月: 2022年12月

What Is a Spherical Washer?

A spherical washer is a washer that uses two washers together in a set: a concave washer with a flat and spherical surface on one side and a concave-convex washer with a flat and convex spherical surface on the other side.

Spherical washers are used to correct the angle of the shaft of a tap or bolt that has been tightened at an angle and cannot be removed.

When a bolt is angled, only a portion of the axial force applied to the bolt is transmitted to the base metal, which reduces the axial force on the base metal, and the remaining force is consumed as a frictional force in the gap.

The angle that can be compensated by a spherical washer is about 3 degrees. If the angle is too large, using a spherical washer will not be effective, so tightening the bolt as much as possible will improve the force being consumed.

Uses of Spherical Washers

Spherical washers are used to absorb and compensate for the angle of a bolt or tap shaft that has been tightened at an angle.

The spherical washer is placed so that the concave side of the washer contacts the base metal and the convex side contacts the top of the bolt. By tightening the bolt in this condition, the angle of the bolt fixed at an angle is reduced, and the bolt can be tightened so that the seating surface does not float.

It should be noted that the axial force is reduced by not transmitting enough force from the bolt.

Principle of Spherical Washers

Spherical washers use two pairs of concavo-convex spherical surfaces on each side to reduce the inclination created between the bolt and the base metal and correct the tightening of bolts that have been tightened at an angle.

As the inclination increases, the area of the bolt in contact with the base metal becomes smaller, causing it to cave in or slip because the axial force is no longer transmitted to the base metal.

The spherical washer is placed between the angled bolt and the base metal, and when tightened in this condition, the convex spherical surface slides over the concave spherical surface as the bolt is tightened. The convex spherical washer naturally corrects itself to the same angle as the bolt axis, preventing the seating surface from floating and ensuring a secure connection.

What Is a Fuel Flowmeter?

A fuel flowmeter is an instrument used to measure the flow rate (fuel flow) of fuel as it is moved through the transfer process.

There are both analog and digital visual meters available for users to read the measured value. In recent years, automation and labor-saving processes for quality improvement and cost reduction in various industries have been progressing, and industrial instruments such as flow meters, thermometers, and pressure gauges are required to be more sophisticated and multifunctional.

The fuel flowmeter is an extremely important measuring instrument for the energy-saving operation of ships and other vessels, as well as for environmental friendliness. It is expected that interest in fuel flow meters will increase in the future.

Applications of Fuel Flowmeter

The fuel flowmeter measures the flow rate of fuels such as gasoline, diesel, kerosene, diesel fuel, and alcohol fuel with high accuracy and high repeatability. They can be used as equipment for engines and vehicle testing, and are widely used to measure fuel consumption for research and development, quality control, and other purposes.

Fuel flowmeters are used in a wide range of industries, including shipbuilding and shipping. In addition to measuring the consumption of fuel used in main engines, generators, and boilers, they are also used to measure the amount of lubricating oil supplied to various engine parts.

Principle of Fuel Flowmeter

Fuel flowmeter is classified into two main categories based on the type of flow rate to be measured: volumetric flowmeter and mass flowmeter.

1. Volumetric Flowmeter

The volumetric flowmeter has a measuring chamber with a rotor inside. The space is formed by the rotor and its enclosing case. When fuel fills the metering chamber, the rotor discharges it, and the volume of the fluid (fuel) is measured by the number of repetitions of this filling and discharging.

If the volume of fluid in the metering chamber that fills with the rotation of the rotor is known, the total volume of fluid can be calculated based on the number of rotations of the rotor. When fluid flows from the inlet, pressure is applied to the tooth flanks of the oval gear (rotor).

Due to its oval shape, the gear spontaneously begins to rotate when pressure is partially applied. If the fuel supply is continuous, the rotating action is also continuous.

2. Mass Flowmeter

The Coriolis flowmeter is a typical example of a mass flowmeter. The Coriolis flowmeter uses the inertial force that a mass experiences in a direction perpendicular to the direction of motion when it is moved in a rotating coordinate system, the so-called Coriolis force, to provide a highly accurate direct measurement of mass flow rate.

Specifically, an exciter is attached to the outside of the measuring tube, which vibrates the tube at a certain period. When fuel is flowing, the inertia of the liquid adds torsion to the vibration, and the Coriolis effect causes the tube to vibrate in different directions at the inlet and outlet simultaneously.

