Due to differences in operating principles, application environments, and structural designs, maintenance priorities for various types of marine heat pump units also differ significantly. The following is an analysis of the maintenance differences among common types:

1. Classified by heat source type

(1) Seawater source heat pump

Core maintenance differences:

The seawater-side heat exchanger—typically made of titanium tubes—requires particular attention to prevent marine organism fouling and salt crystallization. It is recommended to clean it weekly with a specialized antifouling agent and to flush it monthly with fresh water, thereby avoiding blockages caused by shellfish and algae.

Seawater filtration systems (such as filters and screens) must be inspected daily, and impurities should be removed promptly to prevent blockages that could lead to insufficient flow and reduce heat exchange efficiency.

The impeller of the seawater pump is prone to wear caused by silt and sand. The condition of the impeller should be inspected every quarter, and it should be replaced promptly if wear is severe. At the same time, the pump shaft seals should undergo regular anti-corrosion treatments.

(2) Air-source heat pump

Core maintenance differences:

The outdoor heat exchanger (evaporator) is susceptible to salt spray corrosion and dust accumulation, so it should be rinsed weekly with high-pressure fresh water (avoiding electrical components). Every six months, the fins should be treated with an anti-corrosion coating (such as silane treatment).

The fan system requires particular attention to blade balancing, as ship vibrations may cause the blades to loosen. Therefore, the connecting bolts should be tightened monthly, and anti-salt-fog grease should be applied to the bearing areas.

In high-humidity or rainy weather, you should periodically activate the defrost function to prevent frost buildup on the heat exchanger from affecting heating performance. At the same time, check the sensitivity of the defrost sensor.

(3) Freshwater / Ethylene Glycol Source Heat Pump (commonly used for inland waterway vessels)

Core maintenance differences:

The freshwater-side pipeline must be protected against algae growth. Add a bacteriostatic agent every quarter, and replace the circulating water annually (or according to the results of water quality testing).

During winter shutdowns, thoroughly drain the pipelines or add antifreeze (the concentration of which should be adjusted according to the lowest temperature in the navigation area) to prevent freezing and cracking.

The sealing gaskets of plate heat exchangers are prone to aging due to vibration. Inspect them every six months, and promptly replace any gaskets that show signs of leakage with ones capable of withstanding the relevant temperature and pressure conditions.

2. Classified by purpose

(1) Heat pump for cabin air conditioning

Maintenance focus:

The indoor unit’s filter should be cleaned daily (especially on passenger ships) to prevent dust buildup from affecting air quality and airflow.

The ductwork system must be inspected quarterly to ensure that the fire dampers operate sensitively and that air outlets have not shifted due to vibration. If necessary, adjust the vibration-damping devices on the duct supports.

The thermostat’s accuracy must be calibrated monthly to ensure stable cabin temperature (the recommended temperature fluctuation range is ≤ ±1℃) and to avoid frequent on-off cycles.

(2) Hot water supply heat pump

Maintenance focus:

The hot water storage tank’s inner liner needs to be cleaned every quarter to remove scale (a citric acid circulation cleaning method can be used) and prevent a decline in heat exchange efficiency.

Safety valves and pressure controllers must be tested monthly to ensure they can automatically relieve pressure in the event of overpressure, thereby preventing pressure abnormalities caused by ship motion.

The circulating water pump requires attention to changes in head pressure. If the distance for hot water delivery fluctuates due to ship motion, it’s necessary to check whether the pump’s variable-frequency drive system is functioning properly.

(3) Heat pumps for special areas (such as engine rooms and refrigerated compartments)

Maintenance focus:

In the high-temperature environment of the cabin, the heat pump’s compressor cooling fan should be inspected weekly to ensure proper heat dissipation and prevent overload caused by excessively high ambient temperatures.

The low-temperature heat pump in the refrigeration compartment requires regular inspection of the insulation layer’s seal to prevent cold loss, and also demands calibration of the low-temperature sensors (with an accuracy requirement of ±0.5℃).

For explosion-proof heat pumps (such as those used on oil tankers), the explosion-proof seals of electrical components must be inspected monthly. The sealing rings at junction boxes and cable entry points must be intact to prevent sparks from leaking out.

3. Classified by structural form

(1) All-in-one heat pump

Maintenance features:

High integration requires particular attention to the overall seismic protection system. Tighten the base bolts monthly and replace aged shock-absorbing pads.

Due to limited maintenance space, it is necessary to plan in advance the replacement routes for vulnerable components (such as filters and solenoid valves). Spare parts must be custom-made according to the available space dimensions.

(2) Split-type heat pump

Maintenance features:

The connections of the indoor and outdoor unit piping are prone to leakage due to vibration; therefore, they should be inspected weekly using a leak detector. Anti-loosening sealant must be applied at flange or threaded connections.

The protective conduit for the cable must be inspected to ensure it hasn't been worn or damaged due to hull deformation. Every quarter, wrap it with wear-resistant insulating tape to prevent short circuits.

Summary

The maintenance differences among various types of marine heat pumps are mainly concentrated on:

Anti-pollution and anti-corrosion measures for the heat source side (seawater / air / freshwater);

Specialized inspections of functional components for specific applications (such as hot water tanks, ductwork, and explosion-proof components);

Maintenance convenience and vibration protection requirements brought about by the structural form.

In actual maintenance, it is necessary to develop targeted plans that take into account the type of vessel (ocean-going / inland waterway / passenger ship / cargo ship) and the navigation area (tropical / cold climate / high-salt-mist regions), while strictly adhering to the classification society’s specifications for equipment corrosion prevention and safety protection.