投稿者: yako77

What Is a Capillary Tube?

Capillary tubes are thin tubes with an inner diameter of 0.6 to 2 mm.

Capillary tubes for refrigeration cycles used in air conditioners and refrigerators are thin tubes made of copper or steel that control the flow of refrigerant. As the refrigerant passes through the narrow passage, the pressure drops due to flow resistance, a function known as throttling expansion. This drop in refrigerant pressure causes the refrigerant to evaporate and absorb heat from its surroundings.

A similar function is performed by an expansion valve. Expansion valves are more controllable, but they are more expensive. High-precision glass capillary tubes, called capillary tubes, are used for X-ray diffraction and research.

Uses of Capillary Tubes

Capillary tubes are mainly used as cooling devices in small refrigerators, room air conditioners, and electric refrigerators. They are also useful in gas appliances, oil fan heaters, fire alarms, and terminal equipment. They are mainly used in small refrigeration cycles with relatively stable operating conditions.

In the same air conditioner, expansion valves are used in car air conditioners for automobiles because of their wide range of operating conditions. This is because it is difficult for capillary tubes to perform under a wide range of conditions, with outside air temperatures ranging from low to high, and engine-driven compressors from low to high speed.

Principle of Capillary Tubes

Refrigeration cycles for air conditioners and refrigerators consist of a compressor, condenser, evaporator, receiver, and expansion mechanism. Expansion valves and capillary tubes are used in the expansion mechanism.

When refrigerant gas is compressed in the compressor and cooled in the condenser, it becomes a high-pressure liquid refrigerant. The condenser is located in the outdoor unit in air conditioners and in the cabinet in refrigerators. The high-pressure liquid refrigerant is then depressurized by the expansion valve and capillary tubes and enters the evaporator. The evaporator is located in the indoor unit in air conditioners and in the cabinet cooler in refrigerators.

Meanwhile, as the compressor draws refrigerant from the evaporator, the pressure in the evaporator is reduced to a low pressure, and the liquid refrigerant evaporates to become gas. The evaporator is a heat exchanger between the refrigerant and the air, and the heat of evaporation of the refrigerant cools the air. Expansion valves and capillary tubes control the pressure and refrigerant flow rate in the evaporator through the throttling effect, thereby adjusting the cooling capacity.

Types of Capillary Tubes

Capillary tubes are available in many types of fineness and length. Capillary tubes may be connected using copper flare tubes or by brazing. When using copper flared capillary tubing, select the type with nuts on both ends, which already have nuts on both ends of the capillary tubes.

1. Straight Type

Straight capillary tubing is used in simple refrigeration systems where the inner diameter is constant and the refrigerant flow is steady.

2. Coil Type

Coiled capillary tubes are spiral wound and are used when space is tight.

3. Multi-Port Type

Multi-port capillary tubes have multiple ports along their length and are used in systems with multiple evaporators or compressors.

4. Low-Profile Type

Low-profile capillary tubes are very thin and are used when space is limited.

5. Insulated Type

Capillary tubes have an insulating layer on the outside to help maintain the temperature of the refrigerant as it flows through the tube.

How to Select Capillary Tubes

When selecting capillary tubes, there are several considerations for optimal performance and efficiency

1. Refrigerant Type

Capillary tubes should be sized for the refrigerant to be used. 

2. Refrigerant Flow Rate

Capillary tubes should be sized to handle the required refrigerant flow rate of the refrigeration system.

3. Working Pressure

Capillary tubes should be sized to handle the working pressure of the refrigeration system.

4. Superheat

Capillary tubes should be sized so that the superheat value of the refrigerant at the evaporator outlet is appropriate. Superheat is the difference between the saturation temperature, which corresponds to the refrigerant pressure, and the actual refrigerant gas temperature.

If the superheat at the evaporator outlet is small, there is sufficient evaporation in the evaporator, but if some of the liquid refrigerant is sucked into the compressor, it can cause compressor failure. If the superheat is too large, the evaporation function in the evaporator is inadequate, resulting in insufficient performance.

