---
title: An introduction to marine hydraulics
description: With yachts and workboats getting bigger and design features becoming bolder, marine hydraulics is a widely used power and torque delivery system.
---

[The Side-Power blog](https://blog.sleipnergroup.com/en)

# [An introduction to marine hydraulics](https://blog.sleipnergroup.com/en/an-introduction-to-marine-hydraulics)

 Written by [Benny Sorensen](https://blog.sleipnergroup.com/en/author/benny-sorensen) | 5. June 2019

#### Marine hydraulics has become one of the most used power- and torque delivery systems, primarily due to the highly efficient transfer of large both linear and rotary forces and torques.

## One hydraulic system, many applications

The application areas are many. Listed below are some of the uses of marine hydraulic systems:

- Rotary and linear operation of cranes.
- Rotary operation of winches, most common are mooring and anchor winches.
- Rotary and linear operation of stabilizers. 
- Rotary and linear operation of steering machines. 
- Rotary operation of hydraulic bow and stern thrusters.
- Rotary operation of adjustable pitch propellers.
- Rotary and linear operation of remotely operated valves, doors, ventilation flaps, etc.
- Platforms and passerelles.

At Sleipner Motor, we primarily use hydraulic systems for our [stabilizing vector fins](https://slides.sleipner.no/stabilizer-systems/) and our [thruster systems](https://side-power.com/kategori/1685/side-power-thrustersystemer/), but we also manufacture hydraulic steering systems for a range of high-end yachts and work boats. 

## A hydraulic system should require little maintenance

If correctly dimensioned, installed and commissioned, a hydraulic system requires little maintenance, and troubleshooting is pretty easy for personnel with a reasonable knowledge of general hydraulics. The two most important factors for trouble-free operation are:

- Basic knowledge of the layout and operation of the system.
- Cleanliness during repair, dismantling and assembly of all components.

In terms of cleanliness, this cannot be stressed enough on marine hydraulics. The most crucial factor for a problem-free operation is keeping the system clean and the oil-free from impurities.

## Three types of marine hydraulic systems

Marine hydraulic can be divided into three types of systems:

- Open hydraulic systems.
- Closed hydraulic systems.
- Semi-closed hydraulic systems.

Read more: [Pros and cons of different marine thrusters →](https://blog.sleipnergroup.com/en/pros-and-cons-for-different-types-of-marine-thrusters?hsLang=en)

## Open hydraulic systems

The most common system is the open hydraulic system. The open system is characterized by having a pressureless tank to which the oil is returned more or less directly. Contrary to a closed system in which the oil return is directly on the pump's suction side. All [hydraulic systems](https://side-power.com/kategori/1844/hydrauliske-thrustere/) built by Sleipner Motor for our Side-Power systems are open hydraulic systems. Semi-closed and closed hydraulic systems will not be discussed further in this series of hydraulic talks.

*A typical floor-mounted 90 liter tank from Side-Power.*

 

## **Typical marine hydraulic components**

The most common components in an open hydraulic system on boats are:

- Hydraulic oils.
- Hydraulic reservoir.
- Filter technic.
- Valves:  
  - Directional control valves.   
  - Pressure control valves.   
  - Flow control valves.  
  - Proportional control valves. 
- Hydraulic pumps and motors.
- Hydraulic cylinders.
- Installation, Commissioning, Operation and Maintenance.

Read more: [How much power do I need from my bow and stern thruster installations? →](https://blog.sleipnergroup.com/en/how-much-power-do-i-need-from-my-bow-and-stern-thruster-installations?hsLang=en)

## **Marine hydraulic tank: An example **

### **Cooling and filtration**

It is essential for the lifetime and reliability of a hydraulic system that [the oil stays clean](https://blog.sleipnergroup.com/en/an-introduction-to-hydraulic-oil-for-marine-use?hsLang=en) and within correct temperatures to avoid excessive wear and damage to any of the components in the system. The Side-Power hydraulic system is designed to achieve this by having:

  
**A** Air filter and strainer in filler cap.

**B** High-pressure filter with service indicator.

**C** Return filter with service gauge.

**D** Dual internal oil cooler or tank mounted in-line return cooler and drain cooler. Setup and mounting will vary depending on selected tank unit and system setup.

**E** DC or hydraulic driven water pump for the oil coolers (optional).

### **Information and warning system**

For safety and ease of service there are several sources of information and warnings on the tank.

 

**F** Oil level and temperature gauge.

**G **Electric alarm outputs for oil level and temperature to Side-Power control panels with a visual and audible alarm.

**H** Both filters have gauge/indicator for filter element condition.

**I** Pressure gauge on valve shows system pressure.

**K** Pressure sensor for control panel monitoring.

### **Valve and controller system**

 

**L** PHC-3 Controller (Proportional Hydraulic Controller).

**M** Valve system.

 

 

 

 

I will review my experience with these various components in a series of blog articles over the next weeks. If you wish to learn more about marine hydraulics, please do not hesitate to [subscribe to the Side-Power marine blog](https://info.side-power.com/subscribe-to-our-newsletter?hsLang=en). 

 

[View full post](https://blog.sleipnergroup.com/en/an-introduction-to-marine-hydraulics)

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