月: 2023年11月

What Is An Aftercooler?

An aftercooler is a device designed to cool compressed gases. In the automotive context, it’s also referred to as an intercooler. These coolers come in two types: air-cooled and water-cooled. Their primary function is to reduce the temperature of compressed gas to a level suitable for its intended use, particularly important in air compressors where compressed air contains high moisture levels. The aftercooler condenses this moisture and facilitates its removal while cooling the gas.

Uses of Aftercoolers

1. For Air Compressors

Aftercoolers are attached to the discharge port of air compressors to cool the compressed air. This process also condenses water vapor from the atmosphere, which is inherent in compressed air, requiring its removal to prevent equipment damage. Additional moisture reduction can be achieved through drying filters filled with desiccants like silica gel.

Cooling is also crucial to prevent equipment damage, paint bubbling, contamination, or freezing in applications using compressed air. Aftercoolers also convert oil mist in oil-injected compressors into a liquid form for removal. Some compressors integrate aftercoolers for a more compact design.

2. For Gas Compressors

For gases like nitrogen, oxygen, carbon dioxide, hydrogen, and methane, which reach high temperatures when compressed, aftercoolers ensure they are cooled to appropriate temperatures. Compressors dedicated to specific gases often have built-in aftercoolers.

Principle of Aftercoolers

1. Temperature Rise of Compressed Gas

Compression increases the velocity and reduces the distance between gas molecules, generating heat. The extent of this temperature rise is determined by the specific heat ratio, varying with the gas type. For example, ideal gases like helium, hydrogen, nitrogen, oxygen, air, and carbon dioxide have specific ratios influencing their temperature increase upon compression.

2. Cooling by Aftercooler

Air-cooled aftercoolers use air to cool the compressed gas, typically reducing the gas temperature by about 10 degrees Celsius compared to ambient air. Water-cooled aftercoolers, on the other hand, use water for cooling and are ideal when industrial water supplies or cooling facilities like towers are available. In automotive applications, water-cooled intercoolers use radiators to cool the water with air.

Other Information on Aftercoolers

Advantages of Aftercoolers

Cooling of Compressed Gas: Essential for applications sensitive to heat, such as in processing animal feed, baking mixes, or plastic granules. Removal of Moisture and Oil: Effective in protecting equipment from damage caused by moisture and oil in compressed air. Utilization of Input Energy: The energy used in cooling processes like heat exchangers and blowers significantly enhances the overall utility of the compressed gas.

What Is a Concrete Batch-Type Plant?

A concrete batch-type plant is an equipment used to produce concrete by mixing aggregate, cement, water, and admixtures in a batch process.

Concrete can be produced in batch or continuous systems, but the batch system is more accurate and produces a better-quality product. Each material is measured and added from each feeder, and mixed in a mixer for a predetermined period of time to produce fresh concrete.

Uses of Concrete Batching Plants

The plant is generally installed near the site of demand, from where it is transported by mixer truck to the construction site. Fresh concrete hardens over time, so it is important for the plant to control time, and the plant is responsible for supplying the required quantity, at the required time, and with consistent quality. The plant makes meticulous production plans that can flexibly respond to demand.

For large-scale construction projects such as dams and tunnels, dedicated plants may be built near the construction site. This can be handled very efficiently. Mobile equipment is available for use in small-scale construction projects. One set of equipment can be mounted on a trailer, and the equipment can be moved to the construction site for each material to be supplied efficiently. Various sizes are available depending on the size of the project.

Principles of Concrete Batching Plants

The quality of concrete depends on the mixing ratio of materials, which is specified in JIS A 5308 Ready-mixed Concrete. Three types are available: ordinary, lightweight, and pavement. The roles of each material are shown below:

1. Cement

Cement is a setting and solidifying material. It hardens and bonds aggregates.

2. Water

Water assists the cement to harden and determines the softness of the fresh concrete. The ratio of water to cement affects the strength and workability of the concrete. A low water-cement ratio increases strength but reduces workability.

3. Aggregates

Aggregates, such as gravel and sand, account for 70-80% of concrete by weight. Aggregate is a filler, but its role is to reduce shrinkage and heat generation, and to impart stiffness and abrasion resistance. The size of the aggregate influences quality and other factors.

4. Admixture materials

Admixture materials include admixtures. Admixture is a material added in large quantities, such as an expander, to improve quality. Admixtures, such as AE water reducers, are added in small quantities to improve quality.

Structure of a Concrete Batching Plant

The plant consists of material feeders, storage facilities, weighing equipment, and mixers. Aggregate, cement, water, and admixture are weighed one batch at a time, fed into the mixer, and kneaded to produce a precise, uniform quality product.

1. Material feeder

Material feeders are installed at the top of the plant. Aggregate is mostly fed automatically using a turn head. Cement is generally fed automatically by a screen conveyor or chute.

2. Storage facilities

Storage facilities for storing materials are installed at the top of the plant. The material is automatically controlled and discharged by detection signals.