What Is a PC Strand?

PC strands are tensioning materials that apply tension to pre-stressed concrete (PC).

There are three types of tensioning materials: PC strands, which are high-strength steel with a diameter of 8 mm or less; PC Bars, which are high-strength steel with a diameter of 10 mm or more; and PC strands, which are multiple steel wires that are stranded together. PC strands are characterized by the fact that multiple steel wires are strung together.

Other features include high tensile strength, high elongation at break, low relaxation value, and good straightness and workability.

Applications of PC Strands

PC strands are used in a wide range of applications, including road and railroad bridges, sleepers, tanks, construction, and ground anchors.

PC strands increase the resistance of pre-stressed concrete to tension, bending, and torsion. The number of strands to be matched increases the tensile strength, which is why they are often used for reinforcing members of buildings and architectural structures. PC strands that are 5 to 6 times stronger than the material for which drag is to be strengthened are selected for use.

Types of PC Strands

PC strands are classified according to the number and strength of the steel wires to be stranded. The nominal name, standard size diameter, nominal cross-sectional area, mass per unit, test stress to 0.2% permanent elongation, maximum test force, elongation, relaxation value, and strength level are specified in each standard.

PC strands are available in 2-strand, 3-strand, 7-strand, and 19-strand types, with 7-strand types classified as Class A and Class B. Basically, the higher the number of strands, the higher the strength. Basically, the greater the number of strands, the higher the strength. The more the number of pieces, the higher the strength, and the more the area of division and the mass of the pieces tends to increase. Some PC strands are also categorized into normal-strength PC strands and high-strength PC strands, even if the number of strands is the same.

For example, the maximum test force for the same 7 PC strands of 15.2mm is 240kN or more for normal strength, while the maximum test force for high strength PC strands is 317kN or more, or about 1.32 times higher. There is also a difference in tensile strength standards between Class A and Class B. The tensile strength of Class B is about 100 N/mm2 higher than that of Class A.

What Is a Zinc Rich Primer?

A zinc rich primer is a primary rust-preventive paint that contains highly concentrated zinc powder. When applied to metal materials such as iron, the zinc powder contained in zinc rich primer corrodes before the iron base, thereby protecting the metal material inside.

In addition, painting with zinc rich primers forms a protective film, which makes the surface film more dense and prevents air and water from penetrating.

Applications of Zinc Rich Primers

Zinc rich primers are used on buildings, bridges, and steel structures to provide long-term protection against metal corrosion.

Since it contains a high concentration of zinc and is a type of corrosion inhibitor that is applied firmly, it adheres well and can be applied in places where hot-dip galvanizing with similar effects would be difficult to handle, such as seawater.

Examples include coating of ships, offshore structures, marine containers, and vehicles. Other applications include the repair of hot dip galvanized products.

Types of Zinc Rich Primers

There are two types of zinc rich primers: Type 1 inorganic zinc rich primers and Type 2 organic zinc rich primers. 

Type 1 inorganic zinc rich primers are one-component, one-powder paints containing mainly alkyl silicates as the vehicle, and offer superior corrosion protection compared to Type 2 organic zinc rich paints. On the other hand, it has the disadvantage of requiring a high level of primer preparation and “mist coating,” in which a thinner-diluted, low-viscosity paint is applied over the topcoat.

Type 2 organic zinc rich primers are two-component, one-powder or two-component paints with epoxy resin as the main vehicle. Compared to inorganic zinc-rich paints, they are relatively easy to handle, with fewer restrictions on painting, etc., although their corrosion protection lasts shorter.

What Is a Ready Mixed Paint?

Ready mixed paints are long-oil alkyd resin varnishes, which are made by mixing alkyd resin (phthalate resin) and oil components in a ratio of about 65% to 35%, and adding color pigments.

Although they dry quickly, are easy to apply, and cost-effective, they have low levels of weather resistance, and chalking occurs within two to three years, so they must be reapplied every few years.