By measuring these changes in vibration in detail both spatially and temporally, sensors at the inlet and outlet sides can measure the phase difference of the liquid. Based on this phase difference, the mass flow rate is measured.

Features of Fuel Flowmeter

As mentioned above, there are two types of fuel flowmeter: volumetric flowmeter and mass flowmeter. The characteristics of each flowmeter are as follows:

1. Volumetric Flowmeter

One of the features of volumetric flowmeters is their high accuracy, which is about 0.5% to 0.2% of the indicated value. With most flowmeters, the higher the viscosity of the fluid, the narrower the flow range over which accuracy can be guaranteed.

However, with volumetric flowmeters, as viscosity increases, leakage from the gap between the rotor and the container decreases, thus expanding the range of flow rates for which accuracy can be guaranteed.

2. Mass Flowmeter

As a mass flowmeter, the Coriolis flowmeter can directly measure the density of a liquid from its vibration frequency. Since temperature and viscosity can also be measured at the same time, a single Fuel Flowmeter can accurately measure fuels with different properties, such as Fuel Oil A and Fuel Oil C. The disadvantages of the Coriolis flowmeter are that it is more expensive than other detection principles and that it has a larger pressure drop.

However, the disadvantages are that it is more expensive than other detection principles, has a large pressure drop, and is easily affected by vibration.

What Is a Hot Air Dryer?

A hot air dryer is a device that uses heated air to remove moisture from substances or products.

It finds widespread application in industrial processes and manufacturing, effectively reducing humidity and facilitating drying. This not only enhances product quality but also extends shelf life.

For instance, the food industry relies on hot air dryers to dehydrate fruits, vegetables, grains, and meat products. Different materials can be accommodated by adjusting drying time and temperature. Moreover, a diverse range of dryer designs and functions is available to cater to various industries and applications.

Applications of Hot Air Dryers

Hot air dryers have a wide range of applications across various industries and fields. Some common uses include:

1. Food Processing Industry

They are indispensable for drying foods like fruits, vegetables, grains, dried meats, and seafood. Drying enhances food shelf life while preserving quality. It’s also frequently employed in the production of dried fruits and snack items.

2. Pharmaceutical Industry

In pharmaceutical manufacturing, hot air dryers may be used to eliminate moisture from chemicals, thereby improving product stability and extending shelf life.

3. Wood Processing and Ceramics

Wood drying extensively uses hot air dryers to reduce moisture content, minimizing shrinkage and distortion while enhancing durability. They also play a pivotal role in ceramics and ceramic product manufacturing by optimizing the drying and firing processes.

4. Chemical Plants

Chemical plants use hot air dryers to dehydrate chemicals and powders, particularly powdered fuels like coal and ore. High moisture content in these fuels can lead to fuel loss, so a hot air dryer serves as a pre-treatment to remove moisture. They are also used for drying paints and synthesizing chemical products, including pigments, catalysts, and other chemicals.

Principle of Hot Air Dryer

A typical hot air dryer comprises a drying chamber, a heating unit, and an exhaust system.

1. Drying Chamber

The drying chamber houses the material to be dried and is typically designed as a box or cylinder with an internal drying space. Internal walls are equipped with suitable materials like firebricks to control heat and moisture effectively, depending on the required temperature.

2. Heating Equipment

Heating devices, such as electric heaters, gas burners, or steam heaters, generate hot air. These devices allow precise control of air temperature within the drying chamber, maintaining it at the necessary level.

3. Exhaust System

The exhaust system is responsible for expelling moisture and exhaust gases. Operated by a fan or blower, it discharges exhaust gases while delivering hot air into the drying room. There are two main types of fans: push-in and induction, usually installed on the top or side of the drying chamber.

Types of Hot Air Dryers

Hot air dryers come in two primary types: one-pass (single-pass) and recirculation (recycle) dryers.

1. One-Pass Type

A one-pass hot air dryer allows heated air to pass through the drying chamber only once. The air flows unidirectionally from the heating unit to the blower, ensuring that materials are dried in a single passage. Proper blower placement and air distribution control are vital for maintaining temperature uniformity within the chamber. This type suits simpler drying processes requiring efficiency.

2. Recirculation Type

In a recirculation hot air dryer, heated air circulates within the drying chamber, returning to the heating unit. This repeated air circulation enhances heat utilization, resulting in high thermal efficiency and minimal heat loss. Additionally, temperature uniformity within the chamber remains consistent. The recirculation type is ideal for processes requiring temperature uniformity or extended drying times.

