Cost Effective Maintenance rectify Caterpillar D11R engine deposit problems
The Caterpillar D11R engine
Caterpillar 3500 Series
engines were modified in 2004 to meet new, low emission requirements. Since then, there have been some concerning problems for operators. These include High
Oil Soot, Bore Polish, Sludge and Overheating. The factors causing these problems include the introduction of Monotherm Pistons, Exhaust Gas Recirculation Systems and high load factors.
Cost Effective Maintenance have solutions to rectify engine deposit problems ranging from heavy combustion and exhaust space carbon, injector fouling, to severe crankcase sludging. Bore polish, valve failures, broken rings are common end results of such deposits, and if addressed early enough, Cost Effective Maintenance’s corrective action will avert such damage, while eliminating hard engine carbon and sludge.
While the full range of Caterpillar 3500 Series engines could potentially show problems, D11R dozers appear to be the more widely susceptible. The problems as well as necessary corrective and preventative maintenance are described below.
High oil soot:
Oil soot is a product of combustion inefficiencies. Increasing oil soot levels usually result from the amount of soot progressively overloading the oil's detergency/dispersency package. Soot drops out of the oil as sediment, which is then re-suspended into the clean oil. This reduces the oil's potential service life, and allows further soot to settle out as sludge, as the oil service life progresses.
With increasing service hours, soot levels increase. Loss of detergency allows further piston ring deposits to form, which in turn, will reduce oil control. Oil burning can add to deposit problems. Increased oil make up may also mask the actual magnitude of the soot problem, by diluting the soot readings. Exhaust gas recirculation (in low emission engines) puts further soot loadings into the oil.
Corrective action- A twofold action is required to correct and control this problem:
Any soot/sludge residing in the crankcase needs to be removed, so as to provide full available service life to the oil (instead of depleting its additive package from the start). This is achieved with Cost Effective Maintenance’s Flushing Oil Concentrate (FOC), which is formulated with specific detergents that target hard, baked on carbon, and persistent sludge. It is introduced into clean, hot crankcase oil, and operated at a fast idle for about 30 minutes. Its action resuspends sludge and hard carbon (piston ring deposits), so that full cleanliness is restored to the crankcase.
Once these resuspended contaminants are drained, the new charge of oil has full available service life. In addition, full available compression control and oil control are restored. In severe cases, this step may have to be incorporated into the maintenance schedule at certain intervals. FOC has a 15 year history of restoring crankcase cleanliness to chronic high soot engines, grossly sludged engines, and freeing up badly stuck piston rings (even engines out of service for 3-5 years).
Both soot production rate, and its rate of migration past the rings into the crankcase need to be reduced. This is achieved using the FTC/FPC Combustion Catalyst (Decarbonizer). The action of FTC is twofold. Firstly, it catalytically oxidises (burns) all engine carbon contacted by the fuel flame. This includes top ring carbon and piston top land areas, as well as injector tip, piston crown, cylinder head, exhaust valves and spaces, turbochargers and further downstream. Piston top land cleanliness is a strong feature of FTC use, and is the direct cure for bore polish problems. Secondly, the combustion reactions proceed more efficiently, resulting in a marked lowering of the soot production rate. Lower soot production combined with an improved top ring seal result in less oil soot loading. Continuous fuel treatment is required, and leads to restoration of full available service life for severe bore polish situations.
Bore polish, Piston top land carbon:
Accumulation of hard carbon on piston top ring lands causes premature and costly liner wear. The source of the carbon is primarily from fuel combustion inefficiencies, but oil burning can also add to the build up. Customers are reporting bore polish related engine rebuilds from as low as 6000hrs from brand new, and possibly lower. This is an expensive problem, in terms of production downtime and component rebuild costs. Many engines are making less than half their expected service life, while in similar applications, engines using FTC/FPC Decarbonizer are trending out to 16,000hrs target life.
Corrective Action- It is important to treat this problem as early as possible before liner wear becomes excessive. As above, use of Flushing Oil Concentrate and FTC/FPC Decarbonizer will restore full cleanliness and correct the root cause of the bore polish problem.
Engine Overheating Cat D11r's:
This problem is due to an escalation of the oil soot problem, where loss of detergency allows deposit build up around piston rings (reducing thermal conductivity), and under piston skirts (which insulates against heat transfer from this area), and constriction of oil supply to the piston undersides, due to sludging. A strong flow of oil under the pistons is a vital part of the engine's cooling system, and one that is more often than not, neglected when investigating overheating problems.
The corrective action is the same as recommended above. Should further cooling assistance be required, a cooling system chemical, RMI-25 can be used to achieve a minimum 5 to 7 degree centigrade reduction in operating temperature. The manufacturers explain that this is achieved by de-gassing the cooling water to provide improved heat transfer, as well as providing a safe descaling action to all coolant surfaces.
31-Oct-2008