September 1, 2011
By Cash Maitler
A properly maintained hydraulic dredge can be the deciding factor in how much material an operation produces. These general maintenance practices can help keep hydraulic dredges performing well, but actual maintenance practices may vary depending on the type of dredge(s) being utilized. Be sure to refer to your owner’s manual or consult the manufacturer for proper maintenance details.
Periodically inspect the hull and pontoons for possible leaks. To increase the life of the dredge, it is important to keep the hull and pontoons of the machine painted and minimize bare metal exposed to the water. Where thin areas are detected, it is typically possible to seal weld a scab plate over the area and extend the useful life of the hull or pontoon.
The dredge pump is its heart and one of the most critical components to maintain. It is important to check the bearing oil levels or grease the bearings daily, depending on the pump. If your pump is equipped with packing, you should periodically adjust or replace the packing so that a small stream of water leaks from the stuffing box when running. If sand or other material is present inside the stuffing box area, it is important to clean the stuffing box to prevent accelerated wear. If your pump is equipped with mechanical seals, inspect the seals for wear and leaks. In the case of underwater pumps, it is especially important to make sure the bearing housing seals are in proper operating condition to prevent water intrusion and damage to the bearings.
In addition to checking the bearings, it is also important to periodically inspect and adjust the pump for wear. Abrasive materials tend to wear out the “wet end” pump components over time, requiring periodic adjustment and replacement. It is important to check the impeller, case, and liners for wear and make adjustments or replacements in order to maintain efficiency. Over time, if wear occurs, recirculation or other factors can cause performance losses, increasing the cost of production.
Fresh water/jet pump
If your dredge is equipped with a fresh water or jet pump, you should frequently inspect it for proper working order. Most of the same maintenance procedures for the centrifugal dredge pump apply to the fresh water or jet pump. Check to inspect the bearing oil level or grease the bearings. If the pump is equipped with packing, adjust the packing so that a small stream or drip occurs when the pump is operating. Typically, the fresh water pump or jet pump do not need adjustment, but, periodically, it is necessary to inspect the impeller and wet-end components for signs of wear or cavitation.
Check the engines and motors daily or on an operational shift basis. Inspect and tighten any loose belts. Make sure any and all fluids are clean and at operating levels. Change filters according to the manufacturer’s recommendations and refer to your owner’s manual for further instructions.
The winches and cabling need to be inspected and maintained daily. Be sure to inspect your cables for frays, kinks, or any other signs of wear. Check all winches for proper oil levels, leaks, and any signs indicating a need for repair. Check to make sure that the cable is able to properly spool on and off the winches and not create a bird’s nest.
Depending on the type of dredge being utilized, it is important to periodically inspect the cutting and/or jetting system to agitate the material being pumped. For cutting systems, inspect the cutting teeth, arms, chains, and other devices for wear and misalignment. Overlook the drive mechanisms for any signs of leaks indicating possible seal failures. For underwater drives, this is especially important to protect against possible water intrusion into the drive. For jetting systems, you should inspect the jet pump and all connecting piping and hoses for cracks and leaks. Check the bearing oil levels or grease the bearings on the jet pump daily, depending on the type.
Suction and discharge piping
The suction and discharge piping should be periodically inspected for cracks or leaks as the pipes wear. Abrasive materials will wear down the walls of the pipes over time and eventually cause a hole. Bends and elbows are a critical inspection point due to their tendency to concentrate aggregate along the outer wall as it flows through the pipeline. This higher concentration increases friction and wear on the pipes along the concentration area. If capable, it is recommended to rotate the piping one-quarter to one-half rotation to extend the life of the pipes. Aggregates tend to settle and slide across the bottom of the pipes while pumping, wearing the bottom side of the pipes. By rotating the pipes, you can even out the wear pattern inside the pipes and extend the life.
It is important to make sure all controls are functioning properly. For mechanical connections, inspect all ball joints, cables, and levers for motion and function. Lubricate any pivoting or sliding components to reduce friction and extend life. For electrical controls, inspect the wiring and connections for loss of signal or interruption. For hydraulic controls, inspect the hoses and plumbing for leaks.
Check all the hydraulic hoses and connections for leaks. Inspect all the electrical wires for exposed wiring or bad connections. Check all filter indicators for dirty or clogged filters. Inspect the fins of all air heat exchangers for dust or dirt buildup and bent or smashed fins. Straighten bent fins using a knife or small flat head screwdriver. Check keel, cool heat exchangers for dirt or debris buildup, and change any filters accordingly. Grease all fittings daily unless otherwise specified. If equipped with a transmission, check and change the fluid and filter according to the manufacturer’s maintenance schedule. For clutches, typical periodic adjustment is required as the clutch wears. Inspect and tighten any loose drive belts daily, if needed. Replace worn or scuffed belts. AM
Cash Maitlen is a design engineer with VMI, Inc.