instrument fittings

Familiarity with Instrument Tube Fittings

In this article, we introduce precision instrument connections in a comprehensive and practical way in order to get to know more about precision instrument connections or tube fittings. Instrument fittings or instrument fittings play a vital role in various industries in ensuring accurate measurement, precise control and safe operation.

Understanding and getting to know the types of instrument connectors and the function of connectors in instruments is very important for professionals who work in the fields of oil and gas, chemical, pharmaceutical and many others.

instrument fittings

Precision instrument fittings are one of the types of piping equipment and pipelines in various industries, including petrochemical and oil and gas, which have different names such as: precision instrument fittings, precision instrument tube fittings, precision instrument and pipe connectors and instrumentation connections are known.

What is instrument tube fittings?

In the world of industry and production, precision instrument connections play a very important role. These connectors are elements used to connect precision instruments.

Instrument fittings are also known as tube fittings, instrument connectors, work tube fittings, instrument tube fittings. These fittings are one of the types of fittings whose main function is to transfer pure and ultra-pure gas fluids. Types of instrumentation connections include mechanical connections, electrical connections, and hydraulic connections. Mechanical connections include bolts, nuts and bolts and welding. Electrical connections include wiring, connectors, and sockets. Hydraulic connections are also used to transfer liquids in hydraulic systems.

Instrument fittings are special equipment that are used in the installation and connection of piping systems in various industries such as oil and gas, petrochemical, chemical and pharmaceutical. All types of tube fittings are designed and used to create a tight and leak-free connection between pipes. One of the main features of all kinds of instrument connections or tube fittings can be mentioned the possibility of safe and efficient transmission of fluids or gases.

Instrument fittings or instrument tube fittings are parts that are used to change the flow direction of fluids and gases in piping and piping lines of instruments, create branches in instrument tubes, and also to create more paths for fluid or other liquids and gases are produced and used to blind one of the pipe branches or change the diameter of the pipe.

Tube fittings are usually used in applications that require precise control and measurement of fluid or gas flow, such as pressure gauges, flowmeters, and control valves. Instrument fittings or instrument connectors are available in different sizes, materials, models and types to meet the sizes and needs of different plumbing and piping systems.

instrument fittings

Instrument connectors or tube fittings usually consist of three main parts:

Connecting body:

The connecting body is the main part of the assembly and is usually made of stainless steel or other corrosion-resistant material. It has the headers needed to connect to other components or piping.


Ferrules are small, conical rings that are placed on the pipe before the pipe is inserted into the fitting body. By deforming and gripping onto the pipe, they block the way for leaks, multiplying the connection and preventing leaks.


The nut is used to strengthen the connection body to the pipe by squeezing it. This nut compresses the flanges onto the pipe, creating a secure, moisture-tight connection.

Features of instrument fittings or tube fittings

One of the main characteristics of precision instrument connections or precision instrument fittings is to withstand high pressures and temperatures; this makes the instrument connectors suitable for environments with harsh conditions and to be used. Tube fitting equipment is commonly used in industries where safety and accuracy are important, such as chemical plants, refineries, and power generation facilities.

Another feature of instrumentation fittings is their excellent corrosion resistance as well as ease of installation. They are widely used where accuracy, reliability and safety are outstanding, ensuring that the transfer of liquids or gases in complex systems is carried out efficiently and without leakage.

Tube fittings also provide flexibility in installation and maintenance. These equipment are easily removed and installed without causing damage to the pipe, which allows for quick repairs or changes in plumbing and piping systems.

instrument fittings

Technical specifications of instrumentation fittings

Instrument fittings have different specifications. Instrument fittings, or instrument connectors, usually consist of three main parts: the connector body, the ferrule, and the nut. The body of the fitting is usually made of stainless steel or brass and has a thread that attaches to the pipe. A ferrule, also known as a compression ring, is a small, tapered ring that is placed on the pipe before the pipe is inserted into the fitting body. The nut is then pressed onto the body of the fitting, compressing the ferrule and creating a tight seal between the pipe and the fitting (metal to metal sealing).

Advantages of precision instruments

One of the main and key advantages of instrument fittings or tube fittings is the ability to create a reliable, tight and leak-free connection. The ferrule, when properly installed, creates a strong seal between the pipe and the fitting body that prevents any fluid or gas from escaping.

