Inline Refractometers Used in Commercial Food and Beverage Production

Hygienic process in-line refractometer
with control unit and flow cell
Courtesy Flexim

Refractometry is a measuring technique that evaluates the impact of fluid media on light. There are some variants of the basic technology, but essentially it relies upon the media affecting a change in the way in which light waves propagate through a sample. This refraction caused by the sample can be compared to a known standard and information about the sample can be deduced.

Refractometry is a useful measuring method for many liquid processing operations. It is used for concentration and density analysis of process liquids. Portable sample processing units are available, but high volume continuous flow operations benefit from the use of in-line refractometers that do not require manual sampling and handling of process liquids. The measurements are produced in real time to continuously verify the fluid quality characteristics.

Food and beverage manufacturers use refractometry to determine the concentration of sugar, ethanol, ascorbic acid, pectin, artificial sweeteners and other components in their products. Close control of component concentration is a necessary part of delivering a consistent taste in finished products. Large investments are made to establish brand name products, and delivery of a consistent customer experience each time a product is consumed is key to developing and growing a brand. This is a solid example of a marketing based application of science and technology to industrial processing.

In-line refractometers for food and beverage applications will have specific features and construction to make them suitable for hygienic processing. The avoidance of contamination is first and foremost a requirement. Additionally, design features that reduce maintenance requirements and retain the needed measuring accuracy through extended periods of usage add value to the unit and should be a consideration when selecting an in-line refractometer.

Share your in-line refractometry applications and challenges with product specialists, combining your process experience and knowledge with their product application expertise to develop effective solutions.

In-Line Refractometer for Hygienic Operations from MSJacobs-Cali

Simplex vs. Duplex Strainers For Industrial Liquid Processing

Duplex basket strainer, shown with one basket removed
Courtesy Eaton Friltration

Many industrial and commercial liquid systems have mechanical components that cannot tolerate particulate matter in the liquid. Pumps, valves, sensors, and other specialties can experience accelerated wear and tear due to certain types and sizes of particulate matter.

Good practice dictates that the tolerance of the system for particulate matter should be determined and a properly sized and configured device be put in place to remove particulates larger than greatest allowable size. Considerations for connection size and type, construction material suitability for the process media, flow rate, pressure drop, and filter holding capacity should all be a part of the product selection criteria.

Simplex basket strainer with access cover and basket removed
Courtesy Eaton Filtration

One key element of the selection criteria is whether the system can be temporarily shut down for replacement or cleaning of the filtration element. A basket strainer, one of several types of liquid filtration devices, is available in both simplex and duplex variants. A simplex basket strainer functions as a single unit, requiring flow stoppage when the basket becomes clogged with debris. The changeover time may not be long, but some processes cannot tolerate any downtime. A duplex strainer is comprised of two simplex strainers, incorporated into a common housing, with an inlet chamber and diverting valve that selects which strainer basket will process the liquid flow. Changes in pressure drop through the device can be used to signal when it is time to switch operation between the strainer baskets.

Fluid filtration can be an important part of keeping a process in operation, reducing wear and tear on piping system components and equipment. Share your process fluid filtration challenges and requirements with application specialists, combining your process knowledge and experience with their product application expertise to produce effective solutions.

Hybrid Solar TEG Power Systems

Hybrid system shown in remote installation
Courtesy Gentherm Global Power Technologies

There are remotely located instruments and equipment throughout the world in places without available grid power. A suitable and reliable means to provide electric power is required as a standalone system for each of these instances. Photovoltaics is an obvious choice for power source, but there is another option that may provide substantial benefit for many installations.

A hybrid solar TEG (thermoelectric generator) can overcome some of the shortcomings of a pure PV system by delivering battery charging current during conditions when solar generated power is insufficient. The TEG uses heat from burning fuel to produce electric power, and can deliver charging current when the PV portion of the system fails to provide sufficient output.

• Extended periods of bad weather. While this scenario can be compensated for with a larger battery array, there is still a limit to the performance period. Larger battery banks increase unit cost, size and weight.
• Extreme low temperature. Battery capacity decreases during cold weather, requiring a larger battery array to provide design power output and reserve.
• Low solar exposure during certain times of the year, requiring more solar panels to accomodate the system power requirements during times of reduced sunlight. This increases unit size and capital cost.

