This application story explores the technical requirements for monitoring the volume of chemical coagulants within a water treatment facility. It details the selection of a specialized hydrostatic level transmitter designed to withstand the corrosive nature of Ferric Aluminium Sulphate while preventing the common issue of sensor clogging in viscous media.
- High-purity 99.9% Alumina Ceramic diaphragm provides exceptional resistance to aggressive chemical attack.
- Flush-mounted sensor design eliminates the risk of particulate buildup and measurement drift in pasty or polluted fluids.
- PVDF pressure port material ensures long-term structural integrity when exposed to acidic dosing chemicals.
- Capacitive sensing technology offers high accuracy and overpressure protection for low-range hydrostatic measurements.
Monitoring the inventory of Ferric Aluminium Sulphate in a water treatment works presents significant challenges for standard instrumentation due to the chemical’s corrosive properties and its tendency to be viscous or contain particulates. In this specific installation, the liquid is stored in a horizontal cylindrical vessel, where precise level data is essential for maintaining consistent dosing rates. Standard stainless steel sensors often face long-term degradation when exposed to alum-based coagulants, and traditional recessed pressure ports are prone to clogging as the media can leave pasty residues or trap air bubbles, leading to inaccurate readings and frequent maintenance.
The solution involves the implementation of the LMK 351 series, which is specifically engineered for low-pressure applications and aggressive environmental conditions. Unlike traditional strain gauge sensors, this transmitter utilizes a capacitive ceramic sensor element. This technology is particularly advantageous for a 0 to 4 mH2O range because it maintains high sensitivity and stability at low pressures while offering robust overpressure resistance. By using a flush-mounted G1 1/2 inch process connection, the sensor face sits level with the internal wall of the pipework or tank mounting, ensuring that no media can accumulate or “bridge” across the sensing area. This “self-cleaning” geometry is vital for coagulants that might otherwise transition into a semi-solid state or trap pollutants within a standard cavity.
Material compatibility is the primary defense against the aggressive chemical profile of Ferric Aluminium Sulphate. The LMK 351 configuration features a pressure port constructed from PVDF (Polyvinylidene Fluoride), a high-performance fluoropolymer that offers a higher safety margin against corrosion compared to standard 316L stainless steel in chemical dosing applications. Complementing this is a diaphragm made from 99.9% Alumina Ceramic (Al2O3). This high-purity ceramic is nearly inert to most acids and slurries, providing a durable sensing interface that does not suffer from the metallic fatigue or chemical pitting often seen in alloy-based diaphragms. For the internal seals, EPDM was selected due to its proven performance with alum-based water treatment chemicals, ensuring a leak-proof and chemically stable assembly.
To ensure accuracy in a vented storage vessel, the transmitter is configured with a gauge or vented reference. This allows the internal sensor to compensate for fluctuations in barometric pressure, which is critical for maintaining an accurate 4-20mA output signal proportional to the liquid height. Given the typical environment of a water treatment plant, the electrical connection is provided via a high-integrity cable outlet with an IP67 waterproof rating. This setup includes an integrated ventilation tube within the cable, allowing the sensor to “breathe” to the atmosphere while remaining completely protected from moisture ingress or accidental submersion. This combination of advanced material science and application-specific mechanical design provides a maintenance-free level measurement solution for the most demanding chemical storage applications.
LMK351 Flush Ceramic Diaphragm Level Transmitter with PVDF Connection and EPDM Seals
- Part Number: 471-4000-1-3-TA0-M00-3-B-C-000
- Pressure Range: 0 to 4 mH2O (Nominal pressure 0.4 bar)
- Reference Type: Gauge / Vented (atm to +P)
- Accuracy: 0.35% FSO (Standard)
- Output Signal: 4-20mA (2-wire)
- Electrical Connection: Cable outlet with 2m of PVC cable (IP67)
- Process Connection: G1 1/2 male DIN 3852 with flush diaphragm
- Media Exposed Seals: EPDM
- Diaphragm Material: Ceramic Alumina (Al2O3) 99.9%
- Process Connector Material: PVDF (Aggressive media version)