Trendsetting maintenance

With an annual production capacity of more than 6 million tons of cement, Ash Grove Cement is the largest American-owned producer of cement and the fourth largest producer in the US.

In the past three years, the company has more than doubled the capacity of its Durkee plant in Oregon, from 1500 to 3100 tons of Portland cement a day. This was done by adding new capital equipment to increase capacity to 2700tpd, and then fine-tuning the production process and enhancing equipment maintenance so that the plant can run virtually non-stop.

A key factor in the Durkee expansion was the installation of a computerised maintenance management system (CMMS). The CMMS runs on the Avantis.PRO system from the Production Management division of Invensys. 'Our original need was maintenance functionality and some cost tracking information,' says Durkee's maintenance manager, Bernard Sherin, 'so when we saw what Avantis could provide, we were pretty excited. There's a lot of functionality to the software and, in fact, we still probably don't use it to its capacity.'

Originally, Sherin says the system was used as a 'get it into the system so we don't lose the data' type of solution. 'We were successful there,' he says, 'but we didn't take advantage of some of the planning or sorting functions. We've now begun to use those features as well, as part of a new corporate program we call our Maintenance Excellence Process (MEP).'

This MEP program was designed to improve the reliability of Ash Grove's equipment and processes to world class levels. Sherin explains that 'being able to handle the backlog through Avantis has been really easy and we have a much better handle on our workload since we started using some of those other features.'

Avantis provides the features that link Ash Grove's diverse management operation spread out over the several square miles housing the cement mines and plant. The CMMS system uses the 'entity' concept to facilitate recording of costing and maintenance activity records for anything that users want to track. 'Parent-child' relationships can be set up easily to build hierarchies for cost roll-ups and operating statistics. Work management features ensure that maintenance staff have control of incoming work while providing a flexible way to track work in progress.

Avantis.PRO builds a detailed history of equipment information based on day-to-day maintenance activities. Equipment statistics include hours of operation, cause and frequency of downtime, and labour and material changes.

'One of the features we've taken advantage of is the ability to look at historical data and trend it to evaluate whether we need to spend more or less effort in a particular area,' says Sherin. 'It has given us an easy way to determine whether a particular piece of equipment has had an inordinate amount of work done on it. With proper cost justification, we can judge whether we should replace any equipment that is costing too much to maintain. Maintenance efficiency became a critical part of equipment redeployment as we upgraded the plant to increase production - all the way from mining of minerals in the quarries behind the plant to the conveyor systems, production equipment, and bulk distribution of product to trucks.'

In order to perform maintenance schedules when the plant is running 24 hours a day, the maintenance staff take a predictive approach to their schedules, using new techniques for monitoring equipment operation, such as vibration analysis, thermography and even oil analysis of large gear boxes.

'We still do some failure-mode fire-fighting occasionally,' Sherin admits, 'but we're trying diligently to get away from that. It's a challenge to schedule maintenance when you run 24 hours a day, but usually we get a 2-4 weeks outage once a year to do major overhauls. Typically what drives the maintenance outages is the refractory lining in the kiln. We can get about a year out of the lining, but we want to extend that to a two-year cycle, and we feel that by studying the data gathered in Avantis to see any trends, we can further extend the programmed maintenance intervals'.