the life of their equipment and have minimised the wear and tear on the fan bearings.

Finally, the vibration figures speak for themselves.

Before installation of the balancer, the fan registered as high as 9mm/s within 30 to 60 days of sandblasting.

Today, however, Castle Cement reports vibration levels of less than 2.5-3mm/s within the same timeframe thanks to the fan balancing system.

"Lord Corporation's balancing system paid for itself almost immediately", said Hart.

"Reducing our downtime equates to huge monetary savings and we are amazed that we no longer have to shutdown to clean the fan between regularly scheduled outages".

Winzenz said that Castle Cement's success is no aberration, rather, another example of the results achievable with Lord Corporation's fan balancing system.

With dozens of installations of the balancing system on kiln ID and preheater fans in the cement industry, Winzenz said the fan balancing system has proven to save thousands of dollars per year in maintenance costs and lost production.

This solution to a chronic problem is allowing the individual plants and the industry as a whole to recognise increases in production to meet new demands.

Since installation of the Lord Corporation's balancing system, Castle Cement estimates a savings of more than 200 hours per year increased production through the reduction of downtime associated with maintenance and repair.

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