Showing posts with label flow control. Show all posts
Showing posts with label flow control. Show all posts

Monday, April 9, 2018

What is a Pressure Transmitter?

Differential pressure transmitter
Differential pressure
transmitter (Yokogawa)
A pressure transmitter is a transducer that converts pressure into an electrical signal it outputs both analog and digital signals corresponding to the pressure. A pressure transmitter measures three phenomena: differential pressure; gauge pressure; and absolute pressure. The most common and useful industrial pressure measuring instrument is a differential pressure transmitter. This instrument senses the difference in pressure between two ports and produces an output signal with reference to a calibrated pressure range.

Industrial Applications of Pressure Transmitters

Pressure transmitters are commonly used to measure the pressure inside of industrial machinery or in industrial processes. They are used in various industries such as oil and gas, refining, chemical, pharmacy, and so on.

Pressure Transmitters in Industry

Pressure Transmitters in Industry
Pressure Transmitters in Industry
Pressure transmitters are widely used in industry to measure flow, level, and pressure. There are unlimited industrial applications. Oil and gas flow metering applications are found onshore, offshore and in subsea. It is also often used for monitoring filters in water and effluent treatment plants, monitoring sprinkler systems, and remote sensing of heating systems for steam or hot water. It can monitor pressure drops across valves and can be used to monitor pump control.

Differential Pressure for Flow Measurement

DP flow measurement is one of the most common applications for differential pressure transmitters by measuring the difference in fluid pressure. While the fluid flows through a pipe, it is possible to calculate the flow rate for differential pressure flow measurement. A primary and the secondary element are used. The primary element is designed to produce a difference in pressure as the flow increases. There are many different types of primary element, the most common being the orifice plate, Venturi flow nozzle, and pitot tube. The secondary element is a differential pressure transmitter. It is designed to measure the differential pressure produced by the primary element as accurately as possible. In particular it is important that the differential pressure measurement is not affected by changes in the fluid line pressure, temperature, or other properties such as ambient temperature. A good DP transmitter will ensure that the differential pressure is measured accurately regardless of other changing parameters and will reliably transmit a signal to represent the differential pressure. The DP flow transmitter output signal may also include square root extraction for flow calculation, although it is common for this function to be handled in a control system. In a typical control loop, the transmitter signal is fed to the controller whose output is used to regulate the flow rate through a control valve.

Differential Pressure for Flow Measurement
Differential Pressure for Flow Measurement

Differential Pressure for Level Measurement

Differential pressure transmitters can also be used for tank levels by measuring the pressure. The transmitter is installed at the bottom of the tank whose level is to be detected. In case of a sealed tank, a transmitter with capillaries measures a differential pressure between the upper side and the bottom side. The liquid inside the tank at the bottom creates pressure which is higher than the pressure at the top. The difference in these pressures can be used to calculate the level. In case of an open tank, the transmitter measures the differential pressure between the liquid inside the tank and the reference atmospheric pressure. In a typical control loop, the transmitter signal is fed to the controller whose output is used to regulate the tight level through a control valve.

Differential Pressure for Level Measurement
Differential Pressure for Level Measurement

Tuesday, March 13, 2018

The Ideal Flow Monitoring System for a Drinking Water Supply Network

The ideal drinking water flow monitoring system.
Wouldn't it be great if you had a closely woven system of measuring points that monitor flow rates in the drinking water supply network as seamlessly as possible and leaks and hydrological problem zones would be detected and corrected as quickly as possible?

Unfortunately the reality looks somewhat different. Installation of conventional flow measuring points in a drinking water supply network incurs high costs and an enormous amount of effort to maintain.


FLEXIM is a technology leader in the field of non-invasive flow measurement with clamp-on ultrasonic technology. FLEXUS clamp-on ultrasonic systems measure according to the transit time difference method. Since the transducers are mounted on the outside of the pipe no interventions in the pipeline system are necessary. the drift free and long-term stable acoustic measuring method detects even the smallest flows, even those that lie below the response threshold of conventional flow meters. Therefore, fluxes is the ideal instrument for monitoring minimum flow rates at night, and thus the key to effective consumption and leakage monitoring.

