[Federal Register Volume 61, Number 193 (Thursday, October 3, 1996)]
[Notices]
[Pages 51708-51712]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-25314]
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DEPARTMENT OF HEALTH AND HUMAN SERVICES
National Institute for Occupational Safety and Health; Draft
Document ``Engineering Control Guidelines for Hot Mix Asphalt Pavers''
AGENCY: National Institute for Occupational Safety and Health (NIOSH),
Centers for Disease Control
[[Page 51709]]
and Prevention (CDC), Department of Health and Human Services.
ACTION: Request for comments.
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SUMMARY: NIOSH is seeking public comments on the draft document
``Engineering Control Guidelines for Hot Mix Asphalt Pavers'' provided
in this announcement.
DATES: Written comments to this notice should be submitted to Diane
Manning, NIOSH Docket Office, 4676 Columbia Parkway, Mailstop C-34,
Cincinnati, Ohio 45226. Comments must be received on or before November
4, 1996.
Comments may also be submitted by email to: [email protected]
NIOSDT1.em.cdc.gov. as WordPerfect 5.0, 5.1/5.2, 6.0/6.1, or ASCII
files.
FOR FURTHER INFORMATION CONTACT: Technical information may be obtained
from Joann Wess or Ralph Zumwalde, NIOSH, CDC, 4676 Columbia Parkway,
M/S C-32, Cincinnati, Ohio 45226, telephone (513) 533-8319.
SUPPLEMENTARY INFORMATION: The following is the complete text of the
draft document for public comment ``Engineering Control Guidelines for
Hot Mix Asphalt Pavers''.
Background
On July 8-9, 1996, NIOSH convened a public meeting in Cincinnati,
Ohio, to discuss the scientific and technical issues relevant to the
development of recommendations for controlling exposures to asphalt
fume during asphalt paving operations. Representatives from labor,
industry, and government knowledgeable of current control technologies
for asphalt exposure met to discuss the types of remedial action (e.g.,
engineering controls, work practices) needed to reduce worker
exposures. Participants at this meeting included representatives from
the Asphalt Institute (AI), the Federal Highway Administration (FHWA),
the International Union of Operating Engineers, the Laborers' Health
and Safety Fund, the National Asphalt Pavement Association (NAPA), the
Occupational Safety and Health Administration (OSHA), manufacturers of
hot mix asphalt (HMA) pavers, and asphalt paving contractors.
The participants provided detailed information on state-of-the-art
engineering controls currently in use and discussed a draft document on
guidelines for engineering controls in the asphalt paving industry that
was prepared jointly by labor and industry. The draft guidelines
provided in this announcement represent a recommendation of the
participants to minimize asphalt fume exposures by developing and
installing engineering controls on asphalt pavers and by providing
training for workers.
Purpose
The purpose of the document ``Engineering Control Guidelines for
Hot Mix Asphalt Pavers'' is to provide information on the use of
engineering controls for the reduction of worker exposure to asphalt
fumes during hot mix asphalt (HMA) paving operations. NIOSH is
soliciting public comments on the completeness and feasibility of the
recommendations.
Document for Comment
Engineering Control Guidelines for Hot Mix Asphalt Pavers
On July 8-9, 1996, the National Institute for Occupational Safety
and Health (NIOSH) convened a public meeting in Cincinnati, Ohio, to
discuss recommendations for controlling exposures to asphalt fume
during asphalt paving operations. Participants at the meeting included
representatives from the Asphalt Institute (AI), the Federal Highway
Administration (FHWA), the International Union of Operating Engineers,
the Laborers' Health and Safety Fund, the National Asphalt Pavement
Association (NAPA), the Occupational Safety and Health Administration
(OSHA), manufacturers of hot mix asphalt (HMA) pavers, and asphalt
paving contractors. This meeting culminated in the development of these
guidelines that provide information about the use of engineering
controls (i.e., local exhaust ventilation systems) to reduce worker
exposures to asphalt fumes during HMA paving operations.
