‘HYDRA-UW3’ mounted on underwater construction robot Introduced into Vietnam gas pipeline installation work, finally making the first overseas entry

HYDRA-UW3‘, an underwater hydraulic robotic arm developed by R&D Center / Robot Business division of KNR Systems Inc., was mounted in URI-T of ROV.
ROV is KOC Inc.’s underwater construction robot for light work-class. With its installation it was put into the work of installing gas pipelines at a depth of about 120m in the southeast seas of Vietnam since July 15, 2020 for about 85 days. As a result, ‘HYDRA-UW3’ was put into practice for the frist time after passing several tests with the completion of its development and acheved a great success in entering overseas market.

<‘HYDRA-UW3’ mounted on ROV (at the time of 500msw depth rating real sea test)>

The construction of Vietnam’s submarine pipeline is a part of ‘Project of the development of SAO VANG and DAI NGUYET GAS Fields’ carried by the national company, PTSC(Petro Vietnam Technical Services Corporation), and underwater hydraulic robotic arm of KNR Systems Inc. ‘HYDRA-UW3‘ was mounted on URI-T (Underwater Robot It’s Trencher), KOC’s ROV (Remotely Operated underwater Vehicle) which participated for technical cooperative purpose, and was put into pipeline excavation and gas pipeline burial work.

The location of the following project was about 350km southeast of Ho Chi Minh City in southern Vietnam, and the work environment was at a depth of about 120m under the sea. This work was to install 26 inches gas pipe and 18 inches gas pipe which are coated with concrete at a depth of 0.8m each about 22.5km(45km in total) using an underwater unmanned submersible ROV. The ROV that was equipped with the underwater hydraulic robotic arm ‘HYDRA-UW3′ was controlled remotely to excavate pipelines and bury gas pipelines.

<Installation of Vietnam’s submarine pipeline_Provied by The Ministry of Oceans and Fisheries>

It took about 50 days based on 24-hour continuous operation, excluding the period of traveling, etc. Through being put into the first operation via Vietnam gas pipeline installation work, ‘HYDRA-UW3’ again proved its stability and got to increase its precision. It is also expected to gradually secure market competitiveness for domestic and overseas construction markets.

HYDRA-UW3‘ recently succeeded in a 2,800msw depth rating pressurization test from the entire robot arm at Pusan National University’s The Ship and Offshore Research Institute located in Hadong, Gyeongsangnam-do on August 26, 2021. It is planned to carry out 2,500msw level demonstration test in the real sea by the end of this year with its installation on the ROV.

‘HYDRA-UW3’ successfully completed 280 bar pressurization test and secured 2,800msw depth rating performance

On August 26, 2021, R&D Center / Robot Business division of KNR Systems Inc. conducted a 2,500 msw depth rating pressure chamber test on the entire robotic arm at Pusan National University’s The Ship and Offshore Research Institute located in Hadong, Gyeongsangnam-do. In this pressurization test, ‘HYDRA-UW3’ surpassed the initial target of 2,500 msw (250 bar) and showed stable operation even under the pressurized state of 2,830msw (283 bar).

KNR Systems Inc. developed each hydraulic robotic arm for 7DOF and 5DOF for underwater work in 2017. ‘HYDRA-UW3‘ is a hydraulic robotic arm for underwater (deep sea) work that can be controlled remotely by being mounted on the front end of a Remotely Operated underwater Vehicle (ROV).

<‘HYDRA-UW3‘ An Underwater Hydraulic Robotic Arm for 7DOF, 5DOF>

HYDRA-UW3‘ not only has superior performance (payload of 120 kg) compared to the world’s leading robotic arm for deep sea, but also has excellent control performance and high precision (over 19bit). It can also deliver delicate and accurate work with fast inverse kinematics calculation (1kHz). Additionally, user’s (operator’s) convenient coordinate system can be applied as it is equipped with various cameras and their point of view. Each axis has a pressure sensor to apply force control and compliance control. The biggest advantage of ‘HYDRA-UW3‘ is that speed vector commands can be directly used for robotic arm manipulation commands unlike other companies’ underwater robotic arms for deep sea. Therefore, when it’s mounted on ROV, many interface types can be utilized and leads to having higher flexibility than other companies’ products.

HYDRA-UW3‘ is a remote work system which provides high degree of freedom, and it can be utilized diversely in hazardous area where it is difficult for humans to work. For instance, ‘HYDRA-UW3‘ can be used at work that requires waterproofing, disaster prevention/disaster response work, and offshore plant construction as well as work in the water (deep sea). Currently, it is being used in a variety of industries, such as a mud removal robot of intake of nuclear power plant, a nuclear power plant dismantling demonstration test, and a Vietnam gas pipeline project. Its application will be gradually expanded to other fields.

<‘HYDRA-UW3’ An Underwater Hydraulic Robotic Arm for 7DOF, 5DOF>

After the completion of the development of the robotic arm, KNR Systems Inc. has completed the 500msw and 2,500msw depth rating element parts tests, the 500msw depth rating pressurized chamber test of the entire robotic arm, and the operation test in the real sea such as East Sea of Korea and Vietnam, etc.

It is planned to carry out 2,500msw depth rating demonstration test in the real sea by the end of this year with its installation on the ROV.

Advantages and disadvantages of using hydraulic system

In short, hydraulic systems are used in real life because they have many advantages as a device that transmits power by utilizing pressure from fluids.


▶ Response speed is fast.

▶ Unauthorized shift is possible by adjusting the flow rate.

▶ The small device can produce a large output.

▶ Easy to control and easy to operate.

▶ Automatic control and remote control are possible.

▶ Automatic rust and lubrication.

▶ Control of pressure, flow rate and direction by various control valves is simple.

▶ Safety against overload is simple and accurate.

▶ It is possible to accumulate energy.


▶ When affected by temperature, the viscosity of the oil may change and the output may change.

▶ Risk of leakage at high pressure.

▶ Risk of fire.

▶ Composition work is more difficult compared to electric circuits

▶ There is a possibility of failure due to dust or foreign substances.

▶ Operation speed is lower than air pressure.