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As
emission standards for both off-highway and stationary diesel engines become
increasingly stringent, emission control technologies are becoming
increasingly sophisticated. New engines being introduced by the major diesel
engine manufacturers are designed to minimize emissions, and a variety of
catalytic filters are available to treat harmful exhausts. A perhaps lesser-known
but nonetheless important aspect of effective emissions reduction is the
maintenance of high exhaust temperatures. Properly
insulated exhaust and emissions reduction equipment is crucial in order to
ensure that emission reduction targets are met.
Background: Off-Highway and Stationary
Engine Emission Standards
Although Diesel Emission Standards for off-highway engines
have been around since the early 1990's, it wasn't until relatively recently
that stationary diesel engines became
subject to similar controls. In the U.S., beginning in January 2007, all new
diesel engines, whether off-highway or stationary, will be required to
conform to the Environmental Protection Agency's off-highway emission
regulations. These regulation levels, also known as Tier levels, depend on
the kW rating of the engines.
The
regulations are to become increasingly stringent over the next number of
years. By 2015, all off-highway and stationary diesel engines will be subject
to the EPA's highest Tier 4 level of emissions control. Other jurisdictions,
including Canada and the European Union, have standards that closely match
those of the EPA. (For more information on diesel emission standards, please
visit www.dieselnet.com/standards).
Response of Industry to Emission Standards
Be it off-highway or stationary, emission control
standards for diesel engines are intended to reduce the emission of NOx
(Nitrogen Oxides), DPM (Diesel Particulate Matter), HC (Hydro Carbons), and
CO (Carbon Monoxide). Engine and catalyst manufacturers have responded to the
challenge of these new regulations with various strategies aimed at ensuring
compliance.
In general, the approach of industry can be divided into
two categories:
- Engine Modification: In
engine modification, the aim is to reduce harmful emissions at the
engine level via a combination of improved electronic engine control,
better engine design, and turbo-charging systems.
- After-Treatment: This approach
treats the exhaust after it has left the engine. Different types of
after-treatment strategies include the use of a variety of catalytic
filters, fuel modifications (e.g. biodiesel or ultra low sulfur diesel),
secondary fuel injection, and Selective Catalytic Reduction (SCR)
systems.
These
approaches are by no means mutually exclusive. Indeed, especially for larger
stationary engines, engine modifications alone are not always sufficient, and
must be complemented with one or more after-treatment strategies in order to
meet the mandated emissions target.
Whatever approach one chooses to emissions reduction,
proper insulation is an important aspect of ensuring that emission reduction
targets are achieved. Many of the technologies require a high exhaust heat
[in some cases in excess of 800°F (425°C)] in order to function properly.
Without
proper insulation, the exhaust gases lose heat as they travel along the
various pipes and components of the engine and the exhaust system. It is
imperative that the exhaust, catalysts and SCR systems be properly insulated
to maintain internal temperature and ensure optimal performance / burn-off.
Removable insulation blankets are an excellent way to
provide the requisite insulation in a cost-effective manner. The fact that
they can be removed allows easy access to components during periodic
maintenance and replacement. Indeed, major engine users, as well as major
catalyst manufacturers, recommend removable insulation blankets as an
important component of their emissions reduction strategy.
Over the past 3 years, Firwin
has provided the insulation component of the overall emissions control system
to a number of major public and corporate building projects. Two of the
higher profile projects were Washington DC’s Convention Center and the new
Fannie Mae Mortgage Company Headquarters.
Both projects required large auxiliary power systems
to keep their facilities running in the case of a power shortage. Although
the new EPA regulations on stationary engine sets were yet to take effect,
both projects chose to lead by example and incorporate emissions reduction
technology into their facilities. In both cases, being larger stationary
engines, the technology of choice was SCR. Firwin provided the insulation
blankets for both the mixing tubes and the catalyst.
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Washington Convention Center
Washington DC
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Fannie Mae Mortgage Co. Headquarters
Maryland
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Four Mitsubishi 1100 KW engine sets are needed to
provide auxiliary& standby power to service its 2.3 million square
feet, 31 elevators, and 38 escalators.
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Fanny Mae installed its urea injection SCR system for
its 1st stage of six CAT 3516 engine sets that provide backup power for
their corporate computer systems.
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As
increasingly stringent emission standards for both off road and stationary diesel
engines continue to be phased in over the next number of years, we expect
insulation will continue to play a significant role in the various emission
reduction solutions.
Can I touch it? - Insulation surface temperatures
We are
often asked how hot the outer surface of an insulation blanket gets, and
whether it is touch-safe.
To properly answer this question, it is important to
remember that metals conduct heat; fabrics do not. This means that a fabric
surface can be "hotter" temperature-wise than a metal surface and
still be touch-safe. However, until 1998, there was no formal differentiation
made between metal and other types of surfaces. For both, 140ºF [60ºC] was
the accepted standard.
The UL2200 Specification for Stationary Engine Generator
Assemblies, issued in September 1998, was the first authority to actually
quantify acceptable temperatures.
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UL2200 Specification for Stationary Engine Generator
Assemblies
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Contact Surface
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Metallic
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Nonmetallic
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Handles or knobs grasped for holding
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50° C
(122° F)
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60° C
(140° F)
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Handles or knobs that are contacted but do not involve
holding; other surfaces subject to contact and user maintenance
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60° C
(140° F)
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85° C
(185° F)
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Surfaces subject to casual contact
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70° C
(158° F)
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95° C
(203° F)
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As
you can see from the above table, non-metallic surfaces, such as standard
insulation blankets, can reach temperatures as high as 95° C (203° F) and still be considered safe
for casual contact.
Although
space considerations will sometimes limit the thickness of an insulation
blanket, and thus allow for a higher than desired outer surface temperature,
in general, all our industrial insulation blankets are designed to be
touch-safe.
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