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Photoionisation detector (PID) Technology

Introduction

Photoionisation detector or PID sensor are the ideal choice for detecting low concentrations of Volatile Organic Compounds (VOCs). Crowcon’s PID, or photoionisation detector, uses a 10.6 electron volt lamp and offers stability to detect a wide array of VOC’s. Utilising an internal light source, the gas sample passes through and ultraviolet light with an ionisation potential of 10.6 eV smashes an electron from a molecule of gas.

In this way PID sensors break down the VOCs in the air into positive and negative ions, which approach highly charged electrodes, and from the resulting current flow, detect or measure the amount of ionised gas. The current is a function of the concentration levels of the compounds present in the air. PIDs can be used to measure a range of hazardous

Industries

Oil and Gas
Petrochemical
Chemical
Waste Management
Food and Beverage
Industrial Hygiene

Gas Hazards and Risks

Application

Hazard

Confined Space Entry

Unprotected confined space entry work can be dangerous, so it is necessary to undertake pre-entry checks to clarify whether toxic or flammable gases or vapours are present. Once these gases have been recognised and quantified, if it is safe to enter then workers can also utilise the PID sensors to continually monitor the space whilst within it, as well as to monitor levels across a longer period of time.

Fenceline Monitoring

Within the oil and gas sector PID technology can be utilised as part of a fenceline monitoring program within industrial sites and surrounding communities to measure the sites emissions, and to ensure the controls that are put in place are working. Perimeter monitoring offers helpful information as to whether the emissions management systems are working as planned, and if they are not, illustrates a need for action that is required before gas levels become dangerous to workers and the community.

Downstream Oil and Gas

Photo-Ionisation Detection technology is useful within downstream oil and gas applications due to its capacity to detect hundreds of VOCs in addition to a range of other gases. Due to its flexibility and versatile detection capacity, it is ideal for protecting people working in an environment that could expose them to solvents, glues or paints, as well as the VOCs that can be present around oil and gas facilities.

Products

Portable
Gas-Pro

A multi gas detector offering 5 gas support as well as a dedicated pre-entry check mode and optional pump feature

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Factors Affecting PID

PID detectors tend to be the best choice for the detection of multiple heavy gases and solvents in a specific environment. If the gas is known in an environment then Calibrate the PID for that gas type instead of giving it a general calibration.

Dirty and humid environments can adversely impact PID sensor functionality. Humidity in an environment can cause leakage currents or scatter the ultraviolet light and cause a reduced sensitivity. If the sensitivity of the sensor has been impaired too much, which can be ascertained during the calibration process, then the lamp should be cleaned to improve its functionality. PIDS that use electrode stack designs are better choices as these can be designed to reduce humidity interference.

The electrode stack is, however, extremely sensitive and can have a shortened life span if situated within heavily contaminated sites. As it is disposable it is possible to hold a spare electrode stack and to have it on hand in service facilities to replace after PID use in dirty environments, when required. After the electrode stack is replaced the PID should be recalibrated.

Industry Insights

Blog
What are VOCs?
The nature of gas hazards posed by some working environments can be complex and complete protection is not available from a single solution.
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Talking Gas
Maintenance, cleaning and calibration of PIDs

The electronics in the PID sensor, designed to be maintenance-free, are not accessible. Periodic sensor maintenance is required for the electrode stack and lamp.

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Case Study
Upstream Oil and Gas Producer in the Middle East

A major upstream oil and gas company in the Middle East has chosen Crowcon’s Gas-Pro PID portable gas monitors to help protect employees from the risks of volatile organic compounds (VOCs).

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