Critical power systems must be designed to deliver sufficient power under all environmental conditions that can be experienced at the installation site. This drives pure PV system designers to substantially oversize panel and battery arrays to assure power delivery throughout an entire year. A hybrid solar TEG system does not need to have the enormous headroom built into the design that a pure PV does. The TEG can produce power at a known rate, regardless of the surrounding environmental conditions. The potential benefits from the hybrid power system include: 

• Reduction in solar panel array size and cost
• Lower battery count, with reduction in capital cost, replacement cost, unit size and weight
• Longer battery life
• Less on-site fuel vs. a conventional fuel-based system
• No more than once-per-year maintenance visits
• Increased reliability over a pure PV installation

Share your remote installation power requirements and challenges with a product application specialist and bring the benefits of a hybrid solar TEG power system to your operation.

Hybrid Solar TEG Power Systems for Remote Locations from MSJacobs-Cali

Switching Inductive Loads With Relays and Solid State Devices in Process Control

Switching devices must be properly protected for longevity

We connect a lot of black boxes together in our control systems, not really knowing what goes on inside. There is a basic understanding of function, but maybe not enough knowledge to thoroughly assess all aspects of integrating a device into a train of control system components. We range from novice to seasoned expert, so Acromag, manufacturer and global supplier of I/O devices for process control, has provided a useful application note regarding the protection of devices employed to switch inductive loads.

The application paper provides a good explanation of what an inductive load is, and how it can impact the performance and longevity of a switching device. The document further explains how to offset the potentially damaging impact of an inductive load on a connected switching device, with specific examples and recommendations on how to put the protective measures in place. It is useful information.

The paper is provided below. Share your I/O and other process measurement and control challenges with application specialists, combining your own process knowledge with their product application expertise to develop effective solutions.

Recommended Protection Schemes for Switching Inductive Loads from MSJacobs-Cali

Selecting the Right Temperature, Pressure, or Differential Pressure Switch

Temperature, pressure, and differential pressure switches come in a wide variety of configurations
Courtesy Ashcroft

Industrial process control applications present dynamic and varied requirements for measuring, monitoring and control. Each point calls for specific evaluation of the information needed from the process point for use in monitoring process performance, or control to be applied at the process point to regulate an outcome. Sometimes, a continuous analog signal is needed to provide indication across a range of values. Other times, it is only necessary to have notification of, or take action when, a certain temperature or pressure related event occurs. In those cases, a simple and reliable device can adequately meet the project requirements.

Temperature, pressure, and differential pressure switches connect to a process and change their switch position when a setpoint condition is reached. The are simple to understand, easy to install, low in cost, and require little maintenance of attention. The switches are available in an extensive array of configurations, with options to fill out almost any application requirement.

Ashcroft, global supplier of temperature and pressure switches, has produced a simplified guide that enables a designer or specifier to quickly focus their search on the right product. It is provided below for your use. Alternately, you can always share your process measurement and control requirements and challenges with product application specialists, combining your own process knowledge with their product expertise to develop effective solutions.

Selection of Temperature, Pressure, and Differential Pressure Switches from MSJacobs-Cali

CSB Case Study of Industrial Plant Heat Exchanger Explosion

Two heat exchangers at chemical plant

Industrial accidents, whether minor or catastrophic, can serve as sources of learning when analyzed and studied. Operators, owners, and technicians involved with industrial chemical operations have a degree of moral, ethical, and legal responsibility to conduct work in a reasonably and predictably safe manner without endangering personnel, property, or the environment. Part of a diligent safety culture should include reviewing industrial accidents at other facilities. There is much to learn from these unfortunate events, even when they happen in an industry that may seem somewhat removed from our own.

The U.S. Chemical Safety Board, or CSB, is an independent federal agency that investigates industrial chemical accidents. Below, find one of their video reenactments and analysis of an explosion that occurred at a Louisiana chemical processing plant in 2013. A portion of the reenactment shows how a few seemingly innocuous oversights can combine with other unrecognized conditions that result in a major conflagration.

Check out the video and sharpen your sense of awareness for potential trouble spots in your own operation.

Improved Level Measurement Contributes to Reduced Heat Rate in Steam Production

Minimizing heat rate and emissions for steam plants

Steam production is a costly operation in any facility, but is of paramount importance in power generation plants. The bottom line of a combustion based power generation facility is sensitive to the cost of input fuel. Measures that can be taken to reduce fuel input for a unit of power output (called heat rate) can translate directly into profitability. An additional benefit of reducing heat rate is a commensurate reduction in emissions.

A major contributor to heat rate reduction is the recovery of heat from the process and transference of that heat into the boiler feedwater. A sizable feedwater preheater of the shell and tube type is used to recover the heat. Shell and tube heat exchanger efficiency can be maximized with accurate control of liquid level.

