Fluoride Removal Analyzer FX-300-F-AS

 

 

Measure and control fluoride at low pH

 

 

What It Does For You

The fluoride and pH sensors used in the FX-300-F-AS were designed specifically to control fluoride levels in cleaning and etching operations as well as in fluoride waste reduction treatment.

You get more reliable readings with less down time and longer sensor life because the sensors can survive the corrosive nature of the solution as well as the aggressive cleaning required to keep them functional.

 

Risks

Hydrofluoric acid (HF) is a corrosive chemical that is extremely toxic to human tissue that will dissolve glass.

Industrial process streams must be treated to reduce fluoride concentrations to meet mandated waste discharge limits.

HF Uses

HF is used in many industrial processes including: to make refrigerants, as a metal cleaner and stainless steel pickling agent, aluminum can etching, to remove silicon dioxide in semiconductor wafer production, to etch glass, chrome and enamel products.

Problems for Electrodes

Low pH in the presence of high HF levels destroys general purpose fluoride and pH sensors.

HF dissolves the glass in most commercial pH sensors. Etching solutions drain the sensor's reference  of its internal salts, which causes drifting.

In treatment, fluoride is converted to calcium fluoride salt for removal, but also precipitates onto the sensing element and reference surface, reducing sensor response.

Most fluoride ion selective electrode sensing elements and reference junctions are destroyed by the low pH solution being measured.

A Better Fluoride Electrode

The fluoride electrode's sensing element is protected from acidic solutions by a special seal.

The solid state polymer reference junction is engineered to resist acid, fluoride and shifting that can occur in high ionic strength solutions.

The reference surface surrounding the sensor tip can withstand cleaning with concentrated or dilute hydrochloric acid as well abrasive removal, even scraping with a razor knife, of hardened deposits.

The sensor is fully submersible due to chemical resistant materials used for waterproofing.

 

A Better pH Sensor

pH sensors include specially formulated, true HF resistant glass.

Deposits can be removed from the solid state reference surface with concentrated or dilute hydrchloric acid and by abrasive scrubbing or scraping to produce a clean "new" surface.

Thicker pH glass used with some sensors doesn't offer HF resistance, it only slows the rate of degradation.

ISFET and antimony based pH sensors have HF resistance but lack the stability and accuracy of a glass element sensor.

Cable and sensor waterproofing is provided with chemical resistant flexible tubing and sealant to allow full submersion into the process fluid.

System Summary

Concentration range: 0.019 - 19,000 ppm

pH range: 0 - 9.5 pH continuous

Standard System Results: free fluoride, pH, pH compensated total free fluoride

Available with analog or smart digital pH sensors

 

Product Features

The standard system includes Din rail mounted transmitters each with 3-digit LED display and 0/4-20mA output for free fluoride, pH, and pH compensated total free fluoride.

Each module can also display temperature and the absolute millivolt reading.

The total fluoride module also includes RS485 Modbus RTU output of all inputs including temperature.

The standard 7" wide IP65 wall mount enclosure with lift up clear lid features a 6A fused power entry module with 2-meter power cord for AC input from standard US grounded outlets.

The modular system can be supplied in a 10" wide enclosure  for two additional functions that can include temperature output, additional fluoride, pH or other measurements, or data logging.

Download  FX-300-F-AS Brochure

 

pH Compensation

The FX-300-TOT module computes the total free fluoride concentration when the process is below 6pH. It's based on the free fluoride activity at a given temperature and pH;  and the extent of ionization of HF.

The extent of ionization defines the percentage of fluoride that is converted into the unbound form the sensor can detect: the free ionized fluoride species.

The total ISE displayed is the value computed as if all fluoride present is the ionic form.

 

 

The Fluoride Sensor

Sensors can only be submerged into a tank or, if the process allows, inserted into a tank using stainless steel hot tap insertion fittings.

Inline mounting into a pipe is not recommended because the special sealing gasket tends to trap bubbles at the sensing tip, preventing a measurement.

Chemical resistant waterproofing sealing protects both the back of the sensor and cable.

For cable lengths over 20 feet sensors are provided with either an integral or external analog preamplifier. Digital electronics are not available for fluoride.

Cable extensions with water resistant snap connectors make handling easier and minimize replacement sensor cost. You replace only the cable integral to the sensor, not the entire length.

 

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The pH Sensor

One of the few pH sensors available with true high HF resistant reference that can function at low pH in the presence of high concentrations of fluoride.

The solid state reference prevents intrusion of gas or liquids into the junction and can withstand acid cleaning as well as scraping to remove deposits on the sensor.

Chemical resistant flexible tubing seal protects the back of the sensor and sensor cable.

Digital sensors with auto calibration are also available


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Our customer, a supplier to the semiconductor industry, was replacing fluoride and pH sensors weekly due to precipitate buildup and the harsh conditions of their HF waste reduction treatment. After installing the FX-300-F-AS in January 2018, the first replacement sensors were installed 16 months later in May 2019.

A Confidential US Supplier to Semiconductor Manufacturers