(1) Pressure Relief Valve Installation

Some gas chromatographs come with a pressure-reducing valve; if not, one must be purchased. We use two oxygen and one hydrogen pressure-reducing valves. Install the two oxygen pressure-reducing valves and one hydrogen pressure-reducing valve on the nitrogen, air, and hydrogen cylinders, respectively (note that the hydrogen pressure-reducing valve thread is reversed, and attach the included O-ring plastic gasket at the interface for a seal). After screwing the caps tight, close the gas chromatograph pressure-reducing valve adjustment handle (i.e., loosen it), open the cylinder high-pressure valve. The pressure gauge on the pressure-reducing valve should show an indication at this point. After closing the high-pressure valve, the indication pressure should not drop; otherwise, there may be a leak, which should be promptly addressed (using a gasket or sealing tape), as the high-pressure valve may also leak, so attention is needed. Then, rotate the gas chromatograph adjustment handle to expel any remaining gas.

(2) External Air Path Connection Method

Gases from cylinders are introduced into gas chromatographs, with some using stainless steel tubes (φ2×0.5mm) and others opting for pressure-resistant plastic tubes (φ3×0.5mm). Plastic tubes are easier to handle, so gas chromatographs typically use them. If plastic tubes are used, stainless steel liners (φ2×20mm) and some sealing materials are required at the joints. The length of the plastic tube from the cylinder to the gas chromatograph is determined as needed, but should not be excessively long. Then, connect the gas source and the instrument (gas inlet) using the plastic tube.

(3) External gas circuit leak inspection

Load the carrier gas, hydrogen, and air valves on the gas chromatograph's main gas panel, then close the valves. Next, open the high-pressure valves of the gas cylinders, adjust the pressure output of the low-pressure gauge on the pressure reducing valve to achieve a pressure of 0.35~0.6 MPa (approximately 3.5~6.0 kg/cm³) for the carrier gas and air, and 0.2~0.35 MPa for hydrogen. After that, close the high-pressure valves; the low-pressure gauge on the pressure reducing valve should not drop. If it does, it indicates a leak in the gas path of the gas chromatograph, which should be addressed.