What Is a Calorimeter?

A calorimeter is a device designed for measuring the heat generated in chemical reactions.

Calorimeters can quantify the heat produced during chemical reactions, combustion processes, and phase transitions. There are three main types of calorimeters: adiabatic calorimeters, isothermal wall calorimeters, and isothermal calorimeters.

In the manufacturing industry, where large-scale heating of raw materials, chemical mixing, and reactions occur, it is crucial for safety reasons to accurately determine the amount of heat generated during these processes. Calorimeters are instrumental in analyzing the heat involved in each step.

Uses of Calorimeters

1. Gathering Safety and Disaster Prevention Data

Calorimeters are essential tools for collecting safety and disaster prevention data in manufacturing facilities that handle chemical reactions on a large scale. Given the potential risks associated with substantial heat generation during processes, calorimetry is employed to evaluate potential hazards in specific reactions and processes.

2. Analyzing Pyrolysis Temperatures of Materials

Calorimeters also find applications in studying phase transitions of polymers and inorganic materials, as well as assessing the calorific values produced during thermal decomposition using techniques like differential scanning calorimetry (DSC). Researchers rely on calorimeters to measure phase transition temperatures, which vary depending on the chemical and crystal structures of compounds.

Principle of Calorimeters

Calorimeters are devices designed to measure the heat generated during a reaction. Apart from chemical reactions, the dissolution, mixing, and phase transitions of compounds can either release or absorb heat within the reaction system.

The heat to be measured is substituted with a substance of known heat capacity within the calorimeter, and the resulting temperature change is measured. Alternatively, the temperature is maintained constant, and the calorific value is determined based on the amount of latent heat released during melting.

1. Adiabatic Calorimeter

In an adiabatic calorimeter, the heat generated by the sample does not dissipate through the outer walls but is entirely devoted to changing the temperature of the sample container. Achieving thermal insulation involves maintaining both the temperature of the sample container and the surrounding outer wall at the same level, with a pressure reduction of less than 10-4 Pa.

2. Isothermal Wall Calorimeter

In an isothermal wall calorimeter, the sample container experiencing temperature changes is placed within an isothermal container held at a constant temperature, minimizing heat exchange between the two containers. A gap is maintained between them, filled with air for containers with high heat capacity and a vacuum for those with low heat capacity. This ensures stable external temperature conditions and allows thermal changes to occur within the sample container. The calorific value is determined by analyzing the temperature-time curve, incorporating a heat leakage correction to account for apparent temperature changes.

3. Isothermal Calorimeter

For instance, in the case of a phase change isothermal calorimeter, when two phases of a substance coexist at a certain temperature, heat transfers from one phase to the other. The calorimeter quantifies this heat by measuring volume changes that occur during the transfer. Calorimeters also determine calorific values by measuring gas volume changes or weight changes.

Types of Calorimeters

On a small scale, such as in laboratory test tubes, the heat generated by chemical reactions is rarely problematic. However, when reactions are conducted on a larger scale, such as in industrial settings involving tens or hundreds of liters, there is a risk of runaway reactions or explosions due to substantial heat release.

Therefore, calorimeters are indispensable for analyzing the heat generated in each process. Various types of calorimeters are available to suit different applications.

1. Process Safety Evaluation

In the context of process safety evaluation, calorimeters are employed to measure the heat generated during reaction processes within systems that simulate reaction vessels in industrial facilities.

2. Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry (DSC) is used to assess materials by measuring the heat produced at various temperatures in small samples. Phase transition or decomposition temperatures can be analyzed based on the inflection point or peak of heat quantity concerning temperature.

3. Accelerating Rate Calorimetry (ARC)

Calorimeters are also valuable for analyzing runaway reactions. The accelerating rate calorimeter (ARC) measures calorific values and generated pressures of compounds that release heat during decomposition, which may lead to runaway reactions.

What Is a Thermoplastic Elastomer?

Thermoplastic elastomer is a polymeric material that exhibits rubber-like elasticity at room temperature while becoming fluid at high temperatures. Like thermoplastics, they can be easily molded when heated, making them an intermediate material between synthetic rubber and thermoplastic resin.

The elasticity of elastomers is due to the cross-linking of polymer chains, enabling them to return to their original shape. Thermoplastic elastomers are widely used due to their excellent moldability and reusability.

