The main conditions that affect the life of your pH sensor are the process temperature and the presence of various chemicals in your process. A pH sensor installed at 25 ⁰C (77 ⁰F), has a life expectancy of one year. However, if the temperature were increased to 50 ⁰C (122 ⁰F), the life of the sensor would be reduced to six months. Furthermore, if the temperature were to increase to 75 ⁰C (167 ⁰F), then the expected life of the pH sensor would be approximately three months. This can be further accelerated by chemicals that attack the pH sensor glass.
Have you considered protection from chemical attack?
Any process with proteins, heavy metals (Ni, Cd, Cu, Cr, Ag, etc.), sulfides, cyanides, iodides, or any other materials that react with chloride or silver ions will significantly reduce the life of your pH sensor. A solution to this particular issue is using a pH sensor with a double junction reference. A double junction electrode creates an added layer of protection, which will make the sensor last longer.
Are you conducting routine maintenance?
The “glass” part of a pH probe is a porous membrane that allows the transfer of process water to the probe’s internal sensor. This membrane should remain wet, and not be allowed to dry. If they do dry they tend to close so they won’t pass process fluid. In rare cases the membrane can be rehydrated, but often they are not recoverable. There is a pH storage solution available for proper storage of a probe when it is outside of a wet system.
Processes that cause coatings, accumulation of biofilm, or scaling may not only reduce the life of the sensor but also negatively impact performance. Be sure to choose a cleaning solution that will have the best impact on what is causing the interference on the probe. The porous membrane on the probe can gather fats, oils, scale deposits and other contaminants, therefore wiping the probe will likely not be effective. Soaking the probe in the proper cleaning solution for the type of contaminant will yield the best results.
What Should You Do If Your pH Sensor Is Still Not Performing Well?
Even if after proper care and maintenance your sensor is not performing as well as it used to, it may be time to replace the pH sensor! Remember, pH sensors have a typical shelf life of one year. pH Sensors can save you thousands of dollars by ensuring proper water quality in your process. It can be a good idea to have a spare in case of emergencies.
Need additional information?
Furrow Pump stands ready to help with installation, field issues, maintenance or providing replacement sensors. Please give us a call at 1-503-682-4411.