Marine Hydrostatic Release Unit

About product

Marine Hydrostatic Release Unit (HRU) is an essential marine safety equipment used to securely attach free-floating devices, such as life rafts and emergency beacons, to a ship. In the event of a ship sinking or other emergencies, the HRU automatically or manually releases the attached device. It ensures the safe deployment of the life raft when the water depth is no more than 4 meters. HRUs play a critical role in enhancing the effectiveness of emergency equipment for maritime safety.


marine hydrostatic release unit

  • Automatically releases free-floating devices in emergency situations.
  • Operates based on hydrostatic pressure.
  • Consists of a housing with a mechanism sensitive to water pressure.
  • Automatic HRU releases devices when a specific water pressure is reached.
  • Manual HRU allows for manual release of devices regardless of water pressure.

Additional information


glass fiber and reinforced nylon


339 g


18 x 9 x 7 cm

Product Detail

What Is Hydrostatic Release Unit?

A Hydrostatic Release Unit (HRU) is designed to automatically release or detach free-floating devices, such as life rafts or emergency beacons, from a ship in emergency situations. The HRU operates based on the principle of hydrostatic pressure.

The HRU typically consists of a housing or casing that contains a mechanism sensitive to water pressure. When the ship starts sinking or reaches a certain water depth, the increasing hydrostatic pressure activates the HRU.

Types Of Marine Hydrostatic Release Unit

  • Automatic HRU: This type of hydrostatic release unit is designed to release the attached device automatically when a specific water pressure is reached. The HRU’s mechanism, usually a spring-loaded system, is calibrated to activate at a predetermined depth, typically around 4 meters. Once the water pressure exceeds the threshold, the HRU triggers the release mechanism, allowing the free-floating device to detach from the ship.
  • Manual HRU: In some cases, there may be a manual release option available alongside the automatic mechanism. This allows crew members or individuals on board to manually trigger the release of the free-floating device, regardless of the water pressure. The manual release mechanism is typically accessible and easy to operate in emergency situations.

Marine Hydrostatic Release Unit Drawing

marine hydrostatic release unit

How Does The HRU Work?

The HRU (Hydrostatic Release Unit) is a vital component of a liferaft’s deployment system. Its purpose is to automatically release and deploy the liferaft from its cradle or deck in the event of a vessel sinking. Here’s how the HRU works:

  • Components: The HRU consists of several components:
    • Double Looped White Rope Line: This rope line is securely attached to the liferaft cradle or deck.
    • Release Mechanism: The release mechanism holds the liferaft in place until activated.
    • Red Weak Link™: The Red Weak Link™ is a specially designed connection with a specific breaking strength. It holds the liferaft to the ship or cradle until it needs to be released.
  • Activation: When a vessel sinks, the water pressure increases as it submerges. Typically, when the water pressure reaches a depth of approximately 4 meters, it activates the hydrostatic release unit.
  • Release and Deployment: Once the HRU is activated, it triggers the release mechanism. The release mechanism then severs the white strong rope line, which is attached to the liferaft cradle or deck. By cutting this rope, the liferaft is freed from its secured position.
  • Liferaft Inflation: As the ship sinks, the liferaft painter line, which is still connected to the vessel, becomes stretched. This stretching motion triggers the inflation mechanism of the liferaft. The liferaft starts to inflate, gradually taking shape and becoming ready for boarding.
  • Weak Link Breakage: The Red Weak Link™ is designed to have a specific breaking strength. Once the liferaft is inflated and ready, the stretching of the painter line puts tension on the Red Weak Link™. Eventually, the Red Weak Link™ breaks, allowing survivors to safely board the floating liferaft.
Know Who We Are

About our company

Zava Marine Corporation is a leading supplier of marine parts and components. With a strong focus on quality and customer satisfaction, we specialize in providing a comprehensive range of high-quality marine equipment and accessories. Our products include deck equipment, ship accessories, and various other essential components needed for smooth maritime operations.

With a global presence, we serve a diverse customer base, including shipbuilders, shipowners, offshore operators, and marine equipment distributors. We are committed to providing exceptional service and tailored solutions to meet our customers’ unique needs.


Zava Marine offers a comprehensive range of certifications for marine parts in accordance with international standards and regulations. These certifications include those provided by renowned marine classification societies such as Lloyd’s Register (LR), Bureau Veritas (BV), China Classification Society (CCS), Registro Italiano Navale (RINA), American Bureau of Shipping (ABS), Nippon Kaiji Kyokai (NK), and Det Norske Veritas – Germanischer Lloyd (DNV-GL). By collaborating with these esteemed societies, Zava Marine ensures that our certified marine parts meet the highest standards of safety, quality, and performance, instilling confidence in our reliability and compliance within the maritime industry.

The warranty provided by Zava Marine covers defects in materials and workmanship for a period of two years from the date of purchase. During this warranty period, if any marine parts purchased from Zava Marine exhibit issues or failures resulting from manufacturing defects or faulty materials, Zava Marine will take responsibility for repair or replacement of the affected parts. 

Zava Marine has recently opened new molds for European and North American clients, utilizing materials such as metal, ABS, PVC, and more. These successful mold opening projects allow us to provide customized marine parts and components that meet the specific requirements of our clients in these regions.

Typically, Zava Marine can ship samples within 7 days once the product drawing has been mutually confirmed by both parties. This efficient process ensures that customers can receive samples promptly, allowing them to assess the quality and suitability of the products.

Zava Marine frequently utilizes a wide range of materials in our projects. These materials include aluminum, stainless steel, carbon steel, copper, plastics, titanium, and PEEK (Polyether Ether Ketone). Each material offers unique properties and characteristics suitable for various marine applications. 

Yes, we provide customization services for marine parts. We understand that every project and application may have unique requirements, and we are committed to delivering tailored solutions. By collaborating closely with our clients, we can adapt our products to specific specifications, ensuring optimal fit, performance, and compatibility. Whether it’s modifying existing designs or creating entirely new parts, our customization services cater to the diverse needs of the maritime industry.

Absolutely! We offer product design and development services to support our clients’ needs. Our experienced team of engineers and designers can collaborate with clients from concept development to final product realization. By leveraging our expertise in marine engineering and design, we can provide valuable insights and innovative solutions. Whether it’s optimizing existing designs or creating entirely new products, we are equipped to assist clients in bringing their ideas to life efficiently and effectively.

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