Applications of Ready Mixed Paints

Ready mixed paints, also known as SOPs, are easy to apply. Ready mixed paints are now so familiar that they are often referred to as paints. It is also easy to handle, which is why it is used in many paints sold at DIY stores.

In particular, it is used for surface coating of iron and wood parts because of its glossy and aesthetic qualities. Although it is used in a wide range of locations, it should be avoided in contact with alkaline concrete or mortar, as it will cause discoloration and softening.

Types of Ready Mixed Paints

Ready mixed paints are available in two types: Ready mixed paints Type 1 and ready mixed paints Type 2. Ready mixed paints are divided into two types, one for the middle coat and the other for the top coat. 

Ready mixed paints Type 1 are mainly used for both middle and top coats on buildings and steel structures, which means two coats of the same paint. When applying two or more coats, it is necessary to allow at least 16 or 24 hours for drying time.

Ready mixed paints are divided into two types, one for the middle coat and the other for the top coat. The middle coat contains slightly more alkyd resin (phthalate resin) than usual, at 65% or more. This prevents poor adhesion to the subsequent top coat, even if the middle coat is left on.

What Is an Insulated Tool?

Insulated tools are sets of tools for use on energized parts.

They are characterized by the fact that the tools are covered with an insulating material, which insulates all parts except those that come in contact with mating parts, such as screwdrivers and ratchets. A special resin that does not conduct electricity is used as the insulator to protect the operator from electric shock.

The surface of the tool features a red coating that is easily noticeable and has a double coating structure. The manufacturer’s instructions state that use should be prohibited if the red part peels off.

Uses of Insulated Tools

Insulated tools are used when servicing parts that are energized, such as hybrid vehicles, fuel cells, and electric vehicles that carry high-voltage electricity. 

In addition, insulated tools may only be serviced by qualified electricians. The IEC 60900 standard for insulated tools requires the use of insulated gloves for double safety when using insulated tools.

How to Select Insulated Tools

Insulated tools must be chosen in accordance with IEC60900, an international standard for the electrical and electronic fields. It is not necessarily applicable to all equipment as long as it is insulated, since breakdown occurs when a voltage above a certain level is applied, even to insulated materials, and electricity flows through them.

The standard stipulates that no breakdown or ignition will occur even when energized at 5000 V for 3 minutes, and there is an upper limit to the voltage that can be supported.

It is necessary to check whether the withstand voltage listed in the specifications section of the instruction manual or catalog is higher than the voltage flowing through the equipment to be used. If cracks are found at insulated points, dielectric breakdown will occur at lower voltages, so if damage to the insulator is observed, refrain from using the product.

In addition to energization, the standard also includes provisions for non-flammability and impact during freezing. Conformance to the standard proves that the tool has a certain degree of resistance to combustion and strength.

In addition to the performance of the tool itself, the standard prohibits the use of insulated tools from different manufacturers or tools that are not insulated, so it is important to choose the right one.

What Is a Concrete Planer?

Concrete planers are tools that smooth the surface of concrete by scraping it.

The term “planer” is often thought of as scraping a thin film, like sanding wood, but concrete planers are more akin to sanding. A grinder is used for a similar purpose, but the grinder smooths a relatively small area, while the concrete planers can smooth a wide area of concrete surface.

How to Use Concrete Planers

Concrete planers are used to scrape the surface of concrete by crawling and sliding over the surface. Since it produces quite a loud noise, the person using it needs to take countermeasures not only against noise but also with earplugs or earmuffs.

Dust masks are also worn, as considerable dust is also generated. If concrete planers are used over a large area, it is recommended that a dust collector be used at the same time.

How to Select Concrete Planers

When selecting concrete planers, there are three things to keep in mind:

1. The Size of the Grinding Wheel

Concrete planers are equipped with a rotating grinding wheel. If you want to use the canner over a wide area, select a canner with a larger grinding wheel.

2. Rotation Speed

The power of concrete planers is determined by the number of rotations. The higher the rotation speed, the faster the grinding speed and the faster the surface can be smoothed. However, it is important to note that higher rotation speeds tend to make operation more difficult.