3. Weighing equipment

Weighing equipment weighs the input materials on an accurate scale. The accuracy of the scale is defined by JIS standards, and load cells with higher accuracy are generally used.

4. Mixer

A mixer is a device for mixing materials. There are various types of mixers. They include a tilting mixer shaped like the drum of a mixer truck, a tub-shaped pan mixer, and a forced dual-shaft mixer. Recently, forced twin-shaft mixers are widely used. This type of mixer is capable of mixing both hard and soft slumps in a short time.

Other Information on Concrete Batching Plants

1. Slump value of concrete

The slump value of fresh concrete is a measure of its softness before hardening. The higher the slump value, the softer the fresh concrete. Softer concrete has the advantage of being easier to work with, but its strength is reduced.

To measure the slump, place the fresh concrete in the specified slump cone, lay it down on a flat surface, and slowly pull out the cone. The height of the slump cone is the height of the concrete as it is lowered from its original height (300 mm). A large slump value causes adverse effects such as reduced watertightness, reduced durability, and increased drying shrinkage, so JIS has established a standard value.

2. Advantages of Concrete Batch Plants

• Homogeneous production in large quantities

Large-scale equipment can produce homogeneous fresh concrete in large quantities. Each batch allows for accurate weighing of materials and superior quality.

• Efficient production

Automation of weighing and in-plant transport is possible, enabling efficient production.

• Efficient transportation

Since the plant can be located near the construction site, there is no need to transport the material long distances by mixer truck. Required quantities can be quickly supplied.

What Is a Ducted Electric Heater?

A ducted electric heater is a device that heats air and warms objects by means of electric power.

Usually connected to a duct (a pipe that controls air flow), it raises the temperature of an object by heating and feeding air into it. It is often used for rooms such as workplaces and offices. They can be connected to the ducts of a heating and cooling system and incorporated into the central heating system of a building.

Many products use electric heating wires and are characterized by their simple structure. Because they use electricity, they are easy to install and can be used anywhere there is an electricity supply. However, it should be noted that if the unit price of electricity is high, operating costs may be high.

Some products can also circulate indoor air, helping to improve indoor air quality. Some products are also available that introduce outside air.

Uses of Ducted Electric Heaters

Ducted electric heaters are used in a variety of applications. The following are some of the uses of ducted electric heaters:

1. Residential heating

Ducted electric heaters are used as central heating systems in homes. They primarily distribute air through a central heating unit and ducts to heat different rooms in the home. This is a common heating method in cold regions and countries.

2. Commercial buildings

Ducted electric heaters are used to provide heating over a wide area in large facilities such as commercial buildings, factories, and warehouses. In these facilities, ducted heating systems can provide uniform heating for different sections of the building. They are also used in office buildings and hotels in combination with central air conditioning to provide a comfortable environment.

3. Public facilities

Ducted electric heaters are used to heat school classrooms, gymnasiums, and a variety of other facilities. They are often integrated into central air conditioning heating systems to maintain each classroom at the proper temperature. They may also be used to control room temperature in hospitals and medical clinics, and in public swimming pools.

Principles of Ducted Electric Heaters

Ducted electric heaters use electrical energy to heat air and distribute it through ducts to individual rooms in a building.

Usually, electric heating wires or electric heating coils are built in as heating elements. These components consume power and generate heat through resistance. The heat generated by these heating elements can heat the surrounding air.

Ducted electric heaters often incorporate a device called an air handling unit. The air handling unit draws air in with a fan or other device and regulates the air through filters and humidity control devices. This produces clean, comfortable heating air.

Heating air is delivered through ducts to each section of the building. Ducts are often concealed within walls and ceilings, and are structures that effectively control air flow by retaining heat as needed. Each room has an air supply outlet from the duct from which the heated air is released.

How to Choose a Ducted Electric Heater

When choosing a ducted electric heater, it is important to consider several factors. The following are factors to consider when selecting a ducted electric heater:

1. Location

The design requirements for ducted electric heaters vary depending on whether they are installed outdoors or indoors. Outdoor installation requires protection of power wiring, etc., and indoor installation is less expensive. After determining the installation location, select the product accordingly.

2. Power supply voltage

Ducted electric heaters operate on a specific supply voltage. It is important that the power supply voltage of the installation location match the operating voltage of the selected heater. Typical power supply voltages are AC110V or 1φAC110V and 3φAC220V.

3. Power

Power requirements for ducted electric heaters depend on the heating capacity of the heater. It is important to calculate the heating capacity based on the required heating capacity and select a ducted electric heater capable of heating sufficiently. Power requirements for electric heaters are specified in the product specifications.

4. Dimensions

Ducts for centralized air conditioning, for example, are designed based on the required heating and cooling capacity and the required air volume. The dimensions of this product are often chosen to match the installation space while conforming to the duct. Especially when installing in ceilings, make sure that the height and width of the product are within the allowable range.

What Is an Ice Maker?

An ice maker is a machine or device used to produce ice.

