HACH Polymentron 8350SC pH/ORP Sensor

Overview

The HACH Polymentron 8350SC is a high-reliability, industrial-grade pH and oxidation-reduction potential (ORP) sensor engineered for continuous online monitoring in critical water chemistry applications—particularly within fossil fuel and nuclear power generation facilities. It operates on the principle of potentiometric measurement: a glass pH electrode and a noble-metal (typically platinum or ruthenium oxide) ORP sensing element generate a millivolt-level signal proportional to hydrogen ion activity (pH) or electron transfer potential (mV) relative to a stable reference electrode (Ag/AgCl gel-filled). The sensor’s robust, all-in-one probe design integrates the measuring, reference, and temperature compensation elements into a single, pressure-rated body suitable for inline or submersible installation in boiler feedwater, condensate, demineralizer effluent, and turbine lube oil conditioning systems. Its performance adheres to ASTM D1129 (Standard Terminology Relating to Water), ISO 7888 (Water quality — Determination of electrical conductivity), and supports compliance with EPRI guidelines for steam cycle chemistry control.

Key Features

• Integrated dual-parameter sensing: Simultaneous, real-time pH and ORP output via a single analog (4–20 mA) or digital (HART® 7) interface.
• Patented gel-filled Ag/AgCl reference system with low-impedance junction and extended service life—optimized for low-conductivity, high-purity water environments typical in power plant cycles.
• Chemically resistant PEEK and PVDF housing with IP68/NEMA 4X rating; rated for continuous operation up to 10 bar (145 psi) and 105 °C.
• Automatic temperature compensation (ATC) via integrated Pt1000 RTD, enabling accurate pH correction across 0–100 °C per NIST-traceable calibration curves.
• Modular mechanical design: Interchangeable sensing cartridges allow field replacement without recalibration or process shutdown.
• Compatible with HACH SC1000, CL17, and PCA3000 controllers—supporting full diagnostic logging, sensor health monitoring, and predictive maintenance alerts.

Sample Compatibility & Compliance

The Polymentron 8350SC is validated for use in ultrapure water (UPW), deionized water (DI), and low-TDS (< 1 µS/cm) condensate streams where conventional sensors suffer from reference junction clogging, drift, or unstable mV offsets. It meets ANSI/ISA-5.1 instrumentation symbology standards and is designed to support regulatory alignment with U.S. NRC Regulatory Guide 1.69 (Instrumentation and Control Systems) and IEEE 382 (Standard for Qualification of Safety-Related Actuators). Its construction materials comply with FDA 21 CFR 177.2400 (indirect food contact) and RoHS 2011/65/EU. Calibration traceability follows ISO/IEC 17025-accredited procedures when performed using HACH-certified buffer standards (e.g., NIST SRM 186, 187, and 191).

Software & Data Management

When paired with HACH’s Intelligence Platform™ software suite (including Instrument Manager v4.2+ and Asset Insight Cloud), the 8350SC enables secure, audit-ready data handling compliant with FDA 21 CFR Part 11 requirements—including electronic signatures, role-based access control, and immutable audit trails for calibration events, diagnostics, and configuration changes. All sensor-generated diagnostics—including asymmetry potential, reference impedance, slope deviation, and response time—are logged with timestamps and exported in CSV or OPC UA format for integration into DCS, PI System, or Maximo EAM platforms. Firmware updates are delivered via signed, encrypted packages verified through SHA-256 hashing.

Applications

• Boiler feedwater pH control to prevent acid corrosion and caustic gouging in HRSG and drum-type boilers.
• Condensate polishing system monitoring to verify amine treatment efficacy and detect air in-leakage via ORP excursions.
• Steam generator secondary side chemistry surveillance per IAEA NS-G-1.8 and EPRI TR-102393.
• Hydrogen conductivity correlation studies using synchronized pH/ORP/mV data streams.
• Waste heat recovery unit (WHRU) and closed-loop cooling water systems requiring long-term stability under thermal cycling.

FAQ

What is the recommended calibration frequency for the Polymentron 8350SC in power plant service?

Calibration should be performed at least once per shift during commissioning and startup; thereafter, weekly verification is standard for critical loops, with automated drift checks enabled via HART diagnostics.
Can the sensor be used in hydrogen-saturated water systems?

Yes—the platinum ORP element and low-noise reference design ensure stable measurements even under reducing conditions typical of hydrogen-treated condensate.
Does the 8350SC support two-point pH calibration with automatic slope calculation?

Yes—calibration routines in compatible HACH controllers execute full two-buffer (e.g., pH 4.01 and 7.00) slope/offset adjustment with real-time % slope validation against theoretical Nernstian response (−59.16 mV/pH at 25 °C).
Is third-party system integration supported beyond HACH controllers?

Yes—via Modbus RTU (RS-485) or HART transparent mode, enabling integration with Siemens Desigo, Emerson DeltaV, and Yokogawa CENTUM VP using standard device description (DD) files.