Introduction
⌅A textile company implemented biomass boilers for steam generation, achieving an approximate savings of 10,000 gallons of diesel. However, boiler downtime has resulted in significant economic losses, as documented in the specialized literature (Petrucci et al., 1989PETRUCCI, R.H.; CUNNINGHAM, C.M.; MOORE, T.E.: General chemistry, Ed. Macmillan New York, USA, 8.a ed., 1989, ISBN: 0-02-394791-8.; 2002PETRUCCI, R.H.; HARDWOOD, W.S.; CUNNINGHAM, C.; MOORE, T.E.: General Chemistry, Ed. 8, 8.a ed., Macmillan New York, USA, 486 p., 2002.; Jiménez, 1997JIMENEZ, C.C.O.: Cálculos de procesos de vapor en una industria textil, Inst. Facultad de Ingeniería Mecánica. Escuela Superior Politécnica Del Litoral, Guayaquil, Ecuador, 1997.; Neefus & Lee, 2001NEEFUS, D.J.; LEE, I.A.: Industria Textil y de confección, [en línea], vol. I, 108 p., 2001, Disponible en:http://www.insht.es/. ; Sevilla, 2004SEVILLA, H.L.: Orígenes históricos del empleo tecnológico del vapor, 2004.).
Currently, the company has a deficient maintenance system for its biomass boilers, which has led to recurring failures, reduced lifespan, increased production costs, and reliance on corrective maintenance.
The objective of this work is to propose an improved maintenance system for the fundamental components of biomass boilers in textile companies, in order to reduce production costs and improve operational reliability.
Materials and Methods
⌅Biomass Boilers in Textile Companies
⌅The fire-tube boilers used in textile companies operate with a liquid fluid contained in a vessel traversed by tubes, through which high-temperature gases from the combustion process circulate. The water evaporates due to contact with these exhaust gases (Hanesbrands, 2025HANESBRANDS: Nuestra Empresa WEB, [en línea], 2025, Disponible en:http://www.hanesbrands.com.br/es-es/NuestraEmpresa/default.aspx. ).
There are two types of configurations:
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Partially submerged tubes: the water does not completely cover the tubes.
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Fully submerged tubes: the tubes are completely covered by water.
Figure 1 shows a horizontal boiler.
Biomass Boiler Maintenance at the Textile Company
⌅Currently, the company performs inspections and maintenance procedures following the guidelines of the ASME International Code, Section I (American Society of Mechanical Engineers, 1962AMERICAN SOCIETY OF MECHANICAL ENGINEERS. BOILER; PRESSURE VESSEL COMMITTEE: ASME Boiler and Pressure Vessel Code, Ed. American Society of Mechanical Engineers,1962.; 1989AMERICAN SOCIETY OF MECHANICAL ENGINEERS. BOILER; PRESSURE VESSEL COMMITTEE: ASME Boiler and Pressure Vessel Code, Ed. American Society of Mechanical Engineers, 1989.).
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Internal Inspection: The overall condition of the boiler's interior is evaluated, including tubes, furnace, plates, refractories, burners, economizers, superheaters, steam connections, blowdowns, and valves.
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Valve Condition: The boiler must have one or more safety valves, calibrated to release steam at the maximum working pressure without exceeding 6% above that value.
- Hydrostatic Test: This is performed to verify the boiler's integrity and leak tightness:
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After repairs to the boiler shell or pressurized components.
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Every 13 months.
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For new boilers, at 1.5 times the maximum design pressure.
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The minimum duration is 30 minutes, which may be extended at the inspector's discretion.
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A pressure drop of up to 3% is permitted; if it occurs, the cause must be recorded.
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Water quality: The analysis, monitoring, and chemical treatment of the feedwater must be guaranteed, preventing scaling, corrosion, and contamination (oils, chlorides, caustic soda, acids, organic matter, etc.), in accordance with the manufacturer's and service provider's specifications.
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Boiler deformations: A specialized supplier must be contacted for deformations due to buckling, bulging, or pockets that weaken plates or tubes, especially if they cause leaks. Service must be suspended until the affected part is properly repaired.
Results and Discussion
⌅Recurring failures in key components of biomass boilers
⌅Currently, the company's boiler area is experiencing constant failures in the tube bundles, especially due to leaks, poor welding, and wear on the tubes of the two biomass boilers. These problems stem from inadequate maintenance practices, both in plugging and replacing pipes. Several of these failures coincide with the most frequent ones reported in the literature (ECOPETROL, 1987ECOPETROL: Manual de Operación de calderas B-2951/55 de Unidad de Balance, Ed. Grupo III de la Superintendencia de Operaciones III., Unidad de Balance Barrancabermeja ed., Barrancabermeja, 1987.; Justo, 1994JUSTO, C.: Mantenimiento programado de B-2951-4, Grupo III Servicios Industriales, Barrancabermeja, 1994.). Figure 2 shows a poor weld on a biomass boiler.
Figure 3 shows poorly sealed tubes and tube deformation.
Figure 4 shows sediment fouling in the tube bundle.
The accumulation of ash in the tubes reduces heat transfer, accelerates corrosion, and causes ruptures in the tube walls.
