Production and Maintenance Objectives

A production plan was being used to balance development and Longwall production to meet target outputs. The mine was production limited. These target outputs were being used to set availability targets for the Longwall. However, it was my impression that the engineering-maintenance department had not established equipment life plans to achieve these availability targets. Also, I could find no key performance indices for any area of organizational efficiency.

Maintenance Strategy—Life Plans and Preventive Schedule

An outline life plan for the armoured faced conveyor (AFC) of the Longwall cutting system is shown in Table 6–1 and Exhibit 6–1 shows one of the job specifications.

The minor work of the life plan was carried out underground while the major work(the overhaul) was undertaken off-site by contractors (or the OEM). This was typical of most of the underground equipment.

The minor maintenance of the equipment in the development areas was scheduled during the week into windows of opportunity provided by production changeovers. The work was scheduled to avoid clashes and also the weekly two shift Longwall down-day, when minor maintenance (preventive and corrective) arising on the Longwall was carried out. The major Longwall maintenance took place during a Longwall change (locating it to a new production area, which took about three weeks). Major units of Longwall equipment (e.g., the AFC, the shearer, etc.) were held as spares common to all three collieries, which minimized Longwall overhaul and allowed the equipment to be reconditioned off-site.

There appeared to be no scheduled down-day for the trunk convey or and limited maintenance was carried out on it at the weekends.

The Engineering Superintendent was responsible for all maintenance carried out off-site, including work specification and tendering, while the Maintenance Superintendent was responsible for all maintenance carried out within the mine.

Observations

* As regards the minor maintenance work, the development and Longwall equipment life plans were satisfactory.

* The major off-site maintenance work was not being carried out satisfactorily. This was partly due to a lackof communication and understanding, concerning its specification and quality control, among the engineering maintenance departments.

* The life plans for the conveyor systems were satisfactory. However the offline preventive and corrective workaris ing from the inspections was not being carried out. This was partly because of the absence of a down-shift. The windows of opportunity (those provided by shift changeovers and those occurring at the weekends) were not being used for planned maintenance.

* Although the colliery was production limited the management preferred to use mid-weekdown- days for Longwall maintenance (a 13.5% availability loss) rather than sanction overtime or seven-day maintenance shift rostering for the weekends.