They are useful for making beverages and cold dishes because ice can be easily produced. There is no need to prepare ice in advance, and ice can be produced immediately on demand.

Commercial ice machines are also designed to produce ice in a sanitary environment, providing safe, clean ice. This is a more hygienic option than homemade ice. Some ice machines can customize the shape of the ice, allowing for the production of different ice shapes to suit different needs.

However, safety and sanitation must be taken into consideration when using ice machines. It is important to clean them regularly and maintain sanitary conditions to prevent the growth of bacteria and mold.

Uses of Ice Machine

Ice machines have a variety of uses and are widely used in both residential and commercial environments. The following are some common uses of ice machines:

1. Beverages

Ice machines are widely used to serve cold beverages. They are useful for chilling beverages by adding ice to a variety of beverages, such as iced tea and soft drinks. This allows beverages produced and stored at room temperature to be instantly cooled and made drinkable.

2. Food cooling

Ice machines are often used for food cooling as well. Ice is sometimes used to cool food at salad bars and deli counters. This allows for instant cooling of foods that need to be served cold.

3. Medical care

In hospitals and medical facilities, ice is sometimes used to lower the body temperature of patients. It is common to use cooling pads or ice packs with ice water to rapidly lower high patient body temperatures. This helps to control the patient’s body temperature and treat emergencies.

Frozen instruments and materials may also be used in operating rooms and surgical procedures. Ice is advantageous in cooling such materials and protecting tissue during surgery.

4. Ice powder production

Powdered ice is a type of ice that is made by breaking ice into small particles, a characteristic that makes it easy to incorporate ice into beverages and desserts. Thus, it can be used as part of cocktails to create a refreshing cold taste in beverages. It is also used as an ingredient in shaved ice, which can be enjoyed with syrup or fruit.

Principles of Ice Machine

The operating principle of ice machines is based on the process of freezing water to make ice. First, water is supplied to the ice machine. The water is supplied from the ice machine’s supply tank or from the water supply and flows into the ice-making section of the ice machine.

The ice machine has a built-in cooling system that uses a refrigerant to cool the interior. Generally, chlorofluorocarbons or other gases are used, but environmentally friendly products often use CO2. The refrigerant is compressed and expanded to cool the inside of the ice compartment.

Ice makers often have ice molds to determine the shape of the ice. The shape of the ice depends on the design of the ice maker, and a variety of products are available, including cubes and cubicles. Ice molds allow the ice to form and maintain a consistent shape.

After a certain amount of time, the frozen ice is removed from the ice mold. Generally, a heating element, vibrator, or other device built into the ice mold is used to loosen and remove the ice.

How to Select an Ice Maker

There are several factors to consider when selecting an ice maker. The following are factors in selecting an ice machine:

1. Type of power source

There are a variety of power supply types for ice machines, including single-phase and single-phase power supplies. It is important to select an ice machine that has the appropriate power source and matches the equipment. Large commercial ice machines use a 3-phase 200 V power supply, for example, while residential ice machines are often designed for single-phase 100 V household outlets.

2. Ice mold shape

Ice machines come in a variety of ice shapes. Ice cubes and ice balls are common shapes. Select an ice maker according to the ice shape to be used.

3. Refrigerant type

Various refrigerants are used in the cooling system of an ice machine. Different types of refrigerants have different cooling efficiencies and environmental impacts. Ice machines that use energy-saving refrigerants are eco-friendlier and more economical.

4. Ice making capacity

Ice machine capacity is an important indicator of the amount of ice that can be produced per day. Select the appropriate ice making capacity to meet your demand. Commercial ice machines are capable of producing large volumes of ice and are suitable for locations with high demand.

What Is a Copper Wire?

A copper wire is an electrical wire made of copper, which is an excellent electrical conductor.

Copper is a very good electrical conductor and is one of the materials that can transmit electric current efficiently. Therefore, it is used in various applications such as electrical wiring and electronic devices. Taking advantage of this property, copper wires are made of copper.

Copper is a relatively flexible and easily processable material. This allows wires to be manufactured and installed in a variety of shapes. Other materials with high electrical conductivity include gold and silver, which can be manufactured at a lower cost than these materials.

Copper is also highly corrosion resistant and resists oxidation and corrosion. This makes it suitable for use in a variety of indoor and outdoor environments. Copper wires have a long service life and can remain reliable for decades.

Uses of Copper Wire

Copper wire is used as electrical wire in electrical circuits. The list of uses for copper wire is endless. The following are just a few examples of copper wire applications:

1. General Households

Copper Wire is widely used for power supply and electrical wiring in general households. They can be used for a variety of electrical wiring, from wall outlets to lighting fixtures. Copper wire is safe and reliable and supports the efficient operation of electrical systems.

2. Electronic Equipment

Copper wire is often used for internal wiring in electronic equipment. For example, copper wires are used in most electronic devices such as computers and smart phones. Copper’s high electrical conductivity makes it suitable for signal transmission and power supply, ensuring reliable operation.

