The parts that are used by them to change the size, change the direction, and branch the pipelines and connect these lines to other equipment are called connections. Connections are a type of interface between pipes that reduce the dimensions of pipes and divide and change them. The flow path helps.

Types of connections and their use

Brain connectors: It is a piece of metal that is used for connection, and its two ends are screws.
Nut connections are used in piping to connect two parts with an internal rib.

bushing connections

In this type of joints, the pipes are connected by welding and are produced from seamless pipes and in different types of metal, plastic or PVC.

Bushen in the connections of the cylindrical piece, which is usually found in the market of two types of metal (galvanized and brass) and plastic (PVC). In fact, it is a kind of “connecting ring” between two pipes. Also, this cylindrical part is produced in two forms, “screw or rib” and “welded”. The types of “screw” or “white gear” bushings are used only for cold, hot and return water piping. Because the use of non-galvanized ribs will cause the pipes to corrode and rot. The most important thing that affects the price of bushings is the types of bushings and what kind of parts you intend to buy. To familiarize yourself with the types of bushings, we will briefly introduce its different models. Before introducing this connector, you should know that the type, material, brand and country of manufacture also have a direct impact on determining the price of these parts.

Refrigerant fittings

The cooler is one of the types of metal connections, one end of which has a thread and the connection is a gear, and the other end has the ability to weld, and it is considered one of the most widely used types of seals for all types of tanks and connections. One of its functions is to connect pipelines to a valve with the purpose of disconnecting or connecting for the consumer.

Tee connection

In the world of connections and plumbing for water, sewage, gas, oil, petrochemicals, etc., it is considered one of the most important parts. This part is used for branching at the end of an open pipe, or sometimes we come to two paths along the pipeline route. Use this connection. According to the type, diameter, and material of the pipe, we choose the type of tee according to the official standard. According to the mentioned items, it can be said that the main job of the tees is to divide the pipeline or to separate the pipeline from It turns one path into two moving paths.

Types of tees
Three equal ways

In this type of tee, all three openings are equal, which means that the diameter of the inlet and outlet openings and the navel of this part are equal and they are used in the same size paths.

Three unequal ways

In this type of tees, both openings of the pipe are equal and the umbilical part has a smaller diameter. In other words, if the diameter of the pipeline is one inch in a direction and we want to get a branch with a size of one and a half inches, use an unequal one inch tee with a one and a half inch umbilicus. we do.

What kind of tees are available in the market?


This type of tee is produced with seams and without seams with different classifications from category 10 to category 160, which are selected and used depending on the type of fluid or the temperature and pressure of the fluid.

stainless steel

In this type of tees such as steel, things like pressure and temperature are very important, and attention to these things determines whether they are seamed or seamless and the classification. This type of connection is widely used in the petrochemical and food industries.


This type of tee is made of polyethylene material, which is used in materials such as water and gas, even irrigation and sewage, which has a special standard for each of the mentioned items and is produced in these cases to withstand pressure, temperature and Bending is very important.


This type of tee is made of galvanized alloy, which is mostly used in water pipes.

Elbow joints and their types

Welded elbow is one of the key parts in industrial piping that is used to change the flow direction of fluids and gases. Production of welded elbow to connect two pipes with equal or different diameters in order to change the direction of flow under 90°, 45° angles. , 180 degrees, and in limited cases, it takes place under angles of 60 degrees, 120 degrees, and 35 degrees. This change in fluid direction causes a decrease in pressure, acceleration, and sometimes failure in pipeline piping.

Knee boils are classified according to the following parameters:

– Knee angle
– Knee length and radius
– How to connect elbow with pipe
– The material used in the knee

Flange connections

This type of connection is widely used in repairs and has high flexibility, and it is used when two pipes of different diameters are connected and they have different types.
Blind flange, edged flange, facing flange, welded flange. Flanges are steel parts that are used to establish a connection and can connect the pipe to other piping items such as shock absorbers, valves, etc.

There are various methods to connect the pipe and its items to each other or to the equipment, such as welding, etc., one of which is flange connections.

Types of flange connections
Threaded flange connections

In this type of connections, the inner body of the flanges is threaded.

Also, the outer surface of the ends of the pipes must be threaded to establish a connection with this type of flange.

In this way, the pipe is very easily inserted into the flange and the connection is established without the need for welding.

The quality of thread execution in pipe and flange plays a key role in sealing connections.

2-2 Socket Weld Flange

Another type of flange connection is called socket welding flange.

These flanges are suitable for small-sized pipes that work at low operating pressure and temperature.

To establish a connection in these flanges, first the pipe is placed in the socket of the flange.

