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Oilfield Technology
December
2014
remain the same as in Tier 2 engines, resulting in high durability and
increased availability. New turbochargers and wastegate valves in the
air handling system further control exhaust temperature, reducing heat
rejection, eliminating the need for larger cooling packages, improving
engine performance and extending the life of both engine parts and
emissions‑reducing components. These turbochargers alsomanage
SCR aftertreatment systemefficiency by controlling exhaust temperature,
ensuring optimal performance and keeping DEF consumption low,
requiring fewer refills by the user. In total, the improvements to the
QSK50 have increased life‑to‑overhaul by 10% fromTier 1 – approaching
1million achievable gallons, a goal not previously seen for an engine of
this output.
Easeofoperation
The Tier 4 Final solutions are fundamentally simple. Equipment users
retain the power and torque they are accustomed to and receive better
fuel efficiency and sound attenuation with aminimal increase in user
interaction required. Increased fuel efficiency results in low total cost
of ownership comparable to that of Tier 2 products. The ‘drop‑in’
SCR aftertreatment systemprovides better sound attenuation than Tier 2
silencers. In addition, users can continue operating equipment they are
familiar with because Cummins Tier 4 Final engines are also designed to
drop into Tier 2 envelopes and eliminate the need for significant changes
in product design.
Maintenance intervals also continue to expand as a result of newand
improved technology. MCRS fuel systems extend fuel injector life and the
introduction of NanoNet™ fuel filters reinforces both fuel systemand engine
durability. NanoNet fuel filters are capable of filtering particles as small as
5
μ
m, aremuchmore durable than previous filters and are able to capture
and retainmore particles. As little as 50mg of dust can cause extensive
damage to high pressure fuel systems, and the filters’ enhanced capability
protects the fuel system. In addition to their ability to prevent engine
damage, the fuel filters and oil filters have been validated for up to 500 hrs,
doubling themaintenance interval and reducingmaintenance costs and
downtime for users.
IntroductionofDEF
The primary change in user operation fromCummins’
Tier 2 to Tier 4 Final powered equipment comes with the
introduction of DEF to engine and SCR aftertreatment systems.
DEF is a chemical solutionmade up of 67.5%water and
32.5%automotive grade urea, a critical reactant in SCR NOx
reduction processes. The urea is a nitrogen compound that
turns into ammonia when heated, breaking NOx down into
harmless byproducts. In addition, DEF is a eutectic solution,
maintaining a consistent urea concentration even after
repeated freezing and thawing. DEF is non‑toxic, non‑polluting
and non‑flammable and has a shelf life of approximately one
year when stored at normal ambient temperatures in closed
containers and on‑equipment tanks.
The competitive advantages of SCR and DEF far surpass
the additional user interaction required. Practically every new
engine producing less than 751 horsepower uses a urea‑based
SCR aftertreatment systemand, it is predicted that soon, if a
site uses diesel it will use DEF.
DEF is also easy to find. It is readily available across
North America with availability and infrastructure continuing
to expand.
DEF consumption for an application varies according
to its duty cycle, the day‑to‑day fuel consumption and load
factor. Field tests have validated that for typical hydraulic
fracturing duty cycles, Cummins’ engine systems benefit in fuel
efficiency over Tier 2 products offsets the cost of DEF, resulting
in a total cost of ownership without penalty over Tier 2.
Reliability, performance, durability and compliance without higher fluid
consumption costs is a big benefit to operators.
Fieldtestproven
The increases in fluid efficiency, the simplicity of DEF and the reliable,
durable performance of the Tier 4 Final products have already been
proven out in the field. Two field tests in particular showcase the
versatility, efficiency and robustness of the QSK50 platform for the
pressure pumpingmarket. The first field test conducted was a hot
weather test of a hydraulic fracturing rig inWest Texas. The rig used a
2500 horsepower QSK50 and ran over the course of two summers and
one winter, accumulating over 3000 test hours. The West Texas field test
validated themany benefits of the Tier 4 Final QSK50, including:
Ì
Ì
Increased fuel efficiency.
Ì
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Efficient DEF consumption – refills only required every 2 ‑ 3 days.
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Better sound attenuation provided by the SCR system.
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Absence of black smoke through increased in‑cylinder PM reduction.
Throughout the duration of the field tests, the QSK50 engines
provided the durability, reliability and performance the customers
expected with no observable adverse effects from the extreme weather
conditions.
The second field test conducted was a cold weather test in
Alberta, Canada with another 2500 horsepower QSK50‑powered hydraulic
fracturing rig. The rig ran during the three coldest months of winter. In
addition to validating the same benefits shown in the West Texas field
test, the second field test also revealed the total system capability to thaw
DEF far quicker than required by the EPA.
Conclusion
As North America braces itself for the implementation of Tier 4 Final
next year, operators should be comforted by the fact that engine
manufacturers are already working to exceed the emissions standards
and continue to invest in R&D to help ensure oil and gas operations are
run without interruption – fromeither the engines or the regulators.
Figure 2.
Cummins Tier 4 Final QSK50with dual SCRunits.
