bonding and grounding practices Practice Questions

1. What is the PRIMARY purpose of bonding a tank vessel to a shore facility during cargo transfer?

• A.To equalize electrostatic potential between the vessel and the facility, preventing spark discharge✓
• B.To provide a low-resistance path for fault current to trip shore-side circuit breakers
• C.To prevent galvanic corrosion of the vessel's hull during cargo operations
• D.To satisfy the electrical grounding requirement under NFPA 77 for cathodic protection

Why: Bonding connects the vessel and shore facility electrically to equalize their electrostatic potential, thereby eliminating the voltage difference that could produce an incendiary spark at a fuel vapor–air interface.

2. According to 33 CFR 156.120, when must the bonding cable between a tank vessel and a transfer facility be connected?

• A.Before making or breaking any cargo hose or arm connection✓
• B.After all cargo hose connections are completed and tightened
• C.Only when transferring Class I flammable liquids in calm conditions
• D.At any time during transfer operations at the tankerman's discretion

Why: 33 CFR 156.120 requires the bonding wire to be connected before any cargo hose or loading arm connection is made or broken, ensuring static equalization is in place before any potential for spark-igniting vapor release.

3. During a marine petroleum transfer, static electricity accumulation in a cargo tank is MOST hazardous when:

• A.The tank is in the flammable range and a conductive object enters creating a discharge path✓
• B.The tank is fully inerted with oxygen below 8% by volume
• C.The tank is completely full with no ullage space above the cargo
• D.The product has a flash point above 60°C (140°F) and is transferred at ambient temperature

Why: Static discharge is dangerous only when the tank atmosphere is in the flammable range and a conductive path (such as an ungrounded probe or sample thief) creates the discharge, providing an ignition source within the explosive mixture.

4. When transferring cargo through a non-conductive (plastic) hose, what is the primary static electricity concern?

• A.Non-conductive hose cannot dissipate charge, allowing static to accumulate to discharge levels at the nozzle or connections✓
• B.Non-conductive hose has a higher flow resistance, requiring higher pump pressure that heats the product
• C.Non-conductive hose eliminates the need for bonding because no electrical path exists between vessel and shore
• D.Non-conductive hose prevents cathodic protection current from protecting the hull during transfer

Why: Non-conductive hoses do not provide a path to dissipate accumulated static charge, allowing charge to build up and potentially discharge as a spark at metal fittings or flanges where flammable vapors may be present.

5. When is it acceptable to remove the bonding cable between a tanker and a shore facility?

• A.Only after all cargo hose connections have been disconnected and the transfer is completely finished✓
• B.As soon as the cargo pumps are secured, even if hoses remain connected
• C.At any time when no flammable vapors are detectable on a CGI reading
• D.Only after the inert gas system purge of all cargo lines is complete

Why: The bonding connection must remain in place until after all cargo hose or loading arm connections are broken, because disconnecting the hose itself can generate a spark from residual charge unless the bonding cable equalizes potential throughout the entire disconnection process.