How to choose the right gasket to match the flange?

What is flange?

The flange connection is easy to use and can withstand large pressures. In industrial pipelines, flange connections are widely used. In households, the diameter of the pipeline is small and it is low pressure, and flange connections are not visible. If there are flange connected pipes and equipment everywhere in a boiler room or production site.

Types of Flange

LTZC Bearings manufactuers large stock of high quality special welded flanges, flat welding flange, and socket welding flanges for petrochemical, shipbuilding, aerospace, and have become many industry standards.

Features of flange

The flange adopts the principle of surface sealing, with strong connection tightness, which can ensure the safe and reliable operation of the fluid conveying system. And it can still operate stably under high temperature or high pressure working conditions. The manufacturing cost of flanges is relatively low, and assembly through fixing methods such as screws or nuts is simple, which can improve production efficiency and reduce production costs. The flange is designed considering factors such as disassembly, cleaning, maintenance, and replacement, which has good operability and can reduce labor, material, and time costs.

Socket welding is usually used for small pipes with a diameter less than DN40 and is more economical. Butt welding is usually used for parts above DN40. Socket welding is the process of first inserting the socket and then welding it (for example, there is a flange called a socket flange, which is a convex welding flange that is connected to other parts (such as valves). The connection form of butt welding flange and pipeline welding, socket welding usually involves inserting the pipeline into the flange and welding it, while butt welding uses the butt welding flange to weld the pipeline to the mating surface. Although X-ray inspection is not possible, butt welding is acceptable. Therefore, it is recommended to use butt welding flanges to improve the requirements for welding inspection.

How to choose the right gasket to match the flange?

There are a number of factors to consider when choosing the right gasket to match the flange, but here are the key points:

Flange type: different types of flanges, their sealing surface forms are different, and the corresponding sealing gasket needs to be matched. For example, flat gaskets are often used for flat flanges; The convex flange can be selected with a metal wound gasket with an inner ring; The tongue and groove flange is suitable for the use of special gaskets for the tongue and groove surface, which can be better embedded in the groove to ensure the sealing effect.

Pressure class: The gasket is selected according to the working pressure of the piping system. Systems with higher pressure require gaskets with better compressive resistance and sealing properties, such as metal gaskets or high-strength composite gaskets; For low-pressure systems, gaskets made of rubber and other materials can be used. For example, in low-pressure water systems below 1.0MPa, rubber gaskets are usually sufficient to meet sealing requirements; However, in high-pressure steam systems of 10MPa or more, gaskets with good pressure resistance, such as metal toothed gaskets, may be required.

Temperature range: The operating temperature has a great influence on the choice of gasket material. In high-temperature environments, gaskets need to have good high-temperature resistance, such as graphite gaskets, metal gaskets, etc., which can maintain stable sealing performance at high temperatures; The low-temperature environment requires the gasket to have good flexibility and low-temperature adaptability, such as PTFE gasket can still maintain a certain elasticity at low temperature. For example, in the high-temperature heavy oil pipeline of the refining unit (the temperature can reach more than 300°C), it is advisable to use metal graphite winding gasket; In liquefied natural gas (LNG) pipelines (temperatures as low as -162°C), low-temperature resistant PTFE or special low-temperature rubber gaskets are used.

Characteristics of the medium: The corrosiveness, toxicity, flammability and explosiveness of the medium determine the choice of gasket material. For corrosive media, corrosion-resistant gasket materials should be selected, such as PTFE, ethylene propylene rubber, etc.; For toxic or flammable and explosive media, the gasket is required to have higher sealing reliability, and the metal gasket or high-performance composite gasket can be selected, and the corresponding sealing structure is adopted. For example, PTFE gaskets should be used in pipelines transporting sulfuric acid in chemical production; In gas transmission pipelines, in order to prevent gas leakage, metal wound gaskets can be used with reinforced sealing structures.

Installation space: If installation space is limited, you need to choose a gasket with a thin or compact structure for easy installation and removal. For example, in some equipment connections where space is limited, thin metal gaskets or flexible graphite composite gaskets can be used, which can not only ensure the sealing effect, but also adapt to the limited installation space.

Cost factor: On the premise of meeting the sealing requirements, cost is also one of the factors that need to be considered. Rubber gaskets and other products are low in cost and suitable for general industrial occasions; However, metal gaskets and composite gaskets made of special materials have high costs and are usually used in important occasions with strict sealing requirements and complex working conditions. For example, in ordinary industrial water pipes, it is more economical to use rubber gaskets; However, in fields with extremely high requirements for sealing performance and safety, such as aerospace and high-end chemical industries, high-performance metal sealing gaskets are used even if the cost is high.

Flange supplier

LTZC providing a series of services such as research and development, design, production, and sales of  flange products.If you are looking for flange supplier, please contact us for the latest quotation.