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LNG CARRIER GAS DETECTORS FAIL CHECKS

Friday, May 1, 2020 

In the latest alert from Norwegian risk management specialist Gard, the insurer points out that routine port state control (PSC) inspections by the US Coast Guard (USCG) have found that fixed gas detection system sensors on some LNG carriers were outside the tolerances established by the manufacturer and failed subsequent calibration checks.

According to Gard, many incidents in shipping have involved leakage of flammable and toxic gases into pump rooms, void spaces, engine rooms and other compartments. A mixture of gas in the air beyond certain concentration levels can be life threatening for crew entering these spaces and pose a serious fire risk. The International Gas Carrier Code (IGC Code) states that gas detection equipment shall be installed to monitor the integrity of the cargo containment, cargo handling and ancillary systems, and should be tested in accordance with recognized standards. To ensure that the fixed gas detection system operates effectively, timely and accurate calibration of the sensors is critical.

A USCG marine safety alert has highlighted issues with the fixed flammable gas detection system on a few LNG vessels, stating: “during exams on three separate Liquefied Natural Gas (LNG) carriers in Boston, Port State Control Officers (PSCOs) discovered issues with the fixed flammable gas detection system that resulted in the issuance of deficiencies and delay of cargo operations. While witnessing tests, multiple sensors measured outside the tolerances established by the manufacturer and subsequent calibration checks failed”.

The two main reasons highlighted by the USCG for these deficiencies are the use of inappropriate span gas on the sensors, and not following proper calibration procedures.

The type of span gas, or calibration gas, used depends on the type of sensor. There are three main types of sensors: infrared, electrotechnical and catalytic sensors. The PSC deficiencies issued by the USCG for the fixed gas detection systems, related to the improper calibration of catalytic sensors. The span gas selected should reflect the target gas which the crew is trying to measure in a space.

Ship’s crew should fully understand the manufacturer’s testing procedures and permissible tolerances for maintaining and testing fixed gas detection systems. If during testing, a sensor shows a reading outside the tolerances specified, the manufacturer’s instructions on correcting this should be followed. The USCG highlights that “sensors operating outside of established tolerances pose a significant safety threat and could be grounds for vessel control actions, such as delayed departure from port, delayed cargo operations, or detention”.

Gard says that proper crew training and awareness is important, and notes that catalytic and combustible type gas sensors usually have a limited operating life, at the end of which they must be changed.

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