3. Automotive

In the automotive industry, copper wire is a widely used component in automotive electrical systems and engine components. Copper wires are used in electrical components such as automotive battery cables, starter ignition systems, lighting, and sensors. Copper’s high heat resistance and durability make it highly reliable in automotive electrical systems.

4. Power Generation and Substations

At power plants, copper wires are often used to transmit power from generators to transmission lines. Copper wires are also essential for regulating voltage and distributing power at substations. Copper’s high electrical conductivity and durability make it ideal for efficiently transmitting power from power plants to demand facilities.

Principles of Copper Wire

Copper wire has very high electrical conductivity because copper atoms can move electrons freely. Free electrons exist outside the copper atom, and these free electrons carry electric current.

As current flows through the copper wire, the free electrons move through the crystal lattice of copper atoms, moving in response to the electric field. The electric field is the cause of the electric current, and the electrons move within the copper wire in accordance with the electric field, which is how the current is generated. Copper’s high electrical conductivity allows current to be efficiently transmitted, resulting in minimal energy loss.

One important law related to the copper wire principle is the Ohm’s law. According to Ohm’s law, current (I) is proportional to voltage (V) and inversely proportional to resistance (R). Specifically, it is expressed by the following equation:

V = I x R

In the case of copper wire, resistance is very low, resulting in almost no voltage drop when current flows, thus increasing the efficiency of the electrical system.

How to Select Copper Wire

Many factors are considered when selecting copper wire. The following are factors in selecting copper wire:

1. Shape

The shape of copper wire should be selected based on its application. When used as an overhead wire, single-core or thicker wire should be used to reinforce its strength. When laying inside a wall or in a narrow space, stranded wire with a group of thin wires is often used.

2. Allowable Current

Copper wire generates heat when a large current is applied, and it is important that this heat generation be kept within the allowable value. Therefore, it is necessary to select thicker diameter products for copper wires transmitting large currents. Copper wire with excellent heat resistance is often used when equipment needs to be downsized.

3. Insulation Coating and Protection

Since copper wire is a conductive material, it may cause a ground fault or short circuit if it comes in contact with the metal that makes up the column legs or enclosure. Therefore, many products cover copper wires with a resinous insulating material to insulate them. Products in which this insulation is further covered with a shielding layer or a sturdy insulator are called cables, and these products are selected according to the application.

What Is a Pellet Press?

A pellet press is a machine that presses and forms tablets, resins, and other materials.

Pellet presses are generally designed to press various materials into a mold and press a plunger into the mold to form the material. Manual, manual hydraulic, and automatic hydraulic types are available. Formed pellets are used as samples for various measuring instruments, test pieces, electrodes, recycled samples, etc.

Applications of Pellet Presses

Pellet presses are ideal for preparing sample pieces for X-ray fluorescence analysis, infrared spectroscopic analysis, and electron microscopic analysis. There are also applications for pellet presses in the preparation of cathodes and anodes for all solid-state batteries, sample pieces for research and development of dental materials, sample pieces for research and development of new products, and pellets for solid electrolytes.

Other examples of applications include tablet cleaner molding, metal powder molding, magnesium molding, ceramics molding, functional material molding, and food molding. It is also used for molding crystalline materials, zeolite, waste paper and plastic fuel RPF, resins, and silica/alumina.

Machines called press pelletizers or pellet molding equipment are used to solidify and reduce the volume of fuels, fertilizers, feedstuffs, and industrial wastes. Continuous production of pellets is possible. Conical rollers press the raw material with uniform pressure.

Principles of Pellet Press

The pellet press works as follows: First, the material is filled into the mold. Then, the plunger pushes the material into the mold, and pressurization begins. As the pressure increases, the air inside the material is pushed out, increasing the density and defining the shape of the pellets.

Once the maximum load is reached, the pressure is held for a certain amount of time so that the particles of the material adhere to each other, resulting in a stable pellet. Higher pressure ensures reliable molding and pellets with a smooth surface. With the automatic pressurization system, pressure can be controlled in steps, making it possible to create high-quality pellets even from materials that are difficult to mold.

The type that incorporates a heating device in the pellet press can press by increasing the temperature. High-temperature pressing is possible for compression molding tests and sample preparation of resins and powders.

Types of Pellet Presses

1. Classification by Driving Method

• Manual-type

This method uses the principle of leverage to move a plunger by a lever or screw to produce pellets hydraulically. Since hydraulic pressure is increased by hydraulic pressure, the press can be operated with light force. Since it is manual, it does not require electricity and is easy to use. Subtle adjustment of pressure increase and speed is possible. It is used for trial products in laboratories and for making a small number of pellets.

• Manual-automatic type

The built-in electric hydraulic pump allows easy adjustment of pressure. The speed of pressure increase, upper limit of pressure, holding time, etc. can be automatically controlled.

• Automatic type

Programmable, automatic, homogeneous pellets can be produced. For mass production.

