Although there aren't many issues found on gas carriers, the top five deficiencies are:
#1 Gas detection
Gas carriers are required gas detection. It's required to sample many locations around the vessel. The interval period should not to exceed the 30 minutes. It is required to alarm at 30% LEL. It's tested and calibrated with span gas. It's expected to alarm on the bridge and where cargo's controlled. The coastal security will test the system along with a crewmember that is in charge of gas detection. Also, the CS will have the crew member calibrate the system and ensure that it alarms at 30% LEL. Often, the USCG finds problem concerning the calibration and this test.
#2 Emergency shut downs
Gas ships are in need of emergency shut downs that need to be activated from two remote locations. They have fusible elements that are installed over the tank domes and loading stations. Once emergency shut down is activated it’s expected to turn off within 30 seconds. Most of the times, marine inspectors find that the valve does not close within the 30 second requirement.
#3 Maximum Allowable relief valve settings
MARVS or maximum allowable relief valve settings are required to be set in accordance to IGC code and 46 CFR 154. When MARVS are installed, they should be installed under the supervision of the captain and must be inured in the vessel's log. After they’re installed, they have tamper seals that are in place and must remain intact. Many times, marine inspectors find that these tamper seals or settings are incorrect.
#4Deck water spray
Gas carriers need a deck water spray system that covers the cargo deck, tank domes, manifolds, and superstructure. Often marine inspectors find that these nozzles on the water spray are clogged.
The lighting fixtures on a gas ship should definitely be flameproof or pressurized in the gas dangerous zone. All wiring should be in good condition. However, sometimes marine inspectors find problems with the wiring and the cable glands in electoral installations.