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What Is Nylon Tubing?

Figure 1. Overview of Nylon Tubing

Nylon Tubing is a tubing manufactured from nylon resin and intended primarily for plumbing applications.

They are used in a variety of industries for fluids such as air, water, and lubricating oil.

Advantages include excellent flexibility for easy working and low cost. Depending on the product, nylon tubing has excellent pressure resistance, heat resistance, chemical resistance, oil resistance, vibration resistance, and corrosion resistance.

Uses of Nylon Tubing

Nylon Tubing is used for lubrication, pneumatic, hydraulic, and other piping applications as an alternative to copper and other conventionally used pipes. Specifically, nylon tubing can be used in oil and pneumatic equipment, centralized lubrication equipment, coating equipment, and chemical plants.

Nylon Tubing can also be used for piping in tight spaces or where complicated flow lines must be taken, by taking full advantage of nylon’s superior flexibility.

Other types of nylon tubing include more flexible types that can be used in oscillating sections, and special nylon tubing made of nylon that specializes in high pressure and chemical resistance.

Principle of Nylon Tubing

Figure 2. Structural formulas for various nylons

Nylon Tubing, like fiber materials, is strong against expansion and contraction, and has strong abrasion resistance and toughness. At the same time, it has high resistance to heat, impact, and chemicals.

First developed, 6,6 nylon was the world’s first synthetic fiber to be widely used. Today, polyamide is commonly referred to collectively as nylon.

While 6 nylon and 6,6 nylon are commonly used for nylon products themselves, nylon 11 and nylon 12 are often used for Nylon Tubing. This is because nylon 11 and nylon 12 have superior resistance to impacts and temperature changes.

The numbers in these names are derived from the number of carbon atoms in the monomer raw material used to make nylon. Soft hoses are manufactured with plasticizers to provide flexibility, while rigid tubing without plasticizers is called rigid unplasticized Nylon Tubing. Other types of nylon may also be used, such as nylon that has been strengthened by processing.

How to Select Nylon Tubing

Figure 3. Properties of soft and hard nylon tubes

Nylon Tubing varies in pressure resistance, heat resistance, and flexibility depending on the product. It is important to select the product that best suits your application.

1. Flexible Nylon Tubing

Tubing flexibility varies depending on whether or not a plasticizer is incorporated. Soft Nylon Tubing contains a plasticizer and has excellent flexibility. In terms of pressure resistance and heat resistance, the performance is slightly lower than that of unplasticized nylon, but there are products that can handle high pressure. In addition, there is no difference in the fact that the main component is nylon, so the performance is not significantly inferior.

However, low molecular weight substances called monomers and oligomers contained in the resin may precipitate on the tube surface via the plasticizer and adhere to the surface like white powder. Generally, this does not degrade performance such as pressure resistance or chemical resistance, but there is a tendency for the flexibility of the tube to decrease in the future.

2. Unplasticized Nylon Tubing

Those without plasticizers are called unplasticized Nylon Tubing and are the most rigid. It also has the highest pressure resistance and heat resistance, and can be used under high pressure and high temperature.

Some products are available in a variety of colors, and different colors can be selected for each pipe to distinguish them by color coding. However, since black is superior in terms of weather resistance, some manufacturers recommend black tubing if no particular choice is necessary.

In addition, if chemicals are to be used as fluids, it is necessary to check whether the tubing has chemical resistance to the chemicals to be used before use.

What Is an RF Amplifier?

The “RF” in RF Amplifier stands for “Radio Frequency” and refers to the high frequency used in mobile wireless communications such as radios and smartphones.

In general amplifiers, the input voltage or current is amplified and output, but in the case of RF amplifiers, instead of this function, DC bias is used to amplify high-frequency power signals by the gain of the amplifier relative to the input power. Therefore, the power for DC bias can be used for amplifying high-frequency power with relatively high efficiency without loss of DC bias power.

It should be noted that the electrical characteristics required for RF amplifiers, i.e., the type of amplifier, differ depending on whether they are used for receiving or transmitting circuits.

RF amplifiers are characterized by their ability to amplify and convert DC power to high-frequency power without loss of DC power, and are considered to be highly efficient RF Amplifiers. The type differs depending on whether it is used for receiving or transmitting circuits.

Uses of RF Amplifiers

RF circuits for communication are divided into blocks for receiving and transmitting, and the type of RF amplifier generally differs depending on whether it is used for receiving or transmitting.