Failure analysis by component
⌅Table 1 shows that 94.7% of the failures are concentrated in the flue pipes (71 out of 75 failures), justifying focusing maintenance on this critical component.
| Key components of the boiler | ||
|---|---|---|
| Article | Description | Number of failures |
| 1 | Hearth or stove | 0 |
| 2 | Hearth door | 3 |
| 3 | Grates | 0 |
| 4 | Ash pan | 0 |
| 5 | Ash pan door | 0 |
| 6 | Altar | 0 |
| 7 | Masonry | 0 |
| 8 | Flue pipes | 71 |
| 9 | Smoke box | 0 |
| 10 | Chimney | 0 |
| 11 | Draft regulator | 0 |
| 12 | Inspection cover | 0 |
| 13 | Blast door | 0 |
| 14 | Water chamber | 0 |
| 15 | Steam chamber | 0 |
| 16 | Water feed chamber | 0 |
| 17 | Pressure relief valve | 1 |
| Total number of failures | 75 | |
Current Maintenance Costs
⌅Table 2 presents the costs associated with current maintenance methods:
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Pipe plugging: 24 failures, repair cost $14,375 USD, total cost $157,650 USD
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Pipe replacement: 47 failures, repair cost $48,600 USD, total cost $367,850 USD
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Total cumulative cost: $588,475 USD
| Key components of the boiler | ||||
|---|---|---|---|---|
| Article | Descripción | Number of failures | Repair cost (USD) | Cost/Downtime $USD |
| 1 | Pipe blockage | 24 | 14,375.00 | 157,650.00 |
| 2 | Pipe replacement | 47 | 48,600.00 | 367,850.00 |
| Subtotal | 62,975.00 | 525,500.00 | ||
| Grand Total | 588,475.00 | |||
Major Maintenance in December 2023
⌅A major intervention was performed on both boilers, with complete tube installation by contractors:
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Table 3: 600 tubes plugged, repair cost $169,718 USD, downtime cost $2,364,750 USD
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Total cost: $4,063,468 USD
In addition, an extra expense of $2,362,500 USD was incurred for the consumption of 450,000 gallons of diesel during the shutdown, due to the activation of the fossil fuel boiler.
| Key components of the boiler | ||||
|---|---|---|---|---|
| Article | Description | Retubed pipes | Repair cost $ USD | Cost of downtime USD |
| 1 | Boiler Retubing I | 300 | 83,609.00 | 2,364,750.00 |
| 2 | Boiler Retubing II | 300 | 86,109.00 | |
| Sub - total | 1,698,718.00 | 2,364,750.00 | ||
| Grand total | 4,063,468.00 | |||
Technical problems during rework
⌅Following the rework, leaks were detected due to over- and under-drilling of the pipes, which caused plate deformations and leaks in the sealing system. Non-destructive testing revealed cracks in the welds (Figure 5).
Methodological Proposal for Improved Maintenance
⌅Pipe Plugging
⌅The use of prefabricated monoblock plugs (Figure 6) and single-revolution cutters (Figure 7) is proposed for perforating and venting the pipe before plugging.
Advantages:
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Reduced working time and labor costs
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Chemical compatibility with the pipe material
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Ease of welding
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Prevent reactivation due to internal pressure
Economic Comparison of the Proposed Method
⌅Table 4 presents a comparison of the current method against the proposed method to quantify the savings between the two.
Total savings: $5,809.60 USD and a reduction of 0.95 hours
| Saving | ||
|---|---|---|
| Method | Time (h) | Cost $ USD |
| Current method | 10.75 | 55,616.18 |
| Proposed method | 9.8 | 49,806. 58 |
| Difference | 0.95 | 5,809.60 |
Pipe replacement with advanced technology
⌅It is proposed to hire specialists with modern equipment:
Cutting and grinding: power tools (Figures 8 and 9).
Extraction: hydraulic extractor (Figure 10)
Expansion and machining: motor with digital torque (Figure 11) and tube expander (Figure 12)
Economic Analysis
⌅Practical validation: In March 2024, the proposed method was applied to 19 pipes, with no failures in testing or operation.
Similarly, as in the previous case, a flowchart was established for the operations to be preformes.
Table 5 shows the savings of the proposed pipe replacement method compared to the current method.
The proposed method resulted in savings of USD 5809.60 and a reduction of 0.95 hours.
| Method | Time (h) | Cost $ USD |
|---|---|---|
| Current method | 11.52 | 2,392,053.40 |
| Proposed method | 10.24 | 2,080,596.86 |
| Difference | 1.28 | 311,456.54 |
Conclusions
⌅The following advantages were concluded from the technical and economic analysis:
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A reduction in the total maintenance cost of tube plugging of $5,809.00 USD, a 12% reduction compared to the current cost.
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A reduction in the total maintenance cost of tube replacement equivalent to $7,786.41 USD, a 15% reduction compared to the current method.
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Reduced labor costs for both maintenance methods.
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Longer lifespan of the plates supporting the flue pipes because this method is non-invasive.
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Greater precision during tube boring.
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Reduced risk of workplace accidents that could harm the health and safety of workers.
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Reduced risk of accidents that could compromise the boiler's lifespan, as the critical components of the boiler are not compromised, thus avoiding weakening the properties and composition of its materials.
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Reduced CO2 emissions due to shorter commissioning times for biomass boilers.
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Extended lifespan of the flue and flue pipes, key components of the boiler.