When you’re choosing land drilling engines to meet U.S. EPA Tier 4 Final standards, you have two options: engines with Exhaust Gas Recirculation (EGR) technology or engines with Selective Catalytic Reduction (SCR) technology. Both solutions have their strengths, but when you look at the facts, EGR emerges as the clear winner on land, while SCR is a smarter choice for marine and offshore applications. Here’s a quick look at the difference between the two systems and why each excels in a different environment. 

WHAT’S THE DIFFERENCE?

In an EGR system, a portion of the exhaust gas is passed through a cooler and metered back into the engine’s intake, reducing peak combustion temperatures and oxygen levels in the cylinders. Keeping these temperatures under control helps prevent NOx from forming in the first place.

In an SCR system, Diesel Exhaust Fluid (DEF) is injected into the emissions stream, catalyzing NOx into nitrogen and water vapor. It’s an aftertreatment system that breaks down emissions after they’ve been generated.

4 REASONS EGR IS A BETTER CHOICE FOR LAND DRILLING

1. No extra space needed for storage

Space is tight on a drilling rig, and that makes accommodating DEF storage tanks and pumping units tricky. EGR technology is compact and built into the engine, with no DEF storage requirements. The footprint of a Cat® 3512E Tier 4 Final Land Electric-Drive Drilling Engine is about the same as that of the Tier 2 model.

2. No shipping and stocking fluid remotely

Because land drilling typically occurs in isolated areas, keeping a rig stocked with DEF presents logistical challenges — plus extra equipment and costs for shipping it, maintaining it on site and transporting it to the next job. Since EGR technology doesn’t require DEF, that’s one less thing to worry about.

3. No special handling in extreme temperatures

Extremely hot and cold temperatures are common on land drilling sites, and DEF requires additional handling at both high and low temperatures. It degrades at 90°F and above and freezes at 12°F — a big problem during rig moves in cold weather when DEF may remain unheated for days. EGR technology isn’t affected by temperature, so it can operate in nearly any set of conditions.

4. No worries about contamination

Land drilling is dirty work. Since DEF is sensitive to contamination — and contaminated fluid can degrade the SCR catalyst — it requires closed-loop storage and delivery. That adds cost and complexity. EGR systems can function in dusty, grimy conditions with no loss of efficiency.

WHERE SCR EXCELS: OFFSHORE AND ON THE WATER

SCR is NOT an inferior technology. It’s simply better suited for marine and offshore engines, where it allows customers to switch easily between IMO II and IMO III emissions standards to reduce operating costs or to use up 5,000 ppm sulfur fuel in IMO II regions where ultra-low-sulfur diesel isn’t standard or readily available.