Magnetrol, globally recognized leader in level measurement technology, makes the case for using guided wave radar level measurement technology as the most advantageous means for this application. The video below describes the process and how the guided wave radar level transmitter can provide the best performance.

Magnetrol has an information kit devoted to heat rate reduction. Share your steam system and level measurement challenges with a product specialist, and ask how you can get the Heat Rate Reduction Kit. Combining your facility and process knowledge with the product application expertise of a specialist will result in effective solutions.

M.S. Jacobs & Associates - Equipment Engineers

Wastewater treatment is one of the many industrial sectors
served by M.S. Jacobs

M.S. Jacobs and Associates has been a leading manufacturer's representative and distributor of industrial instrumentation and controls since 1945. Expanding from its original focus on the steel industry, MS Jacobs services and supplies products in all major industrial markets, including power generation, chemical processing, pulp and paper, oil and gas production, water and wastewater treatment, and nuclear power generation.

The company's longevity and dedication to the industrial market has resulted in a broad offering of superior quality products for flow, level, pressure, and temperature measurement, as well as filtration products and valves. Everyone at MS Jacobs takes pride in the company's ability to solve tough applications and provide exceptional customer service with a team of trained outside sales engineers and inside customer service representatives.

MS Jacobs' Pittsburgh service center provides instrument calibration and repair for MSJ's complete line of products, as well as those of other manufacturers. The company carries factory authorization for repair of numerous manufacturers' industrial process instrumentation products. The service center also provides custom assembly of instruments and other gear to meet customer requirements. Completed assemblies are tested and certified prior to shipment.

Reach out to MS Jacobs & Associates for the products and services that move your process instrumentation and control projects toward a successful completion.

MS Jacobs Line Card & Product Offering from MSJacobs-Cali

Float and Thermostatic Steam Traps

Float and Thermostatic Steam Trap
Courtesy Colton Industries

Steam traps are found on almost every steam system in commercial and industrial sites. The trap is a self-contained automatic valve that allows condensate to drain from a steam containing system, while retaining the steam within the system. Non-condensible gases can also be removed by a steam trap with a thermostatically controlled port.

Steam based heating relies on the delivery of the latent heat of the steam to a heat exchanger or piece of utilization equipment. Once the latent heat is delivered, condensate (basically hot water) forms. The condensate contains no latent heat and provides comparatively little value as a heat source. Utilization equipment and heat exchangers have their performance predicated upon a supply of steam, not hot water. A properly selected steam trap will remove condensate across a range of steam utilization rates, keeping the system operating at the rated capacity.

The steam trap routes the condensate out of the steam containing portion of the system, often on a return trip to the boiler. Cycling the condensate back through the system for re-boiling contributes greatly to steam system energy efficiency. Condensate removal is accomplished with a float. Non-condensible gases are vented through a thermostatically controlled port on the unit.

More details on steam traps are included below. Share your steam system challenges with a product specialist, combining your facility and process knowledge with their product application expertise to develop effective solutions.

Float and thermostatic steam traps for condensate return from MSJacobs-Cali

Thermoelectric Generator for Remote Site Power Generation

Thermoelectric generators at remote site
Courtesy Gentherm GPT

Some operations, by their nature, dictate the location in which they will be undertaken. An obvious example is oil and gas production, but there are many others. These sometimes challenging locations burden designers and operators with providing remote communications, even on site power generation. Remote installations can often be unattended, yet require reliable continuous electric power to operate. Establishing an on site power source requires thoughtful selection of technology and equipment to provide the best solution.

A thermoelectric generator is one of several solutions to consider as a power source at a remote location. Each generation technology has a set of attributes making it more or less desirable for an application under consideration.

Thermoelectric generators convert heat directly into electricity using a fuel source for heat, a hermetically sealed thermopile, cooling fins, and no moving parts. The TEG delivers a low maintenance and cost effective solution for remote power requirements, having operational and cost benefits over engine driven generators, batteries and solar sources for many applications.

The short document below provides an overview of thermoelectric generator operation and application. Talk to a product specialist about your need to power and communicate with a remote site. A thermoelectric generator may be an option you had not considered, but may prove to be the best solution.

