Galvanometer: a device for detecting and measuring small electric currents by means of mechanical effects produced by the current to be measured.
Gas Detection Instrument: an assembly of electrical, mechanical and chemical components (either as a single unit or interconnected component parts) which senses and responds to the presence of gas in air mixtures.
Gas Volume: in leak detection, this scale represents the percentage of fuel gas in a given atmosphere sample. A catharometer is used to determine this measurement.
GPS: Global Positioning Satellite. Technology that allows a dedicated unit to determine its precise location on earth in terms of longitude and latitude. Currently, GPS accuracy without differentiation or pre-position satellite access is limited to +/- 100 meters. With various techniques available today, accuracy of +/- 1 meter can be achieved.
Guide Bars: A number of bars welded in the 90° branch of a tee. Guide bars prevent a pig from entering the branch connection.
High-Temperature STOPPLE® Fitting: A STOPPLE® Fitting with a LOCK-O-RING®-type flange designed for high temperature. It has a spherical body.
Hydrogen Gas: a colorless, highly flammable gas. Used in FID detectors, usually in a gaseous combination of hydrogen and nitrogen.
Hydrocarbon Gas: any gas mix made up of hydrogen and carbon atoms. Methane, pentane, butane, propane are examples.
HT&P: Acronym for "hot tapping and plugging."
