Subsea HPU/
Safe + EX HPU

Products / Offshore

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Subsea HPU / Safe + EX HPUOffshore/Products

Hydraulic Power Units (HPUs) are compact units that enable the operation of systems by providing the power required to move subsea or Topside valves. They are designed to provide a stable supply of cleaned (classified) hydraulic fluid to the control systems. Thus till today, HPU is still a primary key component in Marine, Offshore and Subsea operations.


Hydraulic Power Unit pix1

On offshore oil production platforms, large valves are adopted and subjected to large upstream and downstream pressure differentials, which makes the effort required to move them above human capacity (some systems use pressures above 10,000 psi ). Other valves are simply located in an environment totally inaccessible to people: the seabed.

For both reasons, robust automation and control systems are used for the operation of these valves, and a power source is necessary to perform the opening and closing movements of the valves, allowing, blocking or directing the flow of accordance with the conditions of the process at that time.

MOWE partners Nakamura Japan for the complete HPU and accumulator package.

Valve Remote Control System Hydraulic Valves Control

Illustrates A Typical Schematic of Hydraulic Valve control System. 


The classification consists of the filtration procedure that guarantees a high cleaning index of the hydraulic fluid to avoid damaging control blocks of valves and other components of the system by the undue presence of solid particles. For Power Hydraulic Units of Submarine Control Systems, a very rigorous international standard is used, such as the National Aerospace Standard (NAS) 1638 and ISO 4406. The efficiency of the classification is guaranteed through analysis of laboratory sample or the use of particle counter online or portable.


Basic Components of a HPU

Storage tanks (return and supply): The return tank normally receives the initial load of hydraulic fluid to be classified and, as its name suggests, the return of fluid from the valve actuators when they are brought to the condition of relief of their actuators returning the fluid in a closed loop to said tank. Periodically, a new classification of the fluid should be made before being transferred to the supply tank which in turn stores the already classified fluid that will be sucked by the supply pumps and, after adjusting the pressure according to project specificities, will be sent to the consumers while maintaining pressurized the bank of hydraulic accumulators.

Filling pump: equipment used to transfer hydraulic fluid from its original containers (usual drums) into the return tank. It is also used for the periodic classification of the fluid, pumping from the return tank to itself through classification filters, through valve manoeuvres.

Hydraulic supply pumps (electrical and pneumatic): Supply pumps are responsible for supplying hydraulic power to the system by raising the fluid pressure, drawn from the supply tank to design values (usually very high ). The projects can provide pneumatic pumps working in parallel with those driven by an electric motor so that the drive of these are less frequent, increasing its useful life.

Filters for classification of hydraulic fluid: selected according to the design conditions in which it will be applied, meet different pressure classes, types of connections and required cleaning classes. They usually have a pop-up indicator and a differential pressure transmitter for automated monitoring.

More than 75% of failures in hydraulic and lubrication systems are due to over-contamination. Dirt particles can cause expensive and large machines to fail.

Photomicrograph of the contaminating particle

Illustrates Photomicrograph of the contaminating particle. Magnified 100x Scale: 1 division = 20 micron * (micron).


* A micron is equal to one-millionth of a meter.  

Relative particle size

Illustrates Relative particle size.  

• Hydraulic fluid specific for the application used: determined according to its composition that will determine properties such as density, viscosity, tolerance to possible contamination by sea water, biodegradability, can be oil-based (more suitable for Topside) or water-based ( indicated for Subsea).

Pressure accumulator bank: Accumulators can perform a very wide range of functions in the hydraulic system. In the case of HPUs, their primary function is to maintain system pressure, conferring stability to the system, and avoiding frequent outlets of supply pumps.

Accumulator application to maintain the pressure of a hydraulic system

Illustrates Accumulator application to maintain the pressure of a hydraulic system.  


Watch Video: 

The video shows the operation of a bladder-type hydraulic accumulator that receives a pneumatic pre-load pressure in the bladder located inside (usually Nitrogen) that will be equalized by hydraulic pressure. By reducing the pressure in the hydraulic circuit the bladder will press the fluid from its interior back to the circuit compensating the system losses, avoiding sudden losses in the pressure.

Pressure regulating valves: HPUs typically produce a higher pressure energy than is strictly necessary to move their consumers, leaving their accumulator bank functioning as a "lung" and allowing only the pressure set correctly to their pressure points consumption. This is the function of the pressure regulating valves, that is, to promote the "pressure break" necessary to feed the consumers, relieving any excess pressurized fluid to the return tank through its own line.

Directional valves: they are responsible for getting the pressure where it is needed, allowing the flow of the pressurized fluid through different ways to perform a job, such as the movement of the remote-actuated valve actuator.

Instrumentation for level and pressure monitoring: a key part of HPU's integration into the automation and process control system of an oil and gas production platform, both essential for productivity and process safety.

MOWE’s designed and integrated HPU system / skids are used in a wide range of applications that requires heavy and systematic lifting as well as other applications where repeated use of powerful and directional force is needed, including :

  • - Automation
  • Mobile Equipment
  • Oil Field
  • Oil Spill Clean Up Equipment
  • Marine Equipment


MOWE provides services to Shell, Petronas, Chiyoda, Toshiba, Tokyo, Mitsui, Cendor2 FPSO and more.

Today, our company offers:

  • Bladder & Piston Accumulators of various materials and pressure ratings
    N2 Booster Pump Skids / Systems
    Customised Hydraulic Systems and Solutions for Offshore or Industrial applications

 Hydraulic Power Unit HPU MOWE

Applications of Hydraulics is in every areas in Marine, Offshore, Oil and Gas

  • Valve Control Systems
    Well head control panels
    Modular hydraulic skids on power or engines
    Chemical Injection skid piston pumps
    Potable / Hot water packages
    Emergency Pump Packages
    Cargo System, Winches & cranes
    Accumulator packages
    Cylinder push and pull packages for bridges, doors and other applications


Features and benefits

  • Provide High-pressure or low pressure hydraulic systems
    Electrical controlled systems
    Packaged with Motor or Engines for Safe or Hazardous Areas.
    Skid, Modular, compact and easy to install
    Interface with ICSS or plain local operations.
    Wide range of components, Valves and options making design options very versatile.
    Skid or Modular, Framed or supplied loose
    - Remote Control (optional)



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Hydraulic Power Unit MOWE