SCR versus EGR: What's the right choice for the rail industry?

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Today, there are two core technologies to reduce emissions within the rail industry: Selective Catalytic Reduction (SCR) and Exhaust Gas Recirculation (EGR). But how do you know which is the right technology for your customers?

A quick internet search for “SCR vs. EGR” will return more than two million results from various sources, but what does it all mean? For decades, people have been debating the merits of each technology, arguing over which is better. We’d argue, however, that the question you should be asking is this: Which technology is right for your customers?

In this article, we’ll provide a clear and practical explanation for SCR and EGR technology in the rail industry.

First, a little background on the SCR vs. EGR technology debate.

EGR or SCR for the rail industry
A mix of technologies - from electronics and controls to aftertreatment systems - are used in the race towards near-zero NOx engine emissions. 

Emission regulations for engines used in heavy-duty applications - from on-road vehicles to locomotives - started in the 1990s and became more stringent in the 2000s. Locomotive manufacturers were able to meet these emission regulations without the use of exhaust gas aftertreatment technologies in most applications. On the other hand, heavy-duty on-road engine manufacturers had to meet more stringent regulations compared to railway locomotives. 

In the 2010s, as emission regulations got more stringent, several heavy-duty on-road engine manufacturers needed to use a combination of SCR and EGR technologies to achieve the required emission levels. For the rail industry, where most applications require the use of larger engines, several engine manufacturers had to choose between SCR or EGR to meet the new emission regulations. This was the beginning of the debate between SCR and EGR technologies. 

A Better Question: What is the right emission reduction technology for your customers? 

From rail operators to locomotive manufacturers, rail industry players have needs unique to their business models and markets served. Instead of making the technology choice the starting point, we have outlined three use cases and the right aftertreatment technology.   

When running hours and fuel consumption makes the engine efficiency an important parameter

Challenge: As regulations require pollutant emissions deceased, engine manufacturers could adjust engine parameters to partially lower the emission of pollutants.

Combustion temperature is one of these parameters, however, a lower combustion temperature reduces NOx emission yet increases fuel consumption. For rail operators focusing on improving fleet utilization, increased fuel consumption could negatively impact their financials and worsen their environmental impact. 

Opportunity: Rail operators can optimize engine combustion for higher fuel efficiency and choose to reduce NOx separately through SCR, since SCR is a solution external to the engine. Given the high proportion of fuel costs in rail operators’ overall running costs, rail operators would likely offset the additional cost of diesel exhaust fluid (DEF) over time through the fuel consumption savings.

When reliability matters, and you want to build upon an already reliable engine

Challenge: Engine manufacturers have the option to introduce varying levels of engine design changes to meet the more stringent emission regulations. For locomotive manufacturers, any extensive change in engine design raises the question of engine reliability. This concern is further amplified for engines, such as the Cummins QSK50 and QSK60, which have proven their reliability over many applications and millions of hours of usage.

Opportunity: Locomotive manufacturers could lower the risk of adversely impacting engine reliability by choosing engines that didn’t go through significant architectural design changes and new part introductions from an engineering perspective. SCR technology helps the engine meet emission regulations with limited architectural design changes in an engine’s combustion chamber.   

When a high degree of commonality helps you create a financial edge through operational savings

Challenge: As emission regulations vary across regions, locomotive manufacturers and rail operators face a dual challenge: offering products that are fit for local needs, while increasing their financial performance. 

Opportunity: Use of SCR technology would likely allow locomotive manufacturers to have higher commonality across variations within a given engine platform. This offers financial and operational benefits. For instance, rail operators managing a fleet with higher engine commonality will benefit from common service methodologies while managing fewer parts. 

“We expect the locomotive manufacturers and rail operators using engines with SCR technology today to be better positioned in the near future when the emission regulations get more stringent. Today’s SCR technology is well suited to meet future emission regulations with less interventions, positioning users of SCR technology a step ahead of users with other emissions technologies,” says Miranda Cross, Global Rail Account Manager of Cummins Power Systems.

Bottom line, it is important to evaluate your customers’ key needs and use cases before making the technology decisions. For customers with the above three use cases, SCR offers a combination of financial and environmental benefits, including greenhouse gas reduction, while also helping locomotive manufacturers and rail operators meet unique local needs.   

To learn more about trends and technologies in rail industry follow Cummins  on Facebook and LinkedIn. To learn more about rail power solutions Cummins offers, visit our webpage. 

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Aytek Yuksel - Cummins Inc

Aytek Yuksel

Aytek Yuksel is the Content Marketing Leader for Cummins Inc., with a focus on Power Systems markets. Aytek joined the Company in 2008. Since then, he has worked in several marketing roles and now brings you the learnings from our key markets ranging from industrial to residential markets. Aytek lives in Minneapolis, Minnesota with his wife and two kids.

