In the period from July 3 to July 5, 2024, specialists of Wellons.RU LLC carried out work on repairing the refractory lining of the arched vaults of KVTm-5000 hot water boilers No. 1 and No. 2 at the customer's boiler house. These works were carried out under the terms of the EPC contract, including the supply of refractory materials, as well as lining work to restore the vaults of hot water boilers.
It should be noted that the refractory lining of the boilers, after a long period of operation since the major repairs for the complete replacement of the refractory lining (the lining of boiler No. 2 has been in operation for 5 years since 2019; boiler No. 1 - 4 years since 2020), is in normal technical condition as a whole. A detailed technical condition of the boiler lining is shown in the report of the technical inspection of the boilers, previously carried out by specialists of Wellons.RU LLC. For further safe operation of the boilers, the following works were recommended and carried out, shown in the relevant sections of this report.
1. WATER HEATING BOILER #1.
Arch No. 1 - the lower arch directly above the grate zone is in normal technical condition. The exception is the first / extreme row of the arch, which is the edge of the arch and is located directly in the combustion zone. Due to the fact that this row is primarily subject to various technological impacts that occur during boiler operation, it was decided to replace it in order to ensure reliable operation of the boiler during its further operation. To restore the arched segment / row, it was necessary to manufacture a circle / formwork, according to the design documentation, as well as the use of special shaped refractory bricks (double-sided end wedge) of two formats. The use of specially selected brick formats allows for the required radius of the arched arch without cutting / hewing the brick. The brick is laid on a mortar prepared on the basis of fireclay mortar. After installing the lock brick, the circle is removed.
To provide additional strength to the structure of the first outer row of the vault, to avoid its extrusion (for example, from the effect of thermal expansion forces of the refractory lining), a reinforcing layer of refractory concrete 50-70 mm thick was installed on three rows of bricks of the arch vault (450 mm long) over the entire surface of the vault. This reinforcing layer ensures maximum structural strength of the vault and, in the event of destruction of the first / outer row of the vault, prevents possible further destruction of the entire structure of the arch vault as a whole..
The vault was wedged with 2 mm thick lining plates to give the vault additional strength in places where the firebricks were slightly exposed (1-2 mm).
Arch No. 2 – due to the important technological component of this arch in the fuel combustion process, namely preventing the “direct flow” of the gas flow into the convective part of the boiler, the destroyed rows of the arched arch require restoration.
The technology for restoring arched rows/vault segments is similar to the procedure described in the section above.
During the repair work, four end rows of the arch vault No. 2 were restored..
Additionally, to ensure maximum structural strength of the vault, a reinforcing layer of refractory concrete was installed, preventing possible destruction of the arched vault from the edge side. The length of the reinforcing layer is 600 mm (four rows of bricks) over the entire surface of the arched segments..
The existing brickwork openings in the upper part of the arch segment (additional 5-7 rows) were completely cleaned, blown with compressed air and sealed with refractory concrete. In this case, refractory concrete, filling the cavity of the opening, forms a wedge that does not allow the brick in the upper part of the vault segment to fall out and thereby destroy the structure of the arch segment..
2. WATER HEATING BOILER #2.
Arch No. 1 – the condition of the vault lining is similar to the technical condition of vault No. 1 of boiler No. 1. In general, the vault lining is in normal condition. The first / outermost row of the vault was replaced according to the procedure described in the corresponding section of boiler No. 1.
Additionally, a reinforcing layer of refractory concrete with a thickness of 50-70 mm was installed over the entire surface of the arched segments for a length of 450 mm (three rows).
On the vault, from the inside (from the grate side) the vault was wedged along its entire length, in places where it was necessary. Wedging was done using 2 mm thick lining plates in visible places of small opening of the vault (1-2 mm).
Arch No. 2 – a detailed inspection showed the need to restore this arch, similar to arch No. 2 in boiler No. 1. To extend the service life of the lining of arch No. 2, four rows of arched segments were dismantled (one was destroyed during operation, three rows were dismantled due to their extrusion outward, due to the absence of the first destroyed thrust row).
The technology for restoring arched segments of the vault is similar to the technology described in the sections above.
To increase the structural strength of this section (vault edge), an additional reinforcing layer of refractory concrete is installed over the entire surface of the arched segments. The length of the reinforcing layer is 600 mm - four rows of the vault.
RESUME:
As a result of the carried out restoration repair of vaults No. 1,2 in the furnaces of hot water boilers No. 1,2, the lining of the boilers is in normal working condition. No additional restoration work of the refractory lining of the hot water boilers is required at this stage, the refractory lining is suitable for further operation. After the end of the heating season of 2024-2025, we recommend conducting a technical inspection of the refractory lining to determine its technical condition and make a decision on the implementation of further necessary measures (restorative repair / major repairs / replacement of the lining).
