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COMMAND A BOND BARGES • A RECENT EXPLOSION ABOARD A TANK BARGE HAS HIGHLIGHTED THE IMPORTANCE OF ENSURING EFFECTIVE BONDING OF BLOWERS DURING GAS FREEING OPERATIONS THE US COAST Guard (USCG) has issued a safety alert, reminding those who are involved in cargo tank cleaning and gas freeing operations to ensure that they should follow the recommendations outlined in its earlier safety alert 10-14 and, in particular, that it is critically important to verify the bonding wire or strap on blowers and fans. The alert comes as an interim measure as part of a current USCG investigation of a recent incident, involving an explosion due to improper bonding of a blower, that caused a breach of the cargo tank and the bulkhead between cargo tanks, as well as damage to the external framing of a tank barge. USCG highlights that the process of gas freeing introduces additional hazards. At this time, cargo tank manway and butterworth openings are opened and the flammable vapours in the cargo tank are removed using mechanical air moving equipment. As outside air is introduced into the cargo tank, the vapour/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 the proper type, is not properly maintained, or is 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 vapour/air mixture.
HCB MONTHLY | APRIL 2020
During its recent investigation, USCG found pneumatic blowers that had either missing or improperly maintained bonding wires. RESPONSIBILITY ALL ROUND Pending the final report of its investigation, USCG “strongly encourages” all personnel working at marine facilities or onboard vessels to follow procedures and practices that meet all the applicable requirements of 33 CFR Part 154 and 29 CFR Part 1915 – any workers who are not mariners with a “substantial connection” to the vessel under repair fall under the jurisdiction of the Occupational Safety and Health Administration (OSHA). All personnel should understand that the proper bonding of blowers and fans used in cargo tank cleaning and gas freeing operations is a federal requirement under 29 CFR §1915.13(b)(11). They should be specifically trained on how to properly secure blowers/fans in place to prevent movement/ rattling due to vibration and how to properly bond blowers/fans to the vessel/barge
structure (e.g. ensure bonding wire/strap is tightly secured to the fan/blower housing and that the clamp for the bonding wire/strap is secured to the vessel structure on bare metal, penetrating any paint coatings). Simply touching/resting the blower/fan to bare metal is not an adequate means of bonding. Policies and procedures should include a requirement to inspect all air moving equipment prior to their first use each day. All attached accessories, such as cones and ducting, must be tightly connected; bonding wires and straps must be undamaged, free of corrosion and securely fastened to the housing of the blower or fan. Clamps used with the bonding wire/strap should also be free of corrosion, with adequate tension to ensure a tight grip/connection when clamped to the vessel/barge structure. Loose, poor and corroded connections greatly increase the risk of an electric arc due to static discharge. USCG also advises that site safety supervisors or other personnel with overall safety responsibility conduct a visual inspection of each blower or fan to ensure that these provisions have been complied with, and that these checks should be completed before the blowers/fans are activated.