With FLEXUS, a flow measuring point can be conveniently setup within half a working day without supply interruptions with out affecting traffic, and without a heavy lifting device.  For the installation of the ultrasonic measuring system, only temporary access to the pipe has to be created.  The service engineer first checks the pipe dimensions. Sturdy mounting devices made of stainless steel ensure that the flow transducers are permanently stable when installed. Even on the transducers themselves, nothing can break. The cable and sensor are firmly connected. No plug can come loose. Water or dirt cannot penetrate anywhere. The ultrasonic transducers have IP68 protection and can operate continuously underwater. Coupling pads, made of elastic plastic, ensure permanent optimal acoustic coupling to the pipe without any wear. Thanks to their unique internal temperature compensation, FLEXIM transducers do not show any drift during temperature fluctuations. Setup of the measuring point on the pipe is completed by positioning and fixing the ultrasonic transducers. Now only the connection to the measuring transmitter, housed in the switch cabinet, has to be created. The calibration data of carefully paired and calibrated transducers are stored on one chip and are automatically transferred to the measuring transmitter. A zero point calibration on site is not necessary. Where nothing flows, FLEXUS reliably measures zero.

Measurement in Progress

The measuring results are either transmitted by cable or wirelessly via GSM to the process control system. Practical self-diagnosis functions allow for safe evaluation of the measurement quality. Done. Now the measuring point can be refilled underground since the pipe line remained completely intact. There was no need to flush the pipe and no need for the final leak test. In the office, the measured values can be visualized and evaluated on a computer.

Friday, February 16, 2018

Campus Metering: Advantages of Using V-Cone for Measuring Chilled Water & Steam in Hospitals, Universities, and Institutions

McCrometer's V-Cone
Typical diagram of V-Cone installation.
(Click for larger view).
McCrometer's V-Cone® Flow Meter is an advanced differential pressure instrument, which is ideal for use with liquid, steam or gas media in rugged conditions where accuracy, low maintenance and cost are important. The V-Cone is especially useful in tight-fit and retrofit installations. 

In most instances the use of V-Cones associated with chillers for chilled water in large institutional users is a matter of space, accuracy, and turndown. The V-Cone needs very little upstream and downstream piping requirements, allowing it to be used in spaces where other meters cannot be used, or to replace existing flowmeters that never proved accurate because of space limitations. 

In many large universities and other facilities, such as hospitals and airports, across the U.S., the reason for initial interest and subsequent purchases of V-Cones to measure Chilled Water was to fit within the confines of the existing and new buildings that were being used to house the chillers. Additionally, the second most important reason was the delivered accuracy. In the past, most usage had been ignored, but with the rising costs associated with cooling, each individual building must be accountable for individual use. This is just good fiscal responsibility and management from an energy balance standpoint. Turndown was an issue because of seasonal swings in usage based on climate and population in the buildings at any particular time. Therefore, the meters needed to be able to have a large flow span (turndown), which remained accurate during continuous use.
McCrometer's V-Cone
Internal view of V-Cone.

V-Cones have recently been selected for Steam service for mostly the same reasons as they are selected for Chilled Water. Space limitations in new and/or older buildings are a serious concern. V-Cones have the smallest piping requirements of practically any flowmeter and continue to deliver accurate measurement, so they are fiscally responsible and cost effective. Additionally, in steam, they allow condensate and/or other small particulate matter to pass without affecting the measurement, thus giving much better accuracy instantaneously and over time. 

They are very rugged flowmeters which require little or no maintenance, and have a very long expected life even in “tough” service like steam. They can be designed with great turndown (span) and therefore can accommodate changes in flowrates based on demand, seasonal or from other factors.

For more information on V-Cone flowmeters, contact Flow-Tech in Maryland at 410-666-3200, in Virginia at 804-752-3450, or by visiting

Monday, November 27, 2017

Small Line Size Flow Measurement without Moving Parts

ST75 Series

Excellent for Gas Sub-Metering, Boiler Fuel-To-Air Mixing, Chemical Injection & Much More

Plant and process engineers who need accurate flow detection or measurement of air, gases, or liquids in smaller pipe sizes will find several diverse flow instrument solutions available from Fluid Components International (FCI).  Using advanced, ultra-reliable thermal dispersion flow measurement technology with no-moving parts, FCI’s ST75 Series and ST100L Air/Gas Flow Meters and FLT93L Flow Switch provide ideal solutions for use in 0.25 to 2 inch (DN6 to DN50) pipe or tubing. They excel where low flows, wide-turndowns, dirty fluids, HazEx or harsh installations are among the applications factors.