2. Classification by Press Method

There are two types of powder press methods using dies: uniaxial and biaxial. Uniaxial pressing is a method in which the lower die is fixed and pressed by the pressurizing force of the upper punch. Friction between the walls of the powder-filled mold can cause a density difference between the upper and lower pellets, resulting in deformation and cracking.

Biaxial molding is a method in which the mold is not fixed, and the pellets are pressed in a floating state. The mold moves up and down in accordance with the movement of the powder during molding, thereby reducing the density difference between the top and bottom.

3. Classification by Added Functions

• Heating device

The specimen can be pressed at high temperatures. There are also high-temperature types capable of temperatures up to 400°C. Some are equipped with a water-cooling device. Some models are equipped with a water-cooling system, which enables fine adjustment of the mold temperature.

• Pressurization equipment

Combined with the pressure-resistant cleaning device CIP, this method applies pressure to the sample and presses it. Pellets are formed by applying uniform pressure from all directions using water pressure. Pressing is possible up to a surface pressure of about 2 tons.

Other Information on Pellet Press

KBr tablet method

The KBr tablet method is a basic method for infrared spectroscopic analysis of solids. It is suitable for measurements when the sample is rare. Potassium bromide KBr to which a small amount of sample is added is pressed into tablets to be used as a sample for the infrared spectrometer.

What Is a Hydrogen Compressor?

A hydrogen compressor is a device that compresses hydrogen gas.

Hydrogen compressors are used to compress hydrogen gas under high pressure or to liquefy hydrogen by cooling it. Compared to gas, liquefied hydrogen is much smaller in volume, which is advantageous for storage and transportation.
Hydrogen compressors come in a variety of forms, including mechanical types such as positive displacement and centrifugal types, and methods that use electrochemical reactions.

A familiar example of a hydrogen gas application is fuel cells. They are gradually becoming popular for use in automobiles, household power generation, and water heating. Hydrogen energy does not produce carbon dioxide gas and emits only water, making it an excellent energy source in this environmentally conscious age. A great leap forward is expected in the future.

Applications of Hydrogen Compressors

1. Storage and transportation of hydrogen

Hydrogen gas is an excellent method of storage and transportation because its volume is reduced to 1/800 when liquefied. Hydrogen can be liquefied by a hydrogen compressor at a hydrogen production plant and stored in a storage tank. It can also be loaded into transportation tanks on ships and tanks of trailer trucks for transportation to the destination.

2.  For fuel cells

Hydrogen is supplied to automotive fuel cells by installing a hydrogen compressor at a hydrogen gas station, increasing the pressure to the required level, and filling the vehicle’s hydrogen tank. In Japan, 70 MPa is used. Fuel cells for home use are cogeneration systems and are used to generate electricity as well as to heat water. In addition, generators using fuel cells are also in practical use.

3. Other Applications

Liquefied hydrogen is used as a raw material in chemical plants, pharmaceutical plants, fertilizer production, etc., as fuel for power plants, engine compressors, etc.

Principles of Hydrogen Compressor

Hydrogen gas is the element with the lowest density, and various methods must be used to increase pressure. Mechanical compressors, such as volumetric and centrifugal types, as well as electrochemical and thermal types, are used.

Mechanical compressors have a high-pressure ratio, so most are multi-stage compressors. They also require high temperatures, so cooling is also important. The maximum discharge pressure is about 100 MPa. Electrochemical reaction type and thermal type have the features of no moving parts, no vibration, no noise, and oil-free.

Types of Hydrogen Compressors

The types of hydrogen compressors used include positive displacement type, centrifugal type, electrochemical reaction type, and thermal type.

1. Positive Displacement Compressors

The positive displacement compressor changes the volume to inhale, compress, and discharge gas. The types of hydrogen compressors in practical use include reciprocating compressors, screw compressors, and diaphragm compressors.

The reciprocating type compresses gas through the reciprocating motion of a piston. Various types are available depending on the arrangement of the cylinders. The swash plate type, in which the piston reciprocates in the axial direction, is also of this type. The screw type compresses gas by rotating a two-axis or single-axis screw to reduce the volume. Diaphragm type compressors compress by reciprocating diaphragms.

2. Centrifugal Compressor

Centrifugal compressors convert the velocity energy of the gas into pressure by rotating an impeller at high speed. Hydrogen gas is the gas with the smallest density, and increasing the pressure requires increasing the impeller speed. Centrifugal hydrogen compressors are in practical use in the U.S., and in Japan, ultra high-speed single-shaft multi-stage and multi-shaft multi-stage compressors are under development.

3. Electrochemical Reaction Type Compressor

The electrochemical reaction type is not a mechanical compressor, but a method of obtaining compressed hydrogen through a chemical reaction. When voltage is applied to the electrodes, hydrogen ions are reduced to hydrogen and hydrogen is extracted from the cathode. This method is now in practical use in Germany and the U.S., and Japan is likely to expand it in the future.

