Ultrasonic, Transit-time Flowmeters

Ultrasonic flowmeters measure fluid velocity by passing high-frequency sound waves along the fluid flow path. Fluid motion influences the propagation of these sound waves, which may then be measured to infer fluid velocity.

Transit-time flowmeters, sometimes called counter propagation flowmeters, are an alternative to Doppler ultrasonic flowmeters. A transit-time ultrasonic flowmeter uses a pair of opposed sensors to measure the time difference between a sound pulse traveling with the fluid flow versus a sound pulse traveling against the fluid flow. Since the motion of fluid tends to carry a sound wave along, the sound pulse transmitted downstream will make the journey faster than a sound pulse transmitted upstream:

The rate of volumetric flow through a transit-time flowmeter is a simple function of the upstream and downstream propagation times:

Where:

Q = Calculated volumetric flow rate

k = Constant of proportionality

t_up = Time for sound pulse to travel from downstream location to upstream location (upstream, against the flow)

t_down = Time for sound pulse to travel from upstream location to downstream location (downstream, with the flow)

An interesting characteristic of transit-time velocity measurement is that the ratio of transit time difference over transit time product remains constant with changes in the speed of sound through the fluid. When this equation is cast into terms of path length (L), fluid velocity (v), and sound velocity (c), the equation simplifies to Q=2kv/L, proving that the transit-time flowmeter is linear just like the Doppler flowmeter, with the advantage of being immune to changes in the fluid’s speed of sound. Changes in bulk modulus resulting from changes in fluid composition, or changes in density resulting from compositional, temperature, or pressure variations therefore have little effect on a transit-time flowmeter’s accuracy.


Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

Industrial Point Level Measurement

As opposed to continuous level measurement, point level measurement is used to measure liquid or bulk solids in a tank or vessel to a single, precise point. Most often used as a notification for high or low level, they are placed at the top or bottom of the vessel. When activated, the point level switch can activate an audible or visual alarm, start or stop a process, and/or notify a supervisory control system. There are several technologies that provide point level control, each with its own advantages and disadvantages. This post focuses the more advanced technology used for point level control, namely capacitance, vibration, microwave, and radiometric.

Capacitance Switch
(VEGA)

Capacitance Switches

• Measure the capacitance of the process medium’s ability to hold an electrical charge.
• Can be used with both conductive or non-conductive liquids and solids
• Looks for step changes in standing capacitance.
• When media reaches the area between the two plates, the capacitance changes, and the switch output changes state.
• Must be installed and set up in process to know the different capacitance values for a vessel that’s full and a vessel that’s empty.

Vibration Switches

Vibration Switch
(VEGA)

• Constantly vibrate at a specific frequency.
• The frequency or amplitude is monitored to determine when a liquid or a bulk solid has reached the switch point. 
• Once the medium contacts the sensing probe, the frequency or the amplitude changes and this change activates the output.
• Easy installation.
• Are "plug and play".
• No media calibration requirement.
• Little or no maintenance costs.

Microwave Switches

Microwave Switch Emitter
(VEGA)

• Non-contact.
• Utilizes an emitter and receiver.
• Use a microwave beam to determine point level. Once the bean is broken, a switch changes status.
• Not only used for high or low level, but also for determining id material is filling a vessel or falling to a conveyor.

Radiometric Switches

• Non-contact
• Utilizes an emitter and receiver.
• A detector measures the amount of gamma radiation from an emitter and determines point level when a threshold is met.
• Can be installed externally, with no vessel penetration.
• Good for volatile and hostile processes.



Radiometric Switch
(VEGA)

• Can measure changes in gamma radiation and be used to detect building vapors.

For more information or any process level requirement, contact Classic Controls by visiting https://classiccontrol.com or by calling 863-644-3642.

Industrial Control Valve Body and Actuator Operation

Control valve (Masoneilan)

The design and operation of industrial control valves  is very important to understand if you work as a process engineer, a plant maintenance person, or if you design process control loops.

Control valves are used extensively in power plants, pulp and paper mills, chemical manufacturing, petro-chemical processing, HVAC and steam distribution systems.

There are many types, manufacturers, body styles, and specialized features, but the they all share some basics operating principles. The video below explains components, operation, and fundamentals.