These flow instruments offer many advantages for service in a wide range of applications: plant, building or lab gas sub-metering, small inlet air/gas feed lines for boilers, gas relief valve monitoring, chemical injection, compressed air systems, CO-Gen or CHP gas fuel measurement and control, sampling systems, and more.  Many small process line applications are difficult to measure reliably with high repeatability due to variations in temperature and pressure, and have wide flow rates.  FCI’s thermal flow meters and switches are unaffected by, or have on-board compensation for, temperature and pressure changes and, in addition to superior detection of low flow rates, provide 100:1 turndown as a standard feature.  FCI’s highly reliable, small line air/gas flow meters and aid/gas/liquid flow switches combine state-of-art electronics technology with application fluid-matched flow sensors and laboratory calibration in rugged packages designed for the most demanding plant operating environments. 
FLT93L Flow Switch
FLT93L Flow Switch

Thermal flow sensor technology developed by FCI relies on the relationship between flow rate and the cooling effect.  With no moving parts and minimal invasiveness, these meters and switches provide a highly repeatable, accurate, low cost, easy-to-install solution and there’s virtually no maintenance required over a long life.  FCI’s ST75 Series Air/Gas Flow Meters are ideal for lines sizes from 0.25 (6mm) to 2 inches (51mm).  Gas or air measurement accuracy is available up to 1% of reading, ±0.5% full scale. The ST75 Meters feature a wide 100:1 turndown and will measure from 0.01 to 559 SCFM [0,01 to 950 NCMH] depending on pipe size.

The meter’s electronics are housed in a rugged, IP67 rated enclosure with dual conduit ports in either NPT or M20 threading. The instrument comes standard with dual 4-20 mA outputs and a 500 Hz pulse output. The models ST75A and ST75AV include HART as well as NAMUR compliant 4-20 mA outputs and a SIL compliance rating and 2 year warranty.  Global agency approvals for Div.1/Zone 1 HazEx installations include FM, FMc, ATEX, IECEx, EAC and more. 

The best-in-class ST100L Air/Gas Flow Meter is a next generation instrument that combines feature- and function- rich electronics with advanced flow sensors. It is designed in a spool piece configuration in 1-, 1.5- or 2-inch tubing, schedule 40 and schedule 80 piping.  It measures air/gas flows from 0.0062 to 1850 SCFM [0.01 to 3,140 Nm3/h] with superior accuracy to ± 0.75% reading, ± 0.5% full scale; and repeatability of ± 0.5% reading. 

ST100L Air/Gas Flow Meters
ST100L Air/Gas Flow Meters
Whether the plant’s output needs are traditional 4-20 mA analog, frequency/pulse or advanced digital bus communications such as HART, Foundation Fieldbus, PROFIBUS, or Modbus, the ST100L is available with any of them.  Its digital bus communications also are certified and registered devices with HART and Foundation Fieldbus.  Global approvals include:  FM, FMc, ATEX, CE, CSA, IECEx, EAC, NEPSI and Inmetro.  It SIL compliant and is an all-welded design to ensure no leakage when used with volatile gases like hydrogen. 

For applications lacking enough straight-run, both ST75 Series and ST100L can be supplied with Vortab flow conditioning built-in to the spool-piece flow body. Its wide selection of available process connections include male and female threaded and flanges are standard.   The FLT93L Flow Switch is a dual function, dual trip point/alarm point precision switch.  It is field settable for trip point on flow rates and temperature, and as any high or low value of either flow or temperature.  The FLT93L’s setpoint range is: 0.015 to 50 cc/sec [0.0009 to 3 fps] for water-based liquids; 0.033 to 110 cc/sec [0.002 to 6.6 fps] for hydrocarbon-based liquids; and 0.6 to 20,000 cc/sec [0.036 to 1198 fps] for air and gases.

