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Enhancing Tanker Safety: The Role of Inert Gas Systems

Writer's picture: AdminAdmin
May 23, 202410 min read

Updated: Jan 4

Inert gas systems have played a pivotal role in enhancing tanker safety since their introduction in the 1980s. These sophisticated systems prevent the formation of flammable atmospheres within cargo tanks. This significantly reduces the risk of devastating accidents. By replacing the air in the tanks with inert gas (typically nitrogen or treated flue gas), the oxygen content is kept below the level necessary for combustion. This creates a safer environment for both crew and cargo.

 

Aerial view of a gas carrier docked at a cargo terminal, with multiple pipelines and storage tanks visible in the background, highlighting the complexities of marine logistics.
Aerial view of a gas carrier docked at a cargo terminal, with multiple pipelines and storage tanks visible in the background, highlighting the complexities of marine logistics.

The International Maritime Organization (IMO) has recognized the critical importance of inert gas systems on tankers. It has implemented a series of regulations to ensure their widespread adoption. In 1980, SOLAS rules mandated the installation of inert gas systems on tankers of 100,000 deadweight tonnage (dwt) or greater. By 1981, these rules were expanded to include tankers of 20,000 dwt and above. As of January 1, 2016, the regulations encompass all tankers of 8,000 dwt or greater with keels laid after that date.


The Oil Companies International Marine Forum (OCIMF) goes a step further. It advises that all oil tankers, regardless of size, should be fitted with inert gas generators.


Key Takeaways

  • Inert gas systems are crucial for preventing fires and explosions on oil tankers by maintaining a non-flammable atmosphere in cargo tanks.

  • IMO regulations have progressively mandated the installation of inert gas systems on tankers of various sizes, with the latest rules covering all tankers of 8,000 dwt or greater.

  • OCIMF recommends that all oil tankers, regardless of size, be equipped with inert gas generators to enhance safety.

  • The maritime industry is committed to adopting advanced technologies and adhering to evolving regulations to improve tanker safety and protect the environment.

  • Inert gas systems serve as a silent guardian, ensuring the safe transportation of oil and protecting the lives of crew members and the marine ecosystem.


Introduction to Inert Gas Systems on Tankers

Inert gas systems are vital for tanker safety, reducing explosion and fire risks in cargo tanks. They introduce inert gases, like nitrogen or treated flue gas, to lower oxygen levels and create a non-flammable atmosphere.



Purpose of Inert Gas Systems

The main goal of inert gas systems is to prevent explosive & flammable atmosphere in cargo tanks. Even without cargo, oil tanks can produce flammable vapors. Inert gas, with less than 8% oxygen, suppresses combustion of these gases. By maintaining a 5% inert gas concentration, the system prevents vapors from igniting, significantly lowering explosion and fire risks.


Inert gas systems also provide additional benefits, such as:

  • Reducing cargo degradation by minimizing oxidation

  • Preventing corrosion of tank surfaces by reducing moisture content

  • Facilitating safe tank cleaning and inspection operations


History and Development of Inert Gas Systems

The need for enhanced safety led to the development of inert gas systems for tankers. Devastating tanker explosions in the 1960s and 1970s highlighted the necessity for controlling tank atmospheres. In 1974, SOLAS introduced regulations requiring inert gas systems on certain tankers.


Over the years, these regulations have evolved, expanding to more tankers and refining performance standards. Today, SOLAS mandates inert gas systems on various tanker types, ensuring enhanced safety.


  • Tankers constructed before 1 September 1984, based on DWT and cargo types

  • Tankers constructed after 31 December 2015 with a DWT of 8,000 or more

  • Tankers constructed after 1 January 2016 with a DWT of 20,000 or more


Tanker Construction Date

Deadweight Tonnage (DWT)

Inert Gas System Requirement

Before 1 September 1984

Varies based on cargo type

Fixed system required for certain specifications

After 31 December 2015

8,000 DWT or more

Fixed system required

After 1 January 2016

20,000 DWT or more

Fixed system required


Advancements in technology have made inert gas systems more efficient and reliable. Modern systems feature automatic monitoring, improved gas distribution, and enhanced safety features. These improvements significantly enhance tanker safety, protecting crew members and the environment.


How Inert Gas Systems Work

Inert gas systems (IGS) are crucial for tanker ship safety, preventing flammable atmospheres in cargo tanks. They replace air with inert gas, which has less than 8% oxygen. This suppresses combustion of hydrocarbon gases, reducing explosion and fire risks.


Principles of Inert Gas Generation

The main inert gas source on tankers is the exhaust from the boiler or main engine. This flue gas, rich in nitrogen and carbon dioxide, has an oxygen concentration of around 2-4%. It is cleaned, cooled, and pressurized in an inert gas plant before being fed to cargo tanks.


