vEFA
United States
Environmental Protection
Agency
Office of Radiation Programs
Eastern Environmental
Radiation Facility
1890 Federal Drive
Montgomery, AL 36109
520585032
December 1985
Radiation
DESIGN AND DEVELOPMENT
OF AN AIR SAMPLER
FOR THE
ENVIRONMENTAL
RADIATION AMBIENT
MONITORING SYSTEM
(ERAMS)
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Design and Development of an Air Sampler
for the
Environmental Radiation Ambient Monitoring System (ERAMS)
Billy J. Miller
Eastern Environmental Radiation Facility
1890 Federal Drive
Montgomery, Alabama 36109
U.S. Environmental Protection Agency
Office of Radiation Programs
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The mention of commercial products, their source, or their
use in connection with material reported herein is not to
be construed as either an actual or implied endorsement of
such products by the U.S. Environmental Protection Agency.
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FOREWORD
The Eastern Environmental Radiation Facility (EERF) in Montgomery,
Alabama, is a field installation of the U.S. Environmental Protection
Agency's Office of Radiation Programs. Broadly, the EERF helps solve
environmental radiation problems and provides radiation data of national
concern as directed by the Office of Radiation Programs. More
specifically,, the EERF conducts field studies on particular radiation
problems; operates a national scope emergency response program; provides
technical assistance to State and local health departments, EPA regional
offices, and other Federal agencies; and maintains a complete radiological
laboratory to support these various activities* A growing segment of the
EERF's work is radiation surveillance. Toward this end9 the EERF operates
the Environmental Radiation Ambient Monitoring System (ERAMS) — a
nationwide network of sampling stations monitoring environmental radiation
in air, water, and milko
Charles R. Porter, Director
Eastern Environmental Radiation Facility
m
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Introduction
The U.S. Environmental Protection Agency's Office of Radiation
Programs operates., through its Eastern Environmental Radiation Facility
(EERF) in Montgomery, Alabama, a national network of stations that monitor
levels of environmental radioactivity. This network, called the
Environmental Radiation Ambient Monitoring System (ERAMS), was formed in
1973 from a group of separate networks that had been established some
years earlier to monitor fallout from above-ground nuclear weapons testing.
A principal task of the ERAMS program is to determine radioactivity
in airborne participates. This is done through a network of continuously
operating air monitoring stations in 67 cities throughout the United
States (see Figure 1). The EERF provides the air sampling equipment and
supplies for each of the stations, which are usually operated by
volunteers from state or local health departments. Particulate filters on
the air samplers are changed twice weekly, and, after an initial field
estimate of radioactivity, are sent to the EERF for detailed radiological
analyses.
The air samplers used in the ERAMS network must operate continuously
for several years. Limited availability of parts, escalating purchase and
operating costs, and several features of the pump used by ERAMS for many
years dictated that the ERAMS air sampler be replaced. This paper
describes the replacement air sampler and its advantages over the one
previously used.
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Fig. 1. ERAMS air monitoring stations
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Limitations of Previous Samplers
Over the many years of operation, most stations have been equipped
with positive displacement air samplers that used rotating lobe pumps (see
Figure 2) driven by a 1.5 horsepower motor, a combination that proved to
be very durable and dependable. The samplers typically operated for 3-5
years or longer with no maintenance except for a routine change of
lubricating oil in the pump. The samplers would move 30 to 40 cubic feet
per minute (CFM) of air through the 4 inch diameter filters used in the
ERAMS network, thus affording large sample volume. The samplers run most
efficiently on 220 volts, and the EERF recommends this if possible.
The current replacement cost for these samplers is $1,200 for parts
plus about 12 man-hours of assembly. The pump can be rebuilt by the
manufacturer for an average cost of $450 plus shipping to the factory and
return.
Even though the samplers are durable and dependable, the initial cost
and repair cost continue to escalate. The weight of the systems, 325
pounds, often makes it difficult to get the samplers to their operating
locations, which, at some stations, is on the roof of a building, thus
requiring rental of a crane. Preference for 220 volts power often
necessitates running special power services. Also, annual power costs to
operate the 1.5 horsepower motor amounts to $963.00 at $.065 per kilowatt
hour of electricity. At some locations, noise from the pumps was
objectionable, measuring 85^ dB at 3 feet from the pump during operation.
