In the period from April 17 to April 23, 2024, Wellons.RU LLC completed work on the project to replace the refractory lining of the flat roof of the thermal oil unit (TMU) at the Customer's site. These works were carried out under the terms of the EPC contract, including engineering, selection and supply of materials, as well as installation work on the installation of a new refractory lining of the TMU vault.
ENGINEERING.
Within the framework of the contract for the performance of lining works, the specialists of Wellons.RU LLC developed a design of the refractory lining of the flat vault of the thermal oil plant, with the selection of technical solutions and the necessary refractory materials, anchor products (ceramic and metal anchors) and their calculation. Based on the graphic and calculation part of the project, orders were placed for the manufacture of refractory, heat-insulating materials, as well as for the manufacture of anchor products. The products were made according to individual drawings. All materials were manufactured in the shortest possible time and delivered to the plant site before the start of the agreed work period.
All materials are selected in accordance with the technical conditions of the boiler plant operation and are designed even for more stringent temperature regimes. For example, refractory concrete with an Al2O3>55% content used in this project is recommended for lining thermal units with an operating temperature of up to 1400°C, ceramic anchors with an Al2O3>70% content have an operating temperature of more than 1500°C, heat-resistant metal anchors are made of heat-resistant steel AISI 310S, rolled thermal insulation Cerablanket-128, with its insignificant weight, has an operating temperature of 1250°C. The use of these materials guarantees the fulfillment of the requirements of the Customer's technical specifications and significantly exceeds the requirements of the specified temperature regime of 950-1050°C in the furnace of the thermal oil unit.
Within the framework of this contract, a Work Execution Plan (WPP) 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.
BREAKING OUT THE REFRACTORY.
Before the start of dismantling works, in order to prevent the possible destruction of the grates as a result of pieces of refractory lining falling from a great height, scaffolding and dense wooden flooring, covering the entire cross-section, were erected both at the top, in the area of direct breakout of the refractory, and in the lower part, at the grate.
The refractory was broken out through the upper covers of the body of the vaulted part of the boiler furnace. For access to the thermal insulation and refractory lining, the metal sheets of the main body, as well as the metal protective plates laid along the transverse beams of the metal structure of the vault, were dismantled.
A preliminary inspection of the condition of the maps of the horizontal section of the flat roof of the boiler furnace showed the presence of two sagging maps and a large number of cracks in the refractory. During the breakout of the refractory, a significant number of torn ceramic anchors (more than 60%) were found, which suggests that the vault cards were actually held by previously installed metal clamps (metal rods with a welded heel), mounted through drilled holes in the concrete and fixed on the I-beams of the metal structures of the vault. Thanks to them, the vault did not collapse during operation. After breaking out the refractory of the working layer, all the beams of the metal structure of the vault were cleaned from the remnants of the old suspension elements of anchors, studs, etc.
Scrap of refractory concrete, materials of the thermal insulation layer were removed from the furnace of the boiler, removed and disposed of at a specialized landfill for construction and industrial waste by a company licensed to handle these types of waste. These measures are confirmed by the contract for waste disposal and accompanying documents, copies of which are given to the plant's specialists.
The breakout of the refractory of the flat roof of the boiler is shown in the most detailed detail in the video "REPLACEMENT OF THE LINING OF THE FLAT VAULT OF THE TMU No. 2. BREAKING OUT THE REFRACTORY".
LINING WORKS.
In the process of preparatory work, namely during the marking of the vault maps, the places of installation of anchor products, the actual discrepancy(both in number and location) of the cross beams in relation to the original design of the manufacturer was revealed. Of the seven cross beams of the original design, only two remain! The standard size of the newly installed beams also does not correspond to the design one - an ordinary narrow-flange I-beam with a flange width of 65 mm was used instead of a wide-flange I-beam with a flange width of 100 mm.
Together with the specialists of the plant, it was adopted A decision to use the existing beams installed after the fact (in violation of the manufacturer's design), due to the lack of preparatory work necessary to restore the metal structures to the design position, as well as due to a significant increase in the repair period (at least up to 3-5 days, subject to the availability of all the necessary materials, namely a wide-flange I-beam 100 mm in the required quantity).
In this regard, we are forced to make small changes that do not affect the structural strength of the refractory lining of the horizontal section of the flat roof of the boiler furnace as a whole. Changes have been made to the size and order of the cards, as well as to the layout of metal anchors and their fastening.
1. RESTORATION OF WALL LINING.
In the process of discussing the design of the existing beams of the boiler vault with the specialists of the plant, the issue of restoring the brickwork of the walls was raised. In accordance with the terms of reference, we undertake to restore the masonry destroyed in the process of breaking out the refractory of the working layer of the vault. We would like to draw your attention to the fact that not a single brick was destroyed during the dismantling of the refractory concrete of the vault, all the bricks were in their places safe and sound (this was shown and explained to the specialists of the plant). At the same time, on the side walls above the technological hatch (right wall) and at the junction of the panels in the upper part (left wall) there were large chips of bricks formed during the technical operation of the boiler. At the request of the plant's specialists, we restored these sections of the walls to normal technical condition from refractory bricks available in the plant's warehouse.
2. LINING OF THE HORIZONTAL SECTION OF THE FLAT ROOF OF THE BOILER FURNACE:
Preparation of ceramic anchors: Prior to the installation of the lining of the boiler furnace vault cards, it is necessary to prepare the ceramic anchors for installation by applying bituminous mastic in one layer (mastic layer thickness up to 1 mm). A layer of mastic is applied to the working surface of the anchor, i.e. to the height of immersion of the anchor in the working layer of the refractory with a small margin. In our case, ~250 mm. This work must be done in advance, to ensure the hardening of this layer, until the anchors are installed in place.
