What To Consider When Choosing A Gas Detector

PSE&G, with about 1.7 million gas customers in New Jersey, has a first responder program to ensure that technicians respond to a leak emergency call within 60 minutes or less1. To meet this goal, procedures are reviewed yearly, new service personnel receive extensive classroom and hands-on training, and apprentices are matched up with experienced technicians in a Field Experience Program for four months [1].

Reliable response to leak complaints relies not only on training but also on proper tools and instrumentation. PSE&G technicians typically use Bascom-Turner Gas Sentry (Model CGC-301) detectors to carry out leak and carbon monoxide investigations. These instruments have a catalytic sensor, a thermal conductivity sensor, and an electrochemical carbon monoxide sensor, and can be used for both natural gas and carbon monoxide investigations.

After the detectors passed PSE&G’s laboratory tests over the specified range of ambient conditions and concentrations of natural gas (0 to 100%) and carbon monoxide (0 to 2,000 ppm), 50 instruments were purchased by PSE&G and used in the field for approximately nine months to establish field reliability, ease of use, and general acceptance by field personnel. Based on this experience, the detectors were gradually introduced to all service personnel. Presently, the instruments have been in the field for eight to ten years with consistent and reliable performance and minimum maintenance.

PSE&G’s experience with instrumentation generally suggests that there are five key factors—accuracy, ruggedness, intuitive use, reliability and ease of calibration—to consider when choosing the right instruments for leak investigations.

Accuracy. The accuracy factor depends on sensor performance, and up-to-date electronics and operating software as well. These factors are inter-related and must work together to yield optimum results for the detector. In recent years, software has become a dominant factor in instrument design. Since all complex software will need to be updated from time to time, ease of software upgrades in the field, either by a simple change of microprocessors or by downloading through a digital interface, is an important criterion in selecting a detector.

Ruggedness. The major mechanical components of a detector are the case and the pump. A detector’s casing must be strong enough to withstand normal in-field wear-and-tear so the machine’s sensors and pump do not incur significant damage. The pump is an important sub-system whose proper function is crucial to the operation of the detector. A diaphragm pump is best for carbon monoxide investigations, but it must be engineered to protect its valves from dust and other debris encountered in the field. Filters and “water-block” attachments are effective in protecting the pump and the sensors from contamination in “dirty” environments, including those encountered in bar-holes.