Product - HPU
​​The Hydraulic Power Unit (HPU) provides pressurised oil to the hydraulic actuation system. A redundant pump system charges the ​bladder accumulator(s) automatically at a high pressure to utilize the ability of the actuators to store energy. A pressure reducing valve system provides the system with a constant stable system pressure. To ensure the oil cleanliness, supervised filters are installed on the pump and return side. Filtration takes place whenever the pump(s) are running. The HPU is provided with analogue transmitters for oil tank leve​​l, temperature and pressure.

Key features​

Redundant hydraulic pumps
  • ​​Two electrically driven high pressure gear pumps, one operational and one standby. Both may run simultaneously if needed.

  • ​Each pump is connected to a supervised pressure filter. Changing filter elements can be done during full operation.

Constant output pressure
  • A logical element together with a pilot pressure reducing valve controls the outlet pressure.
  • A pressure relief valve is installed to limit the output system pressure.
  • Output pressure is monitored via a pressure transmitter.

Surface protection
  • ​As standard, carbon steel parts such as frame, roof and oil tray are painted with corrosion protection for coastal environments with optional coating suitable for seawater areas with high salinity.

Accumulator system
  • ​The HPU can be equipped with 1-3 accumulators, each having a volume of 20-50 litres.
  • ​The accumulator pressure is monitored via a pressure transmitter, and regulated by the Intelligent Pump Control (IPC).
  • By using a proportional valve to create a smooth transition between charging mode and idling mode, pressure peaks in the system are reduced.
  • ​A sealed pressure relief valve limits the maximum accumulator pressure. Accumulators are also equipped with burst discs to prevent overpressure in case of fire.
Intelligent Power Control (IPC)
  • IPC is mounted and fully installed on the HPU.
  • The IPC controls all the functions of the HPU and communicates with the local Distributed Control System DCS.
  • The IPC is also equipped with a display allowing configuration of minor operating parameters, accessing functions on the HPU and showing its status.

​Return filter and oil filling/draining
  • ​A supervised low pressure oil filter is mounted on top of the tank, filtering oil from the idling valve and/or return oil from the system.

​Key benefits

  • Constant supervised system pressure
  • Redundant high pressure pump system
  • Oil cooler as option for ambient 
    temperature above +40-45C

  • Up to 300 litres per minute output oil flow
  • Intelligent pump control logic with safety processor
  • Integrated accumulator system (20 - 150 litres each)
  • Supervised filtering system
  • Oil tray as standard
  • LCD display for HPU operation and status 
  • Integrated flushing function as standard (requires start-up kit)
  • Pressure / level / temperature analog transmitters with LCD readout as standard
  • Instrumentation protection class: IP67
  • Oil tank in stainless steel material as standard

Product Specification

See product brochure on the right for larger image view.


  • Large oil tray capable of housing the entire tank capacity
  • Oil/air cooler, recommened for ambient Temperatures over +40∞C - 45∞C
  • Oil heater, recommended for ambient temperatures lower than 10 to 15∞C
  • Roof (covering mainly IPC and cooler unit)
  • Hand pump for emergency operation
  • Filter kit
  • Startup kit
  • Oil filling pump unit
  • Optional pump controller (PLC)
  • Fully redundant pump controller
  • Redundant temperature / level / pressure transmitters​​

