by Types of Marine Actuators and Valves
One of the key components in marine systems are actuators and valves that help control fluid flow and machinery operations onboard ships and vessels. Let’s look at some of the main types used:
Pneumatic Actuators
Pneumatic actuators utilize compressed air or inert gas as the working pressure medium. They are commonly used for valves in ballast water, bilge, firefighting and engine systems given their simple design and ability to operate in harsh, wet conditions. Dual diaphragm and piston Marine Actuators and Valves are popular types that provide reliable open-close cycling with feedback on position. Actuators may be single acting for on-off duty or double acting for modulating stroke control.
Hydraulic Actuators
Where higher power outputs are required, hydraulic actuators are employed. They make use of pressurized hydraulic oil to generate robust rotary or linear motion for tasks like opening/closing sea chest valves. Cylinder, vane and motorized actuators are commonly applied, with hydraulic fluid filtered and temperature controlled from a centralized system. Proportional valves enable flow regulation for precise positioning of rudders, thrusters or hatch covers.
Electric Actuators
In electrically driven actuators, an electric motor replaces compressed air/hydraulic power. They find increasing usage in Marine Actuators and Valves for applications like bilge valves, fuel tank isolation valves, lubricating oil valves, and ballast system valves. Types incorporate gear, nut, screw and harmonic drives coupled to a motor. These compact units simplify system layouts while enabling remote operation and feedback.
Butterfly Valves
Made of cast metal alloy or fabricated steel construction, butterfly valves are favored for shipboard use in water systems. The design comprises a circular disk mounted on a pivot that ‘rotates like a butterfly wing’ to open/close pipe flow. Stem mounted and flanged versions vary in flow characteristics for duties involving ballast, sewage, bilge and fuel handling. Wafer and lugged styles insert between flanges for easy installation.
Gate Valves
Gate valves provide full bore openings with a clear flow path. Used extensively in marine systems for compartment isolation in case of emergencies or repairs. Typical applications cover sea chests, engine cooling water, bilge systems and fuel/lubricating oil lines. Wedge and parallel slide designs have sturdy construction suited to ship operations. Valves may be manual, air or hydraulic operated depending on location and duty.
Ball Valves
Considered more robust than gate or globe valves, ball valves rotate a hollow sphere within the valve body to start/stop flow. This gives a tight shut-off and reduces fluid leakage potential. Spherical flow passage also lessens friction losses compared to other types. Threaded, flanged and welded end connections cater to diverse installation needs on deck machinery and piping systems.
Control Valves
Control valves play a pivotal role in automatically regulating fluid parameters like pressure, temperature and flow rate. Common varieties found on ships cover diaphragm, globe, rotary and wafer styles constructed from nickel alloys for seawater corrosion protection. Actuators modulate the valve plug/disc based on sensor readings to maintain setpoints. This maintains optimized system operation around the clock.
Valve Actuator Applications
Let’s look at some important applications of actuators and valves in marine systems:
Ballast System
Butterfly or ball valves with pneumatic actuators help blend/discharge ballast to trim vessel stability based on load conditions. Control valves assist maintaining optimal tank levels and exchange rates.
Fuel System
Gate, ball and butterfly valves isolate triple wall fuel tanks from seawater damages. Electric actuators enable remote control from engine room for bunkering/tank transfers.
Seawater Cooling
Hydraulically driven gate valves regulate main/auxiliary engine cooling water intake and discharge overboard. Butterfly valves control sea chest and pipe strainer backflushing.
Bilge System
Remotely operated electrically driven ball valves and pumps handle bilge transfer duties to drainage/overboard discharge points. Check valves prevent reverse flow.
Firefighting System
Butterfly valves with pneumatic fail-safe actuators allow activation of deluge sprinkler systems in case of emergencies from the bridge. Control valves maintain correct pressure.
Lube Oil System
Hydraulically actuated globe valves control storage, transfer and supply lines delivering conditioned lubricating oil to engines and machinery spaces equipment.
Deck Machinery
Electric actuators and valves automate fueling stations, freshwater intakes, swimming pool water treatment, sewage ejectors and sea inlet/outlets for air conditioning plants.
Maintenance and Testing
Proper upkeep and regular testing ensures reliable performance of marine actuators and valves throughout a vessel’s service life. Actuator condition, leaks, calibration and cycle times are checked at scheduled dockings.
Hot or cold water pressure testing validates valve seating and sealing integrity. Automation systems also run diagnostic routines to flag any component faults for preemptive repairs or part replacements. This maintains regulatory compliance and optimal safety/efficiency of vessel piping infrastructure and fluid handling operations.
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