Four key tasks should be part of a dredge maintenance plan to help ensure long-term operation.

Proper equipment maintenance is the key to long-term success, since it reduces production uncertainty by increasing availability, reducing energy consumption, decreasing or eliminating environmental and safety penalties, and allowing major repair scheduling and procurement. Dredges deviate from the typical maintenance model, as they encompass additional challenges because many of the wear items are below the water’s surface and are not visible for frequent inspection.

Performance-based testing generates information on the condition of dredge systems and provides important information on the efficiency and energy consumption of the wearing components.

Original equipment manufacturer (OEM) literature is often the single best source for creating a written maintenance program. Since all dredge manufacturers use other OEM equipment in their products, they must rely on their recommendations to support the dredge. The supplemental manuals provided for the individual components of the dredge should be read and understood. Due to this fact, adherence to a written maintenance plan can be the starting point for successful dredge operation and production. This plan should include sections that identify what systems need to be inspected, the frequency of equipment inspection/maintenance, and the tools required to perform the inspection/maintenance services.

Whether the machine is a pipeline dredge (hydraulic), a dragline (mechanical), or a clamshell dredge (mechanical), its maintenance requirements can be broken down into several key tasks: visual inspection and lubrication, routine sampling and analysis, performance-based testing, and scheduled replacement.

1. Visual inspection and lubrication

Of the four tasks, only visual inspection and lubrication is commonly practiced in the aggregate industry. While this component of dredge maintenance is critical for safety, environmental, and immediate operation concerns, it does not provide enough insight to management to reduce energy costs due to wearing components or to efficiently procure expensive parts on a timely basis.

Visual inspection and lubrication of dredges is critical for safety, environmental, and immediate operation concerns.

Inspection and lubrication schedules, while commonly provided by the equipment manufacturer, can be created or modified by the dredge operator, plant operator, or management. These tasks are accomplished daily by the dredge operator or deckhand without taking apart any components and do not directly involve management; however, it is important that a written record of these tasks is provided to management.

The phrase “cleanliness is next to godliness” cannot be more applicable when dealing with the Mine Safety and Health Administration (MSHA) regarding a dredge. Often, MSHA inspectors do not want to be on the water in the first place, and the last thing they want is to encounter a machine in disrepair, coated with oil and grease, and laced with debris; the dredge should be cleaned at least at every shift change to promote an atmosphere of pride and respect.

Since a dredge is a floating machine, the trim and heel (stability front to back and side to side, respectively) of the vessel should be visually checked upon boarding, departure, and routinely throughout the day. Any noticed change in either draft or lean should be immediately inspected, corrected, and reported to management. Most flotation problems are a result of manholes that are not tightened properly or from corrosion, stress, and rubbing problems that cause a crack or hole in a tank. These issues can be quickly remedied with pumps, epoxy, wooden dowels, or concrete, and can be permanently fixed during regularly scheduled maintenance periods. It should be noted that dredge flotation tanks are often considered confined spaces, and company procedures for entering these tanks must be strictly followed.

On a daily or shift basis, swing, spud, and lift cables should be inspected for fraying, wear, and proper fleet. Lift cables should be replaced immediately, as a failure on a ladder or bucket lift system can be financially, as well as humanly, catastrophic. Frayed swing or spud cables usually only result in downtime and should be replaced at the first scheduled maintenance time.

Sheaves, bushings, and bearings — especially those that are submerged — should be lubricated every shift to prevent wear. Lubrication and inspections usually require less than 30 minutes per dredge shift; the installation of automatic greasing systems can greatly decrease lubrication time, as well as ensure that every grease point is properly lubricated.