Showing posts with label process measurement. Show all posts
Showing posts with label process measurement. Show all posts

Thursday, September 14, 2017

Pressure Measurement Using Isolation Ring



The D81 Isolation Ring from Winters Instrument provides a solution for measuring system pressure in processes involving fluids with potential to clog or damage sensors and impulse lines. The isolation ring has a hollow elastomer that is located between two flanges. A fitting on the elastomer section allows for connection of a gauge or transmitter without disturbing the process fluid. Pressure in the piping system is mirrored by pressure within the hollow portion of the isolation ring, measured by the connected instrument. The instrument does not come in contact with the process fluid, nor are there any small diameter impulse lines to foul or clog. Applications in mining, water treatment, pulp and paper abound. Any challenging fluid is a good candidate for application consideration. Models are available up to 48" line size, with wafer, flanged, or threaded connections.

Share your fluid process measurement requirements with application specialists, combining your own knowledge and experience with their product application expertise to develop effective solutions.



Tuesday, August 8, 2017

Orifice Plate - Primary Flow Element

orifice plate drawing
Orifice plates are simple in appearance, but exhibit
precision machining.
Image courtesy of Fabrotech Industries
An orifice plate, at its simplest, is a plate with a machined hole in it. Carefully control the size and shape of the hole, mount the plate in a fluid flow path, measure the difference in fluid pressure between the two sides of the plate, and you have a simple flow measurement setup. The primary flow element is the differential pressure across the orifice. It is the measurement from which flow rate is inferred. The differential pressure is proportional to the square of the flow rate.

An orifice plate is often mounted in a customized holder or flange union that allows removal and inspection of the plate. A holding device also facilitates replacement of a worn orifice plate or insertion of one with a different size orifice to accommodate a change in the process. While the device appears simple, much care is applied to the design and manufacture of orifice plates. The flow data obtained using an orifice plate and differential pressure depend upon well recognized characteristics of the machined opening, plate thickness, and more. With the pressure drop characteristics of the orifice fixed and known, the measuring precision for differential pressure becomes a determining factor in the accuracy of the flow measurement.

There are standards for the dimensional precision of orifice plates that address:
  • Circularity of the bore
  • Flatness
  • Parallelism of the faces
  • Edge sharpness
  • Surface condition
Orifice plates can be effectively "reshaped" by corrosion or by material deposits that may accumulate from the measured fluid. Any distortion of the plate surface or opening has the potential to induce measurable error. This being the case, flow measurement using an orifice plate is best applied with clean fluids.

Certain aspects of the mounting of the orifice plate may also have an impact on its adherence to the calibrated data for the device. Upstream and downstream pipe sections, concentric location of the orifice in the pipe, and location of the pressure measurement taps must be considered.

Properly done, an orifice plate and differential pressure flow measurement setup provides accurate and stable performance. Share your flow measurement challenges of all types with a specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Monday, January 9, 2017

Summary of Technologies Used For Continuous Liquid Level Measurement in Industrial Process Control

differential pressure transmitter with purge control for downpipe measurement
Differential pressure liquid level transmitter with
integrated downpipe purge control (bubbler method)
Courtesy King-Gage
Automated liquid processing operations in many fields have requirements for accurate and reliable level measurement. The variety of media and application criteria demand continuous improvement in the technology, while still retaining niches for older style units utilizing methods that, through their years of reliable service, inspire confidence in operators.

Here is a synopsis of the available technologies for instruments providing continuous liquid level measurement. All are generally available in the form of transmitters with 4-20 mA output signals, and most are provided with additional outputs and communications. What is notably not covered here are level switches or level gauges that do not deliver a continuous output signal corresponding to liquid level.

Whether considering a new installation or upgrading an existing one, it can be a good exercise to review several technologies as possible candidates for a project. None of the technologies would likely be considered the best choice for all applications. Evaluating and selecting the best fit for a project can be facilitated by reaching out to a product application specialist, sharing your applications challenges and combining your process knowledge with their product expertise to develop an effective solution.

