Features and maintenance of water quality analyzer

1. Features

1. Features of pH meter

The glass on the pH electrode will gradually age over time, the gradient (the change in the electrode output potential caused by the unit pH change) deteriorates, and it takes a long time to reach a stable potential. The service life of general electrodes can be up to two years. In addition, temperature also has a greater impact on aging. The aging degree of storage for several weeks at 100°C is equivalent to that of storage for one year at room temperature. The pH meter has the advantages of high precision, high reliability, easy installation and maintenance, and is also sensitive to pollution. It needs to be calibrated frequently, generally every one to one and a half months, and the electrode is replaced every two years.

2. Features of dissolved oxygen meter

Dissolved oxygen meter has the characteristics of easy installation, long calibration period (3 to 4 months), insensitivity to other substances, and can monitor the use of the electrolyte in the diaphragm and probe. The electrolyte and diaphragm are generally replaced every one to three years. COM252 Dissolved Oxygen Transmitter is an intelligent instrument with HART or Profibus communication protocol. It also has a self-diagnosis function. When a fault occurs, it will display the fault code and prompt the maintenance staff to find out and solve the fault by checking the maintenance manual The method greatly reduces maintenance time and workload.

2. Installation and maintenance

1. Installation and maintenance of pH meter

There are two ways to install the pH meter: flow-through and immersion. Sewage treatment plants generally choose immersion installation. For example, the pH meter of the sewage treatment plant is installed in the outlet overflow tank of the oxidation ditch. The pH value here is more representative and the water flow is stable, which will not cause any damage to the pH meter. Big shock. Regular maintenance helps to accurately measure the meter and prolong the service life of the meter. It should be noted that the dedicated cable between the sensor and the transmitter cannot be damp, otherwise the high-impedance and low-voltage signals of the electrode will not be transmitted to the transmitter. If the electrode is not measuring, the yellow protective sleeve should be put on, which can keep the electrode in a wet state, which is beneficial to prolong the service life of the electrode. Every month or so, the electrode should be cleaned, first spray the attachment with a gentle stream of water, then soak the electrode in the cleaning solution for a period of time, and then wash it with clean water. The sensor holder should also be cleaned. After each cleaning, a buffer solution should be used for calibration. Among the current domestic pH calibration solutions, pH=4 is okay, and pH=7 is not accurate enough, which will affect the calibration results. Therefore, it is best to use the manufacturer’s calibration solution. The manufacturer generally provides two bottles of standard solution, one with pH equal to 7 for calibration of the zero point of the instrument; one bottle with pH equal to 4 for calibration of the signal output slope of the instrument.

2. Installation and maintenance of dissolved oxygen meter

Dissolved oxygen meters are generally installed in immersion type, and it should be noted that the original factory mounting bracket must be used. The mounting bracket provided by the manufacturer is made of stainless steel with a plastic chain. The immersion depth of the sensor can be changed by adjusting the length of the chain. The guide tube on the bracket ensures that the sensor is always in a vertical position. The bracket part is specially designed, it can transmit the fluctuation of the water surface to the immersion tube, thereby causing slight vibration of the immersion tube, so that an additional cleaning effect is produced on the surface of the probe through the immersion tube. In order to reduce investment, some users make their own mounting brackets, which often leads to poor sealing between the immersion tube on the bracket and the sensor, and sewage seeps in, so that the connection between the dedicated cable and the sensor is immersed in the sewage for a long time, which may easily cause damage to the sensor; Some even don’t make a mounting bracket, and put the sensor directly into the water, so that a greater tension will be formed between the sensor and the cable, and the sensor is more likely to be damaged. The dissolved oxygen probe should be gently cleaned with water every week. If the membrane head is damaged, it should be replaced in time, and the electrolyte should be replaced in time if it is contaminated. When the sewage contains H2S, NH3, benzene or phenol, it is harmful to the membrane head. In this case, the membrane head must be replaced frequently. To judge the quality of the electrode in the probe, you only need to look at the color. The reference electrode should be dark gray, the cathode (gold electrode) should be yellow, and the counter electrode must be bright, otherwise it should be cleaned or regenerated.

3. Conclusion

With the increasing emphasis on water resources protection, the purification and treatment of sewage becomes more and more important, and the detection instruments required for the matching treatment process are indispensable. As the most important instrument in the sewage treatment industry, the water quality analyzer is not only correct in the selection and installation, but also regular maintenance and calibration is also very important, and it is the key to making the instrument really function.

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