3. Weight

The operability of concrete planers depends greatly on their weight. Since most operations are performed while holding it by hand, if it is too heavy, it may put a strain on the wrist. When purchasing a canner, it is important to select one that you can actually hold and have enough room for maneuverability.

What Is an Air Riveter?

Air riveters are a type of tool that uses parts called rivets to fasten metal sheets and other materials together.

Air riveters can easily make joints using the power of air and rivets. In addition to air riveters, there are also hand riveters, which manually insert rivets, and rechargeable electric riveters. Normally, welding is used to join metals, but it is dangerous because of the high temperatures and sparks generated.

How to Use Air Riveters

First, insert a rivet into the tip of the air riveter and then press the air riveter against the part to be secured, and pull the trigger to fasten the rivet firmly.

Since compressed air pressure is used to push the rivet into place, no force is required and work efficiency is high. However, it can be difficult to handle because an air hose is attached.

How to Select Air Riveters

The following three points should be considered when selecting an air riveter.

1. Weight

Air riveters can fix various materials, from metal to metal, to different materials, with light force. Basically, the riveter uses air pressure from a compressor to push in the rivets, so most air riveters are lightweight.

2. Applicable Air Pressure

The ability of air riveters to push in rivets depends on the air pressure. The higher the air pressure, the faster the rivet can be inserted. Check if the air pressure of the compressor is within the range of the adaptable air pressure of the air riveters before use. 

3. Shaft Case

After rivets are inserted, the shaft of the rivet core axis is removed. Without a shaft case, the shaft will be scattered, so it is more convenient to use a riveter that comes with a shaft case that automatically collects the rivets.

What Is an Electric Riveter?

Electric riveters are a type of riveter that uses rivets to join metal plates and other materials together.

Rivets are like thumbtacks, which are inserted into the plates to be joined and secured. Normally, welding is the usual method of fastening metals together, but electric riveters make it easier and safer.

In addition to electric riveters, there are also hand riveters, air riveters, and other types of riveters, which have recently been used in DIY projects.

How to Use Electric Riveters

First, insert a rivet into the tip of the electric riveter and then press the electric riveter against the part to be riveted, and pull the trigger to fasten the rivets firmly together.

Electric riveters do not require a strong grip, as all you have to do is pull the trigger, but since most riveters are rechargeable, you need to pay attention to the battery level. If you want to use a riveter for a long time, it is more efficient to use other products such as air riveters.

How to Select Electric Riveters

When choosing an electric riveter, there are three things to keep in mind:

1. Weight

Electric riveters can secure a variety of materials, from metal-to-metal to different materials, with light force. Generally, most riveters are cordless, and only the battery needs to be charged and attached to the electric riveters before starting work.

If the Electric Riveters themselves are heavy, it is difficult for a weak person to work with them.

2. Drive Time

Electric riveters do not vary greatly in their ability to push in rivets. The most important factor affecting the specifications is the drive time. It is recommended to choose a battery that can operate for more than the expected time or to carry a spare battery.

3. Price

Electric riveters are more expensive than hand riveters and air riveters because they are easier to handle. In other cases, other riveters can be used. Selection is made while considering the balance between the application of use.

What Is a Black Oxide Coating Services?

Black Oxide Coating Services is a surface treatment method for metals to prevent rust.

The surface is oxidized by boiling the metal in an alkaline solution to form a black film. Black Oxide Coating Services is mainly used for rust prevention on steel parts.

The advantage of Black Oxide Coating Services is that the film is very thin and there is little change in the dimensional accuracy of the original metal. It has excellent wear resistance and retention properties, and is environmentally friendly as there is no need to dispose of the chemical solution. Another advantage is that it is a rust-preventive treatment at a lower cost than the plating process.

On the other hand, the disadvantage of Black Oxide Coating Services is that it can only be done in black color due to the characteristics of the chemical solution. As with plating or painting, it is basically impossible to match the color with other parts. It is also important to note that a rust inhibitor must be applied to maintain the rust-preventive properties.

