20 Safety


SAFE TRANSPORTATION OF LIQUID FUELS AT SEA GAS AND FLAME DETECTION FOR TOXIC AND FLAMMABLE HAZARDS


Safety signage on board ship


The modern maritime sector relies on gas and fl ame detection for safe operations. Ammonia, Methanol, LNG, LPG, crude oil, and refi ned products tankers carry thousands of tonnes of fl ammable, volatile chemicals, and hydrocarbons daily. These cargoes are all fl ammable and several are toxic. It pays to review the best practices, codes and regulations for gas and fl ame detection.


Fire at refi nery next to the Port of Santos, April 3th, 2015, Santos, Brazil


gases away from gas detection equipment. Flame detectors can be especially valuable around loading arms on jetties and pumping stations.


Alternative maritime fuels such as methanol and ammonia introduce an additional toxicity hazard. Furthermore, ammonia burns with an inorganic fl ame which requires specialised fl ame detection equipment.


Guidance for tankers and terminals Bunkering operations Toxic and fl ammable gas


and fl ame detection Toxic gases can be present in many maritime applications. Hydrogen sulphide (H2


S) is commonly associated with hydrocarbon processing and gas detection of H2 S would be


required on a fl oating processing, storage, and offl oading ship (FSPO) for liquefi ed natural gas production.


Some maritime gas detection requirements are obvious. Others need a detailed understanding of the potential hazards and appropriate gas and fl ame detection equipment that is required to minimise the risks. For example, H2


S can also be present in many


ships since organic matter in wastewater, bilge and ballast water may decompose to release H2


S.


In addition to the offshore maritime applications, shoreside terminals require gas and fl ame detection. Tank farms are often fi tted with open path area monitoring systems that use long range infrared (IR) beams to detect hydrocarbon leaks.


Flame detection is used outdoors as a second line of defence at storage terminals since strong winds wind can blow leaking


Forced ventillation of a confi ned space on board ship prior to entry PIN OCTOBER / NOVEMBER 2023


The International Safety Guide for Oil Tankers and Terminals Issue 6, 2020 (ISGOTT) is a comprehensive document covering safety on oil tankers, terminals, and the transfer of product between them. The Guide details hazards associated with crude oil and petroleum cargoes.


It provides information on safety precautions that should be followed in applications, such as:


i. loading and discharging of cargo; ii. inerting the tanks;


LNG transfer Elefsina LNG Terminal Greece


The ISGOTT explains that piping gases to a centralised monitoring station from a network of distributed gas samplers can be problematic. This mode of operation can result in condensation of some gases in the pipelines if trace heating is not used. It also incurs a delay in sensing the gases since they must fl ow through the pipes. The potential for particle accumulation and sensor damage is also a disadvantage.


The ISGOTT states a preference for the use of gas detection systems that have a distributed network of fi xed gas detection sensors that monitor gases in situ and transmit electrical signals to a central controller. These systems, it confi rms, provide a rapid response and good reliability.


Gas detection equipment must be used to confi rm that adequate ventilation of the enclosed space has taken place. The atmosphere


iii. gas freeing; iv. enclosed space entry; v. tank washing.


The ISGOTT makes recommendations for gas detection systems in terminals that handle crude oil and products containing toxic components. A risk assessment is advocated to consider the need for detection of hydrocarbon and toxic vapours. Fixed gas detectors are advocated close to higher-risk leak points such as loading arms, transfer pumps and valve manifolds. Toxic gas detectors may need to be installed on the air intakes of pressurised and non-pressurised control rooms.


Various types of sensors are described in the ISGOTT. It confi rms that IR sensors have the benefi t of not being susceptible to poisoning, since they do not require a chemical reaction to detect gases. Catalytic sensors are commonly used for % LEL measurement, but the ISGOTT points out that they may require more maintenance than IR sensors in addition to being susceptible to poisoning. On the other hand, IR sensors are not able to detect ammonia, hydrogen, and carbon monoxide. Other sensor types, such as electrochemical cells are therefore required.


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