Thermoelectric Generators - Gentherm Power Technologies de MSJacobs-Cali

Installing a Clamp-on Ultrasonic Flow Meter

Ultrasonic flow meter with clamp on sensor
Courtesy Flexim

Ultrasonic flow meters are utilized throughout the fluid processing industries, as well as for compressed air and energy monitoring. The non-invasive nature of the sensor installation couples with sufficient accuracy and low maintenance requirements to give this technology a competitive edge for many applications.

Producing consistently accurate results with an ultrasonic flow meter depends heavily on a proper installation. Flexim, a globally recognized leader in the manufacture of ultrasonic flow meters, provides us with a video that steps through the installation process, with recommendations and guidance along the way.

Flexim manufactures a full range of ultrasonic flow measurement equipment and instruments for industrial and commercial applications. Share your flow measurement challenges with process measurement experts, combining your process knowledge with their product application expertise to develop effective solutions.

Monitoring Generator Sets in Standby Mode Increases Reliability

Remote Monitoring of Electric Generator in Standy Mode

Electrtic generators used as backup power sources play a critical role in maintaining operations at many facilities. They may be automatically test run periodically, but still sit idle for extended times. Continuous remote monitoring of equipment condition can reduce the risk of a failed start.

Acromag, a globally recognized manufacturer of signal conditioning equipment, has authored an application note outlining the extent of remote monitoring that should be employed and how to accomplish it.

The application note is included below. Share your process signal conditioning and transmitting challenges with product specialists, combining your process knowledge with their product application expertise to develop effective solutions.

Monitoring genset systems in standby mode to assure reliable startup from MSJacobs-Cali

In-Line Thermal Flow Meters

In-line thermal dispersion flow meters
Thermal Instrument Company

Thermal dispersion mass flow meters provide an accurate means of mass flow measurement with no moving parts and little or no encroachment on the media flow path. There are a number of different configurations to be found among various manufacturers, but all function in basically the same manner.

Two sensors are exposed to the heat transferring effect of the flowing media. When the media composition is known, the mass flow can be calculated using the meter reading and the pipe cross sectional area. One of the flow meter sensors is heated, the other is allowed to follow the media temperature as a reference. The heat dispersion from the heated sensor is measured and used to calculate mass flow.

Some positive attributes of thermal dispersion flow meters:

• In-line and insertion configurations available to accommodate very small to large pipe sizes
• Rugged Construction – Stainless Steel with available protective coatings and other specialty metals
• No moving parts
• Measure liquid or gas in general, sanitary, and ultra pure applications
• Measurement not adversely impacted by changes in pressure or temperature
• Wide range of process connections 
• In-line versions provide unobstructed flow path
• Wide turndown suitable for extended flow range
• Back up sensors for extended life
• Sensors do not contact process media
• Flow and total flow measured
• 4-20 mA output interfaces easily with other instruments and equipment

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

Foot Valves: Basic, Hidden, Essential

Foot valve showing inlet filter screen
Colton Industries

A foot valve is a purpose specific check valve. Designed for immersion in a well, tank, or other liquid containing vessel, it serves as a one-way inlet valve on piping leading to the suction side of a pump. Foot valves and their connected piping will extend downward from the pump suction elevation. The purpose of the valve is to maintain prime on the pump by preventing the water column in the suction line from collapsing, due to gravity, and draining all the liquid from the suction side of the pump system.

For industrial applications, there are numerous versions of foot valves available in varying sizes, capacities and materials of construction. The function of the valve is simple, so the key selection criteria can be focused on features that will contribute to longevity and reduce or eliminate any maintenance burden.

The data sheet below provides some good illustrations of a foot valve and how it is installed. Share your fluid processing and control challenges with application experts, combining your process and facility knowledge with their product application expertise to develop effective solutions.

Foot valve for industrial pump applications from MSJacobs-Cali

Pneumatic Volume Booster Function

Pneumatic Volume Booster
Fairchild

A volume booster is used in a pneumatic control system to relay a low flow signal as one with greater flow volume. The common configuration is to provide a 1:1 ratio between the input and output pressure, keeping the input and output signals the same pressure. Products are available that deliver different ratios.

The general purpose of a volume booster is to provide a relay between a system with low flow volume and one with higher volume requirements. A typical example is a pneumatic actuator. The flow available through the pneumatic signal line may be insufficient to deliver the response rate desired from the pneumatic actuator. A volume booster, with control over an independent air supply, solves this challenge with increased flow volume at the same pressure as the control signal.

Volume boosters are simple in operation. The input signal applies force to one side of a diaphragm, the output pressure to the other. An imbalance between the two applied pressures will cause the diaphragm to move, changing the position of the valve and the outlet pressure until the two forces are again in balance. Little maintenance is required when the units are properly installed and supply air is of good quality.

