Projects

Marine HVAC and sewage solutions in action

AHU Reconstruction, Coil Renewal & Ductwork Restoration – Pax

A mid-size passenger ferry reported reduced cooling capacity, high humidity in guest areas, and visible corrosion inside several AHU sections. Our task was to carry out a complete engineering assessment and execute structural, mechanical, and insulation repairs to restore the Air Handling Unit to full operational performance.

Duct Construction, System Modification & Restoration – Pax Vessel

A RoPax vessel undergoing a hotel-area refit required new ducting to support updated ventilation layouts, along with repairs to several aging duct branches showing corrosion, leakage, and poor airflow distribution. The project involved fabrication of new duct sections, replacement of degraded fittings, restoration of airtightness, and on-site installation within restricted spaces.

A technical inspection revealed several critical issues:

• Severe corrosion in the bottom pans of the AHU, with multiple points of condensate leakage.

• Cooling coil degradation, including reduced fin efficiency and partial blockage.

• Air leakage at panel joints, access doors, and duct interfaces.

• Damaged internal insulation with moisture absorption and mold growth.

• Improper airflow due to misaligned baffles and deteriorated seals.

Airflow measurements showed a 22% reduction from design specification, and temperature drop across the coil was significantly below expected values.

1. Initial Assessment

2. Engineering Plan

A structured work plan was developed:

1. Disassembly of the AHU to access internal components.

2. Fabrication of new stainless-steel bottom pans, with redesigned drainage slopes.

3. Manufacture and installation of new cooling coils, engineered as direct-fit replacements.

4. Ductwork repair, including replacement of corroded sections and resealing of all joints.

5. Replacement of internal insulation with closed-cell Armaflex panels to prevent condensation.

6. Reconstruction of the casing, including panel reinforcement and realignment.

7. Functional testing, airflow balancing, and verification of condensate drainage.

All fabrication work followed marine HVAC construction standards and shipboard safety procedures.

3. Technical Execution

3.1 Bottom Pan Reconstruction

Old pans were removed and replaced with marine-grade stainless-steel pans custom-fabricated to match original dimensions.
Improvements included:

• Increased slope angle for faster drainage

• Enlarged drain outlets

• Reinforced support structure

• Full anti-corrosion treatment of surrounding frames

3.2 Coil Renewal

New coils were produced using copper tubes and high-efficiency aluminium fins.
The new coils were:

• Pressure-tested at 25 bar

• Installed with new brackets and gaskets

• Commissioned and checked for thermal performance

Temperature drop improved to 94% of original design value.

3.3 Ductwork Repairs

Corroded duct segments were removed and replaced with galvanized sheet metal.
All joints were sealed using marine-grade adhesive and mechanical fasteners to achieve airtight Class B performance.

3.4 Insulation Replacement

All internal insulation was replaced with Armaflex closed-cell sheets, providing:

• Improved condensation control

• Mold resistance

• Acoustic dampening

• Longer service life in high-humidity environments

3.5 Final Assembly & Testing

After reassembly:

• Airflow increased by 27%, restoring design performance.

• Condensate drainage was stable with no leaks.

• Temperature control in serviced areas improved significantly.

• Visual inspection confirmed structural integrity and proper sealing.

4. Outcome

The refurbished AHU now operates at full efficiency with:

• Eliminated corrosion points

• Improved cooling capacity

• Reduced energy consumption due to restored airflow

• Extended service life (estimated +7–10 years)

• Enhanced reliability in continuous marine operation

The customer reported immediate comfort improvements for passengers and reduced HVAC load on the chiller plant.

5. Key Technical Deliverables

• New stainless-steel condensate pans (custom fabricated)

• New cooling coils (OEM-equivalent performance)

• Repaired and resealed duct sections

• Closed-cell Armaflex insulation installation

• Mechanical restoration of casing and sealing

• Final performance verification report with measurements

During the technical inspection, the following issues were identified:

• Corrosion and perforation in several supply and return duct sections, especially near the AHU discharge line.

• Air leakage at flange joints, inspection hatches, and flexible connections.

• Undersized branches causing airflow imbalance between cabins and public spaces.

• Degraded internal insulation leading to condensation and localized dripping.

• Deformed duct segments due to structural vibration and previous non-standard repairs.

The airflow survey documented an 18–32% loss in multiple branches compared to design flow rates.

1. Initial Assessment

2. Engineering Plan

A construction and repair plan was developed:

1. Fabrication of new galvanized and stainless-steel duct sections, sized according to system requirements.

2. Replacement of deteriorated branches and redirection of supply flows to match the updated layout.

3. Installation of new flanges, gaskets, access panels, and supports.

4. Sealing all joints using marine-grade sealant and mechanical fastening.

5. Installation of Armaflex insulation to prevent condensation and heat loss.

6. Airtightness testing and airflow balancing after commissioning.

The plan included coordination with the vessel’s refit contractor to ensure integration with ceiling, bulkhead, and cabin modifications.

3. Technical Execution

3.1 Duct Fabrication

All duct components were fabricated according to SMACNA / marine HVAC standards using:

• Galvanized steel for general ventilation

• Stainless steel in moisture-sensitive locations

• Reinforced corners and stiffeners for long horizontal runs

Sections included rectangular ducts, transition pieces, elbows, branches, reducers, and splitter boxes.

3.2 Removal of Old Ducting

Degraded sections were removed without disturbing nearby cabling and piping.
Special care was required in:

• Low-ceiling accommodation corridors

• Areas with limited access behind paneling

• Zones with pre-installed furniture and fire insulation

3.3 Installation & System Modification

New ducting was installed with:

• High-strength hangers and vibration-isolated supports

• New flanges with neoprene gaskets

• Access doors for cleaning and inspection

• Realigned airflow distribution boxes to match room layouts

All joints were sealed internally and externally for maximum airtightness.

3.4 Insulation & Condensation Control

Armaflex closed-cell insulation was applied to:

• Cold supply ducts

• Sections close to chilled-water coils

• Ducts passing through unconditioned spaces

All seams were sealed to prevent condensation and microbial growth.

3.5 Final Testing & Balancing

After installation:

• Airtightness test confirmed Class B+ performance

• Airflow was balanced across all cabins and public areas

• Noise levels were reduced due to improved insulation

• Static pressure readings returned to within design range

4. Outcome

The ducting system now meets operational requirements with:

• Restored structural integrity

• Improved airflow distribution and cooling performance

• Complete elimination of leakage points

• Extended service life of ventilation circuits

• Reduced load on AHUs due to improved efficiency

The vessel’s hotel areas reported a notable improvement in temperature stability and air quality.

5. Key Technical Deliverables

• Newly fabricated duct sections (rectangular & round)

• Transition pieces, elbows, reducers, and splitter boxes

• Maritime-grade supports and vibration isolation

• Armaflex insulation on all critical segments

• Airtightness verification and airflow balancing report

• As-built drawings for the modified duct paths