HSI’s TRO sensor has a number of advantages when used in seawater electro chlorination systems. Existing membrane amperometric and reagent feed systems have serious drawbacks in this application.
Flow independence, self-cleaning electrodes and long calibration retention are the HSI TRO Sensor’s greatest strengths. The sensor employs 3 electrode amperometry, bare electrodes and an integrated cleaning system.
Wide Measurement Range
The sensor can also measure TRO levels up to 20 ppm. A magnetically coupled pump in the sensor tip provides a fixed constant flow across the electrodes. All amperometric sensors are flow sensitive. By providing a high, constant velocity, sensitivity and the signal to noise ratio are improved for lower TRO detection levels. The integrated pump uses a Brushless DC motor. The impeller is molded from an engineered polymer formulation with low friction and long life.
– No Membranes Or Electrolyte –
Bare Electrodes are used thus eliminating the need to replace clogged membranes or replenish electrolyte required by conventional amperometric sensors. This results in much lower maintenance requirements. In competing amperometric sensors, diluted electrolyte requires periodic sensor recalibration to compensate for this.
Low Maintenance - Self-Cleaning
The sensor has a cleaning feature. Polymeric beads are captured within the sensor and abrade the electrodes to minimize biofouling and remove calcium carbonate that deposits on the electrodes during operation in seawater. The beads are motivated by the flow from the internal pump.
No Reagents or Waste Stream - Lower Cost Installation and Maintenance
HSI’s sensor does not require reagents or a waste stream for both lower maintenance and installation costs. Colorimetric systems require reagent replenishment every month as well as periodic replacement of pump and optical components. These can be difficult to troubleshoot and the tubing is subject to biofouling. Reagent and parts can exceed $600 per year excluding labor.
Accuracy from Freshwater to Seawater
HSI’s sensor measures five different parameters every minute: TRO, Oxidation Reduction Potential-ORP, pH, Salinity and Temperature. These measurements are used to compensate for changes detected in the water source. While pH of seawater does not change much, in brackish or freshwater, the pH can change drastically. In freshwater, the sensor also uses the conductivity measurement to compensate for signal changes. The temperature sensor enables compensation of all the parameters over -2 ° to 35 °C. This enables the sensor to operate and deliver accurate readings in virtually any water condition that a ship may encounter.
Better Reliability Through Electrochemical Cleaning
An electrochemical stabilization technique is used to prevent passivation of the electrodes. Passivation due to organic poisoning is a frequent problem with bare electrode amperometric sensors. This enables the sensor to stabilize and provide accurate readings, usually within one to two minutes. Other competing bare electrode sensors require up to 24 hours after starting up for reliable readings.
Direct Pipe Insertion for fast response and lower cost installation
The sensor is capable of measurements at velocities from zero to 4.5 meters per second with less than a 5% change in signal thanks to its integrated pump. HSI has the only TRO sensor capable of direct insertion into a pipe.
This coupled with the elimination of the need for a waste stream simplifies the installation and maintenance. The Hot Tap version is shown Figure 2. This enables removal of the sensor from the plumbing without the need to drain the plumbing. This eliminates the need for a sampling pump, switching valves, sampling lines and sample filtration dramatically lowering installation cost.
High Pressure, Rapid Wetting pH Sensor
Halogen uses a unique pH cartridge in its sensor system. The pH cartridge can withstand 10 bar to -0.7 bar pressures and rapidly wets if allowed to dry out. Accuracy is restored within 3 minutes. The pH electrode is only one available with these specifications. It does not require calibration for a year or more. Cartridges are replaced every two years.
Novel Patented Technology
This technology is so novel, that it was granted five US Patents, two Korean Patents, one Chinese patent with other patents pending. In conclusion, the subject sensor has overcome many of the limitations of the existing technologies in the measurement to TRO in seawater.