1. New HMA Pavers
a. Paver manufacturers should develop and install ventilation
systems with controlled indoor-capture efficiencies of at least 80% (as
determined by the tracer gas method described in Appendix A) on the
following equipment:
All new self-propelled HMA pavers weighing 16,000 pounds
or more and manufactured after July 1, 1997.
All new self-propelled HMA pavers weighing less than
16,000 pounds with slat conveyors or with augers detached from the
hoppers and manufactured after July 1, 1998.
b. Paver manufacturers should test the ventilation systems for all
HMA paver models and certify that the systems meet the minimum capture
efficiency of 80% as specified in Section 1.a. To assure performance of
the ventilation systems, manufacturers should install an indicator
device on each HMA paver to monitor the system flow rate. Each HMA
paver manufacturer shall provide a plate attached to the paver that
shows:
schematic of the ventilation system;
acceptable operating range for the indicator device; and
list of operator maintenance procedures.
c. Manufacturers should develop and implement quality control plans
to ensure that ventilation systems on these models comply with the
minimum capture efficiency specified in Section 1.a.
2. Existing HMA Pavers
By July 1, 1998, paver manufacturers should make retrofit packages
available for all self-propelled HMA pavers weighing 16,000 pounds or
more and manufactured after July 1, 1987. These retrofit packages
should be installed by July 1, 1999. Retrofit packages for self-
propelled pavers weighing less than 16,000 pounds with slat conveyors
or augers detached from the hopper should be available by July 1, 1999,
and should be installed by July 1, 2000. Manufacturers should test and
certify that all retrofit packages installed according to the
manufacturer's instructions meet the minimum capture efficiency of 80%
for a specific model or equivalent class design configuration (as
determined by the tracer gas method described in Appendix A). To assure
system performance, manufacturers should include in the retrofit
package an indicator device to monitor the system flow rate.
3. Inspection and Maintenance
Owners of HMA pavers with ventilation systems should inspect and
maintain the systems according to the manufacturer's recommendations.
Each manufacturer should provide an operator manual containing detailed
sketches and performance criteria for contractors to use in their
annual assessment of ventilation systems. Annual performance
inspections should be recorded in the operator's manual.
4. Training Program
The National Asphalt Pavement Association (NAPA), unions, and
equipment manufacturers should develop specific training criteria/
materials (i.e., separate document) on the operation, maintenance, and
repair of HMA pavers.
5. Glossary of Terms
Asphalt Paver: A self-propelled construction machine (either
rubber-tired or crawler-mounted) specifically designed to receive,
convey, distribute,
[[Page 51710]]
profile, and compact paving material by the free-floating screed
method.
Auger: A screw conveyor used to transversely distribute paving
material ahead of the screed.
Automatic Feeder Control: A system for automatically controlling
the flow of paving material to the screed.
Conveyor: A device for transferring paving material from the hopper
to the auger.
Conveyor Flow Gate: A device for regulating the height of paving
material being transferred by the conveyor.
Feeder System: The combined conveyor and auger components which
transfer paving material from the hopper and distribute it in front of
the screed.
Hopper: That section of the paver which receives the paving
material from an external source.
Material Feed Sensor: A device used to detect a quantity of paving
material in front of the screed.
Operator: The person whose primary function is to control the
paver's speed and direction.
Screed: The device which is towed behind the tractor to strike off,
compact, contour, and smooth the paving material.
Screed Arm: The attachment by which the screed is connected to and
towed by the tractor.
Screed End Plate: A vertically adjustable plate at the outboard end
of the screed, to retain the paving material and form the edge of the
mat.
Screed Extension: A fixed or adjustable attachment to the screed
for paving at widths greater than the main screed.
Tow Point: The point at which the screed arm is attached to the
tractor.
Tractor: That portion of a paver which provides propulsion and may
also receive, convey, and distribute paving material.
Tunnel: The passageway through which paving material moves from the
hopper to the auger/screed.
