pH sensor life extended from 3 days to 75 days in fluoride mixture
The customer was measuring pH in a
chemical tank containing fluorides as well as other acids and bases.
The pH swings from concentrated acid (pH = 1) to concentrated
caustic (pH = 14). In this
hostile environment, the customer would consume a non-McNab pH probe in
one or two days. Three days
was the maximum probe life.
To solve this problem, the customer
McNab Aqua-Purometer Model AP-IH pH
analyzer, along with a Model MP-41 antimony pH probe.
The antimony probe uses no glass, and is therefore immune to the
problems of normal glass pH sensors.
Instead, the sensor uses a rugged piece of metal (antimony).
The first probe used got a life of two weeks, four times the
previous longest life. That
first probe was then restored with a light cleaning and was used for an
additional two months.
The analog 4-20 mA output from the AP-IH
drives the customer's control system and the acid addition is now
controlled with much higher stability. Control within + 0.2 pH unit is
achieved for long periods of time.
Cost savings are achieved by the reduced
consumption of pH sensors. However, the most dramatic saving is the
reduction of labor because the system down time and labor required for
replacement of pH probes is greatly reduced.
The stability achieved in this
application gives additional savings. Consumption of caustic and base is
reduced. This stability
also contributes to longer probe life because destructive pH levels
(e.g. pH=1) are avoided.
Questions? Contact McNab
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