The Case for Clamp-on Flow Meters: Part 1
By Thomas Michalowski
Flow, along with pressure and temperature, is one of the most important parameters when monitoring or controlling the fluids in pipes. Temperature and pressure are often measured alongside flow to calculate the energy flow in a pipe, but very often, especially in the water and waste sector, flow rate can
be the sole parameter that is measured, either to quantify the flow for fiscal purposes or to control the flow as part of a process. There is a wide diversity of flow meters and each type has their advantages and disadvantages. Most flow meters are inserted within the flow, often via spool pieces, to ensure the best flow through the meter itself. Sometimes it can be inconvenient to integrate a flow meter within a pipe. Or sometimes a meter provides a temporary replacement or checks on existing equipment. In these cases, the clamp-on flow meter provides a reliable and cost-effective solution.
The Technologies of Flow Metering
Flow metering really goes back to the ancient Egyptians who devised a water clock around 1500 B.C. However, only since the industrial revolution has flow metering developed to satisfy the need to measure flows accurately for billing purposes and/or to monitor industrial processes. The first industrial flow meters relied on fluid displacement and various designs included piston meters, paddle wheels, Pelton wheels and turbine flow meters. Today, displacement meters feature precision rotors with revolutions counted by integral electronic pulse transmitters. Flow meters based on Bernoulli’s equation are still very widespread and range from simple pitot tubes to Venturi meters and orifice plates, all of which function by measuring the pressure differential at a constriction introduced into the pipe flow and then applying the Bernoulli calculation. Over recent years a number of modern technologies have evolved. These include optical flow meters, which use laser light to detect particles entrapped within gases to obtain flow velocity; magnetic flow meters, which use Faraday’s law of electro-magnetic induction; and thermal mass flow meters.
Today, major newcomers firmly establishing themselves in the flow metering portfolio include vortex meters, Coriolis meters and ultrasonic meters.
We will talk about the types of flow meters in part 2!