Then the joint edge is made stronger by welding.

The installation of this type of connection is not very complicated and brings high sealing quality.

3-2 Slip on Flange connections

Among other widely used flange connections are sliding flanges.

The important advantage of this class of flanges is that
They can be easily used for piping systems in different dimensions and sizes.

To install this type of connection with pipes, you need to weld filler on both sides of the connection.

For this reason, its implementation requires more considerations from a technical point of view.

In the situation where we have little space to implement the connection, one of the suitable options is the sliding flange.

4-2 Lap Joint Flange

Lap joint flanges require butt welding to connect to pipes.

This category of flanges is mainly used when we have little space to run pipelines.

In addition, in cases where the piping system needs continuous maintenance, it is recommended to use butt joint flanges.

Because it is easier to make these connections and to separate them than other flanges.

5-2 Weld Neck Flange

Another type of flange connection is known as welding neck flange.

To connect this group of flanges, it is also necessary to butt weld the flange with the pipe.

with the difference that it is possible to use them in piping lines with high operating pressure and temperature.

Also, due to their high ability to withstand bending stresses, they can be easily used in pipelines with high curvature.

6-2 Blind flange connections

Blind flange is used at the end of piping lines to block them.

The structure of this group of flanges is similar to a disk that is connected to the pipe with the help of bolts and nuts.

Proper installation of these flanges will create an excellent seal for pipelines.

Also, they can be easily separated if needed.

2-7 Specialty flange connections

In addition to the types of flange connections that we mentioned above, there are other flanges that
They are designed for special applications.

These flanges are known as specialized flanges.

Among some types of specialized flanges, the following can be mentioned:

Nipo flange
expanding flange
reducing flange
3 types of flange connection surfaces

In addition to the categories we provided above for various types of flange connections,
This group of connections can also be classified based on their level.

Based on this, the types of flanges are classified as follows:

1. Flat face flange

This group of flanges consists of two flat surfaces that are connected to each other by means of a washer.

2. Raised Face Flange

In the design of this group of flanges, a prominent part is considered in the area around the flange hole.

3. Ring Joint Face

This type of flange connections are used for pipelines with high pressure and temperature.

In the design of ring flange, a groove is considered on the outer surface.

A ring washer is placed inside this groove, which acts as a seal.

4. Male & Female Flange

The male and female flange consists of a pair of grooves and protruding parts that are used for sealing.

Of course, the washer in these flanges is placed on the female face and the raised surface is also installed on the male face of the flange.

4# class of all kinds of flange connections

As we mentioned above, flange connections are produced in different dimensions and sizes.

In specialized jargon, the word class is used to classify the types of flanges.

In this way, they recognize from the flange class what temperature and pressure it is suitable for.

Based on this, flanges are classified into different classes, which include:


The higher the class of the flange, the higher the temperature it will withstand, and at the same time the operating pressure will be reduced.

What is a pipe and what are its types?

A pipe is a tube-like piece or hollow cylinder, usually (but not necessarily) with a round cross-section, which is used to transport products from one place to another. Products that can be transported with pipes that can flow. This includes liquids, gases, slurries, powders, and aggregates of fine solids. Petro Ilia Energy examines this issue in this article.

The difference between pipe and tube

Normally, the words pipe and tube are used interchangeably, but in industry and engineering, each of these two words has a specific and specific definition. In short, the tube is measured by the external diameter and the pipe by the nominal diameter. The pipe is generally characterized by the nominal size (NPS), which actually indicates the outside diameter of the pipe (OD). The pipe category or skjol (SCH) indicates the thickness of the pipe wall. The nominal pipe size (NPS) and its outside diameter (OD) are not always the same.

  • In pipes with a nominal size of 12, the nominal pipe size and outer diameter are different.
  • In pipes with a nominal size of 14 and above, the nominal size and outer diameter are the same.

The structure of the pipe is usually hard and has no flexibility.

Tubing is often specified by the outside diameter (OD) and wall thickness (WT), but the inside diameter (ID) may also be used to specify its size. The outside diameter (OD) in a tube is an important and precise measurement. The measured outer diameter and the declared outer diameter are either exactly the same or the difference in their numbers is very small. Usually the price of the tube is more expensive than the pipe, and this is because the production process is more difficult. The tube can be both rigid and flexible.

In general, pipes have a wider application and their size ranges from half an inch to several feet. Tubes are generally used in projects that require smaller diameters. Although 10-inch tubes are common, the use of 10-inch tubes is rare. The difference between the different dimensions of the tube is less than the tube. The meaning of the difference in dimensions here is the difference in diameter, the difference in wall thickness, the difference in the smoothness of the pipe, the difference in its roundness, etc. In general, the inner and outer surfaces of the tubes are softer than the tubes. Tubular structures are almost always connected using fittings such as elbows, tees, etc., but tubes are shaped, bent, and used in various configurations.