Appendix A
Laboratory/Factory Test Procedure
Engineering controls (i.e., ventilation systems) for HMA pavers
will be evaluated in a laboratory setting (i.e., manufacturers' plant,
shop, or warehouse) in which ventilation control efficiency will be
measured using smoke and tracer gas tests. The smoke test will be used
as a qualitative test to visualize airflow patterns around the paver
and ventilation system, and to ensure appropriate testing conditions
for conducting the tracer gas tests. The tracer gas test will be used
to quantitatively measure the volumetric airflow rate and capture
efficiency of the ventilation system.
Ventilation systems will be evaluated in a large bay area at the
manufacturing plant or testing shop. The paver will be parked with the
screed and rear half of the tractor positioned in the bay area
(referred to as the testing area) and with the front half of the
tractor and engine exhaust ducts positioned outside the building. An
overhead garage door or other barrier can be used to separate the two
areas. A garage door can be lowered to rest on top of the tractor, and
the remaining doorway openings around the tractor can be sealed to
isolate the paver's front and rear halves. The screed will rest on the
ground with edger plates extended one foot on each side of the screed.
The flow gates at the back of the hopper should be closed as far as
possible and the remaining tunnel opening should be blocked off. During
the performance evaluations the idle speed for the paver, which can
affect the exhaust rate of the ventilation system, will be set near the
typical revolutions per minute (rpm) that are maintained during normal
paving operations.
Safety
Following are safety precautions for each test:
Handle smoke generating equipment that can be hot with
appropriate caution.
Make sure that the smoke generators do not set off fire
sprinklers or create a false alarm.
Avoid direct inhalation of smoke from the smoke generators
because the smoke may act as an irritant.
Transport, handle, and store all compressed gas cylinders
in accordance with the safety recommendations of the Compressed Gas
Association.
Store the compressed cylinder outdoors or in a well-
ventilated area.
Stand back and let the tank pressure come to equilibrium
with the ambient environment if a regulator malfunctions or some other
major accidental release occurs.
Smoke Test
A smoke generator is used to produce theatrical smoke as a
surrogate contaminant. The smoke is released through a perforated
distribution tube traversing the width of the auger area between the
tractor and the screed and supported above the ground under the augers.
The smoke test helps to identify failures in the integrity of the
barrier separating the front and rear portions of the paver. After
sealing leaks within this barrier, smoke is again released to verify
the integrity of the barrier system, to identify airflow patterns
within the test area, and to visually observe the ventilation system's
performance.
The sequence of a typical smoke test is outlined below:
Position paving equipment within door opening and lower
the overhead door.
Seal the remaining door opening around the tractor.
Place the smoke distribution tube directly underneath the
auger.
Connect the smoke generator to the distribution tube (PVC
pipe, 2-inch diameter, 10 feet long, capped on one end, \1/4\-inch
diameter holes every 6 inches on-center).
Activate video camera if a record is desired.
Activate the ventilation system and the smoke generator.
Inspect the separating barrier for integrity failures and
correct as required.
Inspect the ventilation system for unintended leaks.
De-activate the ventilation system for comparison
purposes.
De-activate the smoke generator and wait for smoke levels
to subside.
Disassemble test equipment.
Tracer Gas
The tracer gas test is designed to: (1) calculate the total
volumetric exhaust flow of the prototype design; and (2) evaluate the
effectiveness in capturing and controlling a surrogate contaminant
under the ``controlled'' indoor conditions. Sulfur hexafluoride
(SF6) will be used as the surrogate contaminant. A real-time
SF6 detector should be calibrated in the laboratory prior to the
test. There are several methods for calibrating the SF6 detector.
The least labor-intensive method requires the use of multiple
compressed gas cylinders with known concentrations of SF6. The
SF6 concentrations should include at least four concentrations
ranging from zero to 50 ppm SF6 in nitrogen. An industrial hygiene
sampling bag such as a 12-liter Milar bag can be filled from
each cylinder, then the bag can be hooked to the detector, and the
response of the detector can be recorded for each concentration.
Another method for calibrating the SF6 detector requires the
use of two compressed gas cylinders, one with pure nitrogen and another
with 50 ppm (or higher concentration) SF6 in nitrogen. Four
different concentrations of SF6 are made by mixing different
volumes of fluid from the two cylinders into sampling bags. The bags
are mixed, hooked to the detector, and the response of the detector is
recorded for each concentration.
