I am working in a refinery in Instrumentation Department. I was assigned by my supervisor the installation of a ph analyzer in a 2" line of caustic soda. I am thinking of a ph analyzer with retractable sensor. For safety reasons, I am thinking of constructing a small by-pass line with 2 block valves and a drain valve. The process connection of the retractable sensor will be between the 2 block valves and when it comes to maintenance the technician will just block the 2 valves, drain the caustic soda and be able to retract the sensor with safety, without the danger of caustic soda.

What concerns me is the flow of the liquid through the sensor. I cannot put the bypass below the line, but only on top or on right. Can anyone suggest something different? My thought can be implemented or I should just put the retractable sensor in the main line?

 

don't reinvent the wheel. use a retractable pH sensor. they go in line and can be removed without closing off the line.

--
Bob
http://ilbob.blogspot.com/

 

If you are using the correct design of retractable sensor, you should not have any or much caustic spill when you extract the sensor. I¹d just tap the main line. I would NOT tap it under pressure, however. Many interesting things can happen when you do.

Walt

Walt Boyes, Life Fellow, ISA; Fellow InstMC
Chartered Measurement and Control Technologist
Spitzer and Boyes LLC

**Spitzer and Boyes LLC publishes the Industrial Instrumentation INSIDER (www.iainsider.com)**

 

I did something similar with concentrated acid. Which is the problem in locate the bypass above the main line?

Will the main line be closed when you are measuring pH?

Also, tell us the temperature and concentration of the NaOH solution.