Magnetic Flowmeters: Principles and Applications

Magnetic flowmeters are well suited for flow measurement
with conductive fluids.
Image courtesy Yokogawa

Fluid process control operations rely on the operator's ability to accurately determine qualities and quantities of liquid or gaseous materials. In terms of appraising and working with fluids (such as liquids, steam, and gases) the flowmeter is a staple tool, with the simple goal of expressing the delivery of a subject fluid in a quantified manner. Measurement of media flow velocity can be used, along with other inputs, to determine volumetric or mass flow. The magnetic flowmeter, also called a magmeter, is one of several technologies used to measure fluid flow.

In general, magnetic flowmeters are sturdy, reliable devices able to withstand hazardous environments while returning accurate measurements to operators of a wide variety of processes. The magnetic flowmeter has no moving parts. The operational principle of the device is powered by Faraday’s Law, a fundamental scientific principle stating that a voltage will be induced across any conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure quality of a substance to be expressed via the magmeter. In a magmeter application, the meter produces the magnetic field referred to in Faraday’s Law. The conductor is the fluid. The actual measurement of a magnetic flowmeter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with other measurements.

The magnetic flowmeter technology is not impacted by temperature, pressure, or density of the subject fluid. It is however, necessary to fill the entire cross section of the pipe in order to derive useful volumetric flow measurements. Faraday’s Law relies on conductivity, so the fluid being measured has to be electrically conductive. Many hydrocarbons are not sufficiently conductive for a flow measurement using this method, nor are gases. On the other hand, water and aqueous solutions tend to exhibit sufficient conductivity to apply magmeter technology.

Magmeters apply Faraday’s law by using two charged magnetic coils; fluid passes through the magnetic field produced by the coils. A precise measurement of the voltage generated in the fluid will be proportional to fluid velocity. The relationship between voltage and flow is theoretically a linear expression, yet some outside factors may present barriers and complications in the interaction of the instrument with the subject fluid. These complications include a higher amount of voltage in the liquid being processed, and coupling issues between the signal circuit, power source, and/or connective leads of both an inductive and capacitive nature.

In addition to salient factors such as price, accuracy, ease of use, and the size-scale of the flowmeter in relation to the fluid system, there are multiple reasons why magmeters are the unit of choice for certain applications. They are resistant to corrosion, and can provide accurate measurement of dirty fluids – making them suitable for wastewater measurement. As mentioned, there are no moving parts in a magmeter, keeping maintenance to a minimum. Power requirements are also low. Instruments are available in a wide range of configurations, sizes, and construction materials to accommodate various process installation requirements.

As with all process measurement instruments, proper selection, configuration, and installation are the real keys to a successful project. Share your flow measurement challenges of all types with a process measurement specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

New Fluid System Connectors From Miller Energy

One of the many series of quick connect hose couplings
from Parker
Image courtesy of Parker Hannafin

Miller Energy now distributes the Parker line of fittings, couplings, quick connects, and hose products for commercial and industrial applications. The addition of this well known and respected brand to the company's product portfolio enables Miller Energy to serve a wider array of customer needs, as well as integrate the new products with its other process measurement and control products to deliver complete, ready to install, solutions for many applications.

An overview of the quick coupling products, just a part of the new product offering, is provided below. To find out more, contact Miller Energy directly and share your hydraulic, pneumatic, and fluid handling requirements and challenges. Leverage your own knowledge and experience with their product application expertise to develop effective solutions.

Quick Coupling Products Guide - Commercial & Industrial from Miller Energy, Inc.

Miller Energy Expands Product Offering

Miller Energy is now a distributor of Asco solenoid
valves for a wide range of general and special applications

Miller Energy, through its acquisition of a New Jersey based distributor, has greatly expanded the company's offering of solenoid valves, pneumatic system components, and fluid handling and control components.

A solenoid is an electrical device, converting electrical energy input to a linear mechanical force. Solenoids are used to provide rapid two state mechanical movement of other devices. In process control applications, those devices are often fluid control valves.

At the basic level, a solenoid is an electromagnetic coil and a metallic rod or arm. Electrical current flow in the coil creates a magnetic field which will position the rod in one of two locations, depending upon whether the coil is energized. The movable component of the solenoid is linked to, or part of, the operating mechanism of another device. This allows the switched electrical output of a controller to regulate mechanical movement in another device and cause a change in its operation. A common solenoid application is the operation of small valves.

A plunger solenoid contains a movable ferrous rod, sometimes called a core, enclosed in a tube sealed to the valve body and extending through the center of the electromagnetic coil. When the solenoid is energized, the core moves to its equilibrium position in the magnetic field. The core is also a functional part of valve operation. It's repositioning causes a designed changed in the valve operating status (open or close). There are countless variants of solenoid operated valves exhibiting particular operating attributes designed for specific types of applications. In essence, though, they all rely on the electromechanical operating principle outlined here.

A solenoid valve is a combination of two functional units.

• The solenoid (electromagnet) described above.
• The valve body containing one or more openings, called ports, for inlet and outlet, and the valve interior operating components.

