What is Chiller Piping? Piping Components and Features

1. Chiller piping

A chiller consists of refrigeration circuit that rapidly cools water, a water tank that stores the water to be supplied, and the piping that connects these components.

The role of piping is to connect each part and reliably transport cooling water to the equipment, but piping must be selected according to the purpose and scale of use.

What is Piping?

Piping is essentially the arrangement of tubular parts that carry fluids such as gases, liquids, and powders, and comes in a variety of shapes and materials depending on the purpose of use.

The word "plumbing" can refer to the pipe components themselves, or it can be used as a verb to mean laying or installing pipes, as in "laying water pipes."

Piping components include familiar items such as water hoses and air conditioning duct hoses, as well as large pipelines that transport oil and other necessities, utility piping at chemical plants, and underground water and sewerage pipes.

This article focuses on piping for transporting and cooling liquids.

Pipe size and maximum flow rate

The most important factor in pipe size is the inner diameter, which affects the maximum flow rate that can be transported through the pipe.

Pipe sizes are designated by three names: "A designation," "B designation," and "common name (colloquial name)." "A designation" is measured in millimeters, and "B designation" is measured in inches.

"Common name (colloquial name)" is a name that has been used for a long time on construction sites, and a 1/8th part of a B designation is called "ichibu" (one-minute), a 3/8th part is called "sanbu" (three-minutes), etc.

The maximum flow rate is the maximum value that can be accurately measured by a flow meter, and is essential for safety use of equipment. Generally, it varies depending on the inner diameter of the pipe and the flow velocity, and can be calculated using the following formula.

Q (flow rate) = (D (inner diameter) / 2)^2×π×V (flow velocity)

Q represents the flow rate, D represents the inner diameter, π represents the ratio of the circumference of a pipe to its diameter, and V represents the flow velocity. The ratio of the circumference of a pipe is the formula for calculating the cross-sectional area of the inner diameter, so if we assume the cross-sectional area is M, the formula can be rearranged as follows:

Q (flow rate) = M (cross-sectional area) × V (flow velocity)

If Q (flow rate) is fixed at 10, then if M (inner diameter) is 10, the flow velocity will be 1, and if M (inner diameter) is 1, V (flow velocity) will be 10. Generally, the appropriate flow velocity in piping should not exceed 2.0 m/s, but even if the flow velocity is 3.0 m/s, circulation is possible under certain conditions.

Domestically produced piping is usually made to JIS standards, but imported piping may be produced to ANSI standard external dimensions.

In this case, even if there are no problems with the maximum flow rate, etc., installation problems may occur, so it is important to check in advance.

2. Types and characteristics of piping

Hoses are components that move fluids in the same way as pipes. They are often made of rubber, vinyl, or plastic, and while they are highly flexible, they are characterized by their poor durability and pressure resistance.

This article focuses on solid piping, excluding hoses.

metal tube

This includes carbon steel pipes, stainless steel pipes, and non-ferrous metal pipes such as copper pipes and aluminum pipes.

Carbon steel pipes are made from alloys containing carbon, and are the cheapest and most widely used for piping. They are processed to suit the application, such as by plating for excellent corrosion resistance or seamless manufacturing for high pressure performance.

Stainless steel pipes, also known as SUS steel pipes, are alloy steels containing 10.5% or more chromium, making them resistant to rust and widely used in water applications such as hot and cold water supply.

A representative example of non-ferrous metals is aluminum pipe, which has the advantages of high thermal conductivity, light weight, and rust resistance, and is widely used in heat exchangers, ship parts, etc. The higher the purity of aluminum, the lower its strength.
Copper pipes, which are also non-ferrous metals, are soft and easy to process, and have excellent thermal conductivity and corrosion resistance, making them suitable for use in water and hot water supply pipes, air conditioning pipes, medical gas pipes, and more.

Resin pipe

Resin pipes, which include rigid polyvinyl chloride pipes, cross-linked polyethylene pipes, and polybutylene pipes, are lightweight, easy to connect and disconnect, and easy to handle. They also have excellent chemical resistance, making them a piping component that is more often used in water supply facilities and residential applications than in factories.

Like metal pipes, it is highly versatile, has excellent earthquake resistance and corrosion resistance, and its smooth inner surface allows fluids to pass through easily.