RF amplifiers used on the transmitting side are called Power Amplifiers (PA), which require high amplification. Because of the large amount of power handled, it is important to have low power consumption, i.e., high amplifier efficiency, in order to maintain reliability by suppressing heat generation and battery power consumption. Also, depending on the application, the amplifier itself must have sufficient linearity to prevent signal distortion.

On the other hand, RF amplifiers used for reception are called Low Noise Amplifiers (LNA). They are characterized by low noise (NF) generated by the amplifier itself to prevent the signal from being buried in the noise and to maintain communication quality by increasing the reception sensitivity during communication.

Principle of RF Amplifier

Si MOSFETs, SiGe bipolar transistors, HBTs and HEMTs using compound semiconductors such as GaAs and GaN crystals are used as semiconductor devices for RF amplifiers. It is important to select the optimum semiconductor device according to the maximum output power, gain, efficiency, linearity, and noise figure of the RF amplifier.

Depending on the RF frequency, the frequency response, called the cutoff frequency (fT), may not be sufficient to draw sufficient amplification. Therefore, the stand-alone frequency response determined from the structure of the semiconductor device is a very important factor in constructing an RF amplifier.

The amplifier characteristics are determined by applying the desired DC bias to the amplifier device and optimally setting the input and output load lines of the amplifier. In addition to the fundamental frequency impedance setting, the harmonic impedance setting is also important, and together with the bias, various operating classes (Class A, Class C, Class F, etc.) can be set.

Other Information on RF Amplifiers

RF Amplifier Characteristics

RF Amplifier characteristics include 1 dB compression, gain, and noise figure. In the gain and power curves, 1dB compression is used as a measure of the maximum amount of power output with 1dB of gain suppressed due to amplifier saturation operation.

Since a large output power is required on the transmit side, it is customary to select an amplifier with a large 1 dB compression region and use it up to its upper limit. An RF amplifier can express its frequency response by its amplification, which is the power ratio between input and output, and its performance is judged by its being within a fixed range of frequency The higher the gain, the better.

Higher gain is desirable, but care must be taken as it is a trade-off between power consumption and noise. The noise figure expresses the degree to which the signal-to-noise ratio worsens. When selecting the RF amplifier for the receiving side, choose a small noise figure.

What Is a Driveshaft?

A driveshaft is a rotating shaft used to transmit the power of a prime mover to rotating equipment.

Driveshafts are generally known as automobile driveshafts, but they are also widely used for power transmission in ships, industrial machinery, construction machinery, railcars, and other vehicles.

Driveshafts do not have to be arranged in a straight line from the power section to the transmission section, but can still transmit power by using constant velocity joints.

Driveshafts are especially needed in automobiles to drive wheels that are subject to large vibration displacement.

Uses of Driveshafts

Driveshafts are also most commonly used in automobiles. Driveshafts in automobiles are components that transfer the power of the engine to the wheels.

In front-wheel drive vehicles, power is transmitted from the engine to the wheels via the Driveshaft. In the case of rear-wheel-drive vehicles, power from the engine is transmitted via the propeller shaft to a differential gear in the rear, which drives the wheels using the Driveshaft.

For applications other than automobiles, the propeller shaft is connected to motors for blowers, pumps, compressors, cranes, reduction gears, etc., and to drive shafts for rolling mill rolls and tension reels in steel manufacturing machinery. They are also used as drive shafts for rolls in chemical machinery, hydraulic pump drive shafts in construction machinery, and hydraulic pump drive shafts in truck mixers.

Further applications include work equipment drive shafts for agricultural tractors and drive shafts for machine tools, printing machinery, and paper manufacturing machinery.

Principle of Driveshafts

Driveshafts in automobiles and other equipment usually do not form a straight line from the engine power unit to the wheel power transmission unit. Therefore, constant-velocity joints are installed at both ends of the shaft to smoothly transmit power at a constant velocity even if the shaft is angled.

There are two types of constant velocity joints: fixed type and sliding type.

1. Fixed Type

This type cannot slide in the direction of the drive shaft. The constant velocity joint has parts called the outer race and inner race, and several steel balls are placed inside the outer race and outside the inner race. The steel balls allow the constant velocity joint to be angled. 

2. Sliding Type

This type can slide in the direction of the drive shaft. There are two types: One type has grooves on the outer race and inner race that are parallel to the axial direction and can slide in the axial direction. The other type has a three-axis component attached to one of the rotating shafts, each end of which has a roller. When rotated at an operating angle, the rollers roll in grooves inside the housing to enable axial sliding.

