Alfa Laval Aalborg-OS-TCi-4.0-7bar
Alfa Laval Aalborg-OS-TCi-4.0-7bar oil-fired vertical steam boiler (oil-fired vertical steam boiler). Evaporation 4000 kg/h, design pressure 7 bar, heating surface 55 m2, weight 6800 kg. Vertical cylindrical design for marine auxiliary steam generation.
Inspector Detail
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Common issues
- Soot and scale buildup on smoke-side heating surfaces reducing efficiency and raising exhaust gas temperature
- Refractory cracking around the furnace/burner throat from thermal cycling
- Burner flame instability or poor atomization from a worn nozzle or fuel viscosity out of range
- Water-side scaling and pitting corrosion from poor feedwater treatment
- Safety valve seat leakage or set-pressure drift over time
- Feed pump or feedwater regulator wear leading to level control problems
- Furnace or tube plate cracking from repeated thermal shock at low-load operation
Inspection checklist
- Internal inspection of furnace, smoke tubes and tube plates for pitting, scaling and cracking
- Check refractory condition at the furnace mouth and burner throat
- Function test safety valves (lift and reseat) at rated set pressure
- Check water level gauge glasses, alarms and low-water cutout function
- Verify burner flame pattern, atomization and combustion air/fuel ratio
- Check soot blower operation and coverage of heating surfaces
- Inspect feed check valve, non-return valve and feedwater regulator
- Check boiler mountings (main steam stop, blowdown valves) for tightness
- Test high/low water alarms and any remote monitoring signals
- Review boiler water treatment chemistry (TDS, pH, chlorides, alkalinity)
Service intervals
| Soot blowing | daily to weekly, depending on fuel quality and load |
| Boiler water chemistry check | weekly |
| Safety valve function test | at least annually, per class requirement |
| Internal survey (furnace, tube plates, refractory) | annually or per the vessel's Continuous Machinery Survey scheme |
| Burner nozzle/atomizer inspection and cleaning | every 500-1000 running hours, fuel-quality dependent |
| Feedwater/level control system function test | every 3-6 months |
| Bottom/scum blowdown | daily |
Typical wear limits
| Furnace/tube plate wastage | condemnation is typically considered once thickness loss reaches roughly 10-15% of original - confirm against class rules and the maker's manual, do not use as a fixed cutoff |
| Safety valve set-pressure drift | generally re-set or overhauled once drift exceeds a few percent of set pressure - follow the class survey requirement for the exact tolerance |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Burner nozzle/atomizer assembly
- Safety valve spares (springs, seats) sized for the 7 bar design pressure
- Water level gauge glass set and gaskets
- Feed check/non-return valve
- Ignition electrodes and flame scanner (photocell/UV)
- Refractory repair material for the furnace throat
- Feedwater regulator (level control) spares
- Manhole/handhole door gaskets
Safety
- Low-water condition risk of pressure part failure or explosion if level alarms/cutouts are untested or defeated
- Hot surface contact burns from uninsulated steam lines and boiler shell
- Steam/hot water release from blowdown valves during operation
- Furnace explosion (puff-back) from unburned fuel accumulation after a failed ignition attempt
- Pressure part failure risk from operating with scaled or uninspected heating surfaces
Class survey
Auxiliary boilers normally fall under Continuous Survey Machinery (CSM) or a fixed special-survey internal/external examination, depending on the vessel's survey scheme. Surveyors expect current safety valve test records, water treatment logs, and internal inspection reports showing no unaddressed pitting or cracking on pressure parts.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Innenseitige Sichtprüfung aller Dampf-/Wasser-Röhren; bei Verdacht Druck-Test durchführen; leckendes Rohr mit konischem Stopfventil nach Stahlbürsten-Reinigung der Rohrenden abdichten. Undichte Rohre müssen erneuert werden.
DP-Transmitter-Einheit prüfen (externe Referenz/Variable Schenkel, 4–20 mA-Ausgang); Speisewasser-Regelventil Funktionsprüfung; Schauglas auf Risse, Verschmutzung; Alarm-Funktion im Steuergerät testen
Zwei Sicherheitsventile unter Volllast-Dampf prüfen: Druckaufbau 7 Min. max. +6% Arbeitsdruck zulässig (Wasserrohre); Pop-Point jedes Ventils max. ±3% von Einstelldruck; Klassenvermerk: Öffnungs- + Akkumulations-Test unter Klassifizierer-Aufsicht durchführen
Furnace-Wände und Refraktärbelag visuell inspizieren (mind. 2x/Jahr); auf Risse, Feuchte, Soot-Ablagerungen prüfen. Untere Rohrplatte (Isolations- + Formrefraktär) überprüfen. Nach 3–4 Wochen Betrieb: Blow-Down durchführen, Kessel inspizieren/reinigen, Schlamm entfernen
Hydrostatic Test: Kessel mit Wasser 21–65 °C füllen (Wasserrohre max. 71 °C). Druck: 1,5× MAWP (nicht eintretbar) oder 1,25× MAWP (eintretbar). Sicherheitsventile mit Klammern sichern. Alle Dichtflächen, Niete, Schweißnähte auf Lecks prüfen. Klassenvermerk: alle 2 Jahre (bis 8J), dann jährlich.
Class Survey: Wasser-Seite (Dampftrommel, Wassertrommel, alle Röhren) auf Korrosion/Risse/Ablagerungen prüfen; Feuer-Seite (Furnace, Fluegas-Bahn) auf Soot/Flockung kontrollieren (mind. 2x/Jahr). Mannlöcher (oben/unten) erlauben Zugang. ggf. Ultraschall/Endoskop für tiefere Defekte einsetzen.
Type-general inspection and maintenance points for this equipment category — not model-specific.
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