TAG number
Number used to identify components in a processing plant (instruments, pipework, containers etc.)

Thermoacoustic oscillations
Oscillations of gas in pipes when one end is cold and the other warm; this results in heat transfer from warm to cold

Transfer line
Insulated pipeline for transport of low-temperature gases or liquids (e.g. vacuum-insulated with superinsulation and possibly an active shield insulation)

vpm
Like ppm, but related exclusively to volume (i.e. parts per million by volume); used mainly to measure gaseous contaminants in gas. Oil in gas is usually measured by weight