Other Information on Driveshafts

1. Life of a Driveshaft

The life of a Driveshaft is generally the time it takes for the constant velocity joint to wear out to the point of noise or breakage. For automobiles, the standard is 200,000 km in terms of mileage.

A symptom of a failing Driveshaft approaching the end of its service life is the production of abnormal noise.

The most common type of vehicles in which abnormal noise can be easily recognized are front-wheel drive (FF) vehicles. When the angle of the constant velocity joint is large due to steering, a rattling noise may occur when accelerating. The cause of the noise is excessive clearance due to wear of the inner race, outer race, and steel balls, which are the key parts of the constant velocity joint.

The main causes of wear are deterioration of lubrication performance due to deterioration or decrease in the amount of grease sealed in the constant velocity joint for lubrication, and accelerated wear due to foreign matter such as sand entering the joint.

Grease deterioration can be caused by aging due to long-term use, early deterioration due to heat generation in the joint caused by continuous high load, and deterioration due to moisture contamination. Most of the causes of low grease level and foreign matter contamination at joints are deterioration or damage to the bellows-like parts called boots that protect the joints. 

2. Drive Shaft Boots

Boots protecting joints are mainly manufactured from rubber or flexible resin. The boots are cylindrical bellows-shaped, installed to cover the entire joint and secured with metal bands tightened at both ends.

The main functions of the boot are to retain lubricating grease in the joint and to prevent foreign matter from entering the joint. When inspecting the Driveshaft externally, it is important to check if the boot is torn or if grease is leaking from the fixed part. Reduced lubrication and foreign matter in the joints accelerate wear.

Replacing the boot used to require removal of the Driveshaft from the vehicle body, but now there are split-type boots that can be replaced without removing the boot from the vehicle body.

After the old boot is removed, the new boot, which is split in two, is installed so that it is sandwiched between the joints, and the mating joints are welded together with adhesive and heat to achieve a strength similar to that of conventional products.

When replacing the boot, the grease inside is also replaced with a new one, thus restoring lubrication performance.

What Is a Polypropylene Sheet?

A polypropylene sheet (PP Sheet) is a sheet made of polypropylene. Polypropylene is a synthetic resin processed into sheet form. It is used for packaging, trays, industrial parts, and daily necessities such as folders, because it is inexpensive, lightweight, and has excellent strength and chemical resistance. Composed of carbon and hydrogen atoms, one of its characteristics is that it does not emit toxic gases when burned. On the other hand, it is vulnerable to direct sunlight and low temperatures, which can cause cloudiness and cracking.

Uses of PP Sheets

Polypropylene (PP), the raw material of PP sheets, is a synthetic, inexpensive, lightweight, durable, and chemical resistant resin. In addition to packaging and containers, polypropylene is also used for automobile and home appliance parts. Among these applications, there are thin PP sheets that can be colored and used for trays for food and medical applications, as well as for industrial and electronic components due to its insulating properties. PP sheets are also bonded to other materials by heat lamination, and because of their low cost, PP sheets are also sold at dollar (100 yen)  stores around the world.

Characteristics of PP Sheets

Polypropylene, the raw material of PP sheets, is obtained by linking (polymerizing) a compound called propylene through a chemical reaction. It has a specific gravity of 0.90, making it one of the smallest plastics, and since it is composed only of carbon and hydrogen atoms, it does not emit toxic gases when burned. It also has excellent heat and chemical resistance.

PP sheets have excellent rigidity and strength, and also feature excellent mechanical properties such as tensile strength and impact resistance. PP sheets are also superior in transparency to polyethylene despite their similar chemical structure, and for this reason PP sheets are able to be used for transparent daily necessities such as clear files.

PP Sheet Points 

PP sheets are convenient, but depending on the environment in which they are used, they may cause damage, etc. Since PP has low weather resistance, it is necessary to be careful about deterioration caused by direct sunlight and brittleness at low temperatures. In addition, since the molecular weight of PP, the raw material of PP sheets, varies depending on the manufacturing process, the mechanical properties of the same PP sheet may differ depending on the product. Therefore, it is recommended to check the product specifications before actual use.

Other adhesives for general plastic materials cannot be used to adhere to PP sheets. Therefore, adhesives specially designed for polypropylene are required for bonding work to PP sheets, including home use.

What Is a Desiccator?

A desiccator (dehumidifier) is a container used to store items that should be kept away from moisture. The oldest types are circular and made of thick-walled glass. A desiccant such as silica gel may be used to maintain a dry condition. The internal air composition and humidity can be controlled. Reagents, samples, electronic equipment, etc., with hygroscopic or deliquescent properties are stored in this type. Desiccators of various sizes and functions are available according to the nature and size of the sample or substance to be stored inside.