[[Page 51711]]
The sampling bags should be clearly marked with the appropriate
concentration of SF6 that each contains. Bags can be reused;
however, they should be emptied prior to reuse and they should only be
filled with approximately the same concentration of SF6. A bag
used to hold 50 ppm SF6 in a previous test should not be used to
hold the 2 ppm SF6 sample in the next test because of the
possibility of residual gas causing an incorrect calibration point.
Using either calibration method or an equivalent method, a
calibration curve, not necessarily a straight line, can then be
calculated to fit the data and convert the detector's response to an
actual SF6 concentration.
To increase the likelihood of independence for each SF6
concentration reading, program the SF6 detector to a minimum
sampling interval of 30 seconds. Larger intervals may be required based
on the model of SF6 detector and the experimental setup.
100% Capture (to quantify exhaust volume): A known volumetric flow
rate (0.90 liters per minute) of SF6 is released into the
ventilation system. The release point must be upstream of the
ventilation system's fan and downstream of the ventilation system's
hood to ensure 100% capture of the released gas. The supply tank of
pure SF6 is connected to the release point via a pressure
regulator, flow controller, and \1/4\-inch tubing.
A \1/4\-inch diameter hole is placed in the ventilation system's
exhaust duct half way between the fan and the outlet of the exhaust
dust. A 12-inch long and \1/4\-inch outside diameter stainless steel
tube (sampling probe) is inserted into this exhaust-duct hole
perpendicular to the exhaust air flow. The sampling probe should be
sealed at the end and have several \1/8\-inch diameter holes, one inch
on-center along one side. The number of holes depends on the diameter
of the exhaust duct. An 8-inch exhaust duct would require use of a
sampling probe with six \1/8\-inch holes. These holes should be
positioned perpendicular to the exhaust air flow and must all be inside
the duct when sampling. The tubing connecting the sampling probe to the
detector should be airtight to ensure that the sample is pulled from
within the exhaust duct and not from the surrounding area. The exhaust
volume is then calculated using the following equation:
where
Q(exh)=volume of air exhausted through the ventilation system (lpm
or cfm) (To convert from liters per minute (lpm) to cubic feet per
minute (cfm), divide lpm by 28.3.)
Q(SF6)=volume of SF6 (lpm or cfm) introduced into the
system
C*(SF6)=Concentration of SF6 (parts per million) detected
in exhaust and the * indicates 100% capture of the released SF6.
If there is more than one ventilation system exhaust duct, then the
above procedure should be repeated for each. Sufficient time should be
allowed between tests for the background readings to drop to below 0.2
ppm SF6. Background readings must be subtracted from the detector
response before calculating the exhaust volume.
To quantify capture efficiency, SF6 is released through a
distribution plenum located under the augers between the tractor and
the screed. A discharge hose feeds pure SF6 at a flow rate of 0.90
lpm from the pressure regulator, through a mass flow controller
(precision rotameter), and into the distribution plenum. Accuracy of
the flow controller will greatly affect the accuracy of the test and
should be #3% or better. The plenum is ten feet long and is designed to
release the SF6 evenly throughout its length. The same multi-port
sampling wand, sampling location, and detector, as used in the 100%
capture test, is also used in this test.
At least five consecutive measurements will be taken and an average
value will be calculated. If the SF6 volumetric flow rate is the
same for both the 100% capture test and capture efficiency test, then
the capture efficiency is calculated using the following equation:
where
=capture efficiency
C(SF6)=Concentration of SF6 (parts per million) detected
in exhaust
C*(SF6)=Concentration of SF6 from 100% capture test
If the SF6 volumetric flow rate is not the same for both the
100% capture test and the capture efficiency test, then the capture
efficiency is calculated using the following:
where C(SF6) and Q(SF6) refer to the values obtained during
the capture efficiency test and Q(exh) was calculated from the 100%
capture test.