Uses of Black Oxide Coating Services

Black Oxide Coating Services are used to improve corrosion resistance, enhance appearance, and prevent reflection.

1. Improvement of Rust-Preventive Properties

The essential use of Black Oxide Coating Services is to improve corrosion resistance by creating a black film. In addition to the fact that dimensional accuracy remains almost the same before and after processing, the processing cost is relatively low, making it suitable for a wide range of applications.

2. Improvement of Appearance

The soothing black color produced by Black Oxide Coating Services gives a luxurious feel and is used to enhance design. It is used not only for industrial products, but also for interiors and artwork.

3. Anti-reflection

Since black processed metal parts are less shiny, they are used to prevent reflections. By preventing light reflection on visible parts such as manufacturing machinery, it is possible to alleviate stress on workers.

4. Improved Lubricity

Black Oxide Coating Services improves the abrasion resistance of steel materials, and the rust inhibitor also improves lubricity.

Principle of Black Oxide Coating Services

In Black Oxide Coating Services, steel is placed in an alkaline solution containing caustic soda and heated to 140-150°C for 15-20 minutes to cover the surface with black rust. The component of this black rust is tri-iron tetroxide (Fe3O4), which is a stable passive film. This prevents red rust from forming on the steel and improves its rust-preventing properties.

Black Oxide Coating Services is a process that has little effect on dimensional accuracy because the thickness of the coating is only 1-2 µm. It is a chemical reaction treatment of the surface and will not peel off like plating or painting. Another advantage is that it is wear-resistant and oil-impregnated. The porous surface retains the rust inhibitor.

Black Oxide Coating Services has the advantage of low heating temperature, which has little effect on material strength and material properties.

Types of Black Oxide Coating Services

Black Oxide Coating Services is sometimes called “black plating,” but the basic method and finish are the same. Similarly, the processing methods called “ferumite treatment,” “SOB treatment,” and “alkali treatment” are not different from Black Oxide Coating Services.

Although there are differences in the color tone depending on the chemical formulation and facilities used, Black Oxide Coating Services itself is not classified into different types.

Other Information on Black Oxide Coating Services

Chemicals Used in Black Oxide Coating Services

Chemicals are used in each stage of Black Oxide Coating Services.

1. degreasing process
In the degreasing process, water-soluble alkaline degreasing agents are used. It is a water-soluble degreasing and cleaning agent with nonionic surfactant, nonflammable, and odorless. It has strong degreasing and cleaning power equivalent to that of chlorine compound solvents. When draining, use dilute sulfuric acid for neutralization due to its low alkali concentration. 

2. Rust removal process
Rust removal is performed using an iron rust and scale remover. The agent is hydrochloric acid to which is added an acid that promotes rust and scale removal, a surfactant that stabilizes the agent, and an inhibitor that prevents hydrogen embrittlement and over-peeling.

3. black dyeing process
A heated black staining agent is used to cover the steel with a jet-black iron tetroxide film. Castings and special steels, which tend to have a reddish tinge, can be finished in jet black. The agent conforms to U.S. Department of Defense MIL standards, U.S. aerospace material standards, International Organization for Standardization standards, German industrial standards, etc.

4. Rust Prevention Process
After the blackening process, a corrosion inhibitor is used. This medium-term rust inhibitor has excellent water displacement properties and is suitable for rust inhibiting treatment on wet parts and in humid environments. The estimated period of rust inhibiting is 6 to 12 months.

What Is a Flame Cutting Service?

A flame cutting service is a process that uses gas and oxygen to cut metals.

A flame cutting service heats the base material to a high temperature using combustion gas and then blasts it with high-purity oxygen to oxidize and dissolve it, thereby cutting the metal. A flame cutting service is also called oxygen cutting because it uses a chemical reaction between iron and oxygen. The gases used in flame cutting services are mainly acetylene, natural gas, and propane gas.

