1.0
Scope and
Application
1.1 Analytes : CAS
No.
Volatile Organic Compounds (VOC) : No CAS number
assigned.
1.2
Scope. This method is applicable for
the determination of VOC leaks from process equipment. These sources include,
but are not limited to, valves, flanges and other connections, pumps and
compressors, pressure relief devices, process drains, open-ended valves, pump
and compressor seal system degassing vents, accumulator vessel vents, agitator
seals, and access door seals.
1.3 Data Quality Objectives. Adherence
to the requirements of this method will enhance the quality of the data obtained
from air pollutant sampling methods.
2.0
Summary of Method
2.1 A portable
instrument is used to detect VOC leaks from individual sources. The instrument
detector type is not specified, but it must meet the specifications and
performance criteria contained in Section 6.0. A leak definition concentration
based on a reference compound is specified in each applicable regulation. This
method is intended to locate and classify leaks only, and is not to be used as a
direct measure of mass emission rate from individual sources.
3.0
Definitions
3.1 Calibration gas means the VOC compound used to adjust the instrument meter reading to a known value. The calibration gas is usually the reference compound at a known concentration approximately equal to the leak definition concentration.
3.2 Calibration
precision means the degree of agreement between measurements of the same known
value, expressed as the relative percentage of the average difference between
the meter readings and the known concentration to the known
concentration.
3.3 Leak definition
concentration means the local VOC concentration at the surface of a leak source
that indicates that a VOC emission (leak) is present. The leak definition is an
instrument meter reading based on a reference compound.
3.4 No detectable
emission means a local VOC concentration at the surface of a leak source,
adjusted for local VOC ambient concentration, that is less than 2.5 percent of
the specified leak definition concentration. that indicates that a VOC emission
(leak) is not present.
3.5 Reference
compound means the VOC species selected as the instrument calibration basis for
specification of the leak definition concentration. (For example, if a leak
definition concentration is 10,000 ppm as methane, then any source emission that
results in a local concentration that yields a meter reading of 10,000 on an
instrument meter calibrated with methane would be classified as a leak. In this
example, the leak definition concentration is 10,000 ppm and the reference
compound is methane.)
3.6 Response factor
means the ratio of the known concentration of a VOC compound to the observed
meter reading when measured using an instrument calibrated with the reference
compound specified in the applicable regulation.
3.7 Response time
means the time interval from a step change in VOC concentration at the input of
the sampling system to the time at which 90 percent of the corresponding final
value is reached as displayed on the instrument readout meter.
4.0 Interferences.
[Reserved]
5.0 Safety
5.1 Disclaimer. This
method may involve hazardous materials, operations, and equipment. This test
method may not address all of the safety problems associated with its use. It is
the responsibility of the user of this test method to establish appropriate
safety and health practices and determine the applicability of regulatory
limitations prior to performing this test method.
5.2 Hazardous
Pollutants. Several of the compounds, leaks of which may be determined by this
method, may be irritating or corrosive to tissues (e.g., heptane) or may be
toxic (e.g., benzene, methyl alcohol). Nearly all are fire hazards. Compounds in
emissions should be determined through familiarity with the source. Appropriate
precautions can be found in reference documents, such as reference No. 4 in
Section 16.0.
6.0 Equipment and
Supplies
A VOC monitoring instrument meeting
the following specifications is required:
6.1 The VOC
instrument detector shall respond to the compounds being processed. Detector
types that may meet this requirement include, but are not limited to, catalytic
oxidation, flame ionization, infrared absorption, and photoionization.
6.2 The instrument
shall be capable of measuring the leak definition concentration specified in the
regulation.
6.3 The scale of the
instrument meter shall be readable to ±2.5 percent of the specified leak
definition concentration.
6.4 The instrument
shall be equipped with an electrically driven pump to ensure that a sample is
provided to the detector at a constant flow rate. The nominal sample flow rate,
as measured at the sample probe tip, shall be 0.10 to 3.0 l/min (0.004 to 0.1 ft
3/min) when the probe is fitted with a glass wool plug or filter that may be
used to prevent plugging of the instrument.
6.5 The instrument shall be equipped with a
probe or probe extension or sampling not to exceed 6.4 mm (1/4 in) in outside
diameter, with a single end opening for admission of sample.
6.6 The instrument
shall be intrinsically safe for operation in explosive atmospheres as defined by
the National Electrical Code by the National Fire Prevention Association or
other applicable regulatory code for operation in any explosive atmospheres that
may be encountered in its use. The instrument shall, at a minimum, be
intrinsically safe for Class 1, Division 1 conditions, and/or Class 2, Division
1 conditions, as appropriate, as defined by the example code. The instrument
shall not be operated with any safety device, such as an exhaust flame arrestor,
removed.
7.0 Reagents and Standards
7.1 Two gas mixtures
are required for instrument calibration and performance evaluation:
7.1.1 Zero Gas. Air,
less than 10 parts per million by volume (ppmv) VOC.
7.1.2 Calibration Gas.
For each organic species that is to be measured during individual source
surveys, obtain or prepare a known standard in air at a concentration
approximately equal to the applicable leak definition specified in the
regulation.
