TOEIC Link Vocabulary — Oily Water Separator and 15 ppm Bilge Alarm Survey Cluster: The Terminology Used to Prove a Ship Does Not Pump Oil Into the Sea

Every engine room leaks a little — fuel drips, seawater seeps, machinery weeps oil — and all of it collects as oily bilge water that has to go somewhere. The law allows a ship to discharge that water overboard only if it has been cleaned below fifteen parts of oil per million, and it must prove this with equipment that watches the discharge and stops it automatically the instant it fails. That equipment is the oily water separator and the 15 ppm bilge alarm, and because pollution offences carry severe penalties, the language around them is exact and heavily audited. Marine surveyors, port state control officers, and superintendents rely on this terminology constantly. This guide assembles the vocabulary of the oily water separator, the 15 ppm alarm, the oil record book, and the survey checks that verify them, and it connects that terminology to the way TOEIC Link actually rewards vocabulary — through paraphrase rather than bare recognition.

Why this cluster rewards TOEIC Link candidates

TOEIC Link, like the broader TOEIC family, tests business and workplace English, and shipping supplies a steady flow of authentic passages: survey reports, port state control deficiency notes, and correspondence over pollution investigations. A candidate who reads "the 15 ppm alarm did not activate the three-way valve when the oil content exceeded the limit" without stumbling keeps their footing through a passage, while one who treats every technical noun as unknown loses time and confidence. The payoff is not collecting rare words; it is building enough domain schema that the surrounding grammar carries the meaning even when a single noun stays fuzzy.

Core layer 1 — The oily water separator

The oily water separator is the equipment that cleans bilge water before it can be discharged, and every term in this layer describes how it does that:

oily water separator (OWS) — equipment that separates oil from bilge water so the water can be discharged within the legal limit.
bilge / bilge water — the accumulated oily water in the lowest part of the engine room.
coalescer / coalescing filter — the stage that merges tiny oil droplets into larger ones that rise and separate.
oil content / ppm — how much oil remains in the water, measured in parts per million.
effluent / discharge — the treated water leaving the separator.
overboard — the direction of a permitted discharge, out to sea.

The word carrying the most weight here is the limit — fifteen parts per million — because the entire system exists to keep the effluent below it. TOEIC Link reading items often hinge on exactly this kind of load-bearing threshold, asking the candidate to grasp why a reading matters rather than simply listing the parts that produced it.

Core layer 2 — The 15 ppm bilge alarm and automatic stop

The 15 ppm bilge alarm is the guardian that watches the effluent and stops an illegal discharge without a human deciding to:

15 ppm bilge alarm — a monitor that measures oil content in the effluent and alarms if it exceeds the limit.
three-way valve — the valve that, on alarm, diverts the discharge back inboard instead of overboard.
recirculate / divert — to send failing water back to the bilge holding tank rather than to sea.
holding tank / bilge tank — where diverted or untreated bilge water is stored.
automatic stopping arrangement — the requirement that the divert happens by itself the instant the limit is breached.

The recurring idea across this layer is automatic prevention, not human judgement — the alarm must stop the discharge without waiting for a decision. Passages describing the alarm lean on words like automatic, divert, and exceed, and the paraphrase question often asks the candidate to explain what the system does when the limit is passed, testing comprehension of the response rather than recall of parts.

Core layer 3 — The oil record book and survey checks

Because pollution is proven or disproven on paper as much as by equipment, the record and survey vocabulary is where defects surface:

oil record book — the mandatory log of every bilge transfer, discharge, and separator operation.
entry / falsification — a logged event; falsifying the book is one of the most serious offences at sea.
functional test / operational test — running the separator and alarm to confirm they actually work, not just that they exist.
deficiency — the term a port state control officer records when equipment or records fail; a heavy word that can lead to detention.
detainable / detention — a deficiency serious enough to hold the ship in port until it is fixed.
rectify / re-test — repair the fault and prove the fix by running the test again.

Note the two-step structure that recurs: a deficiency is found, the ship must rectify it, and then a re-test confirms the fix. TOEIC Link listening items love this cause-and-consequence chain — fault, action, verification — because it tests whether the candidate tracked the sequence rather than latching onto the first fact. Capturing that chain reliably under speech speed is a trainable skill, drilled in numerical and figure capture under fast speech.

How TOEIC Link turns this vocabulary into questions

The test rarely asks "what is an oily water separator?" Instead it embeds the cluster and asks a paraphrase question:

A deficiency note says the alarm "failed to divert the effluent when the oil content exceeded fifteen parts per million." The question asks what was wrong — and the answer option reads "the system did not stop dirty water from going overboard," forcing the candidate to map the technical phrasing onto plain meaning.
A report says the fault was "rectified and the separator re-tested satisfactorily." The question asks what happened — and the correct option says the equipment "was repaired and confirmed working," testing whether the candidate decoded rectified and re-tested satisfactorily as fix-then-verify.

Decoding survey vocabulary through paraphrase, not memorization, is the higher-leverage skill, and it is exactly the recognition move drilled in recognizing answer-option paraphrase without keyword matching.

A five-minute drill you can run today

Take the six terms in Core layer 1 and write, for each, a one-sentence paraphrase a non-specialist would understand ("a coalescer merges tiny oil droplets into big ones so they float up and separate out").
For the 15 ppm alarm, write one sentence explaining what the system does when the limit is exceeded rather than what it is made of — this trains the response comprehension the test rewards.
Read one authentic port state control deficiency note and highlight every word from this cluster, then restate in one plain sentence what the ship must do before it can sail.

Where this cluster connects

Pollution prevention is one node in a wider survey-vocabulary network. The most directly connected clusters are the oil discharge monitoring equipment (ODME) and overboard discharge cluster, which covers the cargo-tank counterpart to this engine-room system, and the bunker delivery note and fuel oil sampling cluster, which shares the same record-and-verify grammar. Reading across these clusters compounds the schema, so a full pollution or deficiency passage in a TOEIC Link section reads as familiar territory.

The takeaway

The oily water separator and 15 ppm bilge alarm cluster is worth mastering because it is dense, high-frequency in authentic environmental passages, and built around exactly the kinds of comprehension the test measures — load-bearing thresholds like fifteen parts per million, response questions like what the system does at the limit, and cause-and-consequence chains like deficiency-rectify-re-test. Learn the terms as paraphrase pairs and response statements rather than isolated words, and an intimidating page of pollution-prevention vocabulary becomes a set of familiar signals that let the grammar carry you through at speed.