American Oil and Gas Reporter - May 2015 - 108

SpecialReport: Gas Compression Technology
optimal substitution rate, but improved
system response and performance.
"The GTI+ system targeted drilling
rigs in particular, where load changes
are rapid, frequent and large. A drilling
rig can spend 70 percent of its time idling,
which is a region where gas substitution
is a challenge," he says. "We can do a
load profile and map the substitution rate
at the optimal point across the entire operating load range, allowing the GTI+
system to respond much better to the
load profile of a drilling rig."
He notes that the GTI+ system also
can be used in hydraulic fracturing pumps.
Another advantage, Brooks points out,
is that Altronic uses its AGV5 valve,
which he says is a mature product with
an impressive record that the company
already had in its production line, to replace the mechanical regulator. The AGV5
valve has been used for fuel control in
natural gas engines for many years. He
says Altronic was able to adapt the valve
for the bifuel application in diesel engines
with some software changes.
"The response of our customers has
been very positive," Brooks states. "It
has given them increased performance
while reducing the footprint of the gas
train."
Brooks says the substitution rate-the
amount of natural gas that can replace
diesel-depends on a number of factors,
including fuel quality, condition of the
engine, engine design, ambient temperature, and engine load profile.
"We develop a base line for the diesel

engine," he outlines. "When you start
substituting gas, the engine will tell you
when it can't take any more. It determines
the substitution rate."
Altronic, as policy, limits the substitution to 70 percent. "There has to be
enough diesel present to ignite the fuel
charge and to allow the governor to have
the required authority range to respond
to load changes," Brooks points out. "The
diesel governor leads, the gas system
lags."
He acknowledges that if a customer's
business model requires the full 70 percent,
it probably is not realistic. "The level is
not always possible across the entire load
range, and may be limited because of
some or all of the conditions listed,"
Brooks says. "Even at an average substitution between 50 and 65 percent, the
savings are significant."
Driving Forces
One of the initial driving forces of the
GTI+ bifuel system, Brooks says, was
its ability to make a tank of diesel fuel
used to power emergency generators for
hospitals and other facilities last longer.
When the shale boom hit, however, Brooks
says the oil and gas industry found Altronic
and its bifuel system, and quickly realized
its economic benefit.
"Drilling rigs can save $700,000 to
$1 million a year in the differential cost
between diesel and natural gas alone,"
he claims.
He says bifuel systems are especially
beneficial in liquids-rich plays such as

the Bakken Shale, where the natural gas
often was just getting in the way. He
relates a statistic that Bakken operators,
at one time, were flaring 55 percent of
the gas in North Dakota because there
wasn't enough infrastructure to handle
the natural gas. That has since been reduced, according to Brooks, partially as
a result of government pressure to reduce
flaring. Bifuel drilling rigs offer one
means to utilize this otherwise wasted
gas.
"It is a great use of an abundant domestic resource," he exudes. "That shows
how far we have come. We are a country
awash in natural gas."
Brooks says Altronic's GTI+ system
is being used in nearly every play across
North America.
Altronic doesn't market its GTI+ as a
way to reduce emissions, although Brooks
says the company has commissioned independent third-party emission tests that
show that it does. In addition, he says,
operators have to haul less diesel fuel.
They can reduce their need for aboveground liquid fuel storage by extending
the run time of diesel fuel tanks, he adds.
In May 2014, Brooks says, Altronic's
GTI bifuel product line received aftermarket certification from the California
Air Resources Board.
"We were the first aftermarket supplier
of a bifuel system to receive such an executive order from the state of California,"
Brooks emphasizes. "The process was
not easy, and we quickly realized we
were blazing a new trail with the cooperation of CARB. But in the end, we were
able to reach common ground and the
GTI system was able to pass the stringent
emission testing required by California.
The bottom line is that the process provides
a path of emission compliance for product
users."
Dual Fuel Operations

Cummins' dual-fuel systems are designed to run on its hydraulic fracturing pumps, and
can operate either on 100 percent diesel fuel or a mixture of diesel and as much as 70
percent natural gas, depending on the quality of gas available. Cummins says the fully
automated system has the flexibility to use 800-1,200 Btu gas.

108 THE AMERICAN OIL & GAS REPORTER

Cannon says Cummins began working
with its customers in 2012 to develop its
dual fuel technology before releasing the
fully functional systems late last year.
The dual fuel kits are designed specifically for Cummins' QSK50 hydraulic
fracturing pumps, according to zur Loye.
He says a dual fuel engine is based on a
traditional diesel engine that has added
dual-fuel-specific hardware.
Cummins' engine can operate either
on 100 percent diesel fuel or a mixture
of diesel and natural gas, but it cannot
operate on natural gas alone. When it is
American Oil and Gas Reporter - May 2015

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