Hydrostatic Release Unit (HRU): The automatic safety solution for life rafts
The hydrostatic release unit plays a crucial role in the timely deployment of life rafts from ships—an essential component of life-saving appliances (LSA) required on all vessels. Today, all life-saving equipment must be released with minimal human intervention, ensuring swift and reliable activation during emergencies.
This means that, when necessary, life-saving devices must be immediately ready for use without delay.
Automation has become a key solution to meet this demand. In scenarios where human intervention is difficult or time-consuming, it’s essential to have mechanisms in place to ensure that the life-saving equipment can be activated promptly.
The release mechanism is the most critical part of life-saving appliances, enabling safe and timely deployment when needed. For life rafts, this mechanism relies on a specialized device called the Hydrostatic Release Unit (HRU).
What is a Hydrostatic Release Unit (HRU)?
The Hydrostatic Release Unit (HRU) is a critical safety device in the maritime industry, designed to automatically activate the release of life rafts from ships in emergency situations. As an essential component of life-saving appliances (LSA), the HRU ensures that life rafts can be deployed without direct human intervention when incidents such as ship sinking or accidents occur.
HRUs are typically installed on commercial vessels, yachts, and maritime transport ships and are regulated under international maritime safety standards in compliance with the International Maritime Organization (IMO). The HRU guarantees that life rafts are safely and swiftly deployed into the water during emergencies, even if crew members are unable to manually release them due to hazardous conditions.
The primary function of an HRU is to operate independently and automatically in emergencies without requiring manual activation. This enhances safety and reduces risks, ensuring life-saving equipment is always ready for deployment in critical moments.
With its significant role in ensuring the safety of lives at sea, the HRU is a vital part of modern life-saving appliances, contributing to the effectiveness of global maritime safety efforts.
How does a Hydrostatic Release Unit (HRU) work?
The Hydrostatic Release Unit (HRU) operates on the principle of hydrostatic pressure, enabling the automatic release of life rafts when a ship encounters an emergency and begins to sink. As the ship sinks to a certain depth, the increasing water pressure activates the HRU’s switch. At that point, the HRU disconnects the rope or pin securing the life raft, releasing it from its storage position and allowing it to float to the surface, ready for rescue operations.
This mechanism is similar to how oxygen masks in airplanes automatically drop when the cabin pressure suddenly decreases. However, instead of relying on air pressure, the HRU is triggered by water pressure to release the life raft.
HRUs are typically installed in critical areas of the ship and are well-protected within sealed casings. When the vessel starts to sink, the rapid change in water level—referred to as draft—creates higher hydrostatic pressure, which triggers the HRU. The HRU is usually set to activate at a depth of 1.5 to 4 or 5 meters below the ship’s maximum design draft.
A key feature of the HRU is its reliability under extreme conditions, including fires or other unexpected incidents. It ensures that life-saving equipment is deployed on time, providing critical protection for those onboard.
By operating independently and automatically, the HRU plays a crucial role in maritime safety, ensuring that life rafts are available without delay in emergencies.
Operational sequence of the Hydrostatic Release Unit (HRU)
The operation of an HRU follows a straightforward yet critical sequence during emergencies. When a ship starts sinking or becomes submerged to a certain depth, the rising hydrostatic pressure is detected by the HRU through its sensor system and membrane that come into contact with water. Upon sensing the change in pressure, the HRU automatically activates.
The activation signal triggers the release mechanism for the life raft, cutting or detaching the securing ropes, pins, or safety straps. If it is an inflatable life raft, it will automatically inflate using compressed gas stored in its chambers and then be released into the water.
This automated mechanism saves valuable time and minimizes the need for human intervention in deploying life-saving equipment. In emergencies, the crew may face disorientation, injuries, or multiple challenges, making the automation of the HRU crucial to ensure lives are protected.
HRUs must adhere to strict safety standards and undergo regular inspections before each voyage as part of the ship’s safety checklist. To ensure optimal performance and reliability, HRUs need to be replaced every 4 to 5 years, depending on the vessel type and operational conditions.
>>>Expiry Date must be marked on the H20 prior to installation onboard