Cummins Custompaks are being used for water management as Thailand struggles with its water crisis

CustomPak on site

Water crisis

Sixty Cummins Inc. CustomPaks are in service in Thailand as part of a critical water management plan aimed at easing the country’s water crisis – a crisis that has caused enormous economic and social damage and stirred conflict among communities.

Over the past several decades, Thailand has continually faced water problems caused by severe drought. Water reserves in dams and reservoirs are insufficient while water resources are often contaminated with toxins caused by urban communities and the industrial and agricultural sectors.

Severe flooding is a threat, too, at a time when the realities of climate change are hanging over the country.

As a result, the allocation of precious water resources, which must be shared among various stakeholders including new and existing industry, large and small agriculture, and cities and villages has become a flashpoint.

Kittithanapat Engineering Co. (KTP), has been involved in the water management system since 1996, working closely with authorities such as the Royal Irrigation Department, Department of Water Resources, Bangkok Metropolitan Authority and others.

CustomPaks on site

600 hp CustomPaks

To help KTP meet its often urgent requirements, Cummins DKSH (Thailand) has recently supplied 60 Australian-built CustomPaks – 45 powered by Cummins’ X15 engine rated at 600 hp, and 15 powered by the QSL9 rated at 325 hp. These fully self-contained powerpacks are emissions certified to Tier 3.

The CustomPaks are coupled to hydraulically-driven, large-volume submersible water pumps sourced by KTP from US company Moving Water Industries (MWI); KTP is the exclusive distributor in Thailand for these MWI Hydroflo pumps.

Prior to Cummins’ involvement, KTP was using another diesel engine brand but service support wasn’t up to the standard required.

Long-serving KTP engineer Kittisak Thanasoot says Cummins DKSH’s reputation for technical and aftersales support along with the reliability of the Cummins product were a key reason behind KTP’s decision to specify the CustomPaks for the Royal Irrigation Department.

The ability of Cummins DKSH to respond to short delivery times was also important.

“Supplying large quantities of high horsepower diesel engines for emergency situations such as flash flooding can be a challenge for KTP,” says Kittisak Thanasoot.

“Responding to the needs of the government agencies to manage such problems in a timely manner and with least impact on communities, KTP has found the answer in our partnership with Cummins DKSH.”

Power, pride and passion

Parked semi truck

The switch back to Cummins power has been beneficial for iconic New Zealand company Uhlenberg Haulage. It's all about whole-of-life costs.

Uhlenberg Haulage is closing in on 60 years in business, having been founded in 1966 by Mike and Carol Uhlenberg.

Based in Eltham, Taranaki, in New Zealand’s North Island, the operation is today owned and operated by their sons Chris, Daryl and Tony Uhlenberg.

Describing the Uhlenbergs as “old school family truckies”, Daryl talks about the company’s time-honored journey with a definite tone of pride, especially the work of his parents in laying the foundations for what is today an iconic fleet in its own right.

Cummins Inc. made its debut in the Uhlenberg fleet in 1971 with an NH250 powering a second-hand Kenworth K923 used in logging. A second Kenworth, a new W924 with a Cummins NTC335, followed soon after hauling an LPG tanker.

The Uhlenberg operation today comprises 40 prime movers and a variety of trailing gear to cater for the myriad of a jobs the fleet is involved in.

A number of Peterbilts feature in the fleet although Kenworth is now the brand of choice with six new units to be delivered over the next 12 months to cater for business growth.

Cummins’ X15 Euro 5 engine rated at 550 or 600 hp is the preferred power specification, with 18 red engines currently in the fleet.

Uhlenberg family in front of truck

Whole-of-life support

“The switch to Cummins has been a very good experience for us. We have nothing but praise for the Cummins organization,” says Daryl.

“The whole-of-life picture is the key thing for us and we’ve got that nailed with the support we get from Cummins – parts availability, scheduled maintenance, life expectancy and in-frame rebuilds.

“So the red engines turn up, we run them to life, which is 900,000 to 1.2 million kilometers, and then Cummins does an in-frame overhaul in a timely manner. If there’s an issue, parts and support are close by.

“The support we get from Cummins Palmerston North is fantastic, second to none.”

Daryl recently looked under a Kenworth that was in the workshop for a service and was surprised to see no oil leaking from the one-million-kilometer X15. “I remember when I was a fitter we had to wear a raincoat when working under a truck,” he jokes.

Fuel agnostic

Acknowledging that the push to decarbonize is now “very real”, Daryl likes the idea of Cummins’ fuel agnostic concept where one base internal combustion engine, optimized to run on diesel, can also be customized to run on ultra-low and zero-carbon fuels like renewable natural gas and hydrogen.

“My father was a pioneer of linehaul trucking in New Zealand and he always embraced new technology. He was never scared of it,” he says.

“I tend to be a little more cautious but I can see where a 500 hp natural gas or hydrogen engine would work for us in short haul applications,” he admits. “We’re certainly willing to look closely at these alternative fuel technologies when suitable infrastructure is in place.”

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