pH meter

There are many types of online pH meters, with flange-mounted versions being the most common; they feature a 4-20mA output, and there are generally no issues with their operational lifespan.

The operating temperature for Mettler-Toledo pH and ORP electrodes ranges from 0 to 110°C, with a pressure range of 0 to 16 bar; at 100°C, the operating pressure is 0 to 6 bar. There is also information available on the forum: http://bbs.hcbbs.com/thread-145630-1-1.html. You can take a look there; Mettler-Toledo offers a variety of sleeves for pH meters.

The nominal temperature range for the most common glass electrodes is generally 0-120 degrees Celsius； But in essence, 120 degrees is the instantaneous sterilization temperature. According to discussions with senior technical personnel from the manufacturers, in normal usage scenarios, it is advisable not to exceed 80-90 degrees. Additionally, the medium is viscous, which can easily lead to accumulation on the glass electrode; although a dedicated cleaning line could be considered, it is troublesome ； Solid particles can easily cause wear on glass electrodes, reducing their lifespan. (Thick adhesion or particle wear – somewhat contradictory and coexisting, requiring on-site testing.) It seems that glass electrodes are no longer suitable for use. There is another type of electrode—the semiconductor electrode. Its suitable temperature range is slightly wider than that of a glass electrode. Flat plate design to reduce medium wear. Disadvantages: 1. The measurement range is relatively narrow; according to the available information, the recommended lower pH value is around 1.0, while the upper limit is around 11.0. The user in question is operating at one of the boundaries, and it is necessary to determine whether the precision meets the required standards ； 2. Semiconductor electrodes are particularly sensitive to alkalinity. It is best to communicate thoroughly with the technicians from the analytical instrument manufacturers and let them help you make the choice. As far as I know, Mettler-Toledo offers semiconductor electrodes; it’s not clear whether other major companies such as E+H and Hach have developed such products in recent years.

If the temperature is high, considering the use of a small heat exchanger is an option.

This approach needs to be handled with caution, depending on the operating conditions. We once developed an external circulation cooling-and-sampling system in a high-temperature and highly corrosive environment, using components such as ABS pipes and heat exchangers with graphite lining, but it ultimately failed. Such production is mostly batch-type; therefore, the sampling pumps and valves need to be controlled, as does the cooling medium (water). In addition, flushing pipelines are required to prevent condensation ； Siphon prevention ； Reduce sampling lag.... and many other things; in the end, the operator still chose to use pH test strips...