Trip point accuracy is ± 0.5% reading or ± 0.04 fps [± 0.012 mps] (whichever is higher) in liquids and ± 0.5% reading or ± 2 fps [± 0.06 mps] (whichever is higher in air or gases.   The FLT93 has been designed for use and longest service life in the most rugged, harsh operating environments. It is available in both aluminum and stainless steel IP67 rated housings, carries HazEx agency approvals for FM, FMc, ATEX, IECEx, EAC, Inmetro, NEPSI, meets CRN and European PED and is SIL 2 compliant. It is available in numerous wetted materials and process connection options, and has universal DC/AC power supply. 

For more information on Fluid Components, Inc. products in Maryland and Virginia, contact Flow-Tech at 410-666-3200 or visit

Monday, August 28, 2017

Installation and Operation of the Brooks Instrument GF40

Brooks Instrument GF40
Brooks Instrument GF40
The Brooks® GF40 (elastomer seal) thermal mass flow controller (MFC) and thermal mass flow meter (MFM) achieves unprecedented performance, reliability, and flexibility in many gas flow measurement and control applications.

At the heart of the GF40 is Brooks’ patented 4th generation MultiFloTM capable device. MultiFlo overcomes a long-standing limitation of many thermal MFCs – when changing gas types, a simple correction factor, such as the ratio of heat capacities between the calibration gas and new gas, cannot account for accuracy-robbing viscosity and density differences. The Brooks MultiFlo database is built on thousands of native gas runs to establish correction functions that account for both thermal and physical differences among gases making the GF40 Series among the most accurate and flexible MFCs/MFMs available today. The Brooks GF40 Series is the perfect choice for customers who use thermal mass flow controllers or thermal mass flow meters on a variety of gases, who need to change gas type frequently, or who need to re-range while preserving gas measurement and control accuracy.

We have provided a Brooks GF40 installation and operation manual below for your convenience. To download your own Brooks GF40 IOM (PDF), click this link.

Friday, July 15, 2016

Installation Recommendations for FCI Single-Point, Thermal Dispersion Flow Meters

Thermal Dispersion Flow Meters
FCI Single-Point,
Thermal Dispersion Flow Meters
All flow meter technologies have recommended installation and engineering practices to ensure they meet their published specifications and for optimal performance, accuracy and repeatability. Flow meter users are frequently challenged with wide variations in their actual  eld conditions and installation constraints that are much different from the ideal conditions under which their  ow meter was calibrated. In fact, the most common installation constraint for most all  flow meter installations is inadequate straight-run.

Flow meter users expect their flow meter suppliers to provide engineering recommendations and solutions to overcome real world application conditions to obtain expected flow meter performance to specifications. This guide provides recommended engineering practices with diagrams and specifications for straight-run, installation orientation and depths, as well as use of flow conditioners as an engineering solution for FCI single-point, thermal dispersion flow meters.

Tuesday, May 31, 2016

The Coriolis Effect Simply Explained. And Then Not So Simply Explained.

This video very simply (and very elegantly) demonstrates the Coriolis Force through the use of a ordinary garden hose.

An Now the Not So Simple Explanation

This force occurs, when the medium being measured is flowing at velocity ν through a tube that is rotating around an axis perpendicular to the direction of flow at angular ϖ.
coriolis force

When the medium moves away from the axis of rotation it must be accelerated to an increasingly high peripheral velocity. The force required for this is called Coriolis force, after its discoverer. The Coriolis force reduces the rotation. The opposite effect occurs, when the medium flows towards the axis of rotation. Then the Coriolis force amplifies the rotation.

The formula for the Coriolis force is as follows:
coriolis force

The entire measurement tube is deformed slightly by the Coriolis forces, in the way shown. This deformation is registered by movement sensors at points S1 and S2 .

For practical exploitation of this physical principle, it is sufficient for the tube to perform sympathetic oscillations on a small section of a circular path. This is achieved by exciting the measurement tube at point E by means of an electromagnetic exciter.

