What safety procedure is recommended when using portable cleaning machines on tankers?

When operating portable cleaning machines on tankers, ensuring that these machines are grounded to avoid static discharge is crucial for safety. Static electricity can build up during the cleaning process, especially in environments where flammable materials are present, such as on a tanker. If a machine is not properly grounded and generates a static charge, this could lead to sparks, which poses a significant fire hazard in such volatile settings.

Grounding the machines provides a safe path for any excess static electricity to dissipate into the earth, thus reducing the risk of ignition of flammable vapors that may be present on a tanker. This procedure is essential to maintain safety standards and protect both personnel and the vessel from potential accidents.

The other options, while they may involve good practices in their respective contexts, do not address the specific danger posed by static electricity in a tanker environment. For instance, connecting hoses tightly is generally important to avoid leaks, and cooling the machine ensures operational safety but does not directly mitigate static discharge risks. Using water without internal wires may address electrical safety in a different context, but does not directly relate to the grounding requirement for cleaning machines on tankers. Therefore, grounding the machines is the most relevant and critical safety procedure in this scenario.