APPENDIX C
METHODOLOGY
Optical Gas Imaging
TARGET specializes in the use of infrared thermal imaging to locate hydrocarbon gas
emissions. TARGET assessment teams utilize the FLIR® GF320 thermal imaging video
cameras as a primary emission detection tool.
The benefits of thermal leak imaging include the ability to:
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Cost-effectively scan hundreds of components simultaneously;
Identify exact source of leaks in real-time;
Provide direct access with a portable, battery-powered camera;
Performed assessments without interruption of operations;
Scan hard-to-reach components from a distance; and
Provide video recordings of emission sources.
Emission Quantification
The Hi Flow® Sampler is the primary method of emission measurement from leaking and
venting equipment components. This technology is extremely reliable, efficient, and
offers a high rate of accuracy (+/- 10%). This technology allows an objective cost-benefit
analysis of each leak repair opportunity.
There are specific cases where the Hi Flow is not used. These cases include emissions
at rates above the upper detection limit of the unit (i.e. above 10ft3/min), equipment in
inaccessible locations and emissions with high H2S content. In these cases, emission
rates are measured using an appropriate flow-through measurement device (depending
on backpressure tolerance of the source) such as:
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an acoustic detector;
a vane anemometer; or
a calibrated volume bag.
Internal Valve Leakage
TARGET utilizes acoustic leak detection to detect internal through-valve leakage. The
VPAC™ system estimates through-valve leakage based on measurements together with
data on valve size, type, and differential pressure.
This technology is sometimes used as a backup when conventional measurement
technology (Hi-Flow Sampler, calibrated bag, anemometer etc.) cannot be used. For
example, a blow down vent line may be inaccessible due to location or size of the vent.
The VPAC may also be used to determine which valve may be causing a transmission
tank emission.
3.4
Methodology
TARGET has developed a standard assessment protocols for undertaking fugitive
assessment surveys.
The following sections outline some of the methodologies and procedures used.
Optical Gas Imaging (OGI) Protocol
Optical infrared leak detection protocol generally consists of the following sequence of
tasks:
1. HAZARD ASSESSMENT - The first step in any assessment entails a thorough
hazard assessment of the task and surrounding environment and conditions. A
site-specific hazard safety assessment and safety review is completed prior to
undertaking any fugitive emission assessment activities. If at any point during an
assessment a safety hazard is identified that may affect the health and safety of
the Fugitive Emission Assessment Team, work will be stopped, the safe work
permit issuer will be informed and a hazard assessment will be performed with the
necessary personnel. The work will only continue after the hazards have been
assessed and adequately mitigated.
2. SURVEY PLAN - Prior to conducting an assessment, the Assessment Team will
consult with Operations Staff and review any accompanying drawings/site maps
to determine the order at which each unit process will be assessed. When
applicable the assessment team will request a site tour with one of the Operations
Staff to provide a general orientation of the facility.
3. CAMERA FUNCTION TEST - Prior to beginning any leak monitoring work, the
optical gas imaging instrument the following function test is conducted:
a. Install a 0.5 liter/minute regulator on a 100% Methane gas cylinder (verify
that the cylinder contains gas). Place the cylinder outside or in a wellventilated area.
b. Set up the optical gas imaging instrument at a recorded distance from the
outlet of the cylinder regulator that will not be exceeded in the actual
distance of the leak survey (the minimum distance is 10 feet)
c. Open the valve on the regulator to set a flow rate (0.5 L/min.) while
observing the gas flow through the optical gas imaging instrument
viewfinder. When an image of the gas emission is seen through the
viewfinder, make a 10 second recording of the emission.
d. Mass flow rate of Methane for the daily instrument check is 22 grams per
hour (0.5 liters/min, 0.02 ft3/min)
4. SCANNING TECHNIQUE - Each unit/process is scanned in two phases; an
external equipment scan and an internal scan (i.e. within facility building, where
applicable). Due to the nature of infrared detection, each piece of equipment is
also scanned from at least two separate viewpoints to increase the probability of
emission detection. Generally, each piece of equipment is first scanned from a
wide angle (a larger view point) and then a number of detailed scans are performed
at a more focused depth (smaller/ closer viewpoint). During the detailed scan, the
assessment crews will scan over the same area a number of times and use
secondary leak detectors (when applicable) to ensure a high probability of leak
detection.