Flow through an orifice is controlled by the movement of the rod or core. The core is enclosed in a tube sealed to the valve body, providing a leak tight assembly. A controller energizing or de-energizing the coil will cause the valve to change operating state between open and closed, regulating fluid flow. There are almost countless variants of solenoid operated valves, specifically tailored for applications throughout industrial, commercial, and institutional operations.

The document provided below illustrates a portion of the broad array of solenoid valves available for industrial control applications. Share your fluid control requirements and challenges with an application specialist. Leverage your process knowledge and experience with their product application expertise to produce effective solutions.

ASCO Solenoid Valve Product Line Overview from Miller Energy, Inc.

Bulb and Capillary Temperature Switches

General purpose temperature switch with bottom connection
for capillary and bulb specific for each application.
Image courtesy United Electric Controls

Not all processes or operations require the use of state of the art technology to get the desired results. Part of good process design is matching up the most appropriate methods and technology to the operation.

One method of changing the state of a switch in response to a process temperature change is a bulb and capillary temperature switch. The switch operation produces a state change in the mechanical switch when the temperature of a process control operation crosses a certain threshold. Bulb and capillary switches have the advantage of operating without electricity, simplifying their application.

The physical operating principle behind the capillary thermostat relies on the use of a fluid. The fluid inside the thermostat expands or contracts in response to the temperature at the sensing bulb. The change in fluid volume produces a force upon a diaphragm or other mechanical transfer device. The diaphragm is connected to, and changes the status of, an adjoining circuit using a snap action switch. For example, a main use of the operating principle in action is when a commercial food company relies on the capillary switch to control temperature related to processing and distribution. Each individual use of a bulb and capillary thermostat is specifically designed based on manufacturer and industry specifications, all of which apply the same physical principle of fluid based physics.

Because of their simplicity and comparatively modest cost, commercial versions of bulb and capillary switches find application throughout residential and commercial settings. Some common applications include warming ovens, deep fat fryers, and water heaters. The HVAC industry uses capillary and bulb switches because the rate of temperature change found in their applications fits the adjoining range offered by the bulb and capillary type switches. Operation of the temperature switches is subject to a few limitations. The switching point is often fixed, so the application must be without a requirement for an adjustable setpoint. The temperature range over which the switches are suitable is comparatively limited, with a matching of the bulb and capillary fluid system to the application temperature range a necessary task in product selection. Within its proper sphere of use, though, bulb and capillary temperature switches offer simple, reliable operation, with little requirement for maintenance.

Bulb and capillary switches are typically used to evaluate average temperature and are especially useful for applications where the temperature is to be maintained at a well-known, consistent value. The bulb portion can be configured to accommodate mounting within the media to be controlled. The devices can be applied effectively to liquid and gaseous media when the proper bulb is used.

Industrial versions of bulb and capillary switches are fitted with appropriate housings for the installation environment. Hazardous location installation can be accommodated, as well as high current ratings and auxiliary functions. There are almost countless variants of bulb and capillary temperature switches available. Don’t overlook these simple mechanical devices as candidates for application in any temperature control process. Share your application requirements and challenges with product specialists for useful recommendations.

Temperature, Pressure, Vacuum, and Differential Switches from Miller Energy, Inc.

Application of Load Cells in Process Measurement

The advanced model G5 can handle input signals from multiple load cells
Image courtesy of BLH Nobel

In industrial application of process measurement and control, principles of the physical sciences are combined with technology and engineering to create devices essential to modern high speed, high accuracy system operation. Years of research, development, and the forward march of humanity’s quest for scientific knowledge and understanding yields packaged devices for process measurement that are easily applied by system designer and operators.

Load cells are the key components applied to weighing component or processed materials in modern industrial operations. Load cells are utilized throughout many industries related to process management, or just simple weighing operations. In application, a load cell can be adapted for measurement of items from the very small to the very large.

In essence, a load cell is a measurement tool which functions as a transducer, predictably converting force into a unit of measurable electrical output. While many types of load cells are available, one popular cell in multiple industries is a strain gauge based cell. Strain gauge cells typically function with an accuracy range between 0.03% and 0.25%. Pneumatically based load cells are ideal for situations requiring intrinsic safety and optimal hygiene. For locations without a power grid, there are even hydraulic load cells, which function without need for a power supply. These different types of load cells follow the same principle of operation: a force acts upon the cell (typically the weight of material or an object) which is then returned as a value. Processing the value yields an indication of weight in engineering units.

For strain gauge cells, deformation is the applied operational principal, where extremely small amounts of deformation, directly related to the stress or strain being applied to the cell, are output as an electrical signal with value proportional to the load applied to the cell. The operating principle allows for development of devices delivering accurate, precise measurements of a wide range of industrial products.

Load cell advantages include their longevity, accuracy, and adaptability to many applications, all of which contribute to their usefulness in so many industries and applications. A common place to find a strain gauge load cell in use is off a causeway on a major highway at a truck weigh station. Through innovation, load cells have been incorporated in an efficient measuring system able to weigh trucks passing through the station, without having each stop. Aircraft can be weighed on platform scales which utilize load cells, and even trains can be weighed by taking advantage of the robust and dependable nature of the transducers.

