Gas Detection: An Essential Safety Component in Marine Vessels

(Image Courtesy: AZERNEWS)

Gas Detectors for vessels is a device that detects the presence of gases in ships, often as part of a safety system. This type of equipment is used to detect a gas leak and interface with a control system so a process can be automatically shut down. Gas detectors measure and indicate the concentration of certain gases in an air via different technologies.

Gas meters are also used on-board ships to measure the hydrocarbon content, explosion hazard risk, and also the oxygen analysers. Under the following circumstances the cargo tank or any enclosed space on-board the ship has to be evaluated to ensure that the particular space is gas-free and has ample amount of oxygen for personnel to work there if required. The circumstances may be:

  • Prior to any repair work (which may be at dry-dock or even at the shipyard)
  • As quality control before loading (A person called the vetting inspector usually inspects the cargo tank)
(Image Courtesy: Nautic Expo)

Tank evaluation is done to ensure that the atmosphere inside the tank is safe enough for personnel to make an entry. There are different types of equipment available on-board for the evaluation of the tank atmosphere:

  1. Combustible gas indicators or explosimeters: An explosimeter is a device used to detect the amount of combustible gases present in a sample of the given atmosphere. This gives the reading in terms of percentage of the LFL (lower flammable limit).
  2. Tankscope or non-combustible gas indicators: A device used for measurement of hydrocarbon gas content in a sample of given atmosphere. This instrument is meant for measuring the hydrocarbon vapour in inert atmospheres. This instrument is not as sensitive as the explosimeter. The reading is only in percentage of the volume of the hydrocarbon vapour and hence used only during the gassing up operations and during inerting.
(Image Courtesy: Weatherall Equipment and Instruments)
  1. Multi-gas analysers: Multi-gas analysers are used to detect only targeted gases and vapours. It is very specific to that type of gas only, so care has to be taken to ensure that correct tubes are used for the particular type of gas. The multi-gas analyser consists of a portable bellows pump and detector tubes. The detector tube is like a vial filled with reagent that will react with the specific chemical.
  2. Oxygen analysers: The oxygen analyser is a device used to measure the concentration of oxygen in a given atmosphere. This device plays a vital role as it provides essential readings after which it is evaluated that personnel will enter the chambers or not. The important checks that are done on the oxygen analysers are: Calibration with fresh air (which contains 21% of oxygen); Battery check. But the batteries should not be charged in dangerous zone.
(Image Courtesy: Discount Marine)

Handy Commercial Tools as Gas Detectors

Portable systems for gas detection can be just as vital in the marine industry. The PS1 (single gas) is a very popular portable gas detector. Small and lightweight it is also very easy to use. It is a single gas detector and is available in oxygen, hydrogen sulphide, carbon monoxide and hydrogen sulphide versions. It also comes with an on-board calibration option should you require it.

Another option is the V!SA (multi-gas).  Like the PS1 it is portable and lightweight, yet incredibly robust. Unlike the PS1, it can monitor up to four separate gases at the same time. It also has on-board calibration options.

Both these products save lives. When working in enclosed spaces they omit a powerful sonic alarm and a brilliant visual one if they detect gas. They can be carried by hand or fitted easily onto clothing leaving your hands free. They also conform to all current legislation for the shipping industry globally.

(Image Courtesy: Container Shipping and Trade)

Gas Detectors save Life & Resources

Gas detection equipment measures a gas concentration against a calibration gas that acts as a reference point. Earlier gas detection monitors detected a single gas, but today, a modern gas monitor can detect several toxic or combustible gases and even combinations.

High temperature surfaces in an engine room, a short circuit in an electrical system, smoking or other domestic sources of fire or a reaction in the cargo, ships are definitely vulnerable to fires. Many seafarers lose lives every year due to toxic work environment. Therefore detecting such hazards before they become fatal, is essential to contain the damage which can take the form a disaster.

(References: Bright Hub Engineering, Gas Measurement Instruments Ltd, The Herald Analyst)

Sea News Feature, March 8