Cara Menggunakan Flange Las dengan Benar

Flensa las banyak digunakan dalam sistem perpipaan di berbagai industri seperti minyak dan gas, petrokimia, pembangkit listrik, pengolahan air, dan pembuatan kapal. Mereka menyediakan koneksi yang andal antar pipa, katup, dan peralatan, ensuring mechanical strength and leak-free performance. Namun, to achieve these benefits, welding flanges must be used correctly. Improper handling, pengelasan, or installation can lead to joint failure, kebocoran, or reduced service life.

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

Flensa Leher Las (WN) – Features a long tapered hub for butt welding to the pipe, offering superior strength and stress distribution.
Flensa Selip (JADI) – Fits over the pipe end and is fillet welded both inside and outside, easier to install but suitable for lower-pressure service.

Pada sasa lonjong, welding flanges are manufactured to meet ASME, EN, DIN, dan standar internasional lainnya, ensuring compatibility and performance in various industrial applications.

Step-by-Step Guide to Using Welding Flanges Correctly

1. Select the Right Welding Flange

Kompatibilitas Bahan – Match flange material to the pipe material to avoid galvanic corrosion and ensure weld quality.
Kelas Tekanan – Choose according to system pressure (misalnya, Kelas 150, Kelas 300, Kelas 600).
Tipe Flensa – Weld neck for high-pressure/high-temperature systems, slip-on for low-to-medium pressure systems.
Kepatuhan Standar – Follow ASME B16.5, ASME B16.47, EN 1092-1, atau standar lain yang berlaku.

2. Prepare the Pipe and Flange

Check Dimensions – Ensure bore size, diameter luar, and bolt holes match the mating flange.
Pembersihan Permukaan – Remove rust, minyak, gemuk, 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, penyok, or other defects on the flange sealing face.

3. Align the Flange and Pipe

Penyelarasan yang Tepat – Misalignment can cause stress concentration, kebocoran, dan kegagalan prematur.
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 (Spesifikasi Prosedur Pengelasan).
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

Inspeksi Visual – Check for cracks, melemahkan, porositas, or incomplete fusion.
Pengujian Non-Destruktif (NDT) – Use ultrasonic testing (UT), 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

Pemilihan Gasket – Choose the correct gasket type (luka spiral, sambungan tipe cincin, 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.
Kontrol Torsi – Follow specified torque values for the bolt size, bahan, dan jenis paking.

7. Pengujian Tekanan

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

8. Pemeliharaan dan Inspeksi

Regular Checks – Inspect bolts, paking, 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, karat, 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.
Kehidupan Layanan yang Diperpanjang – Minimizes wear and corrosion.
Kekuatan Tinggi – Welding creates a permanent, strong bond between pipe and flange.
Keserbagunaan – Suitable for various pressure classes, suhu, and environments.

Kesimpulan

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

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