Marine Cast Iron Ejector WaterEjector Propulsor

I. Product Overview

The marine cast iron Ejector waterEjector propulsor is a high-efficiency power device designed for marine propulsion systems. Made of gray cast iron (HT250) or ductile iron (QT400-18), it generates thrust by ejecting water flow, replacing traditional propellers to achieve ship 前进，steering, and braking. Its core principle is using a centrifugal pump to suck water from the inlet, which is then ejected at high speed through a nozzle to form reactive force for propulsion. After surface anti-corrosion treatment (such as zinc-based plating or epoxy coating), the cast iron material can operate stably in seawater (Cl⁻ concentration ≤20,000ppm), suitable for high-speed boats, ferries, workboats, and other ship types, meeting IMO maritime regulations and classification society (CCS/ABS/DNV) certification requirements.

II. Core Technologies and Material Characteristics

1.Cast Iron Material Selection and Performance

2.Key Technical Parameters

Flow range: 50-2000m³/h, suitable for ships of 10-5000 tons

Ejector speed: 15-30m/s, thrust coefficient 0.85-0.92

Efficiency index: Hydraulic efficiency ≥75%, 10%-15% higher than traditional propellers

Corrosion resistance design: Cast iron surface with Ni-P alloy plating (thickness 20-30μm), passing 1000-hour salt spray test (GB/T 10125) without pitting

III. Technical Advantages and Innovative Design

1. High Maneuverability and Shallow Draft Adaptability

In-situ steering capability: Achieves 360° in-situ rotation through vector control of left-right nozzles, with turning radius ≤1.5 times，suitable for narrow waterway operations.

Shallow draft feature: Submerged depth of the ejector ≤0.5m, 40% less than propellers, suitable for navigation in shoal and estuary areas.

2. Cavitation Resistance and Low Noise Design

Net Positive Suction Head (NPSH) ≤3.5m, impeller with two-phase flow design reduces bubble collapse impact, extending service life by 2 times compared to untreated cast iron.

Operation noise ≤75dB (at 1500rpm), 10-15dB lower than propellers, meeting passenger ship comfort requirements.

3. Convenient Maintenance and Cost Advantage

Modular structure: Pump body and motor can be disassembled independently, eliminating the need for ship lifting during maintenance, reducing repair time by 50%.

Cast iron cost advantage: Overall cost is 30%-50% lower than stainless steel ejectors, suitable for mass application in commercial ships.

IV. Typical Application Scenarios

1. Civil Marine Field

High-speed passenger ships: 40m-class aluminum alloy high-speed passenger ships equipped with QT400-18 ejectors, reaching speeds of 35 knots, saving 12% fuel compared to propeller propulsion.

Ferries and sightseeing boats: HT250 ejectors used in Yangtze River ferries adapt to shallow  waters while reducing passenger bumpiness.

2. Special Operation Vessels

Offshore engineering ships: Ejectors combined with hydraulic steering systems achieve precise positioning (accuracy ≤1m) in drilling platform supply ship operations.

Fireboats: Dual-ejector design provides ≥5000kN thrust while compatible with fire water cannon water supply (flow ≥1000m³/h).

3. Military and Law Enforcement Vessels

Patrol boats: QT400-18 ejectors support high-speed pursuit at 40 knots, combined with water Ejector braking systems, braking distance ≤2 times .

Amphibious landing craft: Ejectors allow direct landing on beaches with draft <0.3m, adapting to beach assault operations.

V. Selection and Maintenance Specifications

1. Key Selection Parameters

Vessel tonnage: HT250 for <100 tons, QT400-18 for ≥100 tons

Speed requirement: High-speed (>30 knots) needs nozzle (contraction angle 8°-12°)

Water quality condition: Install cyclone separator (separation efficiency ≥90%) when sediment content >1%

2. Maintenance Points

Daily monitoring: Check nozzle wear (allowable radial wear ≤1mm) and bearing temperature (temperature rise ≤40℃) daily

Regular maintenance: Clean the suction grille (filtration accuracy ≤5mm) quarterly, flush the pump cavity with fresh water (pressure 0.3MPa) annually

Anti-corrosion maintenance: Reapply epoxy zinc-rich primer every two years (dry film thickness ≥150μm)

VI. Compliance and Certification

International standards: Complies with IMO MSC.122(75) Safety Rules for WaterEjector Propelled Ships

Classification society certification: Passed CCS Rules for the Classification of Steel Ships and ABS Marine Guide for WaterEjector Propulsion

Environmental requirements: Oil content in Ejector water ≤15ppm, complying with MARPOL Annex I anti-pollution standards