What is a flat welding flange?

What is a flat welding flange?

A flat welding flange is one of the commonly used pipe flanges for connecting pipes, also called ordinary flat welding flange or simply flat flange. It usually consists of two flanges, some bolts and gaskets. The connection and sealing of pipes, pumps, valves, instruments and other equipment can be achieved by tightly connecting the two flanges with bolts and gaskets.

A flat welding flange refers to a flange that is connected to a container or pipe by a fillet weld. It is an arbitrary flange. When designing, it is divided into integral or loose flanges according to the degree of integrity of the connection between the flange ring and the straight section. There are two types of flange rings: with neck and without neck. Compared with the necked butt welding flange, the flat welding flange has a simple structure, saves materials, is low in cost, and is easy to install, but its rigidity and sealing are not as good as the necked butt welding flange. Flat welding flanges are widely used in the connection and equipment manufacturing of medium and low pressure containers and pipelines.

The main features of flat welding flanges:

1. Flat welding flanges are usually suitable for low-pressure, low-temperature, and small-diameter pipes.
2. Its connection is simple and easy to operate, and does not require complex operations such as gaskets and flange insertion, which is convenient for maintenance.
3. The manufacturing and assembly costs of flat welding flanges are low and the scope of application is wide.
4. The sealing effect of flat welding flanges is generally good and is suitable for some occasions that do not require too high sealing performance.

Flat welding flanges are not allowed to be directly welded with tees, pipe elbows and other pipe fittings, and straight pipe sections are required.

Specifications of flat welding flanges:

Product specifications: DN10-DN2000
Using pressure: PN0.25MPa, PN0.6MPa, PN1.0MPa, PN1.6MPa, PN2.5MPa, PN4.0MPa

Production process:
It is divided into pure material forging, rough material forging (secondary) suitable for flat welding and butt welding flanges, steel plates are suitable for flat welding flanges, and centrifugal casting and casting flanges.

The specifications of flat welding flanges are usually composed of parameters such as flange diameter, flange thickness, number of bolt holes and bolt hole diameter. Below we will introduce several commonly used flat welding flange specifications in detail.

1. DN15 flat welding flange
The flange diameter of DN15 flat welding flange is 15mm, which is suitable for the connection of small diameter pipes. Its flange thickness is usually 15mm, the number of bolt holes is 4, and the bolt hole diameter is 14mm.
DN15 flat welding flange is suitable for some small flow and low pressure pipeline systems.

2. DN40 flat welding flange
DN40  flat welding flange is suitable for the connection of medium-diameter pipes. Its flange diameter is 40mm, flange thickness is 20mm, number of bolt holes is 4, and bolt hole diameter is 18mm.
DN40  flat welding flange is suitable for some medium-flow, medium-pressure pipeline systems.

3. DN80 flat welding flange
DN80  flat welding flange is suitable for the connection of large-diameter pipes. Its flange diameter is 80mm, flange thickness is 24mm, number of bolt holes is 8, and bolt hole diameter is 18mm.
DN80 flat welding flange is suitable for some large-flow, high-pressure pipeline systems.

Application of flat welding flange:
Slip-On Flange is suitable for pipeline systems with relatively low pressure levels and not serious pressure fluctuations, vibrations, and shocks. The advantage of  flat welding flange is that it is easier to center the  flat welding flange during welding and assembly, and the price is relatively cheap, so it has been widely used. Flat welding flange is a widely used connection method in industrial pipeline systems. The application occasions generally include the following aspects:

1. Pipeline connection in various chemical pipeline systems, petroleum, natural gas, water treatment and other industrial fields;
2. Connection method in mechanical manufacturing fields such as automotive parts and mechanical equipment;
3. Connection of production pipeline systems in industries such as food, pharmaceuticals, and bioengineering.

Quality control of flat welding flange:
As a pipeline connector, flat welding flange needs to have good sealing performance and pressure resistance during use. Therefore, quality control of flat welding flange is very important.

Manufacturers should strictly follow relevant standards to ensure that the size and shape of the flat welding flange meet the requirements. Secondly, appropriate processes and materials should be adopted during the production process to ensure that the material and strength of the flat welding flange meet the requirements. Finally, the produced flat welding flange needs to undergo strict inspection and testing to ensure its quality.

Notes:
When using flat welding flanges, you need to pay attention to the following points:

1. When selecting flat welding flanges, it is necessary to determine the physical properties such as strength and corrosion resistance of the selected materials based on the working medium and its pressure, temperature and other parameters.
2. Flat welding flanges need to be manufactured and installed in strict accordance with relevant standards.
3. Ensure the cleanliness of the flange and pipe connection surface during use to ensure sealing performance.
4. Pay attention to the tightening strength of the bolts during installation, and do not overtighten or over-loosen.
5. Avoid excessive vibration and impact to avoid affecting the connection effect of the flat welding flange.
6. The sealing performance of each connection part needs to be checked and maintained regularly.

In short, as a common pipe connection method, flat welding flange has the characteristics of easy operation, wide applicability and low cost, and is widely used in various industrial fields. However, during use, it is necessary to pay attention to the relevant working parameters and the standard requirements for manufacturing and installation to ensure the sealing performance and safety of the connection.

Read more: ANSI pipe flange standard or Stainless steel pipe fittings vs Carbon steel pipe fittings