Latest News

IMI Critical Engineering digital FAT delivers customer projects on time
07 September 2020
Another big aftermarket win in LATAM for IMI Critical Engineering
18 August 2020
Important Update – COVID-19
18 March 2020
Valve Doctor programme celebrates 20th anniversary
16 September 2019
Unconventional support for the unconventional oil and gas industry
01 July 2019
17 June 2019
IMI CCI showcases choke valve at DUG Rockies conference
04 June 2019
Jackie Hu appointed Divisional Managing Director of IMI Critical Engineering
07 March 2019
Roy Twite to succeed Mark Selway as Chief Executive of IMI plc
05 March 2019
IMI Critical holds Safety Summit
21 September 2018
New HSE handbook to help keep field service engineers safe
10 August 2018
Safety first at IMI Critical
31 July 2018
IMI InterAtiva’s Series RK Valves certified ‘fire-safe’
24 July 2018
IMI CCI participates at regional VPP Safety Summit
08 June 2018
Largest Romanian customer recommends IMI Remosa
10 May 2018
Lean success in IMI Critical back office functions
04 May 2018
Isolation valves adapted for Fluidised Catalytic Cracking applications
30 April 2018
IMI Critical Korea closes in on world-class LEAN performance
27 April 2018
IMI board tours IMI Critical businesses
25 April 2018
New positioner software tools from IMI STI
08 February 2018
Launch of Zero Backlash Scotch Yoke Mechanism
16 January 2018
IMI Critical Korea certified to sell actuators in Europe
20 September 2017
IMI Critical named ‘supplier of the year’ by Korea’s Doosan
19 September 2017
100th Valve Doctor graduates from IMI Critical
13 September 2017
Top HSE certification for IMI Critical’s California site
12 September 2017
Launch of High Endurance Actuator
21 April 2017
Launch of AB6350 valve
06 April 2017
Launch of 100DPC Multi-trim
17 March 2017
Launch of 840GS control valve
22 December 2016
IMI Critical to exhibit new technology at ADIPEC 2016
25 October 2016
New graduates join IMI Critical in four countries
22 September 2016
IMI Critical to take stand at ONS 2016 in Norway
16 August 2016
IMI Critical opens new China plant in Qingpu
27 July 2016
IMI CCI Korea celebrates 2,000 days of no “Lost Time Accident”
25 July 2016
Visit to IMI Z&J Germany by the Russian Economic Bureau from Bonn
11 July 2016
IMI Z&J Düren moves into modern offices
08 July 2016
IMI Critical Engineering forms strategic partnership with MRC Solberg & Andersen
05 April 2016
IMI Way Day 2016 date announced
01 March 2016
NEW IMI Eye – fourth edition
26 February 2016
IMI Critical co-locates China businesses
20 January 2016
IMI CCI Switzerland gains certification for new generation safety valves
18 December 2015
IMI Critical rise to Dragon challenge
30 November 2015
IMI STI achieves CRCC approval for new products
24 November 2015
IMI Truflo Marine Attend the Engineering Technology and Innovation Exhibition 2015
23 November 2015
IMI CCI Sweden secures new contracts on three continents
23 November 2015
IMI Critical Engineering appoints new petrochemicals head
05 November 2015
IMI CCI Czech Republic gains ‘Safe Enterprise’ certification
03 November 2015
IMI Critical announces 90mRMB investment in China
29 October 2015
IMI CCI SriCity wins regional safety award
27 October 2015
Key clients attend grand opening of new Aberdeen facility
23 October 2015
IMI companies ‘act as one’ to deliver for customer
02 October 2015
IMI CCI Sri City approved by NTPC
01 October 2015
IMI Critical Engineering showcases innovation at Valve World Expo Asia
28 September 2015
Nexen awards IMI Orton
25 September 2015
IMI Critical Engineering celebrates opening of new Jubail repair centre
23 September 2015
IMI Critical and IMI Precision join forces at Valve World Expo + Conference Asia 2015
21 September 2015
IMI Critical Engineering opening of new Jubail Repair Centre
18 September 2015
IMI CCI India manufactures first 1050MW turbine bypass valve
20 May 2015
Largest ever contract for IMI Critical Engineering
18 February 2015
New Houston facility opens
12 February 2015
IMI Critical completes acquisition of Bopp + Reuther
02 January 2015
IMI Critical takes family of brands to Valve World 2014
11 December 2014
IMI STI doubles size of Italian plant
20 October 2014

Global sales:
Product - HPU