ДThis bitumen layer acts as a thermal joint between the body of the ceramic anchor and the layer of refractory concrete. This layer is necessary to compensate for the different thermal expansions of the anchor and concrete, since the materials have different chemical compositions and, accordingly, different coefficients of thermal expansion.
Additional thermal insulation of the boiler furnace body beams – in the course of the work, it was discovered that there was no thermal insulation layer at the boundary of the concrete vault / upper load-bearing beams of the boiler furnace, i.e. during the previous works, the thermal insulation layer was removed, and the refractory concrete of the working layer was directly poured up to the square load-bearing beam of the boiler furnace. To prevent the impact of high temperatures on the load-bearing metal structures of the furnace due to the high In order to ensure the thermal conductivity of refractory concrete, the specialists of Wellons.RU LLC made a thermal insulation layer using roll thermal insulation (Cerablanket-128), 50 mm thick, and refractory bricks 65 mm thick.
Installation of anchor products: marking and installation of anchors (ceramic and metal) is carried out on the basis of project drawing No. VB56.01-01-01, on site, due to the actual change in the location of the transverse beams of the metal structures of the horizontal section of the vault part of the boiler furnace. Metal anchors were welded in place directly to the beams of the roof of the horizontal section.
In order to ensure the most reliable fastening of the ceramic anchors of the outer row of vault maps (4th row, the border of the interface of the horizontal and inclined sections of the flat vault), an additional row of T-beams was installed for hanging the anchors. It is not possible to use an existing beam due to the fact that the anchor falls almost on the temperature seam of the card and such installation of the anchor will not ensure the distribution of the uniform load of the refractory on all the anchors of the card. In this case, the risk of cracks and chips, as well as the breakage of anchors, is multiplied.
Construction of cross beams. Drawing your attention earlier to the difference in the standard dimensions of the transverse beams of the original design (wide-flange) and the beams installed in previous vault repairs (narrow-flange), we assumed that this would be a possible problem in the suspension of ceramic anchors. When hitching on adjacent beams, the lower level of ceramic anchors does not coincide in plane ~ by 20 mm due to the difference in the width of the flange of the I-beams – this is not acceptable, because it does not allow to ensure the horizontal plane of the monolithic lining of the vault when arranging formwork and pouring refractory concrete of the working layer. To level the horizon of the ceramic anchors, it was decided to install an additional metal strip with a thickness of 6 mm (width 40 mm, length ~ 200 mm) on the narrow-flange I-beam of the cross beam to equalize the width of the lower flange of the beams and, accordingly, align the lower border of the ceramic anchors horizontally.
At the stage of installation of anchor products, it is necessary to pay attention to the fastening of ceramic anchors. After the ceramic anchors are suspended in the design position, they are fastened with wedges, which are removed without fail after laying the refractory working layer, removing the formwork.
Due to the presence of longitudinal load-bearing beams of the ceiling of the boiler furnace, some of the fastenings of the ceramic anchors of the side cards are installed by welding one side of the suspended elements, in order to avoid cutting the load-bearing structures and, accordingly, a possible reduction in the load-bearing capacity of these floor beams. These forced measures do not have a negative impact on the structure of the flat arch lining as a whole.
Before the formwork is installed, a 5-10 mm thick gasket of thermal insulation roll material is glued to the end part of the ceramic anchors to prevent concrete from getting between the anchor and the formwork. The end part of the ceramic anchor must remain clean, without a layer of concrete. This measure is necessary to prevent possible chips due to thermal expansion of the ceramic anchor.
After the formwork is installed, the pre-prepared concrete mass BORTCAST-55W is poured. An immersion vibrator is used to compact the concrete mass. To form temperature joints, the side surfaces of the cards are glued with a roll of thermal insulation material.
The relining process continues along the entire horizontal section of the flat roof of the boiler according to the procedure described above.
Installation of a thermal insulation layer. After the completion of the pouring of the refractory concrete of the working layer, the laying of a 200 mm thick thermal insulation layer made of rolled thermal insulation material is started. The roll material is cut to size and laid as tightly as possible. The next layer is laid with an offset, with overlapping of the joints.
Upon completion of the installation of the thermal insulation material, protective metal plates are installed on top of the thermal insulation layer. At the end of the work, the working space is covered with metal sheets of the sheathing of the horizontal section of the flat roof of the boiler.
PORTFOLIO OF WORKS ON THE REPLACEMENT OF FURNACE CLAMPING ELEMENTS.
PROJECT SUMMARY:
Due to the use of highly qualified lining specialists, as well as the assistance of the plant's specialists in solving organizational issues, the project for replacing the refractory lining of the horizontal section of the TMU No. 2 vault was completed in the shortest possible time. Work on this project from the beginning of work on breaking out the refractory to the end of the work took 7 days, which is significantly less than the approved schedule for the repair of thermal oil unit No. 2.
The scope of work under the contract for the replacement of the refractory lining of the horizontal section of the furnace of the thermal oil unit was completed in full.
Recommendations for the installation of transverse beams of metal structures of the horizontal section of the flat vault of TMU: due to the fact that in the process of previous repairs to replace the lining of the vault, significant changes were made in the metal structures of the vault (in terms of the number of beams, their standard size, distance between beams, etc.), we strongly recommend that the requirements for the manufacture and installation of new transverse beams be reflected in the new terms of reference for future repairs (or, for example, repair of the vault of TMU No. 1), in order to form "correct" maps over the entire area of the horizontal section. That is, the contractor must select the necessary distance between the cross beams for uniform attachment of ceramic anchors, for the same length / width of the cards in order to evenly distribute the load from the refractory on the metal structures of the roof of the boiler top.