Purpose of use of desiccators

The main purposes of desiccators include the following:

1. Dehumidification and Dry Storage

Glassware, specimens and reagents, samples with tidal characteristics, plant seeds, electronic equipment, etc., are often stored in desiccators. Since desiccators are instruments for maintaining dryness, they are not suitable for wet materials. They should be dried beforehand before placing them in.

2. Storage of Optical Products

Camera lenses and semiconductor components can lose performance due to moisture and mold. For this reason, they may be placed in desiccators (auto-dry type) with powerful dehumidification functions.

3. Prevention of Material Oxidation

For more powerful dehumidification or to store items that need to be shielded from oxygen, it is necessary to control the air inside by gas displacement or vacuum.

Principle of Desiccators

Types of desiccators are classified according to the dehumidification method and can be roughly divided into the following categories:

1. Auto Dry Desiccator

These are equipped with a dehumidifier or similar device that controls humidity through electrical control. They can control the humidity inside the storage and require little maintenance.

2. Gas Displacement Desiccators

This method replaces the air inside the desiccator with an inert gas (nitrogen, argon, etc.) and has the highest dehumidification capacity. It is also capable of expelling moisture and oxygen inside the desiccator, making it suitable for storing samples that can react with oxygen.

3. Vacuum (Decompression) Desiccators

A vacuum desiccator removes air from the inside of a desiccator to create a vacuum. Vacuum desiccators are also used for vacuum drying, degassing, and defoaming (the process of removing gas from liquids).

4. Dehumidifier Type Desiccator

A desiccant agent such as silica gel adsorbs moisture in the chamber. The desiccant requires maintenance but is inexpensive and easy to obtain. Circular glass desiccators have grease applied to the contact points between the body and lid to make them airtight, so care must be taken to keep them dust-free. This type is also called a glass desiccator.

How to Use a Desiccator

This section describes how to use the dehumidifier type vacuum desiccator:

Vacuum desiccators have holes or other openings in the container for vacuuming. Also called glass desiccators, they are now also available in the same shape, made of polycarbonate or stainless steel. There are also products with vacuum gauges and small rectangular products.

Dehumidifier-type desiccators are supported firmly by the lid and body when carried. The mortise between the lid and body should be spread evenly with Vaseline or grease. Some polycarbonate decapitators are dry-sealed with an O-ring and do not require greasing. In this case, be careful to prevent dust from entering.

Place a desiccant in the lower part of the desiccator (under the middle plate). It is easier to replace the desiccant if it is placed in a container such as a crystal dish. In addition to silica gel, other desiccants include zeolite, potassium hydroxide, anhydrous calcium chloride, phosphorus pentoxide, and concentrated sulfuric acid. Silica gel and zeolite can be used repeatedly by regenerating them.

The reagent or sample to be dried is placed on the medium plate. In the case of a greased desiccator, the lid may stick and not open, so the lid should be placed 5 mm away from the body of the desiccator.

For vacuum drying, open the top cock and place a trap between the tubes in the middle of the tube. Suction is applied using an aspirator or similar device to reduce the pressure gradually. Close the cock after completely depressurizing the tube.

If the pressure has been reduced, open the cock to return the pressure to normal, and then open the lid. If air enters the desiccator with great force, the sample may be blown away, so place the filter paper against the glass tube where the air enters and open the cock. Once the filter paper falls out, the inside of the desiccator returns to normal pressure.

Open the lid by sliding it to the side. If too much force is applied, there is a possibility of dropping and breaking the lid. Be especially careful if the glass is made of glass.

Auto Dry Desiccator

Auto-dry desiccators are shaped like a typical storage cabinet or storage shelf.

They vary in size from small (40 cm x 35 cm x 45 cm) to large (nearly 180 cm high). The larger ones usually have casters for mobility.

Most auto-dry desiccators use a dehumidification method based on a solid polymer electrolyte membrane, which directly electrolyzes the moisture in the air inside the chamber and releases it outside the desiccators. Dehumidification capacity with this method can be up to ~25%, the humidity is adjustable, and no condensate is produced. More powerful dehumidification is also possible when used in combination with silica gel. UV-cut and anti-static products are also available.

What Is a Choke Coil?

A choke coil is an element used in electrical circuits and is a type of inductor optimized for use as a choke.

