🔍 Key Concepts

• Fire main system layout on a Mobile Offshore Drilling Unit (MODU) • Purpose of cutoff (isolation) valves in fire main systems • Hazards specific to exposed decks on offshore units

💭 Think About

• Ask what environmental or operational condition on an exposed deck would threaten the integrity of fire main piping and hoses. • Consider why regulations allow isolation of only a portion of the system, not the whole system, and what they are trying to preserve. • Think about which option would most seriously affect the availability of fire-fighting water in an emergency if not controlled.

✅ Before You Answer

• Verify which hazard could damage or disable the fire main piping itself on an open/exposed deck. • Check which choice relates to a safety and survivability concern, rather than just convenience or operational preference. • Confirm that the purpose of the cutoff valve is to protect the system, not to control routine use like washdowns.