Introduction

Steel pipe fitting is one type of pipe fitting that is made of steel, also known as a steel pipe accessory. It plays very important roles in the piping system such as to connect the other pipes, change the direction of pipeline trend, control the flow of media and so on. Considering its importance, how to choose the right steel pipe fittings is truly a complex work. Using raw materials, production standards, and using environments are the necessary thinking factors.

Understanding the Basics of Steel Pipe Fittings

Types of Steel Pipe Fittings

There are many series of steel pipe fittings in the piping systems mainly including elbow, tee, reducer, cap, flange and other series. 

Elbow: applied for altering the direction of pipeline trends, the types of shapes include 90degree, 45degree and 180degree. Customized production is also available. 

Tee: connect the pipes from three directions and can help the pipeline to create a 90-degree branch with equal or different diameters. 

Reducer: used for the connection of two pipes with varying diameters. There are two types: concentric reducer and eccentric reducer.

Cap: Seal the pipes. As a sealing fitting at the end of pipes which is usually used for closing the end of pipeline to prevent the leakage of fluid to ensure transport of the fluid stably. 

Flange: providing the convenience for the installation and maintenance of pipelines. Welding neck flange, slip on flange, socket weld flange, threaded flange and blind flange are the common types.

Materials and Specifications

For these steel pipe fittings no matter various fittings and flanges they all can be produced by many kinds of materials. Carbon steel, alloy steel and stainless steel are the most common three materials in a lot of industrial applications. 

Carbon steel: it is a material with advantages of affordable price and wide applications. Carbon steel pipe fittings are commonly adopted in the low and medium pipelines, general service pressure vessels and some low temperature environments. You can select it as your needs. The specification of carbon steel pipe fittings are generally follow the below:

Alloy steel: it is a special material, which usually improves its properties through adding one or more alloying elements into the ordinary steel. The properties of alloy steel vary because of the type of alloy element and content, which can provide higher hardness, strength, abrasive resistance, corrosion resistance and heat treatment capacities.

Identifying Your Specific Needs

Application Areas

The demands of pipelines of petroleum and gas for the steel pipe fittings are the most important. The installation and repair of pipelines needs various kinds of materials pipe fittings no matter what materials. 

Chemical factories also need steel pipe fittings with big quantities specially alloy steel pipe fittings requested more than other industries. After all, the chemical products usually have corrosivity.

Steel pipe fittings of various materials are the common accessories in the pipelines of ships which are mainly used for fuel system, watertight compartment system, cooling system, and compressed air system. 

Food and pharmaceutical industry also requests lots of steel pipe fittings but due to the particularity of this industry, it needs more precise and higher-grade pipe fittings. Generally stainless steel material is used more.

Performance Requirements

1.Classification for pressure grades in different standards.

Nominal pressure is a reference data about the anti-pressure capacity of a line pipe system. The specification is composed of PN or Class add the following numbers.  

In the EN standard system, the pressure of the piping system is expressed by PN. There are twelve levels in it.

The nominal pressure determines the rated pressure meanwhile the materials’ types and temperatures also need to be clear. For example, one material PN2.5, the rated pressure is 2.5Bar under normal temperature（-10-50℃）but under 100℃ it will be changed to 2.0bar. The other material,  the rated pressure is only 2.2Bar under normal temperature. Thus we can know the rated pressures are mainly determined by material, temperature and PN. 

2.In ASME standard system, the pressure is expressed by Lb.There are seven levels in it class150 ,300, 600, 900, 1500, and 2500. Like EN standard, the rate pressure is determined by pound levels, and also need to specify materials’ types and temperatures. 

3.How to choose suitable wall thickness pressure ratings?

• The pressure on the pipeline: according to the actual needs to choose the suitable pressure levels and wall thickness.
• The medium transported by the pipe: the density and fluidity of different mediums are different as well as the pipe wall thickness requested. 
• The pipeline manufacturing process: the quality of pipes produced through different processing is different and the wall thickness required is different as well. 
• The operating environment of the pipeline: the requirements for steel pipe wall thickness is different under different service environments. Such as more wall thickness needed in the high temperature and acid-base environment.

Choosing the Right Supplier

Choosing suppliers passed certificates

Piping materials are mostly used for some important projects such as petrol oil and gas projects, chemical industry, ship building, medical industry and so on. They have a common feature that they need the products with good quality. That usually requests the manufacturers to have some international standard certificates which clearly specify the production activities of these manufacturers providing the guarantee for manufacturing high-quality products. So when you need piping materials you should try to choose these producers or suppliers who have certificates. 

How to assess a supplier?

1. Checking the website: through visiting the website of a supplier you can know about this supplier generally. 
2. To check the certificates of this supplier.
3. Look at the performance chart: it can prove the supplier’s operating capability for orders. 
4. Field visit to the manufacturer is the most effective way to know more about them.

Cost-Benefit Analysis

Cost-benefit should not only consider the purchasing costs but also consider the installation and maintenance costs.The regular maintenance can effectively extend the service life of the pipelines. 

1. The procurement cost: based on guaranteeing the quality to choose the most moderate prices. 
2. Pay attention to the installation details to ensure the installation quality which can reduce the probability of later damage. 
3. Regular maintenance to reduce the replacing cost.

Conclusion

In one word, if you want to choose right pipe fittings and flanges you need to follow some points.

1. Evaluated the needs of projects to choose these piping materials.
2. To know more about the features of each kind of material and choose the most moderate pipe fittings.
3. Selecting the reliable manufacturers or suppliers. 

Pipe fittings are used for many important and big projects and play very important roles, choosing them rightly refers to the safety of the whole project.