In the period from March 27 to April 1, 2024, Wellons.RU LLC completed work on the project to replace the damaged clamping / diaphragm blocks of the walking hearth heating furnace. These works were carried out under the terms of an EPC contract, including engineering, selection and supply of materials, as well as installation work on the installation of a new refractory diaphragm of the furnace, consisting of composite refractory blocks.
ENGINEERING.
In October-November 2023, after the conclusion of a contract for the manufacture and installation of LOI-type reheating furnace clamping units, the specialists of Wellons.RU LLC developed the refractory blocks themselves in accordance with the main dimensions of the manufacturer's plant. At the design stage, it was necessary to adapt the suspension system of these blocks, which guarantees the most reliable fastening of blocks with a unit weight of 120 to 200 kg, when they are operated in the high-temperature zone of the furnace (~1150–1250°C). The products were made according to individual drawings. To ensure the required strength and heat resistance, the products were made of high-aluminate thixotropic concrete with an Al2O3>70% content. In order to fix these blocks to the bearing beam of the diaphragm, special fasteners/brackets made of heat-resistant steel were developed and manufactured, which in turn are attached with heat-resistant bolts and nuts to the segments of the bearing beam of the diaphragm.
Within the framework of this contract, a Work Execution Plan (WEP) was also developed, which includes all the necessary sections on the organization of work, technology for work performance, industrial safety measures and other necessary sections.
This technical documentation formed the basis for the actual implementation of the project for the installation of a new diaphragm for the clamping of the heating furnace at the metallurgical plant.
MANUFACTURE AND DELIVERY.
We consider it necessary to note the timely work of the plant's specialists in the preparation and conclusion of the contract for this project. This is especially important, because the production of drawing products, and even more so similar furnace clamping blocks, with a unit weight of 120 to 200 kg, takes at least 60-80 days from the date of placing the order, if there is free capacity of the plant. This is primarily due to the manufacture of individual molds and other special tooling for fabrication of such specific drawing items of the project. Timely placement of the order made it possible to obtain high-quality products for replacing the pin / diaphragm of the LOI type heating furnace without haste, in compliance with all stages of the technological process of firing products in tunnel kilns at a temperature of ~1300°C.
The fastening elements of the blocks/brackets are made of high-alloy heat-resistant steel AISI 310S (20X23N18) with a thickness of 8 mm, complete with a bolt fastening (bolt + nut + washer) made of heat-resistant steel A2).
All materials, including fastening elements, were delivered to the customer's site in advance before the start of the overhaul, which in turn made it possible to carry out a number of preparatory works in order to reduce the time for repairing the furnace as a whole.
FURNACE DIAPHRAGM REPLACEMENT WORKS.
1. PREPARATORY WORK:
As part of the preparation for the overhaul of the reheating furnace, the specialists of the repair service of the enterprise manufactured new segments of the bearing beam of the furnace clamping, as well as made temporary metal structures / slipways, on which these segments were installed, according to the manufacturer's recommendations.
2. PRELIMINARY ASSEMBLY OF FURNACE CLAMPING ELEMENTS:
Nodal assembly of furnace clamping elements was carried out on pre-assembled slipways with pre-suspended and fixed new segments of the furnace carrier beam.
Each segment of the I-beam (1400 mm long – 6 pcs. and 1225 mm – 2 pcs.), on the lower flange, has drilled holes for bolt attachment of the suspension / brackets (three holes for one diaphragm block). Five or four blocks of a certain standard size are hung on each beam segment in the order determined by the design documentation of the manufacturer "LOI Italimpianty".
In front of the attachment of the block/blocks itself, a metal suspension/bracket made of heat-resistant steel with a thickness of 8 mm is installed, with the help of bolts, nuts and washers, also made of heat-resistant alloy steel.
