Magnetic Level Indicators

Configurations of magnetic level gauges
Image courtesy Orion/Magnetrol

Fluid process control operations often involve vessel or tank storage of liquids. Continuous and accurate indication of the liquid level within the tank is an essential data point for process control decision making and safety. Several methods and instrument types are available for tank level measurement, each with its own set of attributes that may be advantageous for a particular installation. Selection criteria for a tank liquid level indicator may include:

• Direct or indirect measurement of level
• Level measurement accuracy and reliability
• Tank shape, regular or irregular
• Media compatibility with measurement device
• Requirements for maintenance or calibration
• Compatibility with process temperature and pressure range
• Local display and visibility
• Level indication signal type and transmission
• Level alarm switches or other indicators

The selection of a magnetic level indicator, also referred to as a magnetic level gauge, for the project will likely be based upon at least one of the instrument's strengths. Magnetic level gauges have a host of potentially positive features for level indication.

• Continuous level measurement
• Operable without electric power
• Direct visual tank fluid level indication, regardless of tank shape or profile.
• Wide range of operating temperature and pressure
• Breakage resistant construction
• Range of construction materials available to accommodate corrosive media
• Measuring indicators, switches, and transmitters mounted externally, without contacting the medium being measured.
• Low maintenance operation.
• Readable level indication from greater distance than glass sight gauges.
• Applicable to large fluid level ranges with a single instrument.

Magnetic level indicators have a strong position in the tank liquid level measurement field and should be considered as a candidate for fulfilling those application requirements. There are many options available to customize the level indicator for each specific application. I have included a technical data sheet from Orion Instruments, a manufacturer of level instrumentation, for more detail. Share your application challenges with a sales engineer that specializes in level measurement. Combining your process knowledge with their product application expertise will yield positive solutions.

Magnetrol Orion Magnetic Liquid Level Indicators from Miller Energy, Inc.

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.