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2. Air partTculate pump and motor assembly
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The problems noted above and the lack of a suitable commerically
available replacement Ted to the development of the replacement air
sampler. The new air sampler had to meet the following requirements:
--capable of moving 20-40 cfm of air through a 4 inch diameter filter
-capable of operating 3-5 years with little or no maintenance
-low power consumption to reduce operating cost
-low initial purchase and replacement cost
-ease of operator use, safe
-lightweight for low shipping cost and ease of placement into
operating location
-durable, weatherproof enclosure
-quiet operation
The new sampler assembled for the ERAMS network meets these
requirements. The air mover in the new sampler, which is available from
Lamb Electric Motor Division of Arntek, Incorporated, is a seven stage,
dynamically balanced, centrifugal blower driven by a 120 volt, 60 Hz
motor. The centrifugal design blower has a minimum of moving parts -- no
pistons, lobes, valves, etc., to wear out. The unit is operated in the
vacuum mode and is capable of providing 24 inches water lift at 0 cfm flow.
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The centrifugal design blower is driven by a fractional horsepower
motor that draws only about 2 amperes current at 120 volts AC while
operating in the normal configuration used in the ERAMS samplers. Annual
cost for electricity to operate the unit is 3145.00 at $.065 per kilowatt
hour, compared to $963.00 annually to operate the previously used pump.
The small motor and centrifugal design also reduce operating noise, 6£ dB
at 3 feet compared to 85_ dB at 3 feet for the previously used sampler.
Unlike some of the high volume samplers used by ERAMS in the past,
the Amtek motor uses no brushes, which results in extended operating life
for the units. According to Amtek, life of the blower is usually limited
by deterioration of the bearings supporting the fan shaft. Since heat
build-up contributes to this deterioration, a special air deflector and a
cooling fan were installed on each sampler to reduce operating temperature
and provide extended operating lifetime. The first samplers built for the
network have been in use since May 1, 1983 without a failure. We expect
the units to meet our design criteria of 3-5 years normal operating
lifetime.
For air particulate sampling, the ERAMS network uses a 4-inch
diameter filter mounted in a sampling head designed and built at the
EERF. With this filter and sampling head the blower draws 27 to 31 cfm of
air through the filter, a volume suitable for collecting the desired
sample. Filters are routinely changed twice weekly, except when the
network is in alert status and filters are changed daily.
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The enclosure for the blower and the air sampling head is durable,
lightweight, and weather resistant. Extensive louvers and a
*
thermostatically controlled fan cool the pump. One complete side of the
enclosure is hinged as a door for easy removal and replacement of the
blower unit. The entire blower unit is mounted on a "slide-out" tray for
blower replacement in the field. All electrical connections are plug-in
and the blower connects to the sampling head through a flexible rubber
hose attached with automotive type hose clamps. A defective blower may be
replaced in the field by non-technical personnel in about 15 minutes using
only a screw driver and a 7/16" wrench. All electrical connections in the
unit are enclosed in a utility box and meet electrical safety codes. The
enclosures are made of aluminum to provide long-term durability with no
maintenance and minimum weight. A complete unit weighs about 60 pounds.
Initial installation requires only that the unit be placed at the desired
location and plugged into any 120 VAC outlet. No special wiring is
required. It is desirable in some locations to bolt the sampler legs to a
stable surface to present tipping over by high winds. The sampler should
be mounted in a near vertical position to allow maximum accuracy of the
magnehelic gauge attached to the enclosure door. A photograph of an
assembled sampler is shown in Figure 3.
Costs of producing and maintaining the described samplers are much
lower than those of the previously used samplers. The blower assemblies
cost about $350.00 each and the enclosures 2250.00 each. Other small
parts cost about $50.00 plus 8 man-hours each for assembly. Because of
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Fig. 3. Air participate blower-motor assembly
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the lighter weight of the new blower shipping costs are greatly reduced,
For example, to ship one of the new blowers to the ERAMS operator at
Columbus, Ohio, costs $48.00, compared to $118=00 for shipping one of the
previously used heavier pumps to the same location. Should one of the new
blowers fail at the sampling station in Columbuss Ohio, it is necessary to
ship only a replacement blower assembly. The replacement blower costs
$350.00 plus $8.00 shipping, a considerable savings compared to rebuilding
the previously used samplers.
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Summary
The newly designed air sampler for the ERAMS network meets all the
desired design characteristics. Units have been in use at some ERAMS
stations for more than two years and have operated satisfactorily. No
samples have been lost due to inoperative samplers. Sampling air flow
rates are adequate to collect the desired sample volume.
Purchase cost, operating costs, and repair costs are greatly reduced
compared to the previously used samplerso The small physical size and
light weight result in a unit which is inexpensive and easy to ship and to
get into the operating location. Operating life of the blower is adequate
to minimize the inconvenience and cost associated with frequent
replacement. Ease of operator use and low operating noise result in a
unit that has been readily accepted by the station operators.
Additional details of the sampler may be obtained by contacting the
Eastern Environmental Radiation Facility at 1890 Federal Drive,
Montgomery, Alabama, 36109 or telephone (205)272-3402.
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