Hach 9184 sc Amperometric Free Chlorine Sensor System

Hach 9184 sc amperometric free chlorine sensor system for 0 to 20 mg/L residual chlorine

The Hach 9184 sc is an amperometric free chlorine analyzer that measures hypochlorous acid (HOCl) through a membrane electrode and, together with pH and temperature, calculates total free chlorine (TFC). It is delivered as a pre-assembled panel with a flow cell and the sensors, and it connects to a Hach sc digital controller. Because it uses a membrane system, the manufacturer states that no reagents are needed for the measurement. Seven Star LLC supplies the 9184 sc in Oman and the GCC as an independent supplier in Muscat, and this page explains the measurement principle, options and ordering points.

How the 9184 sc measures free chlorine

The measuring cell contains a gold cathode and a silver anode behind a membrane with electrolyte. Hypochlorous acid diffuses through the membrane and is reduced at the cathode, which produces a current proportional to its concentration. The standard 9184 sc sensor measures HOCl, temperature and pH, then uses dissociation curves stored in the instrument to calculate hypochlorite ions (OCl-); HOCl plus OCl- equals total free chlorine. The data sheet notes that there is no interference from chloramines, whereas chlorine dioxide and ozone do interfere. Free chlorine is the quantity that actually disinfects, so the sensor suits residual monitoring where chloramine would give a false high reading in a total-chlorine test.

Technical specifications of the 9184 sc

Options: acidification, intermittent flow and HOCl-only

• Acidification Unit: keeps accuracy at 2 percent when the sample pH is above 7.5, by forcing the sample pH to between 5.5 and 6.5. It can also inject cleaning solution through the cell, always on or programmed through controller relays. It has a power switch and is NEMA 4X/IP66 compliant.
• Intermittent Flow Unit: programmable through controller relays, it limits sample flow to drain to save water. It connects in series with the analyzer and also needs one controller input.
• HOCl-only version: a sensor that does not compensate for pH, intended for applications where the pH does not fluctuate; the data sheet says it is available only after consultation with technical support.

Calibration, maintenance and consumables

Zero calibration can be done electrically, which is automatic, or with dechlorinated water. Span calibration compares the sensor with a laboratory method on a process sample. The pH cell is calibrated with single- or two-point standards or by comparison with a laboratory method. The manufacturer suggests a calibration interval of two months, a membrane and electrolyte change every six months in typical use and a pH cell replacement every one to one and a half years. Two years of typical maintenance items are included with the system. A fouled or pinched sample line, air in the flow cell or a pH above the compensation limit are the commonest reasons for unstable readings.

Selection and ordering checklist for the 9184 sc

• Sample pH: choose the Acidification Unit if the pH regularly exceeds 7.5.
• Presence of ozone or chlorine dioxide, which interfere with the measurement.
• Sample temperature and pressure within 2 to 45 °C and 0.1 to 2 bar in the flow cell.
• Water consumption limits: consider the Intermittent Flow Unit.
• Controller: SC4500, sc200 or sc1000 with the necessary outputs; controllers accept two to eight sensors.
• Spare membranes, electrolyte and pH cell.

Installation

Mount the pre-assembled panel on a flat, vertical surface close to the sampling point. Provide a clean, representative sample at a stable flow, connect the sample line to the 1/4 inch fitting and run the 1/2 inch drain line to a safe point. Plug the sensor into the controller; as a digital sc sensor it needs no complex wiring. Allow the sensor to polarise and stabilise before calibration, then verify against a lab test of the same sample. Protect the panel from direct sun and heat, since the operating range is 0 to 45 °C.

Typical applications in Oman and the GCC

Typical uses are residual chlorine monitoring in drinking water distribution and storage, chlorination control after desalination and remineralisation, cooling water and industrial water disinfection, and effluent checks before discharge or reuse. The manufacturer lists drinking water, wastewater, pure water and power, and industrial water as markets. Chlorine dosing in a hot climate decays quickly in storage, so continuous measurement helps keep a residual at the required level without overdosing.

Information to send with an RFQ for the 9184 sc

• Model: 9184 sc with options (acidification, intermittent flow)
• Sample pH, temperature and flow
• Controller model and outputs
• Spares for the first two years
• Quantity and delivery site

Documents and quotation

The Hach 9184 sc data sheet is attached on this page. It contains the specification table, the options and the principle of operation.

Send the application data and Seven Star LLC will confirm availability and prepare a quotation.