The Principle and Design of High-pressure Wafer-type Magnetic Flowmeter

Contents

The invention relates to the field of magnetic flowmeters, in particular to a high-voltage wafer-type magnetic flowmeter.

Background of the Invention

Industrial process control systems are used to monitor and control industrial processes that produce or deliver fluids, etc. In such systems, it is typically important to measure "process variables" such as temperature, pressure, flow, etc. Process control transmitters are used to measure such process variables and transmit information related to the measured process variables back to a central location such as a central control room.

One type of process variable transmitter is a magnetic flowmeter (or fluxmeter). A magnetic flowmeter measures flow by using the Faraday induction effect, which is an electromagnetic effect. A magnetic flowmeter includes a coil that is energized to generate a magnetic field across a portion of a flow conduit, such as a pipe. This magnetic field induces an electromotive force (emf) in the process fluid flow. The induced voltage drop across the process fluid flow is related to the flow velocity, which is proportional to the volumetric flow rate and the cross-sectional area of ​​the flow conduit. This voltage drop is typically measured by electrodes connected to the process fluid either directly or via a capacitive coupling.

Electromagnetic flow measurement technology is generally applicable to ionic solutions, water-based fluids, and other conductive fluids. Exemplary environments where magnetic flowmeters can be used include: clean food and beverage production, water treatment facilities, high-purity pharmaceutical manufacturing, and chemical processing including hazardous and corrosive process fluid flows. In addition, magnetic flowmeters are also used in the hydrocarbon fuel industry, including hydrocarbon extraction and processing and hydraulic fracturing technology using abrasive and corrosive cement.

Magnetic flowmeters provide fast and accurate flow measurement in applications where other flow measurement technologies that introduce a flow measurement element (such as an orifice plate) into the process fluid stream are not suitable. One of the huge costs in the manufacture of magnetic flowmeters is the flow tube through which the process fluid flows. The flow tube must withstand the process fluid pressure and must not introduce any leaks into the process. Typically, the flow tube includes a pair of flanges that are bolted to the pipe flange to form a solid process fluid connection. However, in some cases, the added cost of flanged flow tubes may be cost prohibitive.

In this case, a flangeless or wafer-type magnetic flowmeter is used. A wafer-type magnetic flowmeter includes a flow tube without any flanges. Therefore, a wafer-type magnetic flowmeter can be more economical, more compact, and lighter than a conventional flanged magnetic flowmeter. An example of a commercially available wafer-type magnetic flow sensor is available from Emerson Process Management, sold under the commercial designation model 8711 wafer sensor. When the magnetic wafer sensor is paired with appropriate transmitter electronics (such as those sold under the commercial designation model 8732E, model 8712E, or 8712H), a fully operational wafer-type magnetic flowmeter can be provided.

Summary of the invention

A wafer-type electromagnetic flow sensor includes a one-piece chassis having a pair of surfaces and a flow conduit extending between the pair of surfaces.

Each surface of the chassis includes a component configured to engage a metal seal ring. An insulating bushing is disposed in a flow conduit of the one-piece chassis. A plurality of electromagnetic coils are configured to generate magnetic flux in a process fluid flowing through the flow conduit. A pair of electrodes are configured to be electrically connected to the process fluid. A feedthrough assembly is configured to maintain process fluid pressure while allowing a plurality of electrical conductors to pass through the feedthrough assembly.