A total of four pairs of the 100% capture tests and capture
efficiency tests will be performed with the ventilation system's
overall capture efficiency determined from the average of all four
trials.
Between each test (after a pair of 100% capture test and capture
efficiency test), the paver should be shut down and background SF6
measurements should be monitored to determine if any SF6 had
accumulated in the test area. If SF6 has accumulated (>2.0 ppm),
the integrity of the barrier system should be checked and the test area
should be well ventilated before proceeding. Sufficient time should be
allowed between tests for the background readings to drop to below 0.2
ppm of SF6. Background readings must be subtracted from the
detector response before calculations are made.
The sequence for a typical test run is outlined below:
Position paving equipment and seal openings as outlined
above.
Calibrate (outdoors) flow meters at approximately 0.9 lpm
of SF6.
Drill an access hole in the ventilation system's exhaust
duct for insertion of the detector's sampling probe and position the
sampling probe into the exhaust duct.
With the ventilation system activated, begin monitoring
for SF6 to determine background interference levels.
While maintaining the SF6 tanks outdoors or in a
well-ventilated area, run the discharge tubing from the mass flow meter
to well within the exhaust hood to create 100% capture conditions.
Initiate flow of SF6 through the flow meter and allow
it to reach steady-state (should take only a minute).
Continue monitoring until 5 readings are recorded.
Deactivate the flow of SF6.
Remove the discharge tubing to an outdoor location.
End the 100% capture test. (Leave the tractor engine
running.)
Initiate monitoring to establish background interference
until levels drop to <0.2 ppm.=""> Locate an SF6 distribution plenum under the auger
area and connect the discharge tubing of the flow meter.
Initiate SF6 flow through the mass flow meters and
monitor until approximate steady-state conditions appear (about one
minute) and take at least 5 readings.
Discontinue SF6 flow and quickly remove the
distribution plenum and discharge tubing from the auger area and remove
to an outside location.
Continue monitoring to determine the general area
concentration of SF6 which escaped into the test area.
Discontinue monitoring when concentration decay is
complete.
Turn off the ventilation system and paver engine;
calculate the capture efficiency.
Repeat four times.
Example Test Run and Calculations
The paver was positioned and smoke was used to visually test the
system.
[[Page 51712]]
Smoke was seen coming in the top of the overhead door. The opening in
the overhead door was sealed and the smoke test revealed no other
problems.
For simplicity of example, the SF6 detector was calibrated and
adjusted to read directly SF6 in ppms. The SF6 flow meter was
calibrated using a bubble meter.
------------------------------------------------------------------------
Flow rate,
Trial No. lpm
------------------------------------------------------------------------
1.......................................................... 0.903
2.......................................................... 0.908
3.......................................................... 0.899
4.......................................................... 0.900
------------------------------------------------------------------------
The mean flow rate was ((0.903 + 0.908 + 0.899 + 0.900)/ 4)) 0.903
liters per minute (lpm).
The sampling probe was placed in the exhaust duct of the
ventilation system and background samples were registered by the
detector. The tubing (pure SF6 outlet) from the flow meter was
placed through the hood and into the duct of the ventilation system
(upstream of the fan). Readings were as follows:
------------------------------------------------------------------------
Detector
Task Reading No. reading, ppm
of SF 6
------------------------------------------------------------------------
Background................................... 1 0.0051
2 0.0062
3 0.0048
4 0.0050
5 0.0066
6 0.0062
7 0.0058
Start SF6.................................... 8 6.3
9 22.0
10 21.8
11 21.9
12 21.7
13 21.8
End.......................................... 14 21.9
------------------------------------------------------------------------
At least five consecutive measurements are needed; in this case,
the last six data points were used. The eighth reading (6.3 ppm) does
not reflect steady-state and was not used in determining the average.
The mean concentration of SF6 is 21.85 ppm (the average of those
six points). The mean background value is 0.0057 ppm. These values were
used to calculate the volumetric flow rate from Equation 1.
Q(exh)+0.903 / 28.3 / (21.85-0.0057) * 106 = 1460 cfm.