Independent generators and gas turbine plants can also produce inert gas. They offer lower oxygen content, typically 1-2%. These systems enhance control over the tank atmosphere.


Inert Gas (IG) systems must deliver IG with an oxygen content in the IG main not exceeding 5% by volume and maintain a positive pressure in cargo tanks with an oxygen content not exceeding 8% by volume.

The system has two key components:

  1. Production plant: Generates and delivers inert gas under pressure.

  2. Distribution system: Controls inert gas flow into cargo tanks at the right time.


Distribution and Control of Inert Gas

After generation, inert gas is distributed to cargo tanks through a network of pipes and valves.


The distribution system includes PV valves and breakers. These regulate inert gas flow and keep tanks under positive pressure. This prevents air entry and keeps oxygen levels below flammable ranges.


Safety and alarm systems are integrated into the IGS. These include alarms for high oxygen content, temperature, and other critical parameters. They ensure inert gas quality and address any deviations promptly.


Component

Function

Inert gas isolating valve

Isolates the inert gas plant from the cargo tanks

Scrubber tower

Removes particulates and cools the inert gas

Demister

Removes moisture from the inert gas

Gas blower

Provides pressure for inert gas distribution

Pressure regulating valve

Controls the pressure of the inert gas supplied to the tanks

Deck seal

Prevents backflow of cargo vapors into the inert gas system


Key Components of Inert Gas Systems

Inert Gas Generators

Inert gas generators are central to the system, producing inert gas for cargo tanks. They can be standalone units or integrated with the ship's boiler. Using treated flue gas, gas turbines, or dedicated methods, they create inert gas with low oxygen content. Automatic combustion control ensures consistent, safe operation.


Scrubbers and Demistifiers

Before distribution to cargo tanks, inert gas undergoes cleaning and cooling. Scrubbers remove impurities, while demistifiers eliminate moisture. Regularly inspecting scrubbers is vital to detect corrosion, fouling, and damage.


Pressure Control Valves and Monitoring Equipment

Pressure control valves, like pressure regulating valves and vent valves, are vital. They regulate cargo tank pressure, ensuring system integrity and marine fire safety. Non-return valves must be inspected for corrosion and free movement to prevent cargo vapor backflow.


Monitoring equipment, including oxygen analyzers and sensors, continuously measure tank oxygen content. These devices need calibration, and alarm points must be checked for both portable and fixed equipment. This ensures accurate readings and prompt alerts for any deviations from safe levels.


Component

Function

Maintenance Requirements

Inert Gas Generator

Produces inert gas with low oxygen content

Regular inspection, automatic combustion control

Scrubber

Cleans and cools the inert gas

Inspection for corrosion, fouling, and damage

Demistifier

Removes moisture from the inert gas

Regular cleaning and maintenance

Pressure Control Valves

Regulate pressure within cargo tanks

Inspection for proper functioning and calibration

Monitoring Equipment

Measures oxygen content in cargo tanks

Calibration and alarm point checks


Maintenance and Testing of Inert Gas Systems

Regular Inspections and Servicing

Qualified personnel must conduct regular inspections and servicing to ensure inert gas systems operate optimally. These checks should include:

  • Inspecting the piping system and seals for leaks

  • Assessing the condition of critical components like scrubbers, blowers, and valves

  • Confirming the functionality of monitoring and control equipment

  • Verifying the oxygen content of the inert gas supplied to cargo tanks


A massive oil tanker is anchored peacefully at sea under a stunning orange sunset, with distant clouds silhouetting the horizon.
A massive oil tanker is anchored peacefully at sea under a stunning orange sunset, with distant clouds silhouetting the horizon.

The frequency of these activities should adhere to the manufacturer's recommendations and international regulations, such as the International Convention for the Safety of Life at Sea (SOLAS).


The revised Regulation 62 of Chapter 11-2 of SOLAS 1974 mandates specific operational requirements for inert gas systems onboard tank vessels. It emphasizes the need to maintain a non-flammable atmosphere in cargo tanks at all times, except when tanks are needed to be gas-free.

Crew Training and Familiarization

It is crucial for tanker ship safety that crew members are thoroughly trained in inert gas systems. They need to comprehend the system's operation, maintenance, and troubleshooting to react promptly and efficiently during emergencies. Frequent drills and simulations are vital to strengthen their knowledge and skills, improving their capacity to manage critical situations.


Training Topic

Frequency

Key Points

Inert Gas System Operation

Quarterly

- Starting and stopping procedures


- Monitoring and adjusting gas composition


- Emergency shutdown

Maintenance and Troubleshooting

Semi-annually

- Identifying common issues


- Replacing worn or damaged components


- Calibrating sensors and alarms

Safety Procedures

Annually

- Proper use of personal protective equipment


- Responding to gas leaks or system failures


- Evacuation and emergency protocols


Challenges and Limitations of Inert Gas Systems

Inert gas systems can also present challenges and limitations that must be addressed with comprehensive risk management strategies.