Uses for Thermoplastic Elastomers

Thermoplastic elastomers are used in various applications due to their elasticity and moldability. They are used in household goods like mobile phone cases and kitchenware, automotive parts, power tools, and other products requiring abrasion resistance and elasticity. Their lightweight and colorability also contribute to their versatility. In the medical field, they are used in rubber gloves as they do not contain allergens found in natural and synthetic rubbers.

Principle of Thermoplastic Elastomer

1. Principle of Elasticity

Thermoplastic elastomers consist of long polymer chains with hard and soft segments. The hard segments form intermolecular cross-links through hydrogen bonds, creating a mesh structure that acts as pseudo-crosslinks. Soft segments allow for elasticity due to their free movement.

In contrast to synthetic rubbers, where cross-linking is through covalent bonds, thermoplastic elastomers use hydrogen bonding for cross-linking.

2. Principle of Thermoplasticity

The hydrogen bonds in thermoplastic elastomers break at high temperatures, dissolving the cross-linked structure and turning the material fluid. Upon cooling, the hydrogen bonds reform, restoring the cross-links and elasticity. Synthetic rubbers, on the other hand, do not regain their elasticity after heating due to permanent covalent bond dissociation.

Types of Thermoplastic Elastomers

Various types of thermoplastic elastomers include styrenics, olefins, urethanes, esters, and amides.

1. Styrene-Based

Styrene-based thermoplastic elastomers have polystyrene hard segments and polybutadiene soft segments, commonly used in products due to their lightweight and natural rubber-like feel.

2. Olefin-Based (TPO)

Olefin-based (TPO) elastomers are copolymers of ethylene, propylene, and a diene component.

3. Urethane (TPU)

TPU, formed by the reaction of polyol and isocyanate, is used in textiles and some automotive parts for its high elongation and strength.

4. Ester-Based (TPC)

Ester-based (TPC) elastomers, comprising polyester hard segments and amorphous soft segments, are known for their high impact resistance and excellent heat, chemical, and aging resistance.

5. Amide-Based (TPA)

Amide-based (TPA) elastomers, containing polyester or polyether soft segments and polyamide hard segments, offer excellent abrasion and impact resistance, flexibility at low temperatures, and weather and chemical resistance.

What Is a Densitometer?

Densitometers are used to measure the concentration of a specific substance in a gas or liquid.

By measuring the amount of light absorbed or reflected at specific wavelengths obtained through a filter or light (spectrum) divided into fixed increments of wavelengths, the concentration of the substance to be measured is obtained. If the object to be measured is fixed, the sample is irradiated with light of a specific wavelength that is highly absorbed by the object, and the densitometer measures the amount of transmitted (attenuated) light to determine its concentration. Pulse oximeters are also a type of absorbance densitometer that uses light transmission.

Uses of Densitometers

The primary use of densitometers is to measure the concentration of specific substances of interest in liquids and gases. They are used in various industrial fields.

1. Food and Beverage Industry

In the food industry, there are many products whose quality deteriorates due to oxidation reactions caused by oxygen. In the packaging process, it is necessary to keep oxygen concentration low to prevent quality deterioration. Oxygen analyzers are used to monitor whether the settings of filling, sealing, and packaging machines are correct and whether gas filling is being performed reliably.

2. Environmental Measurement

In environmental monitoring applications, densitometers are used to monitor the concentration of various gases such as NOX, SO2, CO, CO2, and HCl in the air. Oxygen analyzers for environmental monitoring are also used for safety confirmation, especially in manholes, sewers, tanks, ships, and other places where there is a risk of oxygen deficiency.

3. Medical Applications

In medical applications, various instruments are used to measure blood oxygen concentration (pulse oximeters) and glucose concentration.

4. Industrial Applications

In industrial applications, densitometers are used to control the concentration of liquids in production lines. Examples include controlling the concentration of resist strippers and acid-alkali cleaning solutions in the wafer manufacturing process and controlling the concentration of recycled chemicals and oxide/nitride film etchants in the semiconductor manufacturing process.

Trace oxygen analyzers are used in semiconductor manufacturing processes, Ar welding, etc., and can measure the concentration of very small amounts of trace oxygen in industrial gases. Other special devices include those used to measure the color density of ink in printing, and salt concentration meters for ready-mixed concrete.

