Transitioning Onshore Drilling Rigs to EPA Tier 4 Final Engines

To meet both application requirements and customer needs, the Cat 3512E Tier 4 Final engine for land drilling uses an optimal combination of emissions-reduction technologies. It’s proven in the field to meet or exceed the reliability standards set by the 3512C without the burden of complex aftertreatment systems or secondary fluid requirements.

Exhaust Gas Recirculation to Reduce NOx

NOx typically forms at high combustion temperatures inside the engine cylinders. Exhaust Gas Recirculation (EGR) reduces the oxygen level and peak combustion temperature inside the cylinder, thereby reducing NOx formation. The 3512E’s NOx Reduction System (NRS) cools and meters the re-circulated exhaust gas.

High-Pressure Fuel Injection System to Reduce PM

PM generally forms due to an uneven air-fuel mixture and combustion inefficiencies within the cylinder. Two common technologies for PM reduction are high-pressure fuel injection and Diesel Particulate Filters (DPF), which filter PM from the exhaust stream. The 3512E uses a high-pressure fuel injection system to finely atomize the fuel mixture in the cylinder and minimize the formation of PM, thereby eliminating the need for a DPF.

Diesel Oxidation Catalyst to Reduce HC and CO

A compact, maintenance-free device that also offers additional exhaust sound attenuation, the 3512E’s Diesel Oxidation Catalyst (DOC) reduces HC and CO to CO2 and water vapor.

Eliminating the Challenges of Selective Catalytic Reduction

An alternative approach to meeting Tier 4 Final emissions standards, Selective Catalytic Reduction (SCR) is an aftertreatment technology that injects Diesel Exhaust Fluid (DEF) into the exhaust to reduce NOx to nitrogen and water vapor with the aid of a catalyst element. For land drilling, SCR technology poses significant challenges:

• The size and arrangement of the aftertreatment, DEF storage tanks, DEF pumping units and associated piping are prohibitive on a land drilling rig.
• Land drilling sites are typically in remote locations. Onsite storage and distribution of large quantities of DEF requires additional logistics and handling.
• DEF freezes at 12°F and shelf life decreases dramatically at temperatures above 90°F.
• DEF injection systems are sensitive to contamination, requiring special closed-loop storage and delivery systems and robust contamination control procedures to prevent equipment malfunctions.
• A loss of DEF or issues with the delivery system can trigger engine de-rates or shutdowns.

SYSTEM INSTALLATION

The 3512E fits into the same footprint as the 3512C, with the NRS and common rail fuel system components factory-installed. The most significant changes to 3512E installation relate to the exhaust and cooling system.

Exhaust System

The exhaust system includes a single DOC between the turbocharger outlet and muffler. The DOC can be mounted in a variety of locations and orientations to fit the design of the exhaust and roof structure with no effect on the overall size of the master skid.

Cooling System

The NRS cools re-circulated exhaust air before returning it to the intake air stream, resulting in higher overall engine heat rejection. However, a new two-stage aftercooler on the 3512E offsets nearly all of the impact on the size of the radiator or cooler. Minor changes to fan designs and speed also minimize the effect on cooling system size.