The unit pictured is from Fairchild, a well recognized manufacturer of industrial pneumatic components, and provides a 1:1 ratio. There are some key points in the selection process, so reach out to a product specialist with your pneumatic system challenges and requirements. Combining your process and facility knowledge with their product application expertise will produce effective solutions.

Volume Booster for Pneumatic Control Signal from MSJacobs-Cali

Knowledge Base and Selection Guide For Magnetic Level Indicators

Magnetic Level Indicators
Courtesy Orion Instruments

Industrial process control frequently involves the storage of liquid in vessels or tanks. Continuous and accurate indication of liquid level within the tank is an essential data point for safety and process management. While there are a number of methods and instrument types utilized to provide tank level measurement, the instrument of choice is often a magnetic level indicator, also referred to as a magnetic level gauge. Its use for providing level indication has a number of positive attributes:

• Construction that is resistant to breakage.
• Measuring indicators, switches, and transmitters mounted externally, without contacting the medium being measured.
• Maintenance free operation. No regular cleaning needed.
• Readable level indication from greater distance than glass sight gauges.
• Magnetic level indicators can accommodate greater fluid level ranges without the need for multiple instruments.

Orion Instruments, a Magnetrol company and industry leader, has produced a comprehensive guide to magnetic level gauges, switches, transmitters, and related products. It delivers experts and newcomers an understandable and clear description of the technology and principals of operation behind magnetic level gauges and instruments. The guide also assists the reader in properly specifying and selecting the best instrument configuration for an application. A table of contents at the front of the document helps readers to quickly find the information they need.

Take a couple minutes to roll through the document and you are likely to find new and useful application tips and product information. Any questions about magnetic level indicators or your process measurement and control applications can be clearly addressed by a product specialist.

Orion magnetic level selection guide from MSJacobs-Cali

Basics of Infrared Flame Detection

Triple IR flame detector
(courtesy if Sierra Monitor)

A flame detector is a specialized sensor used to detect and respond to the presence of a flame, and accordingly notify an operator, sound an alarm, close a fuel supply valve, shut down a pump, and turn on a fire suppression system. 

Flame detectors are fast acting and accurate, much more so than smoke or heat detectors because of the technology they employ. Some flame detectors can detect fires up to 215 feet away and be accurate enough to detect a 1 sq. foot gasoline pan at 215 feet in less than 5 seconds. 

One popular type of flame detection technology used is measuring infrared (IR) light coming from a source. This type of sensor monitors the infrared light spectrum for very specific patterns given off by hot gases. These hot gases are sensed by a specialized fire-fighting thermal imaging (thermographic) camera. 

One method of determining if a fire exists is by looking for the infrared peak of hot carbon dioxide (approximately 4.4 micrometers). Response times of a typical IR detector is 3–5 seconds. 

There is the possibility, however, of false alarms caused by background thermal radiation and other hot surfaces in the area. Another potential concern is with the formation of condensate on the flame detector's lens, which can greatly reduce its accuracy. Direct exposure to sunlight for these types of detectors can also be problematic. 

An approach to overcome these issues is with dual or triple IR sensors, which compare the threshold signal in two or three infrared ranges. Often one sensor looks at the 4.4 micrometer carbon dioxide (CO2) emission, while the other sensors looks at additional reference frequencies. Modern flame detector design allow users to select different sensitivity levels to ensure no other detectors cross-over detection zones. 

Additional important features to be considered are heated windows to eliminate condensation and icing, HART and Modbus capabilities for digital communications, low excitation power, and compact design. 

When selecting a flame detector for any application, it is important to make sure it is approved and certified for that specific use. Check for third party agency approval including FM, ATEX, IECEx, TUV, and CSA. These approvals and certifications assure the highest quality of products and performance.

Finally, the proper application of flame detectors is critical in many applications for the safety and protection of property and personnel. Therefore, it is always suggested that your application be discussed with a qualified application engineer. 

Steps to Installing a Rotameter

Rotameter

A rotameter, also known as a variable area flowmeter, is a device that measures the flow rate of liquid or gas in a closed tube. It measures flow rate by allowing the cross-sectional area the fluid travels through, to vary, causing a measurable effect. They are a cost-effective flow measuring device that provides excellent repeatability, requires no external power, can be made from a wide variety of materials, and may be designed for high pressure and high temperature applications.

