What Regulation 35 covers and how it differs from Regulation 33
Regulation 35 of MARPOL Annex I is titled “Crude oil washing operations”. It sits in Chapter 4, Part C, the part that controls the operational discharge of oil from the cargo area of oil tankers. The regulation does one job: it makes the operation of an already-fitted COW system disciplined, documented, and auditable. It does not decide which tankers must have COW. That is the work of Regulation 33, which sets the requirement to fit a system on every crude oil tanker of 20,000 tonnes deadweight and above delivered after 1 June 1982, and which references the design and equipment Specifications.
The split matters in practice because the two regulations are surveyed and enforced differently. Regulation 33 compliance is a construction-and-equipment question answered at plan approval and at the major surveys: are the washing machines fitted, is the COW main arranged correctly, does the inert gas system cover the tanks. Regulation 35 compliance is an operating question answered by the document on the bridge and the entries in the record book: is the approved manual on board, are the wash programmes being run as written, are the oxygen readings being taken and logged, is a named officer in charge. A vessel can pass a Regulation 33 equipment check and still fail Regulation 35 because its Oil Record Book Part II entries contradict the manual.
This article scopes tightly to the Regulation 35 operating regime and the Operations and Equipment Manual. It does not repeat the Regulation 33 fit requirement (the deadweight thresholds, the 1978 Protocol history, the SBT-or-COW-or-both architecture), which the Regulation 33 article covers in full. It also does not repeat the general tank-cleaning practice (the washing-machine hardware in detail, the load-on-top mechanics, the water washing for gas-freeing, the confined-space entry rules), which the marine tank cleaning and crude oil washing article covers as an operational walkthrough. What follows is the regulatory anatomy of Regulation 35 itself: the manual, the operational controls it imposes, the record-keeping, and the discharge-limit linkage.
The text of Regulation 35: the three operative requirements
Regulation 35 reduces to three operative requirements. The first is the manual. Every oil tanker operating with a crude oil washing system shall be provided with an Operations and Equipment Manual detailing the system and equipment and specifying operational procedures. The manual shall be to the satisfaction of the Administration and shall contain all the information set out in the Specifications referred to in Regulation 33.2. If an alteration affecting the crude oil washing system is made, the manual shall be revised accordingly. This is the document at the center of the whole regime.
The second requirement is conformity. The crude oil washing system, equipment, and arrangements shall comply with the Specifications referred to in Regulation 33.2. Regulation 35 does not write its own technical standard. It points back to the Specifications, which are the Revised Specifications for the Design, Operation and Control of Crude Oil Washing Systems in Resolution A.446(XI), as amended by Resolution A.497(XII) and Resolution A.897(21). The manual is the vessel-specific expression of those generic Specifications.
The third requirement is operation in accordance with the manual, with the oxygen control attached. Cargo tanks shall be crude oil washed only in accordance with the procedures in the manual. Before each tank is washed, the oxygen content is determined and verified at or below the ceiling. The operation runs under a responsible officer, with the system observed for leakage and the inert-gas atmosphere monitored throughout. Each of these elements is unpacked below.
The COW Operations and Equipment Manual: the document Regulation 35 mandates
The Operations and Equipment Manual, often abbreviated to the COW Manual or the OEM, is the single object that Regulation 35 exists to require. It is not a generic safety booklet. It is a vessel-specific document, approved by the flag State or by the Recognized Organization acting on its behalf, that translates the generic COW Specifications into the exact procedures for one ship’s tanks, pumps, piping, & washing machines. A crude carrier without a current approved manual on board is not in compliance with Regulation 35, whatever the physical condition of its washing gear.
The manual has two readerships, and that dual purpose shapes its content. Resolution MEPC.3(XII) states the point directly: the manual provides guidance to the ship’s crew on the proper operation of the system, and it provides information on the system and its operational procedures for inspectors going on board in ports. The crew reads it to run the wash safely and to the approved coverage. The Port State Control officer, the class surveyor, and the terminal representative read it to check that what the ship is doing matches what was approved. Because a generic manual would serve neither reader well, the Administration decided to standardize the format so that any inspector can find any item in a known place.
The manual is approved against the Specifications and is part of the statutory record of the ship. The approved manual ties to the International Oil Pollution Prevention (IOPP) Certificate: the IOPP Certificate Form B records the COW endorsement, and the approved manual is the supporting document. An alteration affecting the system, a change of washing machines, a re-routing of the COW main, a change to the wash programme, requires the affected sections of the manual to be revised and re-approved before the changed configuration is used. The manual is a living document, not a one-time deliverable.
Resolution MEPC.3(XII) and the eighteen-section standard format
The standard format for the COW Operations and Equipment Manual is recommended in Resolution MEPC.3(XII), “Recommendation on the Standard Format for the Crude Oil Washing Operations and Equipment Manual”, adopted by the Marine Environment Protection Committee at its 12th session on 30 November 1979. The Committee developed the format because the manual serves both the crew and the boarding inspector, and a common layout lets an inspector find any operational detail in a predictable section regardless of which yard built the ship or which owner wrote the manual.
The standard format runs to eighteen sections. The manual opens with the text of the Revised Specifications themselves, so the operating crew and the inspector are working from the same regulatory baseline. It then describes the physical COW installation on the ship: the cargo, ballast, washing, and stripping systems; the types of tank washing machines and their standpipe length inside the tanks; the machine revolutions and the methods for checking machine operation; the minimum operating pressure for crude oil washing; the maximum permitted oxygen level in the cargo tanks; and the duration of the washing machine cycles. The later sections deal with the operational considerations: the pressure testