Marine actuators are essential components used on ships and vessels to provide controlled motion and power to various mechanical systems and equipment. As ships operate in harsh marine environments with salt water corrosion, extreme temperatures and pressures, actuators require robust designs and materials to function reliably. Common types of actuators used at sea include electric, hydraulic and pneumatic actuators.
Electric actuators are powered by electricity and use electric motors to produce torque and rotational or linear motion. These are popular options as they provide precise positioning and speed control. However, electric actuators require additional components like gearboxes for applications requiring high torque. Hydraulic actuators utilize pressurized hydraulic oil or fluid to produce powerful forces for tasks like moving and locking heavy valves or machinery. Pneumatic actuators use compressed air or gas and are best suited for applications requiring lightweight and low cost solutions.
Marine Valve Types and Applications
Valves are critical shipboard components that control the flow of liquids and gases through piping systems. Common Marine Actuators and Valves types used in marine applications include:
Butterfly Valves: Excellently suited for throttling and on-off applications in larger piping systems. Their compact design makes butterfly valves ideal for tight spaces in engine rooms and bilges.
Ball Valves: Durable and versatile valves commonly used for on-off service in medium to large pipelines carrying water, fuel, sewage and other fluids. Ball valves provide positive shut-off.
Globe Valves: Effective throttling valves suitable for reducing pressure in steam, gas and liquid systems. Their design allows partial restriction of flow while remaining pressure-tight when closed.
Check Valves: Automatically permit flow in one direction while preventing reverse flow. Check valves find extensive use in circulating cooling water, bilge, ballast and firefighting systems.
Diaphragm Valves: Compact valves suitable for low-pressure applications involving corrosive or abrasive fluids. Their sealed design offers resistance to element contamination.
Gate Valves: Rugged valves suited for high-pressure applications involving fluid cutoff in pipelines where full-port opening is essential. Slide and weir types are common gate valve designs.
Actuator Systems for Marine Valve Operation
Actuator systems play a vital role in controlling valve operation onboard ships. Key factors considered in marine actuator applications include:
Operating Environment: Actuators must withstand heat, vibration, moisture and corrosion from seawater, oil or chemicals. Electric actuators often provide enclosures to IP56/IP57 standards or higher.
Duty Cycle: Actuators are specified based on the number of open-close cycles per hour required for applications like boiler water circulation valves.
Torque Requirements: Valve torque specs determine the actuator motor size and gearing needed to open and close against system pressures.
Position Feedback: Position sensors allow actuators to confirm valve’s open, closed or intermediate positions for automated monitoring and control.
Control Systems: Actuators integrate with DCS, PLC or standalone controls to enact commands from central control rooms or local push buttons. Common interfaces include 4-20mA, 0-10Vdc, modbus and CANbus.
Emergency Operation: Actuators incorporate manual overrides like handwheels or levers to allow local positioning during power outages or system failures.
Actuator power can be sourced from ship’s main or emergency electrical panels. Hydraulic or pneumatic actuators utilize onboard compressed air supplies. Properly specified actuators provide the reliable remote control and automatic operations essential for ship systems.
Valve Actuator Applications in Marine Systems
Sea water systems: Butterfly and globe valves regulating sea chest intakes, circulating pumps and other ocean intake/discharge lines rely on actuators for remote or automatic operation. Ballast system valves moving hundreds of tons of ballast water also utilize large actuators.
Fuel systems: Actuators open and close manifold isolation valves, day tanks suction/returns and other piping to direct fuel from cargo/service tanks to engines as needed. Ball valves on bunkering stations also employ actuators for remote bunkering control.
Boiler water circulation: Circulation, drainage and steam extraction globe valves in steam generation systems open and close on a programmed cycle to maintain boiler levels and pressures. Actuators ensure valves follow control system demands.
Bilge systems: Bilge discharge isolation valves protecting against flooding rely on actuators to open only when controls permit drainage from bilge wells to pump systems overboard.
Firefighting systems: Sprinkler isolation valves and more open promptly on actuator orders from central monitoring panels or local break glass stations during fire emergencies.
HVAC systems: Butterfly dampers and valves regulating airhandling and chill water loops utilize actuators for temperature/flow control.
In, marine actuators and valves form an indispensable partnership in providing remote operation and automated process control essential for the safe, efficient and reliable running of vital onboard ship systems. Proper system integration and component specification ensures years of trouble-free service under challenging marine conditions.
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