Laser Based – Fixed Point Gas Detection
Understanding the Fundamentals
What you need to know
At a glance, here is what you need to know about the Remote Point (RPX) Probe which makes Fixed Point Gas Detection Measurements.
More detailed benefits include:
- Fail Safe Operation: Unlike Traditional Fixed Point Gas Detectors that can unknowingly “fall asleep” or “become sick”, this product provides extremely detailed self-diagnostics.
- No interference from other gases: Provides a quantitative measurement and responds only to the presence of the target gas in the air.
- No Detector Poisoning: After exposure to the target gas, immediate and complete return to zero readings, with no maintenance required.
- Practically No Measurement Drift: With the Internal Reference Cell, the system can automatically and autonomously make the necessary adjustments.
- Simple Installation: Can be carried out by on-site electrical contractors.
- Low Cost of Ownership: No consumables, no moving parts, and no factory required calibrations.
Purpose of Use
Uses of this Enhanced Sensing Element
Often referred to as Laser Based – Fixed Point Gas Detection, this is considered an Enhanced Gas Sensing Element as it can be used for the purpose of:
- Leak Detection/Safety Monitoring: Performance requirements are focused on alarm signaling for such purposes as Safety Warning and Executive Action.
- Industrial Health & Hygiene Monitoring: Focused on the uncertainty of measurement of gas concentrations in the region of Occupational Exposure Limit Values (OELV).
- Leak Detection & Repair (LDAR): Passive Monitoring for incipient fugitive emissions provides operations with another Process Variable (PV) that could provide them with early warning of an abnormal process condition that could require intervention.
- Ambient Monitoring: Quantitative monitoring of specific constituents for compliance purposes.
It is not uncommon for Laser Based – Open Path Gas Detectors to be used for one or more of the purposes listed above.
Often there is one dominant driver to champion the project but multiple stakeholders can derive value and use from these measurements. Examples of these drivers are shown below.
What drives the need?
While these drivers may identify the need for detection, there may be latitude in which sensing elements are selected and how they’re used.
It is important to understand how to best deploy the sensing elements to not only meet the minimum requirements but exceed them as well.
FIRE & GAS SAFETY SYSTEM
What does it do? Why it is important?
For the purpose of Risk Management Mitigation, Fire & Gas Systems (FGS) are utilized to enable the recovery after a Loss of Containment (release and/or accumulation) by performing three basic functions:
- Detect the Hazard with Sensing Elements (e.g. Toxic Gas, Combustible Gas, & Flame Detectors),
- Confirm Loss of Containment with Logic Solvers or Safety System Controller (e.g. DCS, PLC, etc.), and
- Initiate Executive Action with Final Control Elements (e.g. Horns, Strobes, Pumps, Valves, Solenoids, HVAC, etc.).
It is important to note that Recovery Actions (e.g. Annunciation from Horns/Strobes, Manipulation of the Process, Control of HVAC System, etc.), cannot be taken until a Loss of Containment has been confirmed by the Logic Solver which often requires at least two (2) Sensing Elements to detect a leak.
Therefore, it is vital that your Fixed Sensing Element can reliably and repeatably Detect a hazardous release or accumulation of gas as early as practical AND before it is large enough to cause an escalating situation or health hazard.
Enhanced vs. Traditional
Comparison between Fixed Point Gas Detectors
Not all gas detectors are created equal.
Traditional – Fixed Point Gas Detectors such Electro-Chemical Sensors and Catalytic Bead Sensors do not offer the same enhance functional as Laser Based – Fixed Point Gas Detectors.
Below is a comparison table between Laser Based – Fixed Gas Detection and Traditional – Fixed Point Gas Detectors:
Remote Point (RPX) Probe Assembly
Configuration Options available
The Remote Point (RPX) Probe Assembly has the following configurable options:
- Cable Kit Length: From 5 to 300 m of Cabling between the Remote Point (RPX) Probe and the GasFinder.
The Remote Point (RPX) Probe is comprised of the following components:
- Open Path (OPX) Head: This houses the Optical Bench which performs the transceiver functionality and where the Fiber Optic and CAT6/5e are connected.
- Perforated Cage: This provides mechanical protection to keep rain, snow, sleet, condensation, dirt, dust, and debris from accumulating on both the Transceiver and Retro-Window.
- Gray Tape Retro-Array: These are like sections through a thousands of cubes and has three faces that form the inside of a cube and regardless of the angle of incidence of the incoming laser beam, the laser light is always reflected at 180° back to the Optical Bench.
- Mounting Brackets: These allows technicians to easily mount the Remote Point (RPX) Probe either directly to a wall, Uni-Strut, or other flat surfaces.
Remote Point (RPX) Probe
The Components and their Function
The Remote Point (RPX) Probe includes the following components:
- Four (4) Sided Perforated Cage: This item helps to prevent items like rain, snow, sleet, condensation, dirt, dust, and debris from accumulating on both the Window/Retro-Array and creating a beam block scenario.
- Transceiver Configuration: This contains both the transmit and receiving optics on the Optical Bench.
- Gray Tape Retro-Array: This returns the Laser Light back to the Transceiver Optics.
- Mounting Clamps: This easily mounts to Uni-Struct or other mounting structures.
The Optical Bench includes the following components:
- Optical Bench: This formulates the Transceiver Configuration that combines the Transmit and Receive functionality in one efficient enclosure. The Optical Bench can slide back out of the Remote Point (RPX) Probe Enclosure for easy termination of the Single Mode Fiber Optic (FC/APC Connectors) and Shielded CAT6/5e (RJ45 Connectors) Cables.
- Launch Optics: The Laser Light that travels from the GasFinder via Single Mode Fiber Optic Cabling is Collimated within the Optical Bench and launched from the hole on the Collecting Optics.
- Collecting Optics: When the Laser Light is returned from the Retro-Reflector the Collecting Optics focus the Laser Light onto the Photodiode.
- Photodiode: The Photodiode converts the collected Laser Light into a small electrical signal where the GasFinder will perform its Absorption Spectroscopy technique to very accurately and reliably determine the Path Integrated Concentration within the Active Measurement Path.
The Optical Bench includes the following components:
- Optical Bench: The Optical Bench can slide back out of the Remote Point (RPX) Probe Enclosure for easy termination of the Single Mode Fiber Optic (FC/APC Connectors) and Shielded CAT6/5e (RJ45 Connectors) Cables.
- RJ45 Connector: The small electrical signal from the Photodiode is carried to the GasFinder for analysis via Shielded CAT6/5e Cabling.
- FC/APC Connector: The Laser Light is carried from the GasFinder to the Open Path (OPX) Head via Single Mode Fiber Optic Cabling.
- Patch Cable Connection: As part of the Open Path (OPX) Head Assembly, the fittings and lengths of cabling are included.
How It Works
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Looking for documents?
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The documents below are to help you through to first interaction through to final commissioning.