Pulverizers or ball mill manufacturers often suggest their products for critical operation of any coal-fired boiler. The pulverizers are the equipments used for crushing coal into fine powder in order to make it blown within the boiler’s furnace to produce steam. If there is no coal, there will be no fire, and if there will be no fire, there will be no steam. This means without steam, no electricity can be produced. At this utility, each of the two generating units uses total six pulverizers, on a continuous basis (each).

Each mill pulverizer is consumes 130 mw of power. If the coal is in good amount, the unit can run at full capacity on five pulverizers. Thus, when failure occurs, the impact on production is least assuming a second pulverizer doesn’t breakdown.

It is found that certain factors are responsible for extreme failure rate in the gearboxes. These are as follows-

• Excessive load – the gearboxes (1060 HP rated) are coupled to 1200 HP motors
• Viscosity problems – since the gearboxes were splash lubricated was suitable for the gearing, but waste away the bearings. Low viscosity gear oil suits the bearings best, but insufficient to lubricate the gearing.
• High temperatures – due to excessive loads issues, the gearboxes operate at hot temperature. High temperature leads to degradation. In a gearbox, mating component surfaces create hot spots, which further raise the chances of degradation.
• High contamination – Since the condition of coal-fired power plant makes the unit harsh and dusty, the gearboxes had their own cleanliness level of operation as per ISO standard.

How to achieve reliable performance?

Manufacturers have to make changes in specification of the gearboxes and redesigning. They need to reduce the fluid temperatures, control contamination, and feed the lubricant to the bearings forcefully.

But wait; altering the specifications of the gearboxes and redesigning can be a costly affair! And this is why majority of manufacturing units are trying to cut down the fluid temperatures, contamination and have stopped feeding the lubricant to the bearings forcefully.

The experts target the lubrication and contamination issue with the following strategy-

• Install a side-loop circulating system along with air-cooling to lower the temperatures of fluid
• Drill oil passages to lubricate the bearings.
• Use and install a premium quality breather to restrict incoming of contaminants
• Use a filter on the circulating system to expel ingested and generated contaminants.

So this is how ball mill manufacturers are saving their costs and expenses. Do you find it smart way to achieve optimum performance of the pulverizer? Share your thoughts in the comments section.

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