Coriolis flowmeters use the oscillating movement of two symmetric metal tubes that are made to vibrate from an internal driver coil.  When liquids or gases flow through the tubes, a phase shift occurs (like you see in the hose) and pickups measure the “twist” and then relate that value to the actual flow. In other words, the amount of twist is proportional to the mass flow rate of fluid passing through the tubes. The greater the twist, the larger the distance between, and the greater the flow.

The general construction of a Coriolis mass flowmeter looks like the following:
Coriolis flowmeter
Coriolis flowmeter diagram (Yokogawa)

Monday, May 16, 2016

An Economical, No Maintenance Gas and Liquid Flow Measurement Solution for Tight Spots

Wafer-Cone Internal View
Engineers with small line size processes rely on the versatile are challenged finding a flowmeter with accuracy and repeatability. Many times orifice plates are specified for the job. An excellent alternative to an orifice plate, and one that should be carefully considered, is the Wafer-Cone, manufactured by McCrometer.

Unlike an orifice plate, the Wafer-Cone has no sharp edges so extensive maintenance and inspection are not required. The flangeless Wafer-Cone® is a space-saving unit is that is easy to install and ideal for tight-space installations and retrofits.  The cone conditions the flow so the Wafer-Cone requires minimal upstream or downstream pipe runs and can be installed virtually anywhere in a piping system.

Ideal for small line sizes and with no moving parts, no replacement parts or scheduled maintenance,
Components of Wafer-Cone
this meter offers a low cost of ownership and long life.

This device also offers interchangeable cones for flexibility in accommodating changing flow conditions without the need for recalibration. When flow conditions change over time, the cone can be removed and replaced with a cone at a different beta ratio eliminating the need to buy a new meter.

Finally, the Wafer-Cone is available with remote or direct mount configuration. The direct mount option minimizes installation labor while ensuring accuracy. Direct mounting the transmitter eliminates impulse lines, which not only lowers installation costs but also reduces potential leak points by more than 50 percent. Simple plug-and-play mounting ensures the meter is installed correctly the first time and eliminates a potential source of ow measurement errors.

Wafer-Cone with Transmitter
with Transmitter
Common applications are:
  • Natural Gas Wellheads
  • Gas, Water, and CO Injection
  • Gas Lift
  • Compressor Anti-Surge
  • Fuel Gas
  • Separator Discharge
  • Biogas Reactors
  • Cooling Systems
  • Plant HVAC
  • Process Gas Lines
Advantages of the Wafer-Cone
  • No straight pipe runs
  • Maximum flexibility
  • Economical
  • Accuracy to +/- 1%
  • Repeatability to 0.1%
  • Machineable in any material
  • No moving parts, low maintenance

Friday, March 11, 2016

Efficiently Detect Condensate in HRSG Drain Lines

Flexim WaveInjector sensor modified for HRSG Drains
The development of condensate in super heater and re-heater drains leads to trouble in combined cycle and cogeneration plants with heat recovery steam generators (HRSGs). The need to reliably detect and measure condensate in these drain lines is just beginning to emerge.

The Problem 

Heat recovery steam generators were never designed for cyclic service. The move toward renewable energy resources (such as wind and photovoltaic), in tandem with the ability of the combined cycle plant to start-up and stop quickly, is expanding the role of the combined cycle plant as a backup source of power. With frequent starts/stops condensate management becomes a problem. Draining this condensate is critcally important for the safe and reliable operation of the boiler. While the problem of condensate drainage has been around for years, the problem is far greater now with the more frequent start/stop cycle rates. The importance of finding a good solution for detecting condensate in the HRSG drain lines is growing.

Boiler manufacturers address this situation through the use of condensate pots, levels instruments, site glasses, and valves. None of these technologies provide a satisfactory combination of reliability, economy, and efficiency. Knowing when steam converts to water is difficult with this approach. Plus, over cautious systems sometimes release steam instead of condensate, wasting energy. A more reliable and consistent way to sense the presence of water in drain lines had to be found.

The Solution

By designing specialized mounting and tooling, modifying their sensing diagnostics, putting in hundreds of hours of field testing, and investing hundreds of hours improving their firmware for water detection, the manufacturer Flexim developed an ultrasonic flow meter that elegantly and reliably solves the HRSG drain line problem.