5. SCANNING DISTANCE - When scanning the camera operator should stand at
appropriate distances from the equipment. This distance will vary with the size of
the equipment and the accessibility to the equipment. In general, the operator
should position themselves within 5 to 10 feet of the equipment/process of interest.
The operator will then divide the total equipment scene into quadrants based on
the field of view present in the camera view finder. The operator will then scan
each quadrant to look for movement of emitted gas.
6. SCANNING ANGLES – crews must always use multiple camera angles when
scanning one piece of equipment or area. This will increase the probability of
seeing all gas emissions. When choosing which angles to view the equipment, try
to get different background into the scene (preferably at different background
temperatures).
7. CAMERA MOVEMENT - When searching for emitted gas movement it is crucial
to hold the camera still on one scene for a few seconds before moving onto the
next scene. It is difficult to see the gas movement when the camera is in motion
therefore each scene should be analyzed while the camera is still. Within each
quadrant, the camera operator should be moving the camera to view each
individual equipment section and then pausing on that equipment to look for gas
movement. Constantly moving the camera from scene to scene without pausing in
each view to look for gas images can result in missing emissions. It is very
hazardous to walk while looking through the eyepiece of the camera or at the
external viewfinder. When the camera operator has completed a section of
equipment scanning they must stop scanning, remove their eyes from the camera
and then walk to the next scanning area.
8. DETAIELD SCAN - When gas is detected the camera operator can then move
closer to the emission source to determine the exact source of the emission. Be
aware of any hazards when moving in to perform a detailed inspection of an
emission source (e.g. rotating equipment, hot equipment. etc.)
9. LEAK DETECTION - When an emission is detected, a video and digital picture
record is taken at an angle and range which optimizes the visibility of the source.
The source details are then recorded and the leak is marked with a Leak Detection
ID Tag (see Figure 2). All tags are left in place to allow for follow-up action by
facility personnel and to locate past sources during repair confirmation
assessments. The Assessment Team may also mark the precise leak area with an
industrial grease-based pen to allow easy identification of the source.
10. QA/QC REVIEW - Following a unit/process inspection the database entries are
reviewed to ensure data accuracy.
11. LEAK RECORD - When an emission is detected a video and digital picture record
is taken at an angle and range which optimizes the visibility of the source. The
source details are then recorded. Each leak is described from at least three points
of reference; i.e. “2-inch threaded union on fuel gas line, below north side of glycol
re-boiler, east of chemical pump.” The three describers in this example are “the
fuel gas line”, “north side of glycol re-boiler” and “east of chemical pump
Figure 4 – Sample Leak Photo
DESCRIPTION: Pig Trap South/Connector/Plug on top of bleed
valve at pig end, north of ESD FM-59 BV 38514 LP /Sweet Gas
12. LEAK TAGGING Each leak is then marked with a Leak Detection ID Tag (see
Figure 4). All tags are left in place to allow for follow-up action by facility personnel
and to locate past sources during repair confirmation assessments. If applicable,
the Assessment Team will also mark the precise leak area with an industrial high
temperature grease-based pen to allow easy identification of the source. The
following guidelines should be adhered to when completing the information
required on a Leak Detection ID Tag:
a. The assessment technician will write the current date, emission tag number,
and the technician name. In the description portion, only the point of
emission or leak source should be identified (e.g. “Threaded Union” or
“Control Box Seal”). This will tell the maintenance personnel exactly what
they need to fix.
b. If the location of the leak is in an area that is inaccessible or unsafe to enter
then the Assessment Team will not tag the leak (e.g. too high to reach,
surface too hot, too close to rotating equipment, etc.).
Figure 5 – Leak ID Tag
13. PRELIMINARY REPORTING - Following a unit/process inspection the database
entries are reviewed to ensure data accuracy. Following the completion of a facility,
a preliminary report is then generated (either electronically or hard copy) to provide
the unit Operators with immediate information on the number, type, and severity
of leaks.