Classic Controls provides control valve systems for all major industries including chemical, pulp and paper, petro-chemical, power generation, and water treatment.  Classic Control’s experience and engineering background make them a uniquely qualified partner for your next automated valve requirement.

https://www.classiccontrols.com
863-644-3642

VEGAPULS 64: The First 80 GHz Radar Level Sensor

VEGAPULS 64 is the first radar level sensor for liquids that operates at a frequency of 80 GHz. This delivers superior focusing of the radar beam. This means this level sensor can deliver reliable measurements even in vessels with internal installations such as heating coils and agitators. The narrow radar beam avoids these obstacles altogether and buildup on the vessel wall has no effect on performance either. The larger the dynamic range of a radar sensor, the wider its range of application and the higher its measurement certainty. VEGAPULS 64 is able to measure poorly reflective media with significantly better performance than previous radar sensors; for example, the sensor is able to measure poorly reflective liquids down virtually to the vessel bottom. Even with surface foam, extremely turbulent product surfaces, condensation or buildup on the antenna, VEGAPULS 64 maintains its accuracy and reliability.

Download the VEGAPULS 64 brochure here or read about it in the embedded document below.

Classic Controls, Inc.
https://classiccontrols.com
863-644-3642

VEGAPULS 64 Radar Level Transmitter from Classic Controls, Inc.

Replacing the Obsolete Siemens 353 with the Yokogawa YS1000 Series

The Yokogawa YS1000 Series is a drop-in alternative to the obsolete Siemens/Moore 353. The video below provides details as to how and why. The video is composed of a series of presentation slides - if you need more time to focus and a single item, hit the pause button.

Non-invasive, Clamp-on Flowmeters for Boiler Feed Water, Fuel Oil, and Natural Gas Feeds in Power Plants

Clamp-on Flowmeters in Power Plants

Natural gas fired plants burn the gas to heat boiler feed water up and convert it to steam for subsequent electricity generation. It is critical for the safety and performance of the power plant to monitoring and control the flow of boiler water feed lines.

FLEXIM, a manufacturer of clamp-on transit-time ultrasonic flowmeters, offers it's high temperature clamp-on WaveInjector mounting fixture as a very accurate and reliable device that accurately measures flow, even at pipe wall temperature of 400 °C / 750 °F. Since the measurement system is completely non-invasive, there is no concern about the pressurization levels within the pipe. Furthermore, Flexim's component design doesn’t cause any pressure drop and eliminates the need for process shut-downs for installation or service. Flexim also offers a unique integrated technology they call "HybridTrek mode" which can detect steam entrainment in the feed water flows – a clear cause for decreased plant performance.

Another area where non-invasive, clamp-on flowmeters are advantageous on fuel oil or feed gas supply. Flexim "Flexus" meters are also ideal to measure and monitor the flow of fuel oil or gas to the boilers to achieve the optimum efficiency.

Ultrasonic flowmeter for harsh environments.
(Flexim)

Historically, fuel oil feed lines are either monitored by the use of orifice plates and differential pressure or positive displacement meters, both of which require hours of maintenance due to wear and tear by the abrasive and partially clogging medium. A non-invasive ultrasonic clamp-on flow meter technology offers a much better solution. No pipe cutting or welding, zero contact with the process medium, matched and paired transducers, sophisticated high-speed flow calculations and very rugged stainless steel construction make the Flexim flowmeter an excellent choice, even in this harsh
environment.

For gas feed lines, FLEXIM developed a special transducer technology called Lamb wave transducers to offer the most accurate clamp-on flow measurement possible. The clamp-on measurement system is independent from pipe dimensions, material and wall thickness.  There are no upper pressure limits and even on very low pressure lines, the flow meter is capable of carrying out a bi-directional flow measurement over a wide turndown range. By factoring in pressure and temperature (as well as the individual gas composition if needed), the FLUXUS gas flow meter outputs normalized flow rates.

For more information on applying non-invasive ultrasonic clamp-on flow meters in power plants, contact Classic Controls by visiting https://classiccontrols.com or by calling 863-644-3642.

The Best Alternative for the Discontinued Moore / Siemens 353 SLC Controller

Siemens has discontinued their 353 SLC controller. The 353 was used in many process applications for many years. It's discontinuation leaves many companies without an alternative.

Don't worry - you don't have to turn to eBay looking for spare parts? There's a better solution - the Yokogawa YS1700 PID loop controller. The YS1700 is a drop-in SLC replacement for the Siemens 353 and will keep you off of eBay.

The YS1700’s powerful function block programming allows for custom strategies to control many demanding processes such as boilers and steam generators, PH control, dosing control, and many other demanding plant processes. For more information, visit this site.