These clamp-on sensors work by measuring the transit-time difference of an ultrasonic signal, at varying flow velocities, through the process media. Ultrasonic, clamp-on flow meters have no moving parts, are not affected by density, and are mounted non-invasively directly to the pipe.

The most challenging aspects of this application are the high temperature sensor exposure and the thick-walled pipes with small diameters commonly used for drains.  To handle the high temperatures, specialized mounting and tooling were developed for the sensor allowing for pipe temperatures up to 750 deg. F. To overcome the small diameter / think pipe issue, Flexim engineers reconfigured the sensor’s firmware to change from measuring flow rate, and instead measure noise (decibels) as a innovative way to distinguish steam from water.

Flexim’s unique ability to measure the presence of liquid in condensate drain pipes is a revolutionary development. This valuable solution helps customers run longer and safer, minimizing downtime.

For more information, contact:

10940 Beaver Dam Rd
Hunt Valley, MD 21030
Ph: 410-666-3200

Central VA Office

10993 Richardson Rd#13
Ashland, VA 23005
Ph: 804-752-3450

Saturday, February 27, 2016

Accurate Flow Measurement in Harsh Environments with Vortex Flowmeters

Yokogawa digitalYEWFLO
Yokogawa digitalYEWFLO vortex flowmeter
The Yokogawa digitalYEWFLO vortex flowmeter is accurate and stable, even in harsh process conditions, and has a highly reliable and robust design that delivers improvements in plant efficiency and reduced operating costs

Operating Principle

When a shedder bar is placed in a flow, Karman vortices are generated on the downstream side of the bar. The Karman vortices are detected by two piezoelectric elements installed in the upper part of the shedder bar. The vortex frequency is proportional to the  ow velocity in a specific range of Reynolds numbers. Therefore, flow velocity or flow rate can be determined by measuring vortex frequency.

Noise Reduction

Noise caused by strong piping vibration may affect the accuracy of vortex frequency detection. The two piezoelectric elements in the digitalYEWFLO are installed in a configuration that is polarized, so they are not affected by vibration in the  ow or vertical directions. The noise of vortex (lift)- direction vibration is reduced by adjusting the outputs of the piezoelectric elements. Combining these features with the Spectral Signal Processing (SSP) function provides optimum and stable measurement.

Thursday, January 28, 2016

Advanced Differential Pressure Flowmeter Technology

McCrometer V-Cone
McCrometer V-Cone
The McCrometer V-Cone® flowmeter accurately measures flow over a wide range of Reynolds numbers, under all kinds of conditions and for a variety of fluids. It operates on the same physical principle as other differential pressure-type flowmeters, using the theorem of conservation of energy in fluid flow through a pipe.

The V-Cone’s remarkable performance characteristics, however, are the result of its unique design. It features a centrally-located cone inside the tube. The cone interacts with the fluid flow, reshaping the fluid’s velocity profile and creating a region of lower pressure immediately downstream of itself. The pressure difference, exhibited between the static line pressure and the low pressure created downstream of the cone, can be measured via two pressure sensing taps. One tap is placed slightly upstream of the cone, the other is located in the downstream face of the cone itself. The pressure difference can then be incorporated into a derivation of the Bernoulli equation to determine the fluid flow rate. The cone’s central position in the line optimizes the velocity profile of the  ow at the point of measurement, assuring highly accurate, reliable  ow measurement regardless of the condition of the  ow upstream of the meter.

The V-Cone is a differential pressure type flowmeter. Basic theories behind differential pressure type flowmeters have existed for over a century. The principal theory among these is Bernoulli’s theorem for the conservation of energy in a closed pipe. This states that for a constant  ow, the pressure in a pipe is inversely proportional to the square of the velocity in the pipe.

Simply, the pressure decreases as the velocity increases. For instance, as the fluid approaches the V-Cone meter, it will have a pressure of P1. As the fluid velocity increases at the constricted area of the V-Cone, the pressure drops to P2. Both P1 and P2 are measured at the V-Cone’s taps using a variety of differential pressure transducers. The Dp created by a V-Cone will increase and decrease exponentially with the flow velocity. As the constriction takes up more of the pipe cross-sectional area, more differential pressure will be created at the same flowrates.