This ensures the health of the plumbing system and reduces the risk of leaks, which can be costly and dangerous. In addition, tube fittings can be used with a variety of pipeline materials such as stainless steel (alloy steel), copper and plastic and are compatible with different application needs.

In summary, instrumentation fittings or instrumentation connectors play a vital role in the safe and efficient operation of piping systems. They provide a secure, leak-free connection, withstand high pressures and temperatures, and offer flexibility and ease of installation and maintenance. These connections are very important as essential components in industries that depend on accurate fluid or gas control and measurement.

All types of precision instrument connections or tube fittings

There are various types of instrumentation fittings that are used to connect and seal pipes in instrumentation and control systems. These fittings ensure that the connections between the pipes are leak-free and reliable. Below are some of the types of instrument fittings:

Compression Fittings

Compression fittings are widely used in precision tooling applications. These connections include the connection body, nuts and frames. The ferrules are compressed against the pipe by pressing the nut onto the pipe and when the nut is set, creating a tight, leak-free connection.

Mechanical fittings (Bite-Type Fittings)

Mechanical fittings have a ferrule with sharp teeth that are compressed and stuck to the pipe when these fittings are connected. These connections provide a strong, leak-free connection.

Flare Fittings

Flare fittings have a series of tapers at the end of the pipe that match the taper seat in the fitting body. During joint adjustment, the flare head is pressed against the seat, creating a seam. Flare fittings are typically used in high pressure assemblies.

Threaded Fittings

Threaded fittings have male and female nuts that allow pipes or other components to be connected. The internal thread of the nut is used to prevent leakage.

Welded Fittings

Welded joints are used in cases where a permanent connection is required. The pipes are welded directly to the fitting body or welded together using suitable welding techniques.

Push-to-Connect Fittings

Quick-release fittings are also known as quick-connect fittings or quick-release fittings. These fittings provide a simple and easy way to connect pipes without the need for additional tools or parts. The pipe is simply inserted into the fittings and their internal mechanisms hold and fix it in place.

Quick Disconnect Fittings, Quick Connection

Quick disconnect fittings allow quick disconnection and connection of pipes without the need for tools. These fittings are typically used in applications that require repeated piping and disconnection.

These are just some common examples of instrumentation connections. The selection of a particular type of tubing and instrumentation fittings depends on factors such as application-specific requirements, tubing material, pressure and temperature values, and installation conditions and manner. To ensure proper operation and leak-free fittings, it is important to select fittings that are compatible with the pipe material and suitable for specific operating conditions.

Raw materials of fittings

The raw materials for the production of fittings for water and fluids consist of all kinds of metals and polymers. The most used are brass fittings, stainless steel fittings and cast iron fittings respectively. Polymers include polyethylene or Teflon joints and composite joints.

Brass fittings in metals and polyethylene polymer fittings have the necessary standards in terms of health and are much cheaper than steel fittings in terms of cost.

Uses of fittings or connections:

  1. Maintain or regulate fluid flow
  2. Blocking or sealing the pipe
  3. Changing the direction of fluid flow and piping system
  4. Connecting two or more different pipes or hoses together
  5. Connecting various components of the piping system to the main system
  6. Connecting pipes to various devices and equipment, such as filters and pumps

Types of connections


Elbow fitting is one of the most important connections used in piping systems, which is used to change the direction of the pipe. They usually have 90 degree and 45 degree types. The size of the elbows varies according to the dimensions of the pipes and usually their size is expressed by the external diameter of the elbow and as NPS. They are connected to the pipe through various methods, including threaded connection, flange connection, male and female connection, heat press connection, and glue connection.


A tee that looks like the letter T. It is used to create a branch in the pipeline route. It is used when we want to separate a branch from the main path of the pipe. A tee fitting is much more durable compared to an intersection.


Intersections have four different flow channels. They have the ability to connect four pipes to each other, which make a 90 degree angle. Intersection connections include three entrances and one exit, or vice versa, one entrance and three exits.


