Dear All,
Good day! With regards to the subject above, I would like to ask your advice and opinion to solve a problem encountered by our plant. Currently, the reading of our PH analyzer for condensate water is not stable. The reading at some time dropped to around pH 5.0 and returned back to normal at around pH 8.5 after some time. For your info, the lab test result for PH of the process sample is around pH 8.5.
The fluctuation pattern is also nearly duplicated for each day where the PH started to drop during evening time and recovered on the next morning. We have replaced the pH electrode, reference cell and liquid junction and performed calibration few times but the issue still persist. Appreciate your time to go thru the situation and share some ideas on what would be the causes of this kind of problem.
If you have anything that need to be clarified or any additional information with regards to this issue, please do not hesitate to contact me. Thanks!
Kind Regards,
Some questions and then suggestions.
1. Has this pH system always had this issue from commisioning or is this a recent issue?
2. Did the reading ever match the portable pH / Lab result?
3.The sendor model 320Hp is connected to what transmitter model?
4. Does the result ever reach 8.5 or is there always an offset from the expected 8.5 ( Which by the way is the normalexpected pH of condensate , comfirming that the lab result is correct )
Can we assume that the sensor buffers normally? Assuming 7 ph and 10ph in the test pot .
Once you buffer check is confirmed . Take a new process sample and fill the test pot and look at the reading . If the reading is close to the expected 8.5 pH then the sensor and transmitter is functioning ok.
This result could suggest you have an issue with an external ground loop when the sensor is placed back into the normal sensor installation . Ground loops can be difficult to find. Certainly one possibility causing the fault .
If you can answer the questions and give me some idea of the installation then we can continue to look for the answer and offer up ground lop solutions if that is the issue. ( Send picture or schematic of the installation ) .
Thanks, Jim McLelland , Senior Technical Advisor , Rosemount Analytical.