1. Requirements for the analysis room of the chromatograph
(1) There should be no strong magnetic field, flammable and strong corrosive gas around the analysis room.
(2) The indoor ambient temperature should be in the range of 5~35 degrees, the humidity should be less than or equal to 85% (relative humidity), and the indoor air should be kept in circulation. If conditions permit, it is best to install air conditioners.
(3) Prepare a working platform that can withstand the whole set of instruments, with moderate width and height, and is easy to operate. Generally, the cement platform is better (0.6~0.8 meters high) in the factory. The platform should not be close to the wall, and should be 0.5~1.0 meters away from the wall, which is convenient for wiring and maintenance.
(4) The capacity of the power line for the instrument should be about 10KVA, and the power supply of the instrument should not share a line with high-power power-consuming equipment or power-consuming equipment that frequently changes greatly. The power supply must be well grounded. Generally, an iron rod (wire) with a length of about 0.5~1.0 meters is nailed into the wet ground (or perfused with salt solution), and then the grounding point of the power supply is connected to it. In short, the grounding resistance is required to be less than 1 ohm. (Note: It is recommended that both the power supply and the case are grounded, which will work better).
2. Air source preparation and purification
(1) Preparation of gas source
Prepare high-pressure steel cylinders for the gas to be used in advance (generally available in large and medium-sized cities). The cylinders containing a certain gas can only hold this gas. The color of each cylinder represents a gas and cannot be interchanged. Generally, nitrogen, hydrogen, and air are used. It is best to prepare two cylinders for each gas for backup. Some factories can also use hydrogen generators and air compressors, but the air compressors must be oil-free. When the cylinder pressure drops to 1~2Mpa, the cylinder should be replaced. Generally, manufacturers can use 99.99% of the above gas, and the electron capture detector must use more than 99.999% of the high-purity gas source.
(2) Air source purification
In order to remove the moisture, ash and organic gas components that may be contained in various gases, the gases should be strictly purified before entering the instrument. If all cylinder gas is used, some chromatographs are equipped with purifiers and are filled with 5A molecular sieve, activated carbon, and silica gel, which can basically meet the requirements. If a general hydrogen generator is used, the purification treatment of water must be strengthened, so the area of the drying pipe should be increased (the volume should be above 450 cubic centimeters, and the packing should be 5A molecular sieve), and the volume should be larger after the generator. to reduce or overcome the impact of fluctuations in gas source pressure on the instrument baseline. If an air compressor is used as the air source, the air inlet of the air compressor should be strengthened with air filtration, the volume of the purification tube should be increased, and the drying tube should be filled with half 5A molecular sieve and half activated carbon. Generally, domestic oil-free gas compressors (produced in Tianjin) can meet the needs.
3. Complete inspection and placement of chromatograph
After the instrument is unpacked, carry out an item-by-item inventory according to the list of accessories in the information bag, and keep the spare parts of the vulnerable parts properly. Then, according to the requirements of the instrument's instruction manual, place it on the working platform, connect the various parts of the instrument against the wiring diagram and the plugs and sockets, and finally connect the recorder and the data processor. Be careful not to connect the connectors incorrectly.
4. Connection of external air circuit
(1) Installation of pressure reducing valve
Some instruments come with a pressure reducing valve, if not, you need to buy it. Used are 2 oxygen, 1 hydrogen pressure reducing valve. Install 2 oxygen pressure reducing valves and 1 hydrogen pressure reducing valve on the nitrogen, air and hydrogen cylinders respectively (note that the threads of the hydrogen pressure reducing valve are reversed, and add the attached O-shaped plastic gasket to the interface, After tightening the nut, close the adjusting handle of the pressure reducing valve (that is, loosen it), and open the high pressure valve of the cylinder. At this time, the pressure gauge of the pressure reducing valve should have an indication. After closing the high pressure valve, the indicated pressure should not drop. Otherwise, there will be leakage, which should be eliminated in time (sealed with gasket or raw material tape), and sometimes the high-pressure valve will also leak, so pay attention. Then turn the adjustment handle to exhaust the residual air.
(2) External air connection method
The gas in the steel cylinder is introduced into the chromatograph, and some use stainless steel tubes (φ2×0.5mm), and some use pressure-resistant plastic tubes (φ3×0.5mm). The use of plastic tubes is easy to operate, so plastic tubes are generally used. If a plastic pipe is used, there must be a stainless steel liner (φ2×20mm) and some plastic materials for sealing at the joint. The length of the plastic tube from the cylinder to the instrument depends on the needs, and it should not be too long, and then use the plastic tube to connect the gas source and the instrument (gas inlet).
(3) Leak detection of the external gas path
Close the valve knobs of the carrier gas, hydrogen and air on the air surface of the main engine, then open the high-pressure valves of each cylinder, and adjust the output pressure of the low-pressure gauge on the pressure reducing valve, so that the carrier gas and air pressure are 0.35~0.6Mpa (about 3.5~ 6.0kg/cm3), the hydrogen pressure is 0.2~0.35 Mpa. Then close the high-pressure valve. At this time, the indicated value of the low-pressure gauge on the pressure reducing valve should not drop. If it drops, it means that there is a leak in the connecting gas path and should be eliminated.
5. Air tightness inspection of the gas path of the chromatograph
Air tightness inspection is a very important task. If there is a leak in the air circuit, it will not only directly lead to unstable operation of the instrument or decrease in sensitivity, but also cause the risk of explosion. Therefore, this work must be carried out before operation (air tightness). The inspection is generally to check the carrier gas flow path, if the hydrogen and air flow paths have not been dismantled, they may not be checked).
The method is to open the chromatographic column box cover, remove the column from the detector, block the column port, then open the carrier gas flow, adjust the low pressure output pressure to 0.35~0.6Mpa, and open the carrier gas knob on the host panel. When the pressure gauge should indicate. Finally, turn off the carrier gas knob, the pre-column pressure indication value should not drop within half an hour, if there is a drop, there is leakage and should be excluded. If there is a leak in the air circuit of the main engine, remove the relevant side plate of the main engine, use soapy water (preferably sodium dodecyl sulfonate solution) to check the leaks one by one (hydrogen and air can also be used for leak detection), and finally put the soap Dry with water.