Emission Quantification Protocol
Using the Hi-Flow sampler, calibrated bag method, acoustic valve leak detection or
various flow through meters (vane anemometer, thermal mass flow meter or rotameter)
we can measure the flow rate of a leak in cubic ft./min. Normally, the operator will use
the Hi-Flow sampler for measurement, but other methods may be necessary depending
on the gas composition and flow rate.
Hi-Flow Sampler
The Hi-Flow Sampler is the primary emission quantification technology used. The
following steps outline some of the main procedures and precautions or our protocol:
1. CALIBRATION – instrument calibrated every 30 days to assure its accuracy. The
frequency of calibration, however, may increase depending on how often the
instrument is used. Any irregular function or output from the unit will trigger a
calibration event.
2. SAFETY PRECAUTIONS - due to the size and weight of the Hi-Flow Sampler, the
equipment operator must always be aware of the space around them to prevent
tripping and falling hazards. When using the Hi-Flow, one assessment team
member is used as a spotter for the Hi-Flow Operator to help identify clearance
issues and hazards. If the emission source is in an unsafe area and the available
hazard controls are insufficient in eliminating or reducing the hazard, the
measurement will not be attempted.
3. GROUNDING - to prevent the possibility of a static discharge, the Hi-Flow Sampler
must be grounded while conducting a test. The grounding clamp location must be
a metal surface with a conductive connection to the ground (avoid surfaces with
heavy paint or any surface where the ground conduction is questionable).
4. GAS EXPOSURE - When measuring emission sources where the gas detection
readings are within a safe range but there still exists a potential for exposure to
harmful substances (e.g. BTEX), the assessment team members will use
appropriate respiratory equipment. If for some reason the appropriate respiratory
equipment is not available and there is any doubt as to the exposure levels, the
crew will not proceed with the measurement. Crew will avoid sampling gases or
vapors that contain silicones or sulfur compounds. Sour gas (H2S) can form
contaminating compounds on the sensor element (poison the sensor), with
resulting loss in sensitivity.
5. STARTUP - To ensure that the gas sensors are properly zeroed at startup, the Hi
Flow Sampler must be turned ON in clean air (free of combustible gases or
vapors).
6. EMISSION CAPTURE - It is important to capture all the gas being emitted from
the source. Depending on the size of the emission source, the crew may have to
use a variety of accessories to ensure that all the gas is captured (plunger
attachment, vent hood, static free plastic wrap, etc.). If there is any doubt that all
the gas is not being captured, the crew may use the infrared camera as a screening
tool to look for escaping gas.
7. EMISSIONS AT HEIGHT – frequently the use of extension poles is rewired to
reach emission sources (rod packing, blow down vents, tank vents and wet seal
degassing vents). The figure below illustrates how our carbon fiber poles are used
to obtain measurements.
Figure 6 – Extension Pole
Calibrated Bag
The Bag Method which utilizes a special 3 cubic ft. bag and a timer to determine the leak
rate, usually used in instances where the Hi-Flow is maxing out (Leak rate over 10 cubic
ft/min). The use of the bag method requires safe access to the vent line (no lines with
potential pressure release or any toxic gases). The basic methodology requires one crew
member to cover the vent line with the bag opening and the other crew member times
how many seconds it requires to fill the bag. Three consecutive time trials are recorded
for each emission source and averaged to obtain final leak rate.
Vane Anemometer
The vane anemometer is used to measure the rate of gas velocity created by an emission.
This is typically used on vents where there is a hazardous component to the gas (H2S,
BTEX etc.) and it is unsafe to use the Hi=Flow Sampler. The anemometer is placed in a
custom enclosure which is then placed on an extension pole and positioned over the vent
line (se figure below)
Figure 7 – Vane Anemometer Vent Test
The anemometer has data recording capability and that data is used to determine the
average gas velocity of the emission. This velocity is then used to calculate the volumetric
emission rate.
Weather conditions can affect the accuracy of this test. High winds can add erroneous
gas velocities to the test. However, the enclosure uses a rubber damn that slips over the
vent line and a 90-degree elbow at the exhaust line to prevent ambient wind interference.