The Garrett Gas Train is the most widely used portable instrument for the determination of soluble sulfides and carbonate concentrations in drilling fluid. Soluble sulfides include H2S and the sulfide (S-2) and bisulfide (HS–) ions. Total soluble carbonates include CO2 and the carbonate (CO3-2) and bicarbonate (HCO3) ions.
Mud filtrate is acidified inside the gas train, converting all sulfides to H2S or all carbonates to CO2, depending upon the test. The gas train separates the gas from the liquid and an inert carrier gas transports the gasses through the separate chambers. In chamber three, the gas stream is passed through a Dräger-Tube, which responds to H2S or CO2 by darkening along its length, with the stain length proportional to the amounts of concentrations in the filtrate.
For qualitative H2S analysis, lead acetate paper disks may be inserted to determine the presence or absence of sulfides. The Garrett Gas Train consists of a transparent train, pressure regulator assembly, CO2 and N2O cartridges, Dräger-Tubes for H2S and carbonate detection, and a convenient carrying case.
Size: 18.75″ × 14.5″ × 8″ (48 × 37 × 20 cm)
Weight: 17 lb 5 oz (7.9 kg)