Reducers are used to connect two pipes with different sizes and cross sections. It reduces the intensity of liquid flow in the pipe. When the flow enters these connections from the larger side, it experiences pressure drop and speed increase when it exits from the smaller side, and on the contrary, if it enters from the narrower side, it experiences pressure increase and speed drop when exiting. Reducers are used in pneumatic systems and chemical industries. These connections are available in different sizes and have high operational flexibility.

There are two types of reducing fittings:

1.        Concentric reducers or symmetrical

Symmetrical reducers have a cone-like shape and connect two pipes with the same diameters, and its diameter gradually decreases. This can cause air accumulation and damage to the system.

2.         Eccentric Reducer or asymmetric

Asymmetric reducers have a bell-shaped shape, which are used to connect two pipes with unequal diameters. In this type, the edge of the reducer is completely parallel to the edge of the two pipes, and the diameter reduction is done only on one side of the reducer and in a non-gradual and heterogeneous manner. In this type of reducers, there is no possibility of air accumulation and cavitation (formation of air bubbles). One of the disadvantages of these reducers is creating more pressure drop and turbulence in the flow path.


Couplings are very efficient fittings in piping. A type of connection that is used to connect two pipes of the same size and to repair the cross section of the pipe. They are available in two categories:

1.        Compact coupling

It seals both sides of the leaking pipe with its sealant layer.

2.        Narrow coupling

It is placed in the middle of the burst pipe as a sealant.


Union connection is a connection in the form of two female sides or one side is male and the other side is female, and a galvanized coating is used on them to prevent any corrosion. They have a structure similar to the structure of couplings, with the difference that Unions can be easily disconnected from the system at any time, while this is not so easy for couplings.

Olet connection

Olet connections are used when the inlet and outlet pipe sizes are different. It means that there are no connections with suitable sizes. It has different types such as butt weld, socket, elbow, side, flange, nipple, etc.

Y connection

This type of connection is named because it resembles the English letter Y. It is used to connect three pipes together. These fittings are similar to tee fittings, but the friction and fluid turbulence in it is less than that of a tee.

Plug and Cap

Caps and hubs are used to block the flow path.

Plug cap is usually threaded or male and female, which is the connecting cap of male and female pipe. But in the type of cap, Cap is female and male tube.


Bushings usually have a threaded structure. It is used to connect two pipes of different sizes. They are much denser than reducers. They are usually made of copper, brass, nickel chrome, galvanized steel, carbon steel, stainless steel, plastic, PVC, etc.


Flanges are for connecting pipes and valves. They are used to seal and prevent leakage. Flanges are usually welded or bolted. They are made of stainless steel, cast iron, aluminum, brass, bronze, plastic, etc.

Hose Nipple

The valve head is used to connect the hose with the water pipe. This type of connection has only one male end that is connected to the water pipe and the other end enters the water hose.

Hexagon Nipple

A nipple is actually a type of nipple and instead of connecting two pipes, it connects two fittings to each other. Its two ends are male and are produced in plastic, steel, galvanized and copper types.

These ribs make it possible to use them to connect pipes. Another use of hexagon nipple connections is to increase and decrease the diameter of pipes. One side of this type of brain has a larger diameter than the other side; therefore, two pipes with different diameters can be connected together.

Mechanical cover (Clamp)

The inner layer of this fitting is made of resin and there are screws around its body. It is used to connect two pipes. The mechanical cover is tightened with a screwdriver, and the resin inside seals the pipe.

The sizes of fittings or tube fittings

There are various types of instrument fittings or instrument fittings in different sizes to accommodate different dimensions and sizes of pipes and piping systems. Common sizes for instrumentation fittings are determined by the outside diameter (OD) of the tubing. These sizes typically range from 1.16 inches to 1 inch, although larger sizes may be available.

An important thing to note is that these sizes may vary slightly depending on the specific manufacturer and industry standards. It is important to remember that instrument tubing fittings are designed to fit securely and leak-free to certain sizes of tubing.

When choosing instrument tubing pieces, make sure the piece size matches the outside diameter of the tubing you are using. Also, consider the type of part, such as a compression part, serrated type part, and other variations, as they may come in different sizes.

Always refer to the manufacturer’s documentation or consult with the supplier to determine the proper size of instrument tubing pieces for your particular application.

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