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Ask a Darley Engineer

Asked by Heather Devries, Skeeter Brush Trucks: As a builder, what do we need to know about the new tier 4 diesel offerings in terms of operation and mounting?

Answered by Tim Dewitz, CMfgT, Senior Engineer

Depending on the brand of engine, the new tier 4 engine can mean a number of new exhaust aftertreatment considerations when laying out and installing a diesel-powered pump. The different aftertreatment options have different costs, complexities, and size constraints. The different exhaust after treatments are:

  • DOC: Diesel Oxidation Catalyst.
  • SCR: Selective Catalytic Reduction – uses DEF (Diesel Exhaust Fluid).
  • EGR: Exhaust Gas Recirculation – some exhaust gas is recirculated back into the combustion chamber to lower the oxygen concentration, lower the temperature of the combustion chamber and exhaust temperature.
  • DPF: Diesel Particulate Filter – the filter traps particulates Particulates need to be removed periodically through a regeneration cycle where the particulates are burned off at a very high temperature, leaving ash behind. During the regeneration cycle the engine performance and operation is limited and controlled, affecting the performance and operation of the equipment being powered by the engine.

Some engines may even use a combination of diesel exhaust after treatment to be in compliance. DOC is the simplest for the end user as well as the builders. Like all of the after treatments, there are controls involved, but the DOC controls typically only monitor the use of the catalyst to properly signal if it needs replacing. The catalyst can be incorporated right in the muffler.

No matter what exhaust gas after treatment is being used, the operating conditions and installation will greatly affect the ability of the engine to operate in compliance. Engine suppliers need to review the application to ensure the proper conditions are being met. In many cases this can be done through the review of drawings, but in some extreme cases, on site testing may be required.

Darley’s new lineup of diesel-powered portables utilizes DOC exhaust gas after treatment right in the muffler providing the most compact, least complex, and lowest maintenance for end users, requiring no DEF (diesel exhaust fluid) and no regeneration during operation.

Check out our complete lineup of EPA Tier 4 compliant diesel-powered portable pumps on www.darley.com.


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