The meaning of choke in this case refers to the ability to keep AC currents above a certain frequency relatively high and to facilitate the passage of currents below that frequency, and is implemented in an electrical circuit.

The typical coil construction consists of a laminated plate of silicon copper or other steel plate as the core (iron core), around which conductors are wound in a spiral shape.

There are three types of choke coils: smoothing choke coils, active filter choke coils, noise filter choke coils, and power line choke coils. Each is used for different purposes.

Uses of Choke Coils

As mentioned above, there are four major types of choke coils depending on the application.

1. Smoothing Choke Coils

Choke coils are used to reduce the distortion of the current when AC current is converted to DC by a smoothing circuit or AC/DC converter, and to smooth the current. 

2. Choke Coil for Active Filter

Used as a high-frequency countermeasure in active filters used in analog signal input circuits such as measuring instruments. 

3. Choke Coil for Noise Filter

Choke coils are mounted in power supply circuits that are prone to noise inflow and used as noise countermeasures.

4. Choke Coil for Power Supply Line

Choke coils are used to match the load of RF power amplifiers and to reduce impedance resistance and losses in power supply lines.

Principle of Choke Coil

A choke coil consists of a core made of a laminated plate of silicon copper or other steel plate, around which conductors are wound in a spiral shape.

The choke coil is characterized by a higher inductance value than the coils used in general.

General coils and choke coils differ in the following characteristics:

• General coil
  Easy to conduct direct current and difficult to conduct alternating current.
• Choke Coil
  Easy to carry DC current and low frequency AC current, and hard to carry high frequency AC current.　

The reason why choke coils have the above characteristics is that they have a high inductance value and when an AC current of high frequency flows, an induced electromotive force is generated, which is opposite to the direction of the current flow, making it difficult for the current to flow.

When used as an active filter or for noise suppression, external noise that attempts to flow into a measurement device from its input terminal or power supply terminal of a power circuit has a high frequency. Choke Coils are often used in such applications because they can block high-frequency noise.

Other Information on Choke Coils

1. About Toroidal Coils

Choke Coils are often made by winding a conductor around a doughnut-shaped magnetic core, unless they are ultra-compact chip components, such as those used in smartphones. This is called a toroidal coil and can confine the magnetic flux in a closed loop (right-hand thread law). The advantage of toroidal coils is that they can achieve a larger inductance in a smaller size by utilizing this confined magnetic flux.

Important factors for inductor characteristics include Q-value and maximum allowable current. Based on the recent demand for compact, high-density packaging, manufacturers are competing to improve these inductor characteristics while reducing the size of the inductors.

2. Material of Magnetic Core

Various materials are used for the magnetic core of a choke coil, including laminated steel plates. One of the most commonly used magnetic core materials is ferrite material, which can be broadly classified into nickel-based and manganese based materials.

Nickel-based ferrite materials have very high insulation properties and are often used at high frequencies above 100 MHz.

Manganese-based ferrite materials are inexpensive and have high magnetic permeability and saturation flux density, and are often used in common mode chokes for low-frequency power lines.

What Is a Check Valve?

A Check Valve is a valve that controls the flow of fluid in a pipe in one direction only and prevents flow in the opposite direction.

Synonyms include Non-Return Valve, One-way Valve, Reflux Valve, Pressure Retention Valve, and Back-Flow Prevention Valve.

Uses of Check Valve

A Check Valve is used when you do not want fluid to flow backward.

The basic uses of Check Valves are as follows:

• Prevention of mixing of two fluids
• Preventing backflow
• Controlling flow direction
• Preventing water hammer

When installed at a point where two fluids merge, the check valve prevents the mixing of the two fluids and controls the flow of only one of them.

When installed in a rising piping section on the discharge side of a pump, fluid flows while the pump is running, and after the pump is stopped, the Check Valve closes to prevent fluid in the piping at a higher level downstream of the pump from flowing back to the pump.

In steam piping, it is also used to prevent water hammer. Water hammer is a phenomenon in which the pressure in a piping temporarily rises and falls due to a sudden change in fluid velocity. The pressure fluctuations caused by water hammer can damage pumps and piping, and Check Valves are used as a preventive measure.

Principle of Check Valve

In a Check Valve, the valve disc is actuated to open and close by the pressure difference between the inlet side (primary side P1) and the outlet side (secondary side P2) of the fluid.