Displacer – A displacer is essentially a float and a spring that are characterized for a particular liquid and range of surface level movement. The displacer moves in response to liquid level, changing the location of a core connected to the displacer by a stem. The core is within a linear variable differential transformer. The electrical output of the transformer changes as the core moves.

Guided Wave Radar – A radar based technology that uses a waveguide extending into the liquid. The radar signal travels through the waveguide, basically a tube. The liquid surface level creates a dielectric condition that generates a reflection. Calculations and processing of the emitted and returned signals provide a measure of distance to the liquid surface. No moving parts.

Magnetostrictive – A method employing measurement of the transit time of an electric pulse along a wire extending down an enclosed tube oriented vertically in the media. A magnetic float on the exterior of the tube moves with the liquid surface. The float’s magnetic field produces the return signal to the sensor. Processing the time from emission to return provides a measure of distance to the liquid surface.

Pulse Burst Radar - A radar based technology employing emissions in precisely timed bursts. The emission is reflectex from the liquid surface and transit time from emission to return is used to determine distance to media surface.  Not adversely impacted by changes in media conductivity, density, pressure, temperature. No moving parts.

Frequency Modulated Continuous Wave Radar – Another radar based technology that employs a radar signal that sweeps linearly across a range of frequencies. Signal processing determines distance to media surface.  Not adversely impacted by changes in media conductivity, density, pressure, temperature. No moving parts.

RF Capacitance - As media rises and falls in the tank, the amount of capacitance developed between the sensing probe and the ground reference (usually the side metal sidewall) also rises and falls. This change in capacitance is converted into a proportional 4-20 mA output signal. Requires contact between the media and the sensor, as well as a good ground reference. No moving parts.

Ultrasonic Non-Contact – Ultrasonic emission from above the liquid is reflected off the surface. The transit time between emission and return are used to calculate the distance to the liquid surface. No contact with media and no moving parts.

Differential Pressure – Pressure sensor at the bottom of a vessel measures the pressure developed by the height of the liquid in the tank. No moving parts. A variation of this method is often called a bubbler, which essentially measures hydrostatic pressure exerted on  the gas in a tube extending into the contained liquid. It has the advantage of avoiding contact between the measuring instrument parts, with the exception of the dip tube, and the subject liquid.

Laser - Probably one of the latest arrivals on the liquid level measurement scene, laser emission and return detection is used with time interval measuring to accurately determine the distance from the sensor source to the liquid surface.

Load Cell - A load cell or strain gauge can be incorporated into the support structure of the liquid containing vessel. Changes in the liquid level in the vessel are detected as distortions to the structure and converted, using tank geometry and specific gravity of the liquid.

All of these technologies have their own set of attributes which may make them more suitable to a particular range of applications. Consulting with a product specialist will help determine which technologies are the best fit for your application.

Tuesday, September 27, 2016

Multivariable Flow Measurement For Liquids, Gases, and Steam

Insertion flow meter for steam, liquids, or gases
RIM 20 Rotor Insertion Flowmeter
Courtesy Spirax Sarco
Combining multiple measurement capabilities into a single instrument is generally advantageous over installing separate devices to cover an array of parameters. A simple reduction in fittings and connection complexity can bring enough benefit to justify a selection of an instrument with expanded functionality.

Spirax Sarco provides a multivariable rotor insertion flowmeter, available in four configurations to match a broad range of flow measurement needs. All are based on a turbine rotor which is inserted in the fluid flow path. The instrument detects passage of the turbine blades by a sensor, using the measured frequency to determine flow velocity. Further processing with other measurements can provide volumetric and mass flow.

One version of the instrument delivers only volumetric flow rate. A second variant adds a temperature sensor and is capable of providing a temperature compensated mass flow reading. This model is often applied for measuring saturated steam.