One of their biggest limitations is the potential for increased corrosion in cargo tanks due to sulfur dioxide in the inert gas. Proper maintenance and the use of scrubbers can mitigate this issue, but it requires additional resources and crew attention.


Also, a major challenge associated with IGSs are the hazards that inert gases pose risks to the crew, necessitating strict adherence to safety protocols and the use of specialized equipment such as Self-Contained Breathing Apparatus (SCBA) and protective suits when entering inert spaces.


Advancements in Inert Gas System Technology

The maritime sector has seen significant progress in inert gas system technology, enhancing tanker ship safety and marine risk management. These advancements focus on boosting efficiency and reliability, ensuring optimal performance in maintaining a safe atmosphere within cargo tanks.


Improved Efficiency and Reliability

One significant advancement is the introduction of compact nitrogen generators. These generators can produce up to 10,000 m3/h of nitrogen and reduce electrical power consumption by 30% compared to traditional membrane systems. This cuts down operational costs for tanker operators.


Integration with Other Safety Systems

Modern inert gas systems are designed to complement fire detection and suppression systems, cargo monitoring systems, and other critical safety components on board tankers. This integration ensures a comprehensive approach to tanker ship safety.


Conclusion

Inert gas systems on tankers have transformed tanker safety, drastically lowering the risk of explosions, fires, and cargo spoilage. These systems, now crucial in tanker operations, guarantee the safe transport of flammable goods worldwide.


They work by displacing oxygen, creating an inert environment in cargo tanks. This prevents the creation of explosive mixtures, thus boosting safety on tankers.


The advent and adoption of inert gas systems are a direct result of strict international standards, like SOLAS and the Fire Safety Code. These rules, updated in 2016, now require their installation on oil and chemical tankers of 8,000 dwt or more. This underscores their critical role in safeguarding cargo tanks.


Advancements in technology promise to make inert gas systems more effective, dependable, and integrated with other safety measures. Research and development are ongoing, aiming to enhance these systems' performance. By continually refining inert gas systems, the maritime sector reaffirms its dedication to safety, upholding the highest standards in transporting flammable cargoes.


FAQ

What is the purpose of inert gas systems on tankers?

Inert gas systems on tankers serve to introduce inert gas into cargo tanks. This suppresses the combustion of flammable hydrocarbon gases by maintaining oxygen content below 8%. It creates an atmosphere where hydrocarbon vapors cannot burn, significantly reducing the risk of explosions and fires.


How do inert gas systems work?

Inert gas systems generate inert gas from the exhaust gases of the ship's boiler or main engine. The high-temperature gas mixture is then treated in an inert gas plant. Here, it is cleaned, cooled, and supplied to individual tanks via pressure/vacuum (PV) valves and breakers. The inert gas is then fed to the cargo tank, increasing the lower explosive limit (LEL) and decreasing the upper explosive limit (UEL), creating a safe atmosphere.


What are the key components of an inert gas system?

An inert gas system consists of several key components. These include an inert gas generator (either a separate plant or the ship's boiler), scrubber tower, demister, gas blowers, pressure regulating valves, deck seals, non-return valves, deck isolating valves, PV breakers, cargo tank isolating valves, and a mast riser. These components work together to generate, clean, and distribute the inert gas to the cargo tanks.


What are the benefits of using inert gas systems on tankers?

Inert gas systems offer several benefits for tanker safety. They prevent explosions and fires by maintaining an inert atmosphere in the cargo tanks. They also reduce cargo degradation and corrosion by minimizing oxygen presence. Lastly, they ensure compliance with international safety regulations such as SOLAS.


What regulations govern the use of inert gas systems on tankers?

The International Convention for the Safety of Life at Sea (SOLAS) mandates the use of inert gas systems on new tankers and most existing tankers of 20,000 dwt and above. SOLAS also requires the duplication of essential parts of the steering gear and navigational equipment on tankers to ensure control in case of mechanical failure.


How are inert gas systems maintained and tested?

Proper maintenance and testing of inert gas systems are crucial for their reliable operation and effectiveness. Regular inspections and servicing should be carried out according to the manufacturer's guidelines and international regulations. Crew members must be well-trained and familiar with the operation, maintenance, and troubleshooting of the inert gas system to respond effectively in case of any malfunctions or emergencies.


What are some challenges and limitations of inert gas systems?

Challenges and limitations of inert gas systems include ensuring proper functioning under all operating conditions. Failures or malfunctions can compromise safety. The presence of sulfur dioxide in the inert gas can also lead to increased corrosion in cargo tanks. These challenges can be mitigated through proper maintenance, the use of scrubbers, and continuous advancements in inert gas system technology.



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