PH measurement 4

[1BT]

We are looking to replace a ph system that has three sensors ( triple validation ) on the suction side of a self priming pump. We have to replace the sensors due to drying out problems. for various operational reasons it will be difficult to re engineer the pipe work.
Any tips or advise on this application would be appreciated.

Regards

Bill

 

[saxon]

1BT, A mandatory preventive maintainence program. pH sensors are the most troublesome of any of the analytical instrumentation. These things connot be just stuck in a process and left to their own devices, like must other sensors. Depending on application, these things need to be washed/cleaned and calibrated from at least once day to once a month or more or less frequently.

Hope this helps.
saxon

 

[abcmex]

In difficult applications I have seen pH sensor system, Unical 900 from Knick (

http://www.knick.de)

that clean and calibrate online (well not exactly) but without any human help. I think I like more a calibrated sensor than three wit a slight drift ;-)

KInd regards

 

[m777182]

What about some other measurement? Conductivity is more comfortable, low impedance measurement(compared to pH)and will react on pH change as well.
m777182

 

[scorcher]

We are trying to use conductivity in preference to pH measurement (approx 13pH). However, process fluctuations are resulting in conflicting results and poor control. Conductivity is maintained well, but corresponding pH less so. Lab trials had not given any sigh of this issue. Conductivity seems to only be a good indicator when everything ele is stable.
This link may give a further alternative, I havnt had a chance to read it properly yet so appologies if it is a wild goose chase.

http://www.socsa.org.uk/SONAR.htm

 

[jalvarez]

The problem is drying out, not the pH meter. You then need to solve the real problem; try to avoid the drying out, e.g. adding a kind of tub or bucket where you still have movement of the liquid. Solution will depend on the geometry, like vertical or horizontal line, etc.
Have a safe and healthy day.
J. Alvarez

 

[jmw]

Hi Bill,
this link is to an alternative method using ultrasonic sensors.
Note: suitable for solids/bubbles at <10%volume and I understand surface coating may not be a problem as the coating layer is thought to be insignificant conmpared to the sensor gap (see their other data).

http://www.sensotech.com/sources/65_01.pdf

JMW

http://www.viscoanalyser.com

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[yulinios]

Hi there!
We use a sampling rack for all Ph-meters, it consist of reduce the pressure and cooling the sample until 25°C (cooler/heater), finally ph-meters cell is located which is cleaned and calibrated everyweek, but everyday laboratory people compares the values to assure water quality.
Bye There

 

[hacksaw]

Probe drying should not be a problem if they are properly stored prior to use and kept wetted during use.

Having dealt with that issue, however, you still have to deal with a greater problem: placing pH probes on a pump suction is generally a bad idea.

 

[Procman]

I would also suggest conductivity measurement. We use it at our plants and have less trouble with it. I would still suggest two meters. If you had three pH meters, it was probably so for safety reasons. A backup is therefore always good.

 

[RichardJennens]

There are also pH sensors available that are not destroyed by air exposure. Using a sensor with an ISFET sensing element instead of the standard glass membrane can avoid the problem.

Examples are TopHit from Endress + Hauser, Durafet II from Honeywell and TupHet from Emerson.

Alternatively an automatic system could be used that retracts the probe into an isolated (and wetted) standby position when the process line is shut down. These are available from Endress + Hauser, Knick, Mettler-Toledo, Emerson, and probably a few others.

 

[EdStainless]

You might also look at some solid state ion specific probes. Maybe tracking the actual composition would work better. I have used some and have been very pleased.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[CARF]

This one works good with our application.

http://www.pfaudler.com/gle/instmnt.htm

The probe remains in place during batch operation or shutdown and can be stored dry ...

Regards,
CARF