Company Profile

Electromagnetic Meters and Electromagnetic Flow Meters: High-Accuracy In-Line Wastewater Trackers

Quick Answer

Silver Instruments electromagnetic flow meters measure wastewater flow inline with no moving parts and no pressure drop. Standard accuracy is plus or minus 0.5 percent of reading for sizes from DN15 to DN2000. Send your pipe size, flow range, and wastewater type to get a technical quote.

What These Meters Do in Wastewater Lines

An electromagnetic flow meter works by measuring voltage generated when conductive liquid moves through a magnetic field. In wastewater service this method avoids rotors, gears, and other mechanical parts that clog or wear. Many wastewater plants call these magmeters. Silver Instruments supplies these meters for raw sewage, treated effluent, sludge return lines, and chemical dosing flows.

Accuracy and Repeatability for Inline Tracking

The standard accuracy for Silver Instruments electromagnetic flow meters is plus or minus 0.5 percent of reading. For clean water or low solids streams we can supply a calibration option with plus or minus 0.2 percent. Repeatability is plus or minus 0.1 percent in most sizes. Because there is no obstruction in the pipe, pressure loss stays close to zero even on DN300 and larger lines.

Key Specifications for Wastewater Service

Most wastewater sites order sizes from DN25 to DN600. We also produce DN15 for chemical dosing and up to DN2000 for large effluent mains. The minimum fluid conductivity is 5 µS/cm. Standard liners include PTFE, PFA, and polyurethane. Electrode options include 316L stainless steel, Hastelloy C, titanium, and tantalum.

Output options cover 4-20 mA HART, pulse, and RS485 Modbus. Power options are 220 V AC, 24 V DC, or battery powered for remote sites. Process temperature ratings go to 60°C for polyurethane liner and 120°C for PTFE liner. Pressure ratings are PN10, PN16, PN40, or ANSI 150 depending on flange type.

Liners and Electrodes That Last in Wastewater

Raw sewage often contains sand, fats, and small solids. We recommend polyurethane liner for abrasive sludge because it resists wear better than PTFE in many low temperature lines. For chemical dosing or higher temperature, PTFE or PFA works better. For sludge with viscosity above 100 cP, the full bore design still performs because there are no moving parts.

Electrode selection depends on the effluent chemistry. 316L is enough for most municipal wastewater. If the stream contains chlorides or acids, Hastelloy C or titanium gives longer service life. Tantalum is available for severe chemical conditions.

Installation Advice from Field Sites

In practice, most installation problems come from poor grounding or partially full pipes. Silver Instruments electromagnetic flow meters include empty pipe detection. We recommend mounting the meter in a location where the pipe stays full. For straight run, allow 5 pipe diameters upstream and 2 pipe diameters downstream. For pump discharge lines, install the meter at least 10 pipe diameters downstream of the pump to reduce turbulence.

Most engineers skip this part until a meter reads zero. Empty pipe detection then becomes useful. We have seen this on customer sites many times. A wastewater contractor in Surabaya, Indonesia installed a DN100 meter close to a pump outlet and saw unstable readings. After moving the meter to a full pipe section with proper straight run, the reading stabilized and matched the plant totalizer within 0.4 percent.

Recommended Models for Wastewater Tracking

For general raw sewage and effluent lines, the Silver Instruments SI-EM series is the standard choice. It covers DN15 to DN2000 and includes 4-20 mA HART plus Modbus. For sludge with high solids, we specify polyurethane liner and stainless steel grounding rings. For hazardous areas, we supply ATEX Zone 1 appr