MODERNIZATION OF THE RECOVERY BOILER FLOOR AREA – REPLACEMENT OF FLOOR TUBES AND ELBOWS (SANICRO® 38)

April 29, 2026

Sweden | The recovery boiler modernization using Sanicro® 38 included the replacement of floor tube sections and elbows in the most heavily loaded area of the installation.

PROJECT SCOPE: REPLACEMENT OF FLOOR TUBE SECTIONS AND ELBOWS USING SANICRO® 38 MATERIAL

We carried out specialized mechanical and welding works involving the modernization of key components of the recovery boiler floor.
The scope included the replacement of worn sections of tubes and elbows in the most heavily loaded furnace zone, using Sanicro® 38 material with enhanced corrosion resistance.

PRO-WELDING INDUSTRY SERVICES

PROJECT PHASES AND KEY CHALLENGES

1. Dismantling and Access Preparation

Work began with preparing access to the boiler bottom area and the pressure parts of the installation:

Dismantling of primary air ducts
Selected sections of the primary air ducts were removed to expose the working area.
This operation was necessary to gain access to the boiler floor and elbows, as well as to ensure safe conditions for installation and welding activities.
Cutting out worn tube and elbow sections
Degraded sections of floor tubes and elbows were removed by cutting them out from the existing system.
The work was carried out while maintaining the geometry of the installation and preparing the system for the installation of new components.
Edge preparation for new joints
The ends of the existing tubes were prepared for new welded joints through cleaning and fitting in accordance with the requirements for pressure parts.

2. Installation and Welding of Sanicro® 38 Tubes

Following system preparation, new tube panels made of high-alloy steel were installed:

Installation and fitting of panels
New studded floor tube sections made of Sanicro® 38 were installed.
The panels were fitted with the required slopes to ensure proper flow of molten smelt during boiler operation.
Execution of circumferential welds
The new sections were connected to the existing system using circumferential welds.
Welding was carried out in accordance with procedures dedicated to high-alloy materials, including Sanicro® 38.
Membrane welding
Membrane welding of fins between the tubes was performed, creating a continuous and tight boiler floor structure.
This solution ensures proper operation of the installation under high-temperature conditions and exposure to aggressive environments.

3. Quality Control and NDT Inspection

All completed welds were subjected to quality control:

Penetrant Testing (PT)
Surface inspection of welds to detect discontinuities and confirm weld quality.
Radiographic Testing (RT)
Full radiographic inspection of circumferential welds, confirming the correctness of weld execution in pressure parts.

4. Reinstallation of Infrastructure

After completion of installation works and positive inspection results:

primary air ducts were reinstalled;
full functionality of the under-boiler air distribution system was restored.

WHY SANICRO® 38?

The use of Sanicro® 38 in the floor and elbow sections results directly from the operating conditions of the recovery boiler.
This material is characterized by high resistance to chemical corrosion caused by sodium compounds, which translates into:

increased durability of components
reduced wear in the most heavily loaded areas
minimized risk of failures and unplanned shutdowns

SUMMARY

The result of the project is the restoration of full technical performance and the assurance of stable, reliable operation of the boiler in its most heavily loaded zone.

The use of Sanicro® 38 enabled the installation to operate under exposure to aggressive chemical compounds typical for recovery boilers. Combined with properly executed installation and welding processes, this results in extended service life of the modernized components.

All completed welds were subjected to a full scope of non-destructive testing (PT and RT), which confirmed the quality of workmanship and compliance with the requirements for this type of installation.

INDUSTRIAL WELDERS AND FITTERS IN EUROPE

We deploy teams of highly qualified welders and fitters with proven experience in recovery boiler projects and other installations operating under high-temperature conditions and aggressive chemical environments.

We execute projects based on proven work organization, qualified welding procedures, and close on-site cooperation between teams — from preparation, through installation, to final quality control.

This enables us to efficiently deliver complex scopes during shutdowns, while meeting strict quality requirements and project schedules.

Contact us to discuss the scope and execution options for your project.