Tankerman

Roles and qualification:

- A Tankerman-PIC may supervise the transfer of liquid cargo in bulk; a Tankerman-Assistant works under the direction of a PIC. - The PICs of the transferring and receiving facilities must be in continuous communication using an agreed means and agreed signals.

Pre-transfer conference:

Before transfer, the PICs review the operation, agree on the cargo, sequence, rates, the maximum allowable transfer rate, topping-off plan, and the signals for normal stop and emergency shutdown.

Continuous watch:

A continuous watch over the transfer is required so leaks, hose ranging, level changes, or an emergency can be detected and the transfer stopped immediately.

Declaration of Inspection (DOI):

Before transfer begins, both PICs complete and sign the DOI — a written checklist confirming the system has been inspected and both parties agree on procedures, communications, and emergency shutdown. Required items include: scuppers plugged, connections made up properly, sufficient personnel on watch, warning signs and signals displayed, no-smoking enforced, and emergency-shutdown means tested.

Flash point:

The lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture near its surface. A low flash point (grades A/B) means a greater fire hazard during handling.

Flammable range (explosive range):

The band of vapor-in-air concentrations that will burn, bounded by the Lower Flammable Limit (LFL) and Upper Flammable Limit (UFL). - Below the LFL: "too lean" — not enough fuel vapor to burn. - Above the UFL: "too rich" — too much vapor and too little oxygen to burn. - Only between LFL and UFL will the mixture ignite.

Vapor pressure:

A measure of a cargo's volatility. High-vapor-pressure cargoes evaporate readily and build pressure in a closed tank, requiring venting through the P/V valve.

Toxicity — H2S and benzene:

Some crude oils contain hydrogen sulfide (H2S), which is highly toxic and can paralyze the sense of smell at hazardous concentrations, so odor cannot be relied on for detection. Atmosphere testing and respiratory protection are required where toxic vapor may be present.

Oxygen control:

A properly inerted tank is maintained at 8 percent oxygen by volume or less — below the roughly 11 percent needed to support combustion of hydrocarbon vapor.

Sources of inert gas:

- Flue-gas (boiler uptake) systems scrub and cool exhaust gas. - Inert gas generators burn fuel to produce low-oxygen gas. - Nitrogen from a generator or shore supply on some chemical/gas carriers.

Positive pressure:

Tanks are kept at a slight positive pressure so that any leak is outward — air cannot be drawn in. During discharge, inert gas replaces the volume of liquid pumped out so the tank never draws a vacuum or admits air.

Purging and gas-freeing:

To gas-free safely, the tank is first purged with inert gas to bring hydrocarbon content low enough that, when air is then introduced, the atmosphere passes from inert to safe without ever becoming flammable.

Static accumulators:

Low-conductivity (clean) products such as some refined petroleum can retain a static charge. Precautions: - Reduce the initial loading rate until the fill-line outlet is submerged (avoids splash/free-fall loading). - Avoid free-fall and spraying into the tank. - Observe a settling/relaxation time before gauging or sampling so the charge can dissipate.

Ship/shore electrical isolation:

Current U.S. guidance is to fit an insulating flange (or one length of nonconductive hose) in the ship/shore connection. This breaks the metallic path and stray-current loop between vessel and shore, preventing an arc when the connection is made or broken. A separate bonding cable across the connection is generally NOT recommended for marine transfers.

Control of ignition sources:

Smoking, open flame, spark-producing tools, and non-explosion-proof electronics are prohibited in the cargo area during transfer. Only intrinsically safe or explosion-proof equipment may be used where flammable vapor may be present.

Closed gauging:

Closed gauging measures tank level through a sealed device so the tank is never opened to atmosphere. It avoids vapor release, static risk at the ullage port, and personnel exposure to toxic or flammable vapor — preferred over open ullage-port gauging.

Pressure/Vacuum (P/V) valves:

The P/V valve relieves overpressure (from loading or thermal expansion) and admits gas to break a vacuum (during discharge or cooling), protecting the tank structure while keeping it closed during normal operation.

Overfill protection:

- High-level alarm: warns the PIC before the tank reaches its maximum fill so transfer can be slowed and stopped. - Independent overfill (high-high) alarm: a backup to manual gauging and the high-level alarm.

Topping off:

At the end of loading, reduce the transfer rate so ullage on each tank can be watched closely and valves shut in sequence — stopping before the maximum allowable fill is exceeded.

Line clearing:

After transfer, drain or blow down hoses and arms before disconnecting so trapped liquid is not spilled when the flange is broken.

Scuppers and containment:

Deck scuppers are plugged before transfer so any spill stays on deck. Drip pans or fixed containment under each manifold connection catch minor leaks before they reach the deck or sea.

Discharge reporting:

A discharge of oil into U.S. navigable waters that causes a sheen or violates water-quality standards must be reported IMMEDIATELY to the National Response Center (NRC). The person in charge makes the report.

Oil Record Book:

Oceangoing tankers keep Oil Record Book Part II for cargo and ballast operations (loading, internal transfers, discharge, tank cleaning, ballasting), in addition to Part I for machinery-space operations. Entries are made promptly and signed.

Crude oil washing (COW) and slops:

COW uses the crude cargo itself, sprayed through fixed machines in an inerted tank, to redissolve clingage — reducing both residue left aboard and the water washing that creates slops. Oily washings are collected in a slop tank for oil/water separation (load-on-top) or discharge to a reception facility, within MARPOL discharge criteria.

SOPEP/VRP:

Tank vessels carry a shipboard oil pollution emergency plan and (in U.S. waters) a vessel response plan describing spill response, notification, and resources.

Safe-for-entry atmosphere:

Before anyone enters a cargo tank, a competent person tests the atmosphere and verifies: - Oxygen at least 19.5 percent (normal air is 20.9 percent), - Flammable vapor below 10 percent of the LEL, - Toxic gas (H2S, benzene) below permissible exposure limits.

Gas-free certificate and hot work:

Before hot work (welding or cutting) on or near a cargo tank, a Certificated Marine Chemist (or other authorized person) tests the space and issues a certificate that it is gas-free and safe for hot work. No ignition source is permitted until the certificate is in hand.

Entry permits and standby:

Enclosed-space entry requires a permit, continuous or periodic atmosphere monitoring, ventilation, an attendant standing by at the entrance, and a means of rescue and communication.

Why purge before air:

A tank under inert gas is purged with more inert gas to drive hydrocarbon content low before fresh air is admitted, so the mixture goes from inert to safe without passing through the flammable range.