4. Thermal Compressor

This method boosts pressure by applying heat to hydrogen gas. When hydrogen gas is stored in a hydrogen storage alloy, heat is generated, and metal hydride is formed. Then, when heat energy is applied to the metal hydride, hydrogen is separated, and high-pressure gas is obtained. The output pressure is about 25 MPa. Metal hydride is a stable substance and very safe. Heating is an environmentally friendly method since waste heat can be used. In Scandinavia, it is deployed in hydrogen stations.

Other Information on Hydrogen Compressors

1. Lubrication system of Hydrogen Compressors

Three types of lubrication systems are used.

• Lubrication type

This method injects oil into the sliding and sealing parts of the cylinder and screw to lubricate, seal, and cool. There are methods such as splashing, oil pumping, and pressure lubrication. Oil mist is contained in the discharged gas.

• Oil-free type

This method does not use any oil or water in the gas passage. No oil or water is contained in the discharged gas.

• Water circulation type

Water is injected into the screw to lubricate, cool, and seal. The oil rate of the discharged gas is zero.

2. Advantages of oil-free type

Oil-free hydrogen gas has many advantages. Many industries require pure hydrogen. These include the mobility sector, power generation/storage, chemical/petrochemical, fertilizer, and refining. The advantage of oil-free is that it does not affect the chemical reactions used in its production. It is also important that it does not affect the process or equipment.

What Is a Construction Bulldozer?

A construction bulldozer is a piece of construction equipment used mainly in construction work to remove, transport, and level the ground.

A bulldozer is a heavy machine with an earth removal plate called a blade attached to the front of its body. Its main role is to push earth and sand in the direction of travel to level the ground. By changing attachments, the bulldozer can perform various types of work. There are two types of drive systems: crawler (infinite track) type and wheel type.

Uses of Construction Bulldozers

Bulldozers are used for earth removal, pushing, and leveling in construction work. These include civil engineering, dam construction, building construction, and site development. They are also used for snow removal and wetland work. By changing attachments, bulldozers are used for digging up and moving large rocks, root cutting, etc.

Bulldozers are available for special work. At disaster sites, they are operated by radio control. Amphibious bulldozers work by radio control and are used in places where dredgers cannot enter or leave. Underwater bulldozers can travel on the seabed and are remotely controlled by divers.

Principle of Construction Bulldozer

Pushing earth and sand out of the ground requires a great deal of force and driving power. Crawler type bulldozers are often used because of their high driving force. The gears are reduced along with the engine speed to produce powerful propulsive torque.

To dig up and crush large rocks, a jaw called a ripper is used. The ripper helps break up rocks and separate rocks from sediment. Bucket-type blades can efficiently transport sediment.

Operations using blades require the blade to be tilted from the vertical or oriented to the left or right relative to the direction of travel. Hydraulic pressure is used to change the angle of inclination.

Features of Construction Bulldozers

1. A wide variety of attachments

By changing attachments, various types of work can be performed. There are various types of attachments such as blade shape, jaw type ripper, bucket type, radio remote control, snow removal type, winch type, etc.

2. Various types of crawler shoes

There are various types of crawler shoes for wetland work, including standard types, which can be selected according to the application. The cross section of the shoe is triangular and wide. Shoes for snow and rock are also available.

Types of Construction Bulldozers

There are many types of bulldozer blades and rippers.

1. Classification by Blade

• Straight-type

This is a standard type of blade. It can be tilted to the vertical direction when viewed from the side by a hydraulic cylinder, and has a large capacity to push out a large amount of material at one time.

• U-type

This type of bulldozer has a U-shaped blade with both ends bent forward to push out a large amount of earth and sand. This type is used for super-large bulldozers.

• Angle-type

The blade is angled to the left or right in the direction of travel. It is used for one-sided cutting work and heaping and spilling work. In power angle dozers, the blade angle can be changed hydraulically from the operator’s seat.

2. Classification by Ripper

• Multi-shank type

This is a standard 3-jaw ripper. It crushes large rocks. The number of shanks can be changed according to the hardness of the rock.

• Giant-type

Long shanks for deep drilling.

• Parallel link

Equipped with a parallel link mechanism to maintain a constant penetration angle even if the penetration depth is changed.

3. Classification of bulldozers

The standard classification of bulldozers by weight is as follows: small size: 3 to 12 tons, medium size: 13 to 24 tons, large size: 28 to 42 tons, and super large size: 44 tons or more. Another classification by the location where they are used is dry-land bulldozers and wet-land bulldozers. Wetland bulldozers are designed to work in soft ground.

Other Information on Construction Bulldozers

1. Characteristics of Bulldozers in Japan

In Japan, many bulldozers for wetlands can be used at construction sites on soft ground. The ground contact area of the crawler is widened to reduce ground pressure, and a specially shaped shoe is used. It has better lateral sliding characteristics and excellent rolling pressure effect.