The type of pipes

Pipes are made of different types and materials, including metal, alloy, ceramic, glass, fiberglass, concrete and plastic. Engineering companies have experts to determine the type of pipes, who determine the type and type of pipe according to the type of project. The choice of pipe material depends on the fluid service, pressure and temperature design, costs and some other factors. Most of the pipes used in the oil and gas industry are classified according to the type of pipe as follows:

  • Carbon steel pipe
  • Stainless steel pipe
  • Alloy steel pipe
  • Galvanized metal pipe

In addition to the pipes mentioned above, cast iron, cement, plastic, etc. pipes are used in some special projects, but their use is very limited.

Pipe production

Pipes are usually produced by two different methods, which ultimately lead to the production of two types of pipe, the Mannheim (seamless) pipe and the seamed pipe. In both methods, raw materials are first poured into the mold. Then, by drawing the steel, you can get the Manisman pipe (seamless) or you can turn the raw materials into a sheet and produce a seamed pipe by bringing the two ends of the sheet together and welding them.

Manisman tube (seamless)

Seamless pipe (Manisman), as its name suggests, is a pipe that does not have any seams or welds. Mannesmann steel pipe is made from a round and solid steel branch. This steel branch is heated and deformed to resemble a hollow tube. Then, this hollow tube is placed inside the device that performs a combination of ironing and mandrel, and its outer thickness is reduced, which causes the inner thickness of the Mannesmann tube to increase.

welded pipe

Welded seam pipe is produced with rolled sheet metal, the entire seam is welded along the length of this pipe. The production process of the seamed pipe begins with rolling the steel coil to obtain a smooth sheet with the desired thickness. The desired sheet is cut with a width that fits the size of the pipe. The tube is formed by moving on a cut coil and a set of rollers. Then the seam on the pipe is welded in a chemically neutral environment. The seam or welded joint in the welded pipe is the weakest part of the pipe, which limits the strength of the pipe to the strength of the pipe weld.

The difference between manisman and seamed pipe

  • Manisman pipe (seamless) does not have welded seams. In general, welded pipe seams have always been considered as a weakness. This weakness makes the pipe more vulnerable to damage and corrosion. Although today, the process of producing seamed pipes has improved a lot and the strength and performance of these pipes have increased. However, Mannesmann's pipe still lacks this weakness due to the lack of seams. In general, seamed pipes can withstand 20% less pressure than Manisman pipes.
  • Mannesmann pipe can withstand higher working pressures than its similar size and material seamed pipe, and this is due to the absence of seams or welds in the pipe body.
  • Manisman metal pipe is very resistant to corrosion because there is little potential for impurity, cracks and lack of flexibility in this pipe, this is if the sealed pipes have the potential for these problems.
  • There is no need to perform a welding accuracy test for Manisman metal pipe (seamless), if this test must be performed for seamless pipes.
  • Manisman metal pipe hardens after production, so there is no need to perform heat treatment for this pipe. However, most of the welded pipes need heat treatment after production.
  • The price of the seamed pipe is cheaper than the Manisman metal pipe and it is available in different lengths.
  • Manisman iron pipe can replace the seamed pipe, but due to the seams and welds in the seamed pipes, it may not always be possible to replace the Manisman pipe.
  • The wall thickness of seamed pipes is more uniform than the wall thickness of Manisman pipes. Obtaining a steel sheet that has the same thickness all over and making a metal pipe with it is easier than making an industrial Manisman pipe with the same thickness through extrusion. Also, the surface quality of the seamed pipe is much better than that of the steel Manisman pipe.
  • The time required for the Mannheim pipe production process is longer than the time required for the seamed pipe production

Manisman pipe size and category (nominal pipe size and category)

The size of pipes is determined by national and international standards. There are two ways to determine the outside diameter (OD) of pipes. The US method is known as Nominal Pipe Size (NPS) and is based on inches. The method used in Europe is called nominal thickness (DN) and is based on millimeters. Determining the Mannheim pipe size based on the outer diameter has the advantage that all pipes of the same size can be placed together regardless of their wall thickness. Since the outer diameter is fixed for a certain size of the pipe, the inner diameter varies depending on the thickness of the pipe wall. For example, a 2-inch Class 80 Mannmann pipe has a thicker wall than a 2-inch Class 40 Mannmann pipe, because the inside diameter of the Class 40 pipe is smaller.