Glossary — O

11 terms starting with O.

• Ocean-Going Tug
  Long-endurance tug used for ocean towage of barges, rigs, or disabled ships.
• Offshore Support Vessel (OSV)
  General class of vessels supporting offshore oil/gas/wind operations: PSVs, AHTS, MPSVs, ROV vessels, etc.
• Oil Discharge Monitoring and Control System (ODMCS)
  Equipment on oil tankers that continuously monitors the oil content and flow rate of overboard discharges to ensure MARPOL compliance.
• Oil Mist Detector (OMD)
  A crankcase monitoring device that samples air from each crankcase compartment and alarms if oil mist concentration reaches explosive levels.
• Oil Record Book (ORB)
  A mandatory log in which all oil-related operations including bilge pumping and bunkering must be recorded under MARPOL Annex I.
• Oiler
  An engine department rating who lubricates machinery, maintains oil records, and stands engine room watches.
• Oily Water Separator (OWS)
  Equipment that separates oil from bilge water to reduce oil content to 15 ppm before overboard discharge under MARPOL.
• On-Board Quantity / Remaining On Board (OBQ / ROB)
  OBQ is the oil, water, and sediment in a tanker's cargo tanks before loading; ROB is what remains after discharge. Both are gauged to establish the true quantity transferred.
• Open Moor
  Two anchors set with cables forming a wide V to limit swing in restricted anchorage.
• Open-Loop Scrubber (EGCS)
  Exhaust gas cleaning system that uses seawater as the alkali source to remove SOx, then discharges treated wash water overboard.
• Ordinary Seaman (OS)
  Entry-level unlicensed deck rating assigned general duties under the supervision of ABs and the bosun.