The Office of Investigations and Casualty Analysis has recently published a Marine Safety Alert, focusing on the dangers related with improper tank cleaning and gas freeing operations. Following several investigations on a tanker barge which exploded during cargo tank cleaning, USCG makes recommendations to avoid such incidents.
USCG has said that if the safety regulations under Title 29 Code of Federal Regulations (CFR) Part 1915 and Title 33 CFR Part 154 are not followed, then cargo tank cleaning and gas freeing operations can lead to serious accidents. Equipment must be properly maintained and inspected before each use.
Although USCG is still investigating the tanker explosion, it has published a list of best practices.
USCG advice
– When on a gas freeing operation, cargo tank manwat and butterworth openings are opened and the flammable vapors within the cargo tank are then removed using mechanical air-moving equipment. While the outside air is being introduced into the cargo vessel, the vapor/air mixture within the tank, and near the tank openings, will fall into the flammable range.
– If the air moving equipment used to gas free the cargo tank is not properly maintained or not properly electrically bonded and secured to the vessel’s structure, static electricity generated by the air moving equipment can discharge as an electric arc and ignite the flammable vapor/air mixture.
In light of the situation, USCG strongly advises all the crewmembers who work at marine facilities or are onboard ship involved with cargo tank cleaning and gas freeing operations, to take the following actions:
– Ensure that the recommendations outlined in Coast Guard Marine Safety Alert 10-14 have been incorporated into the SOPs used by personnel when on cargo tank cleaning/gas freeing operations.
– Make sure that actions and practices taken by crewmembers involved in cleaning and gas freeing, follow all the applicable requirements of 33 CFR Part 154 and 29 CFR Part 1915.
– All the personnel must be well-educated on the critical importance of the bonding wire/strap on air moving equipment (blowers/fans), while understand that the proper bonding of blowers/fans used in cargo tank cleaning and gas freeing operations is a federal requirement under 29 CFR § 1915.13(b)(11).
– All the crewmembers must be specifically trained on how to secure blowers/fans in place to prevent movement/rattling properly, due to vibration and how to bond blowers/fans to the vessel/barge structure. Simply touching/resting the blower/fan to bare metal is not an adequate means of bonding.
– Install policy/procedures in order to inspect all air moving equipment, such as portable blowers/fans, prior to first use on each workday.
– Ensure that all attached accessories are tightly connected to the blower/fan, and that each blower/fan has a bonding wire/strap that is undamaged, free of corrosion, and securely fastened to the housing of the blower/fan.
– Implement a policy in order to require the site Safety Supervisor, SCP or PIC of the cleaning/gas freeing operation to visually inspect each blower/fan to ensure that they are properly secured to prevent movement/rattling and that they have been securely bonded to bare metal on the vessel structure by use of a bonding wire/strap with clamp (or other mechanical means to provide a secure connection). These checks should be completed before activating the blowers and fans.
Read the Marine Safety Alert in full: USCG-Marine-Safety-Alert-2020_02