2. Qualifications Required

To handle a bulldozer, a qualification is required: to drive and operate a vehicle of 3 tons or more, it is necessary to obtain a national qualification in vehicle-based construction machinery operation skills. The course consists of a classroom lecture and practical skills training at a designated training institute. The content of the course includes the structure and handling of traveling equipment, structure, handling, and working methods of work equipment, driving knowledge, and laws and regulations. Practical skills include driving operation, operation of work equipment, and signaling.

3. Manufacturers of Construction Bulldozers

There are very few manufacturers of bulldozers, with Caterpillar of the U.S. and Komatsu of Japan almost monopolizing the world market. Komatsu has developed radio-controlled bulldozers for use at disaster sites or to improve work efficiency. And in recent years, Komatsu has introduced bulldozers that use GPS satellite positioning systems and 3D CAD design data to assist operators and automatically control blades.

Caterpillar also developed a bulldozer in 2009 that is powered by an engine and driven by an electric motor. This product can be said to be environmentally friendly.

What Is a Plastic Adhesive?

A plastic adhesive is an adhesive that is particularly suitable for bonding plastics.

Some plastics can be bonded with general adhesives, but there are some materials that are difficult to bond with general adhesives. In such cases, a special adhesive or primer is necessary.

In some cases, even plastics made of easily bondable materials can be bonded more firmly using plastic adhesives. There are various types of plastic adhesives, so it is important to choose the right one depending on the application and situation.

Uses of Plastic Adhesives

Plastic is a resin material that is widely used in everyday items around us.
Plastic adhesives have the following applications:

• Repair of kitchenware, bath components, and other water-related items
• Interior repairs
• Repair of toys
• Various daily necessities and small articles
• Electronic devices
• Home appliances
• DIY and crafts

In DIY and crafts, adhesives are used to make plastic models and figures. Some types of adhesives can also be used for works that are expected to be exposed to water (e.g. snow globes).

Adhesives for professional-use are used for joining gaskets, bonding various plastic components, fixing parts, and laminating large areas and flat plates.

Principles of Plastic Adhesives

One method of bonding difficult-to-bond plastics is to use a primer. Primer is used to improve the adhesion of material surfaces.

It is a low-viscosity liquid with low non-volatile content. In addition to improving adhesion, it also stabilizes the surface, prevents corrosion of metal surfaces, improves adhesion, and prevents deterioration of the adhesive. Primer must be allowed to sufficiently dry before applying the adhesive, and must not be mixed with the adhesive. The type of primer required depends on the type of adherend and adhesive.

Some acrylic adhesives using methacrylate, etc., can adhere to difficult-to-bond plastics without a primer by using a mechanism that fills gaps with microbeads or other contained particles.

Types of Plastic Adhesives

Plastic adhesives are available for household and commercial use. Different types of products are used depending on the material and application.

1. Household Plastic Adhesives

There are various types of household-use plastic adhesives, such as those that come with a primer set and can easily bond PE and PP, and those that can be used with only one adhesive. There are also adhesives with different characteristics, such as heat-resistant, water-resistant, and impact-resistant adhesives, as well as adhesives that can be used for metals and woods other than plastics.

Heat- and water-resistant products are particularly effective for repairing parts exposed to heat and water in kitchens, baths, and other areas, and for crafting works that are exposed to water. Regular instant adhesives can also be used for ABS and PVC.

2. Professional-Use Plastic Adhesives

Plastic adhesives for professional-use include synthetic rubber-based adhesives and acrylic adhesives using methacrylate, etc. In particular, adhesives for hard-to-bond plastics can be used. Some adhesive products, especially those for hard-to-bond plastics, contain microbeads or other fine particles to improve adhesive performance.

Cyanoacrylate adhesives, epoxy adhesives, polyurethane adhesives, and silicone adhesives are also used for plastics that are easy to bond, such as ABS, acrylics, and nylon. The appropriate one should be selected according to the application.

Other Information on Plastic Adhesives

Types of Plastics

There are various types of plastics made of different materials, and the ease of joining them with adhesives depends on the type. Polyesters such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) are thermoplastic and used in a variety of applications, but all are difficult plastics to bond.

Acetal resins such as POM (polyoxymethylene) and PTFE (polytetrafluoroethylene) are also known as difficult plastics to bond.

ABS resin, polyvinyl chloride (PVC), acrylic resin, and nylon are other known materials that are relatively easy to bond and can be used with ordinary adhesives. All of these materials have high plasticity and are commonly used for building materials, household goods, and equipment components.

However, in the case of acrylic materials, since many products utilize the transparency of the material, high transparency and non-yellowing characteristics are basically required for the adhesive as well. In the case of PVC, the ease of adhesion differs depending on the formulation of the same polyvinyl chloride. In particular, recyclable polyvinyl chloride manufactured using relatively new formulations is a relatively difficult material to bond.

What Is a Metallic Adhesive?

Metallic adhesives are adhesives that can bond on metal surfaces.

