1. Instrument maintenance

The furnace and electrodes were cleaned every 50 analyses or twice a day. For every 500 analyses, replace all chemical reagents. After the solid sodium hydroxide absorbs water, its color also changes (light gray). If the water absorbent cakes, it indicates that the magnesium perchlorate is saturated. It must be replaced before the water absorbing agent completely agglomerates. In addition to filling reagent tubes with reagents, plug some lead-free glass wool at the bottom of the tube. The filling thickness of glass wool should be filled exactly according to the instructions. Too thick can block the airway. When it is too thin, magnesium perchlorate particles will be deposited on the bottom of the tube through the glass wool, causing serious damage to the instrument.

Change the electrode every 1000 times or when the electrode material turns to grayish white. Because the furnace is in a high temperature environment, the graphite base and top electrode will wear out and must be replaced at any time. Otherwise, there will be voids or even no contact between the crucible and the upper electrode, so there will be no current.

For every 3,000 analyses, replace the copper oxide catalyst in the catalytic converter. Remove the electrode from the furnace and clean it with a brush.

Check the O-ring regularly for replacement. When removing the old O-ring, be sure not to damage the seal area. Place the O-ring in the groove and wipe it with a vacuum grease. After the O-ring is installed, apply vacuum grease, otherwise the O-ring will rotate with the glass tube.

Prevent the glass tube from getting dusty. Once the quartz dust is contaminated, replace it immediately.

2. Failure analysis and processing

(1) The oxygen and nitrogen blanks exceed 20. This condition is due to the small air flow, which does not drive out the air in the furnace. The gas flow rate can be adjusted to adjust the carrier gas pressure at 0.2 to 0.4 MPa. Turn on the instrument carrier gas, place a graphite crucible on the lower electrode, turn on the main power switch, click the shut off button on the software, turn off the stove and wait 10 seconds. Adjust the flow regulator until flow meter a shows 30 L/h and turn on the stove. Adjust the regulator until the flow meter b shows 50 L/h and turn off the furnace again. If the above settings are not stable, increase the flow to 100 L/h and repeat the adjustment until the instrument is stable.

(2) The power supply is normal and the communication is normal. After the confirmation button is pressed, the analyzer does not work. This is the case if there is no water flow, the furnace temperature is too high or the instrument channel voltage is abnormal. If there is no water flow, the oven temperature is too high and these messages are displayed on the monitor screen, but no information is displayed indicating that both are normal. Next, check the instrument channel zero voltage. If it is more than 1V higher than ±3V, it is probably because the cylinder is empty or air enters the analyzer. Check and replace chemical reagents. If there is air entering the thermal conductivity cell, the voltage of the thermal conductivity cell will be <-6V. At this time, open the right door and block the furnace gas inlet. After 10s, the voltage of the thermal conductivity cell must increase. . After one by one investigation, it was finally confirmed that there was a problem with alkali asbestos and the instrument was normal after replacement.

(3) The ammeter shows that the current value is zero during the analysis. This condition is a poor contact of the electrodes in the furnace. After observing the gap between the upper part and the lower part of the furnace, the spacer between upper and lower parts was adjusted to eliminate the gap, but the instrument was still not normal. After further observation, it was determined that the electrode wear resulted in poor contact, and the instrument was normal after replacing the upper and lower electrodes.

(4) Displayed when the instrument starts. No flow! The system analyzes the current cutoff and the analysis stops. This situation is that the water flow detector is not normal, the water pump is not working, and the pipeline is blocked. Remove the right panel of the instrument, observe the flow detector, squeeze the plastic water bottle by hand, and find that the water flow is normal and the display is normal, which proves that the flow detector is normal and the pipeline is open. The circulating pump is started, but the analyzer shows that there is no water flow. At this time, it can be determined that the pump is abnormal. Open the pump rotor seal port, start the pump to find out the normal operation of the motor, then close the water, remove the pump and find the impeller off. It is understood that the determination is due to the external cooling water stop, the circulating water temperature in the instrument is too high (water temperature should be ≤ 70 °C), resulting in the impeller (impeller material PVC) thermal expansion and de-axis. After bonding the impeller with an adhesive, it is adhered to the impeller shaft. After the adhesive is solidified and tested, the instrument runs normally.