After the installation of the last first bracket, the final broaching of the bolted connection, the corresponding block, with the help of the existing overhead crane, is inserted into the bracket and adjusted to the design position. For safer work, together with the specialists of the company's repair service, a block feeding mechanism was developed based on a rack and pinion jack and a U-shaped holder mounted on a trolley. With the help of an overhead crane, the unit, its lower part is installed in a U-shaped bracket and raised to a given height using a rack and pinion jack, after which, due to the movement of the trolley, it is placed in a bracket and lowered to the design position.
After all the blocks are installed in the design position and aligned, in order to strengthen the suspension of the blocks (to prevent possible deformation / "opening" of the bracket under the influence of high temperatures and a large unit weight of the blocks up to ~ 220 kg), the "reinforcement" / side plates are installed and welded directly to the bracket using electric arc welding.
As a result of the preparatory work carried out for the manufacture of assembly slipways and segments of the load-bearing beam of the furnace clamping, the preliminary assembly of the furnace clamping segments was carried out before the furnace shutdown, which made it possible to ensure the minimum time for repair work on the replacement of the diaphragm of the LOI type walking hearth reheating furnace.
3. DISMANTLING OF THE EXISTING SUSPENDED ELEMENTS OF THE FURNACE CLAMPING.
After the heating furnace was shut down, the repair service specialists dismantled the auxiliary equipment (sections of air ducts, gas pipeline, etc.) at the upper level of the furnace, to ensure unhindered access to the elements of the furnace clamping beam and, accordingly, to dismantle these elements.
Before dismantling the segments of the existing furnace beam with the existing blocks, the mineral wool seal between the suspended clamping elements and the refractory, heat-insulating lining of the roof of the first and second chambers is removed. The space between the lining and the blocks should be free to avoid wedging the blocks when they are lifted and removed from the furnace.
4. INSTALLATION OF PRE-ASSEMBLED BEAM SEGMENTS OF THE FURNACE CLAMPING.
After the dismantling of all segments of the furnace clamping beam is completed, a visual inspection is carried out, the joints of the interfaces of the refractory lining of the first and second chambers, i.e. the place of installation of the new furnace clamping beam system, are carried out. Possible tides, broken sections of the old lining, slag, scale, etc. are removed to ensure the unimpeded passage of suspended elements/blocks between the two ceilings (lining of the roof of the first and second chambers).
Installation of pre-assembled beam segments starts from the extreme position. Installation is carried out using an electric overhead crane with the installation of beam segments in the design position.
The main broaching of bolted joints is carried out after all beam segments are installed in the design position. In case of misalignment of the bolt holes, the cross beams are welded by electric arc welding in the places where they are attached.
After the installation and fastening of all segments of the furnace beam to the design position, the joints between the newly installed suspension blocks and the existing lining of the roof of the first and second chambers are "embossed". For this purpose, Cerablanket-128 ceramic fiber with a thickness of 13 mm is used.
After the completion of the installation of all segments of the load-bearing beam of the furnace clamping, the space between the brackets for fastening the clamping elements is closed with ceramic fiber to the upper level of the existing thermal insulation layer of the arch lining.
PORTFOLIO OF WORKS ON THE REPLACEMENT OF FURNACE CLAMPING ELEMENTS.
PROJECT SUMMARY:
The project for the replacement of damaged elements of the walking hearth furnace clamp, thanks to the timely conclusion of the contract, as well as the excellent preparatory work on the part of the specialists of the repair service of the plant, was completed in the shortest possible time. Without taking into account the time of work allocated for parallel work on the restoration of the working layer of the refractory lining and mechanical work on the restoration of the walking hearth beams of the heating furnace, the installation of the ready-made assembled segments of the load-bearing beam of the furnace clamping with suspended elements/blocks took no more than two days (plus two days for the assembly of the beam segments of the furnace clamping), which is significantly less than the approved schedule for the overhaul of the furnace.
The scope of work under the contract for the replacement of damaged elements of the furnace clamping with new ones was completed in full.