5. Experimental Science

In experimental science, the color reaction caused by an enzyme reaction is measured to convert the value of enzyme activity. Densitometers are also used to measure the concentration (quantitative analysis) of proteins and nucleic acids.

Principle of Densitometers

Densitometers used to measure liquid concentrations are often based on the principle of absorbance spectrophotometry.

1. Absorbance Spectrophotometry

In the absorbance spectrophotometry method, light of a certain wavelength is irradiated into a container (cell) containing a sample to be measured. The light transmitted through the cell is detected by an electrical signal from a detector, and the light transmittance (attenuation) is used to measure the substance’s densitometer.

When the intensity of irradiated light is I0, the intensity of transmitted light is I, the molar concentration is C, the optical path length (thickness) is l, and the molar absorption coefficient is ε, and -logI/I0 is defined as absorbance A, the following equation is established: absorbance A is proportional to sample concentration C. By creating a calibration curve from this relational equation, the concentration of an unknown substance can be determined. (A = εCl)

2. Spectrophotometer

There are several methods for obtaining a specific wavelength from the white light of a light source, including the filter method, which uses a filter such as colored glass, the prism method, which uses a prism made of quartz or quartz, and the grating method, which uses a diffraction grating to obtain continuous spectroscopy.

For example, in the filter type, a complementary color filter is placed between the sample and the light-receiving part, and light is measured through a red, green, or blue filter.

3. Light Source and Detector

The main light sources used are deuterium discharge tubes, tungsten, and LEDs. Detectors include photosemiconductors (photocells) and photomultiplier tubes (photomultipliers). Since the wavelength range that can be measured is divided according to the method of spectroscopy and type of detector, it is necessary to select the equipment and cell material according to the purpose.

On the other hand, in the case of densitometers such as oximeters, which have a specific substance to be measured, only specific wavelengths that are highly absorbed by the target substance are irradiated from the light source, and the light obtained by the detector is converted into an electrical signal and displayed as a concentration.

Types of Densitometers

Densitometers, as mentioned above, have a variety of applications, including those that measure gases and those that measure liquids. Among densitometers that measure liquids, in addition to absorbance spectrophotometry, some measure concentration from the viscous resistance created by vibrating a piece of sensor part in a liquid, and multi-component densitometers that combine ultrasonic waves and electrical conductivity.

There are also various types of oxygen analyzers. For example, there are those for physical and chemical applications that measure concentrations in chambers, glove boxes, and incubators, those for environmental measurements, those for detecting trace amounts of oxygen in production lines, and those for measuring oxygen concentrations inside the packaging. Each application has a different measurement range and limits, so it is necessary to select the right one for the application.

Other types of densitometers include dissolved hydrogen meters used to monitor the hydrogen concentration of dissolved hydrogen gas solutions and ozone meters.

What Is a Turbidimeter?

A turbidimeter is an instrument used to evaluate the turbidity of liquid samples. It is used for environmental monitoring and process control of industrial products. There are several measurement methods used in turbidimeters, including the scattered light method, transmitted light method, scattered light/transmitted light method, integrating sphere method, surface scattered light method, and particle counting method.

Turbidimeters are also available in two types: portable types, which integrate the sensor and indicator, and in-line types, where the sensor is installed in a piping system.

Applications of Turbidimeters

Turbidimeters are used in water treatment plants for controlling raw water, filtered water, and wastewater. They are also used in environmental monitoring, sewage treatment plants, and industrial manufacturing process control. Examples include monitoring water quality in public water bodies and maintaining wastewater from factories and industrial plants. 

In process control, turbidimeters monitor the quality of products and control the quality of pure water used in production.

Principle of Turbidimeter

Turbidimeters use principles such as light scattering and transmission to measure turbidity. Clean water transmits more light, while turbid water scatters more light and transmits less. The standard for turbidity is determined by a turbidity standard solution, and proper calibration using these solutions is crucial for accurate evaluation.

Types of Turbidimeters

Various methods and principles are used in turbidimeters:

1. Surface Scattered Light Method

This method shines light on the liquid surface and determines the concentration of suspended solids based on light scattering. It observes the liquid surface and does not require a window in contact with the measured liquid, minimizing contamination impact.

2. Transmitted Light Method

Light is irradiated from one side of the sample, and turbidity is determined from the attenuation of transmitted light. While simple, it can be influenced by colored liquids and window dirt, making it less suitable for environmental measurements.