Adhesives for metals include those that can bond between metals such as stainless steel, iron, and aluminum, as well as those that can bond between metals and non-metallic materials (e.g., plastic, wood, ceramics, and carbon fiber). Many products have excellent heat resistance, water resistance, and impact resistance.

Uses of Metallic Adhesives

Metallic Adhesives are used in a wide range of applications, whether for household, industrial, or architectural use. Metals that can be bonded include stainless steel, titanium, aluminum, iron, galvanized steel, copper, brass, and many others. Other non-metallic materials that can be bonded to metals include plastics, wood, glass, ceramics, carbon fiber, and many others.

1. Household Use

Household metal adhesives are used in applications such as DIY furniture, repair of kitchen, bathroom, and other water-related items, cord repair for digital equipment, car body and muffler repair, water pipe repair, and fence repair. It is also possible to repair eyeglass frames and accessories such as necklaces. Other applications include handmade accessories, gluing and repairing model trains, and repairing fishing tackle such as lures.

2. Industrial Applications

In industrial applications, metal adhesives are used as an alternative welding method to mechanical fastening and welding. Typical applications include bonding metal parts such as electronic components, heaters such as wire thermocouples, sensors, and other building materials and structures.

Principle of Metallic Adhesives

Metallic Adhesives, like general adhesives, bond by adhesive force and cohesion. Adhesion is the force that binds different molecules together, while cohesion is the force that holds the same type of molecules together. Adhesives are effective when they adhere to the surface of an object in liquid form as a liquid substance and cure. Curing is caused by polymerization, chemical reactions with curing agents, and evaporation of solvents.

There are several types of adhesives that can be used for metals, and each type has a different adhesion mechanism. The adhesion strength of adhesives is usually due to physical (mechanical) bonding, chemical bonding, or dispersion bonding.

1. Epoxy Resin-Based Adhesives

Epoxy resin-based adhesives are one type of adhesives that can be used on metals, and are available in one- and two-component types. Generally, the two-component type is the most common, in which adhesion proceeds through a chemical reaction caused by mixing two liquids. Compared to ordinary adhesives, this type of adhesive has the characteristic that its volume does not decrease easily when it cures. Other than metals, it can be widely used for bonding to wood, ceramics, glass, etc., and can also be used for bonding to non-metals. These adhesives have particularly excellent properties in terms of durability, heat resistance, and water resistance.

2. Elastic Adhesives

Elastic adhesives are adhesives that remain soft even after curing and have rubber-like elasticity. They are particularly suitable for bonding materials that are made of different materials. However, it cannot be used for bonding metals.

When bonding different materials, cracking, warping, or peeling may occur over time due to differences in the coefficient of thermal expansion. The coefficient of thermal expansion is a value that indicates the rate at which the length and volume of an object expands as the temperature rises. Elastic adhesives are less likely to crack, warp, or peel because the adhesive becomes elastic and rubber-like after curing. Also, since the adhesive layer absorbs shock, it is often relatively resistant to impact and vibration.

Types of Metallic Adhesives

Metallic Adhesives can be broadly divided into those for household and commercial use. Different products have different characteristics such as thermal conductivity, electrical conductivity, heat resistance, and UV resistance, and should be used according to the intended use. In addition, some types of metal adhesives can bond metals and non-metals, but not metals to metals, so care must be taken.

1. Household Use

For household use, instant adhesives for metals, epoxy resin-based adhesives, and elastic adhesives are used. Instant adhesives for metals are instant adhesives with high adhesive strength to metal surfaces. Instant adhesives cure by chemical reaction, so they can bond instantly without waiting for time to dry. The main reaction proceeds with moisture in the air or on the surface of the substance to be bonded.

Among various metal adhesives, the time to dry, capacity, impact resistance, water resistance, heat resistance, and UV resistance vary depending on the product. It is necessary to select the appropriate one for the application. For example, a quick-drying adhesive that cures in a short time is suitable when the range of use is narrow, such as for bonding metal fittings of accessories or repairing various small parts. On the other hand, if the area of use is large, such as repairing houses, cars, motorcycles, etc., a long curing time will be easier to work with. The longer the time to cure, the easier it is to make corrections after application.

Impact-resistant types are appropriate for areas subject to loads and impacts such as joints, while heat resistance is required for electronic equipment and areas around car engines. Water-resistant adhesives are required for use in kitchens, bathrooms, and other watery areas. For crafts and handicrafts such as accessory making, adhesives with a transparent finish can be used to keep the adhesive from being visible and to maintain its aesthetic appeal. In addition, since adhesives may stick to the container if stored for a long period of time, it is appropriate to select a small volume product if the amount or frequency of use is small.

2. Commercial Use

Metallic adhesives for professional use are alternatives to welding, screws, etc. Specific types include epoxy resin adhesives, acrylic resin adhesives, hot-melt adhesives, and light-curing adhesives. Curing time, dischargeability, workability, impact resistance, water resistance, heat resistance, and electrical conductivity vary depending on the product, so it is necessary to select the right one for the application.