Lined Pipe

A highly durable metal pipe lined (bonded) with a highly corrosion-resistant resin material is called lined steel pipe.

Resin lining materials include polyvinyl chloride, polyethylene, and non-tar epoxy, and are widely used in water supply systems and fire hydrants.

3. Piping connection methods and features

Chiller installation can take many forms depending on the factory or facility. Appropriate piping is required to efficiently cool the heat generated by the machinery.

To achieve this, a connection method suited to the application is required. Let's take a look at the methods and features of connecting pipes.

screw connection

One of the most common connection methods is the "screw connection." This type of connection joins the pipes to be connected with male and female threads, and while it is relatively easy to connect, it has drawbacks such as the threads coming loose and the fluid leaking easily, making it unsuitable for high-pressure applications.

In the case of chillers, since the fluid is water, it is common to use liquid seal or sealing tape in gaps in the joints. Sealing tape should always be wrapped clockwise.

Flange Connection

Flange connections are a connection method that achieves high strength and ease of work by joining plates called flanges together with screws.

The biggest advantage is that even after installation, piping can be easily disassembled, allowing for pinpoint inspections and maintenance if a problem occurs.

Welded connection

Welded connections are a method of directly connecting pipes together by welding, and are used in pipelines under high temperature and pressure. Because the joints are welded, they can also be used for high-pressure piping.

There are two types of welding: "socket welding," in which a pipe is inserted into a female socket and the joint is welded, and "butt welding," in which pipes of the same size are butted together and the joint is welded.

Glue Connection

Adhesive connections are a method of connecting plastic pipes used for water supply and drainage. The adhesive method used depends on the material of the pipe.

For polyethylene pipes, a method called "fusion welding" can be used, where the pipes are bonded using heat, but for common PVC pipes such as water pipes, adhesives are used.

However, care must be taken with the amount of adhesive used; too little can lead to leaks, while too much can cause problems with the durability of the piping.

4. Technical terms to remember

Finally, we will explain some useful terminology to know about chiller piping.

seal

Seals are materials used to prevent water leakage from pipe connections. They come in liquid and tape forms, and liquid seals are usually used for large pipes with an inner diameter exceeding 50mm (A designation). The surface where pipes are joined together is called the sealing surface.

leak

The word "leak" means "to leak," and in the case of piping, it means "the leakage of fluid contents due to a leak in the pipe." On-site, it is sometimes used to say things like "this connection is less likely to leak." A test to check for leaks in piping is called a leak test.

There are several leak test methods, including the liquid immersion method, pressure change method, and flow measurement method, and the most suitable test method must be adopted depending on the installation situation.

Water hammer

Water hammer is a phenomenon in which the pressure inside a pipe rises or falls due to a sudden change in flow velocity inside the pipe.

There are two situations in which water hammer occurs. One is when the flowing fluid is suddenly blocked, causing an increase in pressure, and the vibration force that shakes the pipes causes an impact noise.

The other case is when a pump or other device that was generating the flow stops, causing a drop in pressure, leading to separation of the water columns (generation of a gas phase), and the pressure recovers, causing the water columns to collide with each other, resulting in an impact.

The clanging sound you hear when you suddenly open or close a water faucet is also a type of water hammer.

seal

Seals are materials used to prevent water leakage from pipe connections. They come in liquid and tape forms, and liquid seals are usually used for large pipes with an inner diameter exceeding 50mm (A designation). The surface where pipes are joined together is called the sealing surface.

pressure loss

When a fluid passes through a pipe, its flow rate slows down due to friction with the inner wall, resulting in a decrease in the flow rate. This is called pressure loss. There are two main causes of pressure loss: friction loss due to contact with the wall, and turbulence loss due to vortices and turbulence.

If pressure loss is not taken into consideration when designing, the expected flow rate cannot be secured, which can have a significant impact on productivity.

Cavitation Erosion

When the pressure of a fluid inside a pipe or water tank drops, many small bubbles may form, a phenomenon known as cavitation.

When the pressure recovers and disappears, these bubbles generate a very large impact pressure, which can damage the surface of pipes, etc., causing erosion. This is called erosion, and the series of physical phenomena is called "cavitation erosion."

Factors that cause cavitation include impurities in the liquid, flow rate, turbulence, pressure, and the physical properties of the liquid (viscosity and compressibility).