The pressure difference and valve operation are as follows:

Open: Inlet side (primary side P1) pressure is higher than outlet side (secondary side P2) P1 > P2
Closed: Inlet side (primary side P1) pressure is lower than outlet side (secondary side P2) P1 ＜ P2

When the pressure at the outlet side (secondary side P2) is higher, the disc is pressed against the seat surface by back pressure and adheres tightly to prevent fluid backflow. The disc automatically opens and closes according to this pressure difference, and the fluid flows or does not flow.

Types of Check Valves

There are five types of Check Valves. The features of each are as follows:

1. Swing Check Valve

Swing check valves have a straight fluid flow and are mounted directly on an arm or disc with the disc attached to a hinge mechanism. The disc rotates with the hinge as a fulcrum and opens or closes the valve according to the pressure difference of the fluid.

Figure 1. Swing check valve

Features

• Generally, when the disc is fully opened at the full port, the disc does not block the flow path and the pressure loss is small.
• Full port means that the flow path of the valve body is the same diameter or larger than the inside diameter of the piping.
• When the disc weight is heavy, the minimum pressure differential for valve opening and the cracking pressure will be large. For lighter discs, the minimum pressure difference to open the valve and the cracking pressure will be smaller.
• Cracking pressure is the pressure difference for a given flow rate.
• Since the disc rotates on a hinge shaft, the shaft and bearing side will wear out due to long-term use and frequent operation. This can result in poor opening and closing action of the disc and reduced sealing between the disc and the seat.
• Since the disc rotates at a relatively large angle from fully closed to fully open, its response to sudden pressure changes is low. Heavy discs also have the problem of greater impact on the seat during abrupt valve closure.

Installation

When the piping is horizontal, or when the piping is vertical, it is used when the fluid flows from downward to upward. It cannot be used when the fluid flows from upward to downward.

2. Lift Check Valve

The lift check valve is a mechanism in which the fluid flow is S-shaped and the disc to which the shaft is attached rises and falls. The disc rises or descends depending on the pressure difference, and opens or closes the valve.

Figure 2. Lift check valve

Features

• The flow path is S-shaped and pressure loss is high.
• Due to the heavy weight of the disc, the minimum pressure differential for valve opening and the cracking pressure are large.

Installation
Limited to grounding only when piping is horizontal. Cannot be used when piping is vertical and fluid flows vertically.

3. Wafer Check Valve

Wafer check valves are wafer-shaped valves that are installed by sandwiching the valve body between flanges and tightening bolts and nuts. The fluid flow is nearly linear and incorporates two semi-circular discs with a hinge mechanism.

The two discs rotate to open the valve due to the difference in fluid pressure using the hinge as a fulcrum, and rotate in the opposite direction to close the valve due to the coil spring attached to the discs.

Figure 3. Wafer check valve

Features

• The flow path is almost straight and the pressure loss is small.
• Wafer-shaped body is thin and lightweight.
• Can be directly attached to pumps and other equipment.
• The disc is forced to rotate by a spring and immediately closes, thus reducing water hammer phenomenon.
• It has high sealing performance with high hermeticity.
• It may be somewhat less responsive and less durable to cavitation and unbalanced fluid flow.
• Some have a built-in bypass channel, eliminating the need to drain residual fluid or install bypass piping for priming.

Installation
Piping can be used in a variety of orientations, including horizontal, vertical, and inclined. When the piping is vertical, the fluid can be used in either vertical or horizontal flow direction.

4. Ball Check Valve

The ball check valve is a mechanism in which the fluid flow is S-shaped and the ball of the valve plug rises and falls. The ball rises and falls depending on the pressure difference to open or close the valve.

Figure 4. Ball check valve

Features

• The flow path is S-shaped or straight, and pressure loss is not so large.
• Since the disc motion is unrestrained, some foreign matter in the fluid is tolerated.
• Not effective in preventing water hammer.

Installation
Piping is available for horizontal and vertical applications. The vertical version opens and closes under the ball’s own weight, so it cannot be used when fluid flows from below to above. 

5. Spring Disk Check Valve

The spring disc check valve is a mechanism in which the fluid flow goes around the disc in an S-shape and the disc to which the shaft is attached rises and falls. The disc rises due to the pressure difference and descends by spring force to open or close the valve.

Figure 5. Spring disk check valve

Features

• The flow path is S-shaped and flows around the disc, resulting in a large pressure drop.
• The disc is lightweight, and the minimum pressure differential for valve opening and the cracking pressure are small.
• The operating distance between fully open and fully closed is small, resulting in excellent responsiveness.

Installation
Piping can be used in either horizontal or vertical direction. When the piping is vertical, the fluid can be used in either vertical or horizontal flow direction.

