3516C Marine Engine Product Description Caterpillar

Product Description
1.1. Aftertreatment system description
2.2. Dosing Cabinet
3.2. DEF Tank
4.2. Reactor Housing
5.2. Selective Catalytic Reduction Substrate

The 3516 C Marine Engine is an electronically controlled diesel engine. The engine has an electronic unit injector. The engine can be equipped with either separate circuit aftercooling or jacket water aftercooling.

Engine efficiency and engine performance depend on adherence to proper operation and maintenance recommendations. Use the recommended fuels, lubrication oils, and coolant. Pay special attention to the air cleaner, to the fuel system, to the lubrication system, and to the cooling system maintenance. Refer to the Operation and Maintenance Manual, "Maintenance Interval Schedule" for more information on maintenance items.

Table 1
3516C Engine Specifications    
Item     Specification    
Rated speed (rpm)     1800 RPM    
Cylinders and arrangement     60 degree Vee 16    
170 mm (6.7 inch)    
215 mm (8.5 inch)    
Type     4-stroke cycle    
Compression ratio (1)     14.7:1    
Compression ratio (2)     n/a    
Aspiration     Turbocharged    
Method of cooling the turbocharged air     Separate circuit aftercooling    
Displacement per cylinder    
4.9 L (297.2 in3)    
Total displacement    
78 L (4760 in3)    
Rotation (flywheel end)     Counterclockwise rotation    
Fuel     See this Operation and Maintenance Manual, "Fluid Recommendations".    
Method of fuel injection     Electronic fuel injectors    
Method of starting     Electric starting motor or air starting motor    
Exhaust back pressure (customer piping)    
6.7 kPa (26.92 inch of H2O)    
Total back pressure    
18.65 kPa (75 inch of H2O)    
Maximum inlet air restriction    
2.5 kPa (10 inch of H2O)    
( 1 ) Except for serial numbers beginning with T3W
( 2 ) Serial numbers beginning with T3W

Illustration 1g00308357

3516C Engine

(A) Inlet valves

(B) Exhaust valves

(C) Flywheel

Aftertreatment system description

Illustration 2g03684316

AVSpare supplied aftertreatment components are illustrated with dashed line rectangles.

Selective Catalyst Reduction (SCR) catalyst technology is used to reduce NOx emissions and particulate matter.

The aftertreatment system is comprised of the following components:

  • Air compressor (OEM supplied)

  • DEF Dosing cabinet

  • DEF Injector

  • DEF Mixing tube

  • DEF Supply tank (OEM supplied)

  • SCR catalysts

  • SCR reactor housing

Engine exhaust flows into the SCR System reactor housing through the exhaust inlet. Once sufficient temperature is achieved, the DEF is injected into the exhaust. Exhaust flows through a mixer assembly in the mixing tube to ensure that exhaust is stratified for uniformity. This mixing will ensure complete disbursement across SCR catalyst section. Precise DEF injection is monitored and controlled by an electronic controller in the dosing cabinet. The following components provide signals to the controller to control DEF injection for emission reduction:

  • Thermocouple located in the reactor housing.

  • Inlet NOx sensor located in the exhaust before the inlet to the SCR catalyst reactor housing.

  • Outlet NOx sensor located in the exhaust at the outlet of the SCR catalyst reactor housing.

DEF fluid is injected into the exhaust stream before entering the SCR. When injected into the exhaust stream, the DEF is atomized into droplets. The atomized droplets are then sent through the mixer. The mixer disrupts the exhaust flow and allows DEF to be distributed throughout the exhaust gas. Water evaporates due to the high temperature of the exhaust. This process will cause the DEF to decompose and release ammonia (NH3) that was bound to the DEF. NH3 is free to react with the NOX and the oxygen present in the exhaust system stream. This reaction occurs on the SCR catalyst. NH3 and NOX are converted into gas particles of nitrogen and water. The inlet and outlet NOX sensors read the levels of NOX and determine how much DEF needs to be injected into the exhaust.

Dosing Cabinet

The dosing control cabinet controls the following:

  • Rate of DEF flow to the injector

  • Compressed air pressure

The aftertreatment ECM located in the dosing cabinet and the Cat ECM are designed to communicate with each other. This communication controls the complete engine/emission system in order to meet emission levels.

DEF Tank

There are two separate DEF tanks in the dosing system.

  • DEF tank 1 is the customer installed DEF tank. DEF tank 1 is the bulk DEF tank. A DEF high and low-level switch in tank 1 will notify the operator when the tank requires refilling.

  • DEF tank 2 is the buffer tank located in the dosing cabinet. Tank 2 is a small DEF tank that is filled from DEF tank 1. Tank 2 provides DEF to the DEF pump to be injected into the exhaust.

Reactor Housing

The reactor housing contains the following:

  • SCR catalyst substrates

  • DEF injector

  • DEF mixing tube

  • SCR catalyst temperature and pressure sensors

  • NOx sensors

The aftertreatment ECM uses the sensors on the module to determine how much DEF needs to be injected into the exhaust system.

Selective Catalytic Reduction Substrate

The Selective Catalyst Reduction (SCR) substrates are located in the reactor housing. These catalysts allow exhaust to flow through the substrate while converting the NOx into N2 and H20.