Today, in large and small water supply networks in different regions of our country, various types of polyethylene pipes and fittings are used. Polyethylene has improved the performance of water supply pipelines due to its unique features and advantages compared to other types of pipes. These lines, which have different lengths and diameters, are set up by a variety of polyethylene pipes. But another important point is how they connect in different parts along the pipeline. Special connectors must be used to make changes in the plastic pipe flange route and to connect the polyethylene pipes to each other.
Unique Characteristics of plastic pipe flange
One of the types of connectors in polyethylene pipes in water supply networks are flanges. , which is used to change the direction of the pipes or change their diameter. Most flanges are made by casting, machining, or molding, and are made of steel, steel alloys, cast iron, and other metals. The flange connection includes three separate sections called flanges, gaskets and screws. The shape of the flange is in the form of a disc piece that is always a pair and with the help of bolts and nuts, it can connect the pipe piece together and it can also be easily opened. The flanges are sealed by a gasket placed between them.
According to the standards provided for fittings, the specifications of the flange, including the brand of the flange manufacturer, the nominal size of the pipe (the outer diameter of the pipe to which the flange will be welded), the amount of tolerable pressure (also called the flange class) , The shape of the flange surface (the shape of the flange surface is the most important part of a flange), holes (sometimes also expressed as wall thickness), flange materials (according to ASTM standard this number indicates the specifications of the raw materials used to make the flange). ) And the number or code for the heat treatment performed on the flange must be engraved on it.
Class in Flanges:
Flanges are divided into different classes according to the type of material and according to the pressure they bear.
1- Pressure classification class according to ANSI B 34 ٫ 16 standard. According to this standard, steel flanges and their alloys are divided into classes of 150-300-400-600-900-1500-1500- These numbers are the highest pressure according to PSI that flange They can withstand the maximum allowable temperature and typically have a working pressure of about 2.4 times that of the above numbers. (The relationship between pressure and temperature for different sexes is specified in the above standard)
2- Pressure classification according to ISO standard In this standard, the pressure tolerance of steel flanges and their alloys with PN is shown, which indicates the nominal pressure in BAR. For example, PN30 means the operating pressure of the flange is 30 BAR.
3. Standard pressure classification (API 6A-6B-6BX) These flanges have a higher pressure tolerance than ANSI group flanges and are classified into classes 5000-3000-2000-155000-10000.
Types of flanges and their applications
In general, due to the use of polyethylene flange dimensions, different types of flanges are used in pipeline connections.
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pipe flange 3/4 used in conventional equipment and services of polyethylene networks and are easy to install, and the pipe is easily aligned, and in addition, it does not require much care to cut the pipe to a certain length. It is also resistant to internal pressures of two-thirds and to fatigue loads of one-third of the welded nozzle flange, but its installation cost is slightly higher.
As mentioned, surface flanges are less resistant to shock and vibration. The distance from the tube to the end of the flange is sixteen inches. The mechanism of connection of this type of flange to the pipe is that the pipe is placed inside it so that it is as far as the thickness of the pipe plus 1.6 mm to 3.2 mm of pipe from the plate inside it and welding inside and outside. Lips to lips. Surface flange is available for all pressures and under ASME standard, its use is allowed for classes 300 and 150, and it is often used in places where there is no space for a welded collar flange.