What Is a pH Meter?

A pH meter is a precise instrument used to measure the pH, or hydrogen ion concentration, of a liquid, which is an essential indicator of water quality. These devices are vital in various fields, including environmental monitoring, food production, and medical research.

Uses of pH Meters

pH meters play a critical role in industries where water quality is paramount, such as waste management at incineration plants, boiler maintenance at thermal power plants, and wastewater management in construction. In the food industry, pH levels directly impact the taste and safety of products, necessitating accurate pH measurement.

Principle of pH Meters

The glass electrode method, commonly used in pH meters, involves measuring the potential difference between a glass electrode and a reference electrode. This potential difference, which changes with pH, allows for precise determination of a liquid’s pH level.

Electrode of pH Meters

Modern pH meters typically combine a glass electrode and a temperature sensor for accurate readings. The glass electrode, which has largely replaced platinum/hydrogen electrodes, contains an internal buffer solution sensitive to pH changes. This setup allows for a wide range of solution measurements.

Recent advancements have led to the development of composite electrodes, which integrate measuring and reference electrodes, simplifying the measurement process and enhancing the device’s versatility.

Measuring Soil With a pH Meter

Soil pH measurement is crucial in agriculture to ensure optimal growth conditions for various crops. However, measuring soil pH requires different techniques compared to liquid measurement. The MAFF provides guidelines for a simple indicator method, and portable pH meters are also available for direct soil testing.

What Is a Duct?

A duct is an air conditioning system and refers to an air passageway. They are used for ventilation, air conditioning, and smoke exhausts in buildings, as well as for large machines to exhaust internal heat and impurities.

There are various types of ducts, and their sizes and materials vary depending on the installation location and intended use.

Use of Ducts

Ducts are used for the ventilation and air conditioning of buildings.

By using a blower or other device to create a flow inside the building and then ventilating it outside through ducts, fresh air, and temperatures can always be maintained inside the building.

There are two types of ducts: square ducts and round ducts. The uses of each are explained below.

1. Square Duct

Square ducts are used in straight and curved sections and are considered to have higher exhaust performance than round ducts. Therefore, they are used in kitchens, where a lot of exhaust air is required.

2. Round Duct

Round ducts are stronger and are used in places where durability is required, such as housing complexes and offices.

Principle of Ducts

First, let us start by explaining the difference between “ducts” and “piping. The biggest difference between “ducts” and “pipes” is that “ducts” allow only airflow, while “pipes” allow not only air but also water, various gases, and other fluids to pass through. Another difference is that “piping” tends to be a large-scale operation, whereas “ducting” is a simple operation.

The following is a list of the four main materials used for ducts.

1. Galvanized: the most used material. It is used for air conditioning and exhaust air.
2. Stainless steel: stainless steel has excellent corrosion resistance. Used in rust-prone areas such as food factories and air conditioning units.
3. Galvanized steel: synthetic plating of aluminum and zinc. It has excellent corrosion and heat resistance and is less expensive than stainless steel. 4.
4. PVC-coated steel: resin-coated zinc plating. It is mainly used in pharmaceutical plants because of its superior resistance to alkalis and chemicals.

Care must be taken when installing ducts, especially regarding bends and slopes. Bends should be minimized as much as possible, extreme bends should be avoided. The length should be as short as possible because bends cause turbulence and resistance to airflow. In addition, ducts should be sloped because condensation can cause water to accumulate in the ducts. Ducts also make noise due to vibration, etc., so it is necessary to use reinforcement materials to prevent noise.

Outlet and Inlet of Ducts

There are various shapes of duct outlet/intake ports.

In office buildings and department stores, ceiling-mounted air outlets called “amonestats” are the standard, and they are available in round or square shapes. Amonestats have a cross-sectional structure with multiple overlapping wings, and the air that is blown out radiates, spreading the air throughout the room.

A “garage” is widely used at the intake port for taking in outside air. To prevent rainwater from entering outdoor use, the structure is fitted with drainage and water-return wings. Since they are used outdoors, weather-resistant and durable materials such as stainless steel are used. In addition, measures must be taken to install stainless steel netting to prevent insects and birds from entering.

In addition, various other types of blowing and intake ports are used according to the purpose. This includes the nozzle type to deliver air widely in large spaces such as gymnasiums and the universal type with movable wings attached.

Cautions for Duct Installation

Duct installation also requires attention to the following four points.

