Multiquip DCA220SSCU4i manual Emission control, Diesel Oxidation Catalyst DOC, DPF pre-alarm

Maintenance

Emission control

The emission control system employed with the Cummins QSB&-G6 diesel engine consist of a Diesel Oxidation Catalyst (DOC) and a Diesel Particulate Filter (DPF). The oxidation catalyst and particulate filter are housed in one unit. See Figure 61.

These devices help in filtering out large amounts of harmful Nitrogen Oxides (NOx) and Particulate Matter (PM) which are emitted by diesel engines. These exhaust emissions pose serious environmental and health risks. It is important to maintain and service this DOC/DPF emission safety device on a periodic basis.

Diesel Oxidation Catalyst (DOC)

The DOC does not filter particles it oxidizes them. This catalyst (honeycomb like structure) uses a chemical process to break down pollutants in the exhaust stream into less harmful components. In general this catalyst collects/burns accumulated particulates.The DOC contains palladium and platinum which serve as a catalysts to oxidize hydrocarbons and carbon monoxide.

Diesel Particulate Filter (DPF)

A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter (soot) from the exhaust gas of a diesel engine. This type of filter usually removes about 85-95% of the soot.

Soot accumulated in the DPF is removed via the "regeneration process". Regeneration is the process of removing the accumulated soot from the filter. This regeneration process can occur in a few different ways.

„„Passive Regeneration — Occurs during normal operation, typically under heavy load applications. Soot is oxidized faster than it is collected.

„„Active Regeneration — Occurs when engine exhaust temperatures are not high enough to oxidize the soot collected in the DPF. Active regeneration requires assistance from the engine to help increase the heat level in the after-treatment system.

Active regeneration occurs at a normal engine speed of 1800 rpm. In addition active regeneration is initiated automatically by the Engine Control Module (ECM) timer based program every 96 hours.This timer base program will reset at the end of any regeneration mode.

„„Forced (Stationary) Regeneration — A forced regeneration only occurs when the operator has initiated this action at the ECU and the ECM recognizes a pre- programmed set point of soot in the PDF to allow a forced regeneration cycle.

This process can take anywhere from 30 minutes to 1-1/2 hours. When forced regeneration is in process all loads must be removed from the generator, all circuit breakers must be placed in the OFF position (OPEN), and the engine speed set to idle.

DPF pre-alarm

In the event the Engine Control Unit (ECU) determines the soot level back pressure and/or tempertaure has reached a pre-determined trip point the ECU will indicate a maintenance action is required by the operator.

This maintenance action will be shown on the LCD display (DPF Warning Symbol) and the AMBER pre-alarm LED on the ECU control panel will be ON (lit). See Figure 59.

ECU Series 800 Controller

Engine Started

DPF STAT Shutdown

Pre-Alarm

Alarm	Screen	Option	Program
Acknowledge Change			Exit

Figure 59. ECU DPF Pre-Alarm

The DPF pre-alarm status symbol displayed in Figure 59 indicates the soot level buildup has exceeded a pre- determined level and a "Forced Regeneration" action is required.

NOTICE

If the AMBER pre-alarm warning LED is ever ON, the operator should always take immediate action to correct the problem. If the engine is allow to run under this condition, a higher pressure differential will be created in the DPF and will result in the RED status LED being ON, causing an engine shutdown.

page 40 — dca220sscu/4i 60 hz generator • operation and Parts manual — rev. #0 (10/25/12)