溶接フランジの正しい使い方

溶接フランジは、石油やガスなどの業界の配管システムで広く使用されています。, 石油化学, 発電, 水処理, そして造船. パイプ間に信頼性の高い接続を提供します。, バルブ, と設備, ensuring mechanical strength and leak-free performance. しかし, to achieve these benefits, welding flanges must be used correctly. Improper handling, 溶接, or installation can lead to joint failure, 漏れ, or reduced service life.

This article explains how to use welding flanges correctly, covering preparation, welding techniques, 検査, 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:

溶接ネックフランジ (WN) – Features a long tapered hub for butt welding to the pipe, offering superior strength and stress distribution.
スリップオンフランジ (それで) – Fits over the pipe end and is fillet welded both inside and outside, easier to install but suitable for lower-pressure service.

で ササフランジ, welding flanges are manufactured to meet ASME, EN, DIN, およびその他の国際規格, ensuring compatibility and performance in various industrial applications.

Step-by-Step Guide to Using Welding Flanges Correctly

1. Select the Right Welding Flange

材質の適合性 – Match flange material to the pipe material to avoid galvanic corrosion and ensure weld quality.
圧力クラス – Choose according to system pressure (例えば, クラス 150, クラス 300, クラス 600).
フランジタイプ – Weld neck for high-pressure/high-temperature systems, slip-on for low-to-medium pressure systems.
規格への準拠 – Follow ASME B16.5, ASME B16.47, EN 1092-1, またはその他の該当する規格.

2. Prepare the Pipe and Flange

Check Dimensions – Ensure bore size, 外径, and bolt holes match the mating flange.
表面の洗浄 – Remove rust, 油, グリース, 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, へこみ, or other defects on the flange sealing face.

3. Align the Flange and Pipe

適切な位置合わせ – Misalignment can cause stress concentration, 漏れ, 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 (溶接手順仕様書).
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. Post-Weld Inspection

目視検査 – Check for cracks, アンダーカット, 気孔率, or incomplete fusion.
非破壊検査 (NDT) – Use ultrasonic testing (ユタ州), magnetic particle testing (MT), or liquid penetrant testing (PT) as required by the project specification.
Dimensional Check – Verify that the flange remains within tolerance after welding.

6. Gasket Installation and Bolt Tightening

ガスケットの選択 – Choose the correct gasket type (螺旋状の傷, リングタイプジョイント, ソフトガスケット) 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.
トルク制御 – Follow specified torque values for the bolt size, 材料, とガスケットの種類.

7. 圧力試験

静水圧試験 – Checks for leaks at a pressure higher than operating pressure.
空気圧試験 – Used for low-pressure systems or where water is unsuitable.
Safety Precautions – Always follow safety standards when performing pressure tests.

8. 保守・点検

Regular Checks – Inspect bolts, ガスケット, 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, さび, 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.
耐用年数の延長 – Minimizes wear and corrosion.
高強度 – Welding creates a permanent, strong bond between pipe and flange.
多用途性 – Suitable for various pressure classes, 温度, and environments.

結論

Using welding flanges correctly involves more than just attaching them to a pipe. From selecting the right flange type and material to proper welding, 検査, そしてメンテナンス, every step must follow strict industry standards and best practices. When installed and maintained correctly, welding flanges deliver excellent sealing performance, 構造的完全性, and long service life in industrial piping systems.

With expertise in manufacturing high-quality welding flanges and providing technical guidance, ササフランジ ensures that customers get reliable, 準拠した, and durable flange connections for even the most demanding applications.