1. Loss Resistance of Ducts

Loss resistance in ducts obstructs the internal airflow and increases the air-blowing power, resulting in wasted energy.

The first step is to make the duct length as short as possible. In addition, supply and exhaust ports, branches, and bends create large loss resistance, so these should be minimized as much as possible. Nevertheless, unreasonable duct connections create significant loss resistance. Therefore, it is important to avoid forced connections while minimizing distances and bends and branches as much as possible.

2. Condensation in Ducts

Condensation may occur in ducts in some cases. Condensation in ducts can lead not only to corrosion of the ducts but also to electrical leakage and fire due to water entering a crisis through the ducts. To prevent this, a slope may be provided to drain the water in the ducts to the outside.

3. Vibration and Noise of Ducts

If ducts are installed incorrectly, vibration from blowers and other motors can be transmitted to the ducts, causing vibration and noise, so these measures are necessary.

One of the countermeasures is to install “deflection joints” to prevent equipment vibration from being transmitted to the ducts. In addition, by using “flexible ducts” with a bellows structure at the connection, not only can vibration be suppressed, but they can be used in locations where installation is difficult because they can be flexibly bent. Noise reduction can also be achieved by installing a sound-deadening box. The sound deadening box is filled with rock wool or glass wool inside to provide sound absorption and muffling functions.

What Is PCR Tube?

PCR Tubes are plastic tubes made specifically for use in PCR experiments. Polypropylene is usually used as the material, and a wide variety of sizes, shapes, and colors are available.

Uses of PCR Tubes

Figure 1. PCR tube and principle of PCR

PCR is an acronym for polymerase chain reaction, a technique that uses DNA polymerase to amplify a target DNA sequence from one to several million copies in a short period of time. Specifically, the series of reactions 1-3 below are called “cycles,” and by repeating 25-35 cycles, copies of the target DNA are synthesized exponentially.

1. Denaturation: The double-stranded DNA template is heated to separate the DNA strands
2. Annealing: short DNA molecules called primers are attached to adjacent regions of the target DNA
3. Elongation: DNA polymerase synthesizes complementary strands of the template in the 3′-end direction starting from each primer

The device used to automatically control the temperature cycle and incubation time in PCR is a thermal cycler; PCR Tubes are manufactured for use in a thermal cycler. In order to select the correct PCR Tube, it is necessary to correctly understand the specifications of the thermal cycler you will be using.

In addition, since there are various types of PCR such as standard PCR, gradient PCR, real-time PCR, and qPCR, it is necessary to select the appropriate PCR for your purpose. At the same time, it is also important to properly prepare the experimental apparatus and reagents according to the type of experiment.

Structure of PCR Tube

Figure 2. Various PCR tubes (Single tube) / Figure 3. Example of 8-row PCR tube

Polypropylene is usually used as the material. Polypropylene is chemically inert and can withstand rapid temperature changes during thermal cycling. In addition, the tube walls are manufactured to be thin and uniform to enhance heat transfer from the thermal cycler.

In addition, they are manufactured with the utmost care to ensure that they are free of dust and impurities such as endonucleases, pyrogens, DNA, lubricants, dyes, heavy metals, and fillers. This is because if the product becomes contaminated during manufacturing, dust particles can remain and interfere with PCR, or DNA fragments can serve as templates for nonspecific amplification, resulting in reduced experimental accuracy.

The structure consists of a tube portion that holds the sample and a cap portion, and is available in a single type with one separate tube, or an 8- or 12-tube type with multiple tubes.

There are two types of cap shapes: flat and domed, one with one cap per tube, and one with multiple caps in a row, which are separate from the tube.

There are two types of tube sections, one with a normal height (standard profile) and the other with a lower height (low profile). In addition to the transparent clear type, white ones are also available.

How to Select PCR Tubes

It is important to choose according to the type of experiment and to use the appropriate one for the thermal cycler you are using. For example, clear tubes (transparent type) make it easy to check the contents, while white tubes increase the sensitivity of qPCR by preventing fluorescence from refracting and diffusing outside the tube.

Domed caps allow rapid heat transfer from the thermal cycler, while flat caps can be marked with a marker and are easier to puncture with a needle during sample collection.

Low-profile tubes with a lower height minimize the space area in the reaction vessel, thus reducing the effects of evaporation and increasing the thermal conductivity compared to normal ones. Low-profile tubes are sometimes referred to as fast tubes because they are compatible with fast thermal blocks.

PCR Tubes are suitable for small- to medium-scale PCR experiments, and when the scale is larger, PCR plates are appropriate.