The advantage of a flame cutting service is that even thicker metals can be cut quickly. It requires relatively little equipment and is superior to other cutting methods in that it does not require electricity. The disadvantage is that the cut surface is rough due to manual labor. It is also important to note that because flammable gas is used, there is a risk of accidents. Flame cutting services operators are required to take a “gas welding skills training course.”

Uses of Flame Cutting Services

1. Steel Cutting

Flame cutting services are highly efficient in cutting steel, and can cut steel plates as thick as several hundred millimeters. On the other hand, it is not suitable for cutting materials such as aluminum and stainless steel, which do not oxidize easily. Flame cutting services are not suitable for aluminum and stainless steel because they produce oxides with high melting points. In such cases, plasma or laser cutting is used.

2. Underwater Cutting

Equipment called an “underwater cutter” is used for underwater metal cutting. Currently, it is possible to work in water depths of up to approximately 70 meters.

Principle of Flame Cutting Services

Flame cutting services are a method that uses chemical reactions of oxidation and combustion. Simply heating a metal to a high temperature is not enough to cut it. Oxidation is the compounding of metal and oxygen, which produces heat as it oxidizes.

Combustion is a redox reaction that violently oxidizes and produces light and heat. Flame cutting services cut steel materials by artificially creating the principles of oxidation and combustion.

Specifically, flame cutting services first heats the cutting area to 800-900°C with combustion gas to oxidize it. Next, a fire is set and high-purity oxygen is sprayed to cause combustion, melting only this portion of the material. Flame cutting services are possible because the oxygen gas blows off the melted portion, and combustion and melting continue one after another.

Features of Flame Cutting Services

1. Thick Materials Can Be Cut

Flame cutting services are more suitable for cutting thicker materials than plasma cutting services or laser cutting services. Flame cutting services can cut materials as thin as a few millimeters to as thick as several hundred millimeters, and are mostly used for cutting thick steel plates of 50 mm or more. 

2. No Electricity Required, Small Equipment

Flame cutting services do not require electricity compared to plasma, laser, and arc cutting methods. Flame cutting services require only a torch, gas cylinder, pressure regulator, and hose. It is an inexpensive method to introduce. 

3. Operator Skill Is Required

Flame cutting services have a rough cross-section and rely heavily on the skill of the operator. Manual adjustment of fire intensity, oxygen level, cutting speed, and arm movements require skill. In particular, cutting is not only straight lines but also curves, arcs, and other various shapes, requiring the ability to improve accuracy.

4. Slow Cutting Speed and Susceptible to Thermal Deformation

Flame cutting services have the disadvantage of slow cutting speed compared to plasma cutting, laser cutting, and arc cutting. Another disadvantage is that the material is easily deformed due to local heating. Preheating of the entire part is used.

Types of Flame Cutting Services

Flame cutting services can be broadly classified into the following three types according to the gas used.

1. Acetylene Gas Flame Cutting Services

Acetylene gas is the oldest gas in use, dating back more than 100 years, and is still widely used today. Its specific gravity is lighter than that of air, making it suitable for outside work, and its high combustion temperature makes it easy to work with.

2. Propane Gas Cutting

Propane, also called LP gas, is the second most widely used gas after acetylene. It is heavier than air in specific gravity, so it is not suitable for work in a small room. It takes longer to work with propane because of its relatively low combustion temperature, but there is less risk of ignition and it is safer.

3. Methane Gas Cutting

Methane is also known as LNG or city gas. It is lighter than air in specific gravity and less flammable, making it relatively easy to handle. It has a lower combustion temperature and is less efficient than propane.

Other Information on Flame Cutting Services

Qualifications for Flame Cutting Services

Flame cutting service operators are required to take a “gas welding” skills training course. This course is open to those 18 years of age or older and includes both classroom and practical training. The course covers three subjects: laws and regulations, knowledge of oxygen and gases, and the structure and handling of facilities and equipment.

After obtaining the gas welding skills training qualification and at least three years of work experience, the trainee will be qualified to take the gas welding operator’s license examination. This qualification is necessary to direct and manage gas welding operators.