A fuller featured version incorporates a pressure sensor along with the temperature sensor and can function as a flow computer, providing instantaneous readings of mass flow rate for gases, liquids, or steam. Several output signals can be configured to provide a selection of mass flow rate, volumetric flow rate, pressure, temperature, or density.

There is also a product version specifically intended for energy monitoring in applications involving steam, chilled water, or hot water. This multivariable version provides energy usage readings in selectable units, as well as supply and return temperatures, delta T, mass total and energy total.

The unique insertion design measures liquids, or gases, including steam, and can be installed without line shutdown. The unit is suitable for applications on line sizes from 2" to 80". More detail is found on the data sheet included below. Contact an instrumentation specialist and share your flow measurement requirements and challenges. The combination of your process knowledge and their product application expertise will produce effective solutions.

Friday, April 29, 2016

Simple BTU Metering For Commercial and Industrial Applications

Illustration of simple BTU metering system showing components
Simple BTU metering setup for closed loop heating or
cooling system
Monitoring thermal energy usage at logical or localized points of consumption can provide a manager some insight into the real costs of process or space operation, as well as where the greatest benefits may be reaped from efforts at maximizing energy efficiency.

Heating and cooling systems or loops that employ water as the heat transfer medium can be simply and economically metered to determine the thermal energy usage of a space or process. The simple setup consists of a flow meter, two temperature sensors, and a calculating module that collects the output from all three devices and produces a summation of the total heat transferred through the system portion served by the subject piping. This arrangement is commonly called BTU Metering.

The size of the system being metered may be an important factor in determining the most effective metering equipment specification. A larger capacity fluid system is likely to benefit from highly accurate measurement equipment, since inaccuracy in temperature or flow measurement is leveraged by the large amount of liquid moving through the system. Heating or cooling systems of small or moderate size tend to be well suited for the application of moderate to good accuracy metering equipment, with its substantially reduced cost of installation and ownership. The key to success is selecting equipment that is well applied for the whole range of anticipated flow rates and temperatures.

If your building, plant, or process currently does not have any thermal metering, the installation of this simple device can provide information that assists in making significant progress in building an energy saving plan. More information is available from product application specialists, as well as consultation on how to most economically accomplish your process energy metering goals. Share your process measurement and control challenges with a product specialist and work together to develop effective and sensible solutions.


Monday, December 14, 2015

Process Measurement - Tank Fluid Level Measurement

industrial magnetic level indicator
Industrial Magnetic Tank Level Indicator
Courtesy Granzow
Industrial process control often requires the storage of liquid in vessels or tanks. Continuous and accurate indication of the liquid level within the tank is an essential data point for safety and process control. There are a number of methods and instrument types utilized to provide tank level measurement, each with attributes that may be advantageous for a particular installation. Some of the selection criteria for a tank fluid level indicator may include:
  • Direct or indirect measurement of level
  • 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
When the instrument of choice is a magnetic level indicator, also referred to as a magnetic level gauge, the selection has usually hinged upon one of this instrument's strengths. Its use for providing level indication has a number of positive attributes:
  • 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.
These process measurement devices have a strong position in the tank level measurement field and should be considered as a candidate for fulfilling those application requirements. I have included a technical data sheet from Granzow, one of several manufacturers of this type of instrument, so you can see 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.

Monday, August 10, 2015

Chemical Flow Meters for Hazardous Environments


ISTEC Aquametro Chemical Flow Meter
Chemical Flow Meters for Industrial Process Measurement
Courtesy ISTEC
ISTEC Corporation’s Aquametro Domino line of Chemical Flow Meters provide accurate measurement of water and liquid chemical flows using rotary piston or vane wheel technology. Versions of the instruments are designed for use in safe and hazardous areas (ATEX). The Domino line has flexible mounting configurations to minimize installation space, and is suitable for conductive or non-conductive liquids. Proper operation and accuracy of the instrument is not diminished by flow disturbances. The rugged units are manufactured in a wide array of sizes and configurations to accommodate every application.

Review the product literature below, or contact a product specialist to discuss your water or liquid chemical flow measurement requirement.