What do the terms mean?
- ppm by volume (ppmv)
- Parts per million by volume (ppmv) is a unit in which one ppm of oxygen is one volume of oxygen in a million volumes of gas.
- Percent by volume (% vol)
- Percent by volume expresses oxygen as a share of the gas volume, and one percent by volume is 10,000 ppm.
- Air ingress
- Air ingress is air entering a gas system through leaks, open hatches or low-pressure equipment, and air is about 21 % oxygen.
- Thief hatch
- A thief hatch is a hatch on a storage tank that is used to gauge or sample the tank, and if it leaks or is left open, air can enter the vapor space.
- Vapor recovery unit (VRU)
- A vapor recovery unit is equipment that captures vapor from storage tanks and other low-pressure sources and compresses it into the sales line.
- Rod packing
- Rod packing is the set of seals around a reciprocating compressor's piston rod, and when it is worn it can let air in if suction is near or below atmospheric.
- Custody transfer
- Custody transfer is the point where gas changes ownership, usually a meter at the fence line, and it is where quality limits such as oxygen are enforced.
- Fence line
- The fence line is the boundary where gas leaves a producer's or gatherer's facility and enters the next party's system.
- Tariff
- A tariff is the published terms of a pipeline, including gas quality limits such as maximum oxygen content.
- Electrochemical (galvanic) cell
- An electrochemical (galvanic) cell is an oxygen sensor in which oxygen reacts at an electrode and generates a current, and the cell is consumed as it measures.
- Optical oxygen analyzer
- An optical oxygen analyzer measures oxygen with an optical sensor instead of an electrochemical cell.
- Class 1 Division 2 / Zone 2
- Class 1 Division 2 and Zone 2 are hazardous-area classifications (NFPA 70, the National Electrical Code, Articles 500 and 505) for locations where ignitable gas is not normally present but may occur under abnormal conditions.
- IP67
- IP67 is an ingress protection rating defined in IEC 60529, where 6 means dust-tight and 7 means protected against temporary immersion in water.
- Detection limit
- The detection limit is the smallest oxygen concentration that an analyzer can tell apart from none. OxyScout's limit of detection is ≤ 0.5 ppm O₂ (Ultra-Trace), 50 ppm O₂ (Trace), 0.01 %vol O₂ (Percent 0–1 %) and 0.1 %vol O₂ (Percent 0–10 % and 0–21 %).*
- Response time
- Response time is how quickly the reading moves after the oxygen level changes. OxyScout's typical response time is under 10 seconds.*
- Cross-sensitivity
- Cross-sensitivity happens when a sensor responds to a gas other than the one it is meant to measure.
- 4–20 mA loop
- A 4–20 mA loop is a standard analog signal in which 4 mA and 20 mA represent the low and high ends of the measurement range.
- Modbus RTU (RS-485)
- Modbus RTU over RS-485 is a serial communications protocol that reads measurements from a device into an RTU, PLC or SCADA system.
- Blanket gas
- Blanket gas is natural gas or nitrogen that is supplied to a tank's vapor space to keep air out.
- Flare header
- A flare header is the piping that collects relief and waste gas and carries it to the flare.
- Stripper well
- A stripper well is a low-rate, mature well, and stripper wells often run at low pressure with limited maintenance.
*Based on controlled lab conditions.
References for the standards named here