7.2 Cylinder Gases.
If cylinder calibration gas mixtures are used, they must be analyzed and
certified by the manufacturer to be within 2 percent accuracy, and a shelf life
must be specified. Cylinder standards must be either reanalyzed or replaced at
the end of the specified shelf life.
7.3 Prepared Gases.
Calibration gases may be prepared by the user according to any accepted gaseous
preparation procedure that will yield a mixture accurate to within 2 percent.
Prepared standards must be replaced each day of use unless it is demonstrated
that degradation does not occur during storage.
7.4 Mixtures with
non-Reference Compound Gases. Calibrations may be performed using a compound
other than the reference compound. In this case, a conversion factor must be
determined for the alternative compound such that the resulting meter readings
during source surveys can be converted to reference compound
results.
8.0 Sample
Collection, Preservation, Storage, and Transport
8.1 Instrument
Performance Evaluation. Assemble and start up the instrument according to the
manufacturer's instructions for recommended warmup period and preliminary
adjustments.
8.1.1 Response Factor.
A response factor must be determined for each compound that is to be measured,
either by testing or from reference sources. The response factor tests are
required before placing the analyzer into service, but do not have to be
repeated at subsequent intervals.
8.1.1.1 Calibrate the
instrument with the reference compound as specified in the applicable
regulation. Introduce the calibration gas mixture to the analyzer and record the
observed meter reading. Introduce zero gas until a stable reading is obtained.
Make a total of three measurements by alternating between the calibration gas
and zero gas. Calculate the response factor for each repetition and the average
response factor.
8.1.1.2 The instrument
response factors for each of the individual VOC to be measured shall be less
than 10 unless otherwise specified in the applicable regulation. When no
instrument is available that meets this specification when calibrated with the
reference VOC specified in the applicable regulation, the available instrument
may be calibrated with one of the VOC to be measured, or any other VOC, so long
as the instrument then has a response factor of less than 10 for each of the
individual VOC to be measured.
8.1.1.3 Alternatively,
if response factors have been published for the compounds of interest for the
instrument or detector type, the response factor determination is not required,
and existing results may be referenced. Examples of published response factors
for flame ionization and catalytic oxidation detectors are included in
References 1-3 of Section 17.0.
8.1.2 Calibration
Precision. The calibration precision test must be completed prior to placing the
analyzer into service and at subsequent 3-month intervals or at the next use,
whichever is later.
8.1.2.1 Make a total of
three measurements by alternately using zero gas and the specified calibration
gas. Record the meter readings. Calculate the average algebraic difference
between the meter readings and the known value. Divide this average difference
by the known calibration value and multiply by 100 to express the resulting
calibration precision as a percentage.
8.1.2.2 The calibration
precision shall be equal to or less than 10 percent of the calibration gas
value.
8.1.3 Response Time.
The response time test is required before placing the instrument into service.
If a modification to the sample pumping system or flow configuration is made
that would change the response time, a new test is required before further use.
8.1.3.1 Introduce zero
gas into the instrument sample probe. When the meter reading has stabilized,
switch quickly to the specified calibration gas. After switching, measure the
time required to attain 90 percent of the final stable reading. Perform this
test sequence three times and record the results. Calculate the average response
time.
8.1.3.2 The instrument
response time shall be equal to or less than 30 seconds. The instrument pump,
dilution probe (if any), sample probe, and probe filter that will be used during
testing shall all be in place during the response time determination.
8.2 Instrument
Calibration. Calibrate the VOC monitoring instrument according to Section 10.0.
8.3 Individual
Source Surveys.
8.3.1 Type I -- Leak
Definition Based on Concentration. Place the probe inlet at the surface of the
component interface where leakage could occur. Move the probe along the
interface periphery while observing the instrument readout. If an increased
meter reading is observed, slowly sample the interface where leakage is
indicated until the maximum meter reading is obtained. Leave the probe inlet at
this maximum reading location for approximately two times the instrument
response time. If the maximum observed meter reading is greater than the leak
definition in the applicable regulation, record and report the results as
specified in the regulation reporting requirements. Examples of the application
of this general technique to specific equipment types are:
8.3.1.1 Valves. The most
common source of leaks from valves is the seal between the stem and housing.
Place the probe at the interface where the stem exits the packing gland and
sample the stem circumference. Also, place the probe at the interface of the
packing gland take-up flange seat and sample the periphery. In addition, survey
valve housings of multipart assembly at the surface of all interfaces where a
leak could occur.
8.3.1.2 Flanges and
Other Connections. For welded flanges, place the probe at the outer edge of the
flange-gasket interface and sample the circumference of the flange. Sample other
types of nonpermanent joints (such as threaded connections) with a similar
traverse.
8.3.1.3 Pumps and
Compressors. Conduct a circumferential traverse at the outer surface of the pump
or compressor shaft and seal interface. If the source is a rotating shaft,
position the probe inlet within 1 cm of the shaft-seal interface for the survey.
If the housing configuration prevents a complete traverse of the shaft
periphery, sample all accessible portions. Sample all other joints on the pump
or compressor housing where leakage could occur.