3. Scattered Light/Transmitted Light Method

This method irradiates light onto a sample and measures both scattered and transmitted light. The ratio of these measurements determines the turbidity, with less influence from power supply fluctuations or lamp deterioration.

4. Integrating Sphere Method

Light from a source is captured in an integrating sphere, measuring the total incident light versus scattered light. This method is less affected by the sample but is more suitable for laboratory use due to maintenance considerations.

5. Surface Scattered Light Method

Similar to the first method, this one shines light on the liquid surface and measures scattered light intensity to determine turbidity, suitable for high-turbidity samples.

6. Particle Counting Method

Using a semiconductor laser, this method counts particles, suitable for low-turbidity samples. It measures both particle concentration and turbidity without the need for zero calibration.

Additional Turbidimeter Information

1. Turbidity Standards and Turbidity Units

Turbidity standards and units vary for different measurement methods. The JIS K0101 Industrial Water Testing Method specifies standards and units for methods like visual, transmitted light, and scattered light, using solutions like carion and formazin.

2. Points to Be Noted Due to Differences in Measurement Methods

Different measurement methods in turbidimeters may yield varying results even with the same standard solution, due to differences in particle size distribution, optical properties, and detection sensitivity. Consistency in method and standard solution type is key for continuous control.

What Is a Dissolved Oxygen Analyzer?

A dissolved oxygen analyzer measures the amount of oxygen dissolved in water. They range from portable instruments to stationary instruments installed at measurement sites and can transmit data to centralized control devices, such as a DCS for real-time display. These analyzers are essential for water quality control, fisheries, environmental surveys, and more, providing accurate measurements of dissolved oxygen in water.

Uses of Dissolved Oxygen Analyzers

Dissolved Oxygen Analyzers are used in wastewater treatment facilities to monitor water contamination and in aerobic wastewater treatment processes. They are crucial in ensuring sufficient oxygen for effective treatment. In the food industry, these analyzers measure fermentation levels in fermented foods.

Principle of Dissolved Oxygen Analyzer

Dissolved oxygen analyzers use the diaphragm electrode method or the fluorescent method for measurement

1. Diaphragm Dissolved Oxygen Analyzer

Diaphragm types use an electrolyte solution and a membrane sensor. Regular maintenance, including electrolyte replacement, is necessary

2. Fluorescent Dissolved Oxygen Analyzer

Fluorescent types are suitable for sewage and wastewater treatment plants. They do not require a membrane or electrolyte and can be measured in environments without flow. Many are waterproof and can measure additional parameters like pH.

Types of Dissolved Oxygen Analyzers

Dissolved Oxygen Analyzers are available as stationary, portable, and tabletop models.

1. Stationary Type

Stationary models monitor water quality in rivers and industrial effluents, featuring automatic cleaning mechanisms to maintain detector sensitivity.

2. Portable Type

Portable models are lightweight, compact, and easy to use, ideal for aquariums, aquaculture, and outdoor water quality surveys. They often have dustproof and waterproof features.

3. Tabletop Type

Tabletop models are used in research institutes and laboratories for high-precision measurements. They are compact and portable like the portable models.

Other Information on Dissolved Oxygen Analyzers

Dissolved Oxygen Analyzer Calibration

Dissolved oxygen analyzers should be calibrated periodically.

Zero calibration using a zero standard solution (approximately 25 g of anhydrous sodium sulfite as specified in JIS K 8061 dissolved in water and adjusted to 500 mL by adding water) to accurately measure low concentrations of dissolved oxygen or to adjust the zero point of the dissolved oxygen analyzer to a theoretical value if the low concentration value is considered abnormal. 

Another method is to use the fact that the partial pressure of saturated dissolved oxygen in water is almost equal to the partial pressure of oxygen in air. There are two methods: a simple span calibration using the partial pressure of oxygen in the atmosphere, and a saturated water calibration using water saturated with dissolved oxygen (about 500 mL of water aired for 10 to 20 minutes).

However, since saturated water calibration is also affected by atmospheric pressure, a manual calibration method is also available, in which the measured water is measured with a reference instrument and adjusted to that value. Since there is no standard solution traced to a national standard for the calibration of dissolved oxygen analyzers, a calibration certificate cannot be issued.

What Is a Wet Dust Collector?

A wet dust collector is a device that uses water to capture particles from the air. It serves as a treatment device for exhaust gases and dust, effectively removing small particles and harmful substances from the air.

