Как правильно использовать приварной фланец

Welding flanges are widely used in piping systems across industries such as oil and gas, нефтехимический, производство электроэнергии, очистка воды, и судостроение. They provide a reliable connection between pipes, клапаны, и оборудование, ensuring mechanical strength and leak-free performance. Однако, to achieve these benefits, welding flanges must be used correctly. Improper handling, сварка, or installation can lead to joint failure, утечка, or reduced service life.

This article explains how to use welding flanges correctly, covering preparation, welding techniques, инспекция, and maintenance to ensure long-term reliability and compliance with industry standards.

What Is a Welding Flange

A welding flange is a type of pipe flange designed to be permanently attached to the pipe by welding. The two most common types are:

Приварной фланец с горловиной (ВН) – Features a long tapered hub for butt welding to the pipe, offering superior strength and stress distribution.
Съемный фланец (ТАК) – Fits over the pipe end and is fillet welded both inside and outside, easier to install but suitable for lower-pressure service.

В Сасафланж, welding flanges are manufactured to meet ASME, EN, DIN, and other international standards, ensuring compatibility and performance in various industrial applications.

Step-by-Step Guide to Using Welding Flanges Correctly

1. Select the Right Welding Flange

Совместимость материалов – Match flange material to the pipe material to avoid galvanic corrosion and ensure weld quality.
Класс давления – Choose according to system pressure (например, Сорт 150, Сорт 300, Сорт 600).
Тип фланца – Weld neck for high-pressure/high-temperature systems, slip-on for low-to-medium pressure systems.
Стандартное соответствие – Follow ASME B16.5, ASME B16.47, EN 1092-1, or other applicable standards.

2. Prepare the Pipe and Flange

Check Dimensions – Ensure bore size, внешний диаметр, and bolt holes match the mating flange.
Очистка поверхности – Remove rust, масло, смазка, and dirt from both the pipe and flange.
Bevel the Pipe End – For weld neck flanges, bevel the pipe to the correct angle for butt welding.
Inspect for Defects – Ensure there are no cracks, вмятины, or other defects on the flange sealing face.

3. Align the Flange and Pipe

Правильное выравнивание – Misalignment can cause stress concentration, утечка, and premature failure.
Use Alignment Tools – Spacers, jigs, or pipe alignment clamps help maintain accuracy.
Match Bolt Holes – Ensure the bolt holes are in the correct orientation before welding.

4. Welding Procedure

Qualified Welders – Only certified welders should perform welding according to WPS (Спецификация процедуры сварки).
Preheating – Some materials, such as alloy steels, require preheating to prevent cracking.
Weld Type:
- Butt Weld for weld neck flanges – Provides a smooth internal bore for fluid flow.
- Fillet Weld for slip-on flanges – Requires welding on both the inside and outside.
Multiple Pass Welding – For thicker flanges, apply multiple passes to ensure complete penetration.
Avoid Overheating – Excess heat can distort the flange or damage sealing surfaces.

5. Послесварочный контроль

Визуальный осмотр – Check for cracks, подрезать, пористость, or incomplete fusion.
Неразрушающий контроль (неразрушающий контроль) – Use ultrasonic testing (ЮТ), magnetic particle testing (МТ), or liquid penetrant testing (ПТ) as required by the project specification.
Dimensional Check – Verify that the flange remains within tolerance after welding.

6. Gasket Installation and Bolt Tightening

Выбор прокладки – Choose the correct gasket type (спиральная рана, соединение кольцевого типа, soft gasket) for the service condition.
Bolt Lubrication – Apply approved lubricant to threads and nut faces for accurate torque.
Tightening Pattern – Use a cross or star pattern in multiple passes to ensure even compression.
Контроль крутящего момента – Follow specified torque values for the bolt size, материал, и тип прокладки.

7. Испытание давлением

Гидростатические испытания – Checks for leaks at a pressure higher than operating pressure.
Пневматические испытания – Used for low-pressure systems or where water is unsuitable.
Safety Precautions – Always follow safety standards when performing pressure tests.

8. Техническое обслуживание и осмотр

Regular Checks – Inspect bolts, прокладка, and sealing surfaces periodically.
Corrosion Prevention – Apply protective coatings or anti-corrosion tape if exposed to harsh environments.
Re-Torque Bolts – For systems subject to vibration or thermal cycling, bolts may need re-tightening during initial operation.

Common Mistakes to Avoid When Using Welding Flanges

Incorrect Material Selection – Leads to corrosion or thermal expansion mismatch.
Poor Alignment – Causes leakage and uneven gasket compression.
Over-Tightening Bolts – Damages gaskets and sealing surfaces.
Skipping NDT – Increases the risk of undetected weld defects.
Inadequate Cleaning – Oil, ржавчина, or debris can compromise weld quality and sealing.

Advantages of Correct Welding Flange Usage

Leak-Free Connections – Proper welding and bolt tightening ensure tight seals.
Увеличенный срок службы – Minimizes wear and corrosion.
Высокая прочность – Welding creates a permanent, strong bond between pipe and flange.
Универсальность – Suitable for various pressure classes, температура, and environments.

Заключение

Using welding flanges correctly involves more than just attaching them to a pipe. From selecting the right flange type and material to proper welding, инспекция, и обслуживание, every step must follow strict industry standards and best practices. When installed and maintained correctly, welding flanges deliver excellent sealing performance, структурная целостность, and long service life in industrial piping systems.

With expertise in manufacturing high-quality welding flanges and providing technical guidance, Сасафланж ensures that customers get reliable, совместимый, and durable flange connections for even the most demanding applications.