The following are helpful, general guidelines in the proper installation of rotameters:

1. Inspect meter for damage that may have occurred during shipping. Report any damage to the container to the freight carrier immediately. 
2. Make sure your pressure, temperature, fluid and other requirements are compatible with the meter and components (including o-rings). 
3. Select a suitable location for installation to prevent excess stress on the meter which may result from: 
• Misaligned pipe. 
• The weight of related plumbing. 
• “Water Hammer” which is most likely to occur when flow is suddenly stopped as with quick closing solenoid operated valves. (If necessary, a surge chamber should be installed. This will also be useful in pressure start-up situations.) 
• Thermal expansion of liquid in a stagnated or valve isolated system. 
• Instantaneous pressurization which will stress the meter and could result in tube failure. note: In closed thermal transfer or cooling systems, install the meter in the cool side of the line to minimize meter expansion and contraction and possible fluid leaks at the threaded connections. 
4. Handle the meter carefully during installation. 
• Use an appropriate amount of teflon tape on external pipe threads before making connections. Do not use paste or stick type thread sealing products. 
• Over tightening of plastic connections may result in fitting damage. 
5. Install the meter vertically with the inlet port at the bottom. 
6. Meters with stainless steel fittings will support several feet of pipe as long as significant vibration or stress resulting from misaligned pipe are not factors. 
7. Meters with plastic fittings must be installed so that fittings are not made to support any part of the associated plumbing. In addition, meter frame should be fastened to bulkhead, panel or column. 
8. Meters used in gas service should have suitable valves plumbed in at the inlet and outlet of the meter. These valves should be no more than 1-1/2 pipe diameters from the meter ports. The valve at the outlet should be used to create back pressure as required to prevent float bounce. It should be set initially and then left alone. The inlet valve should be used for throttling purposes. Depending on the installation, valves may not be essential, but they are most useful in many installations. Remember: To get a correct reading of flow in gas service, it is necessary to know the pressure right at the outlet of the meter (before the valve). 
9. Pressure and temperature maximums must never be exceeded. 

Thermal Dispersion Flow and Level Technology

Thermal dispersion level and flow
instruments (courtesy of Magnetrol)

Thermal dispersion instruments work on the basis of heat transfer. The sensing probe consists of two separate components, both RTDs (temperature detectors). One RTD is used as the reference point and measures the temperature of the fluid right where the probe is immersed. The second RTD is self-heated to a known temperature and maintained. A resulting a temperature differential is created between the two RTDs. By varying the power to the self-heated RTD, the set point can be changed which allows the user to set the instrument for a specific application.

Convective heat is the mechanism of heat transfer for thermal technology level switches based on the principle that a liquid has a thermal conductivity far greater than the thermal conductivity of its corresponding vapor. When the sensor is dry, there is a temperature difference between the two sensors. When fluid comes in contact with both RTDs, there is a cooling effect as the liquid absorbs the heat from the self-heater RTD. The resulting temperature differential drops, and creates a point for high level reference. When the level drops and the sensor goes dry, the temperature difference increases again. The instrument electronics senses the increase in temperature difference and provides a low level reference.

When used for flow applications, the temperature difference under a low flow or no flow condition is controlled by the set point. As the flow rate increases, the sensing RTD is cooled by the fluid moving past the heated sensor - the greater the flow, the greater the cooling. Conversely, the reduction in the temperature differential between the two RTDs indicates that the flow rate is exceeding the set point of the instrument.

Float Operated Level Switch Fundementals

Float Level Switch
(courtesy of Magnetrol)

Float operated level switches are suitable for use on clean liquid applications alarm, pump control and safety shutdown applications.

These float type units are typically designed, fabricated and certified to compliance with ASME B31.3 specifications.

The design of float operated level switches is based upon the principle that a magnetic field will penetrate non-magnetic materials such as 316 stainless steel. In the case of a float type level switch, the float moves a magnetic attraction sleeve within a non-magnetic enclosing tube which in turn trips an electrical switch mechanism. The enclosing tube of housing provides a pressure seal for the chamber as well as the process.

As the liquid level rises in the chamber (refer to Figure 1), the float moves the magnetic attraction sleeve up within the enclosing tube, and into the field of the switch mechanism magnet. Resultingly, the magnet is drawn in tightly to the enclosing tube causing the switch to trip, “making” or “breaking” the electrical circuit.

As the liquid level falls, the float drops and moves the attraction sleeve out of the magnetic field, releasing the switch at a predetermined “low level” (refer to Figure 2). The tension spring ensures the return of the switch in a snap action.