Safety Valves of the Marine Boilers

Safety valves are critical components of marine boilers, designed to prevent over-pressurization that could lead to catastrophic failures. These valves automatically release steam if the pressure exceeds safe levels, thus ensuring the safety of the boiler system and the vessel. According to SOLAS chapter II-1 regulations, every steam boiler and un-fired steam generator must be equipped with at least two safety valves to ensure adequate capacity for pressure relief​​.

There are three main types of safety valves used in marine boilers: the Improved High Lift Safety Valve, the Full Lift Safety Valve, and the Full Bore Safety Valve. The Improved High Lift Safety Valve, for instance, is designed to increase valve lift by utilizing waste steam pressure acting on a piston. This design helps to improve steam flow and reduce the risk of valve seizure. These valves are adjusted to open at a pressure slightly above the boiler’s maximum allowable working pressure, ensuring that any excess pressure can be safely vented​​.

Easing gear is another important feature associated with boiler safety valves. It allows for manual operation of the safety valve in cases where it fails to open automatically when the boiler is over-pressurized. This manual intervention can be crucial in preventing accidents. Easing gear also facilitates regular testing of the valves at sea to ensure they are functioning correctly. The gear is designed to achieve a maximum lift of D/4 of the safety valve(one-quarter of the diameter (D) of the safety valve’s orifice), allowing for the effective release of excess pressure​.

Safety valves and their associated components, such as easing gear, are subjected to regular maintenance and testing. This includes hand trying of boiler safety relief valves and ensuring that drains associated with these valves are clear to prevent buildup and incorrect operation. During maintenance, it’s critical to ensure that the valves lift at the designed lifting pressure, with manual adjustments made as necessary to maintain proper operation and safety​​.


Safety valves are essential for the protection of marine boilers, preventing over-pressurization and potential damage or danger to the ship and its crew. Regular maintenance, testing, and correct adjustment of these valves are paramount to ensuring the safety and efficiency of boiler operations at sea:

Regular maintenance, testing, and correct adjustment of safety valves are critical practices for ensuring both safety and operational efficiency of marine boilers. Let’s delve into why each aspect is essential:

Regular Maintenance: Safety valves, being mechanical devices, are subject to wear and tear, corrosion, and accumulation of deposits over time. Regular maintenance ensures that these valves remain in good working condition and can operate freely when needed. Maintenance activities typically include cleaning, inspecting for damage or wear, replacing worn parts, and ensuring that moving parts are lubricated. Regular maintenance helps in identifying potential issues before they lead to valve failure or malfunction.

Testing: Periodic testing of safety valves is crucial to confirm that they will operate as expected under emergency conditions. Testing can reveal if a valve is stuck, if its spring has weakened, or if there are any leaks that could impair its function. Testing often involves lifting the valve using easing gear to simulate an overpressure event and observing if the valve opens and closes correctly at the designated pressures. This helps in ensuring that the valve provides an effective safety barrier against overpressure situations.

Correct Adjustment: The correct setting of safety valves is vital to ensure that they open at the correct pressure, preventing excessive pressure buildup while also avoiding unnecessary release of steam or boiler pressure under normal operating conditions. The pressure settings must be adjusted in accordance with the boiler’s design parameters and operational requirements. Incorrect adjustment can lead to valves not opening at the required pressure or opening too frequently, which can compromise safety and efficiency. Adjustments should be done carefully, often in the presence of a certified surveyor or inspector to ensure compliance with safety regulations and standards.

Together, these practices form a comprehensive approach to managing the health and reliability of safety valves on marine boilers. They prevent accidents and operational disruptions, thereby ensuring the safety of the vessel and its crew, as well as optimizing the boiler’s performance and efficiency at sea. By adhering to a schedule of regular maintenance, testing, and adjustment, ship operators can mitigate risks associated with boiler operations, comply with international safety standards, and ensure the longevity of the boiler system.

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