Thanks to their widespread incorporation and the sequential evolution of technology, load cells are a fantastically useful tool in process measurement and control. Share your process weighing challenges with application experts, combining your own process expertise with their product knowledge to develop an effective solution.

Product Update: SMARTDAC+ GX/GP Series Recorders & GM Series Data Acquisition System Release 4

Updated SMARTDAC line of data acquisition instruments
Image courtesy Yokogawa

Yokogawa Electric Corporation announced it's Release 4 of the SMARTDAC+® GX series panel-mount type paperless recorder, GP series portable paperless recorder, and GM series data acquisition system.

With this latest release, new modules are provided to expand the range of applications possible with SMARTDAC+ systems and improve user convenience. New functions include sampling intervals as short as 1 millisecond and the control and monitoring of up to 20 loops.

Overview

Recorders and data acquisition systems (data loggers) are used on production lines and at product development facilities in a variety of industries to acquire, display, and record data on temperature, voltage, current, flow rate, pressure, and other variables. Yokogawa offers a wide range of such products, and is one of the world’s top manufacturers of recorders. Since releasing the SMARTDAC+ data acquisition and control system in 2012, Yokogawa has continued to strengthen it by coming out with a variety of recorders and data acquisition devices that meet market needs and comply with industry-specific requirements and standards.

With this release, Yokogawa provides new modules with strengthened functions that meet customer needs for the acquisition and analysis of detailed data from evaluation tests. These modules decrease the cost of introducing a control application by eliminating the need for the purchase of additional equipment.

Enhancements

The functional enhancements available with Release 4 are as follows:

High-speed analog input module for high-speed sampling.

To improve the safety of electric devices such as the rechargeable batteries used in everything from automobiles to mobile devices, evaluation tests must be conducted to acquire and analyze detailed performance data. For this purpose, sampling at intervals as short as 1 millisecond is desirable. However, this normally requires an expensive, high-performance measuring instrument. When the new high-speed analog input module, a SMARTDAC+ system can sample data at intervals as brief as 1 millisecond, which is 1/100th that of any preceding Yokogawa product. This is suitable for such high performance applications such as measurement of the transient current in rechargeable batteries to vibration in power plant turbines. A dual interval function has also been added that enables the SMARTDAC+ to efficiently and simultaneously collect data on slowly changing signals (e.g., temperature) and quickly changing signals (e.g., pressure and vibration).

PID control module for control function

In applications that need both control and recording, such as controlling the temperature of an industrial furnace or the dosage process at a water treatment plant, there is a need for systems that do not require engineering and can be quickly and easily commissioned. In a typical control and monitoring application, a separate recorder and controller is required to control temperature, flow rate and pressure. At the same time, a data acquisition station must communicate with the controller to ensure data is being capture and recorded. It is time consuming and oftentimes confusing, to ensure the controller and the data acquisition station is communicating seamlessly. By combining continuous recording function of the SMARTDAC+ and PID control module into a single platform, customers can now seamlessly control and record critical process data in one system. The SMARTDAC+ can control, monitor and record up to 20 loops. Each PID control module comes with 2 analog inputs, 2 analog outputs, 8 digital inputs and 8 digital outputs.

Four-wire RTD/resistance module for precise temperature measurement

While three-wire RTDs are widely used in many fields such as research institutes to manufacturing, some applications require higher level of precision and accuracy that is only possible with 4-wire RTDs. A 4-wire RTD is the sensor of choice for laboratory applications where accuracy, precision, and repeatability are extremely important. To satisfy this need, Yokogawa has released a 4-wire RTD/resistance module for the SMARTDAC+.

Target Markets

GX series: Production of iron and steel, petrochemicals, chemicals, pulp and paper, foods, pharmaceuticals, and electrical equipment/electronics; water supply and wastewater treatment facilities.

GP series: Development of home appliances, automobiles, semiconductors, and energy-related technologies; universities; research institutes.

GM series: Both of the above target markets.

For more information on the SMARTDAC+ GX/GP Series Recorders & GM Series Data Acquisition System contact Miller Energy at (800) 631-5454 or by visiting the company website.

Electronic to Pneumatic Converter

Component schematic using electronic controller and pneumatic
control valve
Image courtesy of Yokogawa

A straight forward device, the current to pneumatic converter produces a pneumatic output signal that is proportional to an electrical control level input signal of 4 to 20 mA or 10 to 50 mA. This provides a useful interface between electronic controllers and pneumatically operated valves, air cylinders, or other air operated control elements.

Pneumatic signals are regularly used throughout many installations as matter of safety, legacy, or because a pneumatic signal can provide motive power to an operating device such as a valve positioner. Electrical control signals can be transmitted long distances across wires to deliver control signals to operating elements. The current to pneumatic converter provides a bridge between the two systems and allows the most beneficial aspects of each to be brought to bear on process operation.

Converters are available in standard variants that accommodate a number of hazardous location designations, as well as several output pressure ranges and calibrations. Share your process control connectivity challenges with application specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Current to Pneumatic Converter from Miller Energy, Inc.