8.3.1.4 Pressure Relief Devices. The
configuration of most pressure relief devices prevents sampling at the sealing
seat interface. For those devices equipped with an enclosed extension, or horn,
place the probe inlet at approximately the center of the exhaust area to the
atmosphere.
8.3.1.5 Process Drains.
For open drains, place the probe inlet at approximately the center of the area
open to the atmosphere. For covered drains, place the probe at the surface of
the cover interface and conduct a peripheral traverse.
8.3.1.6 Open-ended Lines
or Valves. Place the probe inlet at approximately the center of the opening to
the atmosphere.
8.3.1.7 Seal System
Degassing Vents and Accumulator Vents. Place the probe inlet at approximately
the center of the opening to the atmosphere.
8.3.1.8 Access door
seals. Place the probe inlet at the surface of the door seal interface and
conduct a peripheral traverse.
8.3.2 Type II -- "No Detectable Emission". Determine the local ambient VOC concentration around the source by moving the probe randomly upwind and downwind at a distance of one to two meters from the source. If an interference exists with this determination due to a nearby emission or leak, the local ambient concentration may be determined at distances closer to the source, but in no case shall the distance be less than 25 centimeters. Then move the probe inlet to the surface of the source and determine the concentration as outlined in Section 8.3.1. The difference between these concentrations determines whether there are no detectable emissions. Record and report the results as specified by the regulation. For those cases where the regulation requires a specific device installation, or that specified vents be ducted or piped to a control device, the existence of these conditions shall be visually confirmed. When the regulation also requires that no detectable emissions exist, visual observations and sampling surveys are required. Examples of this technique are:
8.3.2.1 Pump or
Compressor Seals. If applicable, determine the type of shaft seal. Perform a
survey of the local area ambient VOC concentration and determine if detectable
emissions exist as described in Section 8.3.2.
8.3.2.2 Seal System
Degassing Vents, Accumulator Vessel Vents, Pressure Relief Devices. If
applicable, observe whether or not the applicable ducting or piping exists.
Also, determine if any sources exist in the ducting or piping where emissions
could occur upstream of the control device. If the required ducting or piping
exists and there are no sources where the emissions could be vented to the
atmosphere upstream of the control device, then it is presumed that no
detectable emissions are present. If there are sources in the ducting or piping
where emissions could be vented or sources where leaks could occur, the sampling
surveys described in Section 8.3.2 shall be used to determine if detectable
emissions exist.
8.3.3 Alternative
Screening Procedure.
8.3.3.1 A screening
procedure based on the formation of bubbles in a soap solution that is sprayed
on a potential leak source may be used for those sources that do not have
continuously moving parts, that do not have surface temperatures greater than
the boiling point or less than the freezing point of the soap solution, that do
not have open areas to the atmosphere that the soap solution cannot bridge, or
that do not exhibit evidence of liquid leakage. Sources that have these
conditions present must be surveyed using the instrument technique of Section
8.3.1 or 8.3.2.
8.3.3.2 Spray a soap solution over all
potential leak sources. The soap solution may be a commercially available leak
detection solution or may be prepared using concentrated detergent and water. A
pressure sprayer or squeeze bottle may be used to dispense the solution. Observe
the potential leak sites to determine if any bubbles are formed. If no bubbles
are observed, the source is presumed to have no detectable emissions or leaks as
applicable. If any bubbles are observed, the instrument techniques of Section
8.3.1 or 8.3.2 shall be used to determine if a leak exists, or if the source has
detectable emissions, as applicable.
9.0 Quality
Control
Section : Quality control measure : Effect8.1.2 : Instrument calibration precision check : Ensure precision and accuracy, respectively, of instrument response to standard10.0 : Instrument calibration
10.1 Calibrate
the VOC monitoring instrument as follows. After the appropriate warmup period
and zero internal calibration procedure, introduce the calibration gas into the
instrument sample probe. Adjust the instrument meter readout to correspond to
the calibration gas value.
Note: If the meter readout cannot be adjusted to the proper value,
a malfunction of the analyzer is indicated and corrective actions are necessary
before use.
15.0
Waste Management.
[Reserved]
16.0
References.
1. Dubose, D.A., and G.E. Harris. Response Factors of VOC Analyzers at a
Meter Reading of 10,000 ppmv for Selected Organic Compounds. U.S. Environmental Protection Agency,
Research Triangle Park, NC.
Publication No. EPA 600/2-81051. September 1981.
2. Brown, G.E., et al. Response Factors of VOC Analyzers
Calibrated with Methane for Selected Organic Compounds. U.S. Environmental Protection Agency,
Research Triangle Park, NC.
Publication No. EPA 600/2-81-022.
May 1981.
3. DuBose, D.A. et al. Response of Portable VOC Analyzers to
Chemical Mixtures. U.S.
Environmental Protection Agency, Research Triangle Park, NC. Publication No. EPA 600/2-81-110. September 1981.
4. Handbook of Hazardous Materials: Fire, Safety, Health. Alliance of American Insurers. Schaumberg, IL. 1983.
17.0
Tables, Diagrams, Flowcharts, and Validation Data.
[Reserved]