The average background value, 0.0057 ppm, was subtracted from the
average 100% capture value, 21.85 ppm. In this case, the background
value was negligible.
The same flow meter and SF6 flow rate were used for the
capture efficiency test. The tubing was removed from the ventilation
system hood and connected to the 10-foot distribution plenum. Readings
were as follows:
------------------------------------------------------------------------
Detector
Task Reading No. reading, ppm
SF6
------------------------------------------------------------------------
Background................................... 1 0.092
2 0.084
3 0.078
Start SF 6................................... 4 28.1
5 18.8
6 19.6
7 19.7
8 20.9
9 17.3
10 19.4
11 18.9
12 19.6
------------------------------------------------------------------------
At least five consecutive measurements are needed; in this case,
the last eight will be used. The fourth reading (28.1 ppm) was high; in
this case it reflects the flow controller overshooting the set point
during the startup of SF6 flow, and this point is not used in
determining the average. The mean concentration of SF6 is 19.28
ppm; the average background concentration was 0.0847 ppm.
Because we used the same SF6 flow rate in both the exhaust
volume test and the capture efficiency test, the calculations are
simplified. From Equation 2, the capture efficiency is (19.28-.0847) /
(21.85-0.0057)* 100 = 87.9%.
This procedure was done four times with the following results:
------------------------------------------------------------------------
100% Capture Capture
Trial No. capture, efficiency, efficiency,
ppm SF 6 ppm SF 6 %
------------------------------------------------------------------------
1.................................. 21.84 19.20 87.9
2.................................. 21.67 19.95 92.1
3.................................. 21.74 18.10 83.3
4.................................. 21.93 19.01 86.7
------------------------------------------------------------------------
Statistics
Calculate the overall average of the means:
m = (87.9 + 92.1 + 83.3 + 86.7) / 4 = 87.5%
Calculate the estimated standard deviation:
s={((87.9-87.5)2 + (92.1-87.5)2 + (83.3-87.5)2 + (86.7-87.5)2) /
(4-1)}0.5
={ (0.16 + 21.16 + 17.64 + 0.64) / 3}0.5 = 3.63
If the number of trials, n, is different from 4, then (n-1) is used
in the denominator of this calculation and the numerator is the sum of
all n squared differences, rather than just 4. Choose the number t
(from the Student's t-distribution table at the 95th percentile) from
the following table, based on the value of n:
t: 6.31 (n=2) 2.92 (n=3) 2.35 (n=4)
2.13 (n=5) 2.02 (n=6) 1.94 (n=7)
1.90 (n=8) 1.86 (n=9) 1.83 (n=10)
Calculate a test statistic (T):
T=m-t*s / n0.5
For this example: T = 87.5-2.35 * 3.63 / 40.5 = 83.2.
If T > 80.0, then decide (with 95% confidence) that efficiency is
greater than 80%. In this example, we are 95% confident that the
efficiency is greater than 80%.
If T 80.0, then the conclusion that the efficiency is
greater than 80% cannot be made from these data.
Equipment
Smoke Test
Smoke generator
2 inch x 10 foot Schedule-40 PVC perforated distribution pipe
Tracer Gas Tests
Compressed cylinder of 99.98% SF6 with regulator
Flow controller such as a precision rotameter
\1/8\-inch ID x 20-foot Teflon tubing and snap valves for SF6
distribution
Primary Flow Calibrator
\1/2\-inch ID x 10-foot Copper tubing with \1/32\-inch holes every 12
inches SF6 distribution plenum
Gas monitor calibrated for SF6
Calibration gases, nitrogen and at least one SF6 concentration in
nitrogen
12-liter Mylar gas sampling bags
Ventilation System Evaluation
Air Velocity Meter
Micro manometer w/Pitot Tube
Dated: September 27, 1996.
Linda Rosenstock,
Director, National Institute for Occupational Safety and Health Centers
for Disease Control and Prevention (CDC).
[FR Doc. 96-25314 Filed 10-2-96; 8:45 am]
BILLING CODE 4163-19-P