Wet dust collectors not only capture particles but also remove harmful components from the air, posing less fire hazard and generating less static electricity than dry dust collectors. They also serve as a noise control measure due to their lower exhaust volume.

Applications for Wet Dust Collectors

Wet dust collectors are widely used in industrial settings, construction sites, and medical facilities.

1. Industrial Fields

In industrial environments, wet dust collectors remove dust and particulates from production processes, maintaining a clean work environment. They are also used in woodworking shops for collecting wood chips and debris.

2. Construction

At construction sites, wet dust collectors reduce dust impact generated by machinery and tools, helping to protect workers and the environment.

3. Medical Field

In hospitals and research facilities, wet dust collectors help remove airborne particulates to prevent the spread of infectious diseases and microorganisms.

Principle of Wet Dust Collector

Wet dust collectors operate by using water to capture airborne particles. They have an inlet to draw in dust, with a tank or vat where water is stored. Particles impinge on the water’s surface, dissolving or being absorbed, effectively separating them from the air.

Types of Wet Dust Collectors

There are two main types of wet dust collectors: wet scrubbers and Wet electrostatic precipitators.

1. Wet Scrubber Type

Wet scrubbers use water to clean airborne particles and harmful substances. Air is passed through a flue where it contacts water, with particles and toxic substances being removed via separators and filters. This method is effective for particulates and gaseous substances and is widely used in industrial environments and exhaust gas treatment facilities.

2. Wet Electrostatic Precipitator

A wet electrostatic precipitator is a wet dust collector that collects minute particles and dust in the air using static electricity. The basic structure consists of a collection chamber with collecting plates and electrodes, a liquid storage tank, and a high-voltage source.

First, air containing dust is introduced into the collection chamber where DC high voltage is applied, and the dust is attracted to the collecting plates by electrostatic force. The collecting chamber is supplied with water, which dissolves the dust attracted to the collecting plates and washes it away.

An electrostatic precipitator is characterized by the fact that the particles it can collect are smaller in size than those collected by other methods. The use of water also has the effect of cooling the heat generated in the equipment. Large rectifiers and other devices are used as DC high-voltage sources and are often installed at the top of the equipment.

They are widely used in metal smelting processes. In addition, since the dust collection plates are generally washed with water periodically, multiple units are often installed in parallel for backup purposes.

What Is a Wet Grinding Mill?

A wet grinding mill is a device that uses liquid to grind objects. Particles can be milled in different ways, depending on their size and condition. Wet milling is suitable for milling finer particles. Relatively small particles are close to ideal strength and cannot be crushed by simple collision alone. Therefore, by adding a liquid such as water and beads together with the particles, the surface is scraped and the particles are crushed into smaller particles. This process is particularly useful in the medical field for pulverizing pharmaceuticals. Wet grinding mills are used in the medical field to grind pharmaceuticals, and are particularly useful in the medical field.

Uses of Wet Grinding Mills

Wet grinding mills are used to grind fine particles. Wet milling pulverizes particles not only by impact but also by friction and stress, with beads placed together with the liquid. Wet milling can crush particles that could not be crushed by dry milling, and can crush small particles down to a few microns or less. It is used in a variety of situations where fine grinding is required and is specifically used in the manufacture of the following products.

• Pharmaceuticals
• Pigments and Cosmetics
• Rubber Products and Paints
• Capacitors

Principle of Wet Grinding Mills

This section introduces the specific principles of wet grinding mills, as well as their advantages and disadvantages.

First, in addition to the particles to be ground, a liquid such as water and beads involved in the grinding process is fed into the wet grinding mill. These are rotated at high speed in the grinding chamber, causing the beads and particles to collide with each other, resulting in crushing. The crushed beads are diffused, and one after another, the beads are used to break the particles into smaller and smaller pieces. The beads used here are generally about 2 mm or smaller. In the past, balls of several centimeters in diameter were used for grinding, but beads are now used because it is more efficient to fill the mill with a large number of fine beads.

The greatest advantage of wet grinding mills is that they can grind smaller particles than dry mills. The high-speed rotation of the beads with the liquid increases their fluidity and makes them more easily collide with each other. In addition, the surface of the beads is removed by friction and stress, resulting in smaller particles than with the dry method. On the other hand, there is a disadvantage in terms of cost. The use of water and other solutions makes grinding more expensive than the dry method. It is also inferior in terms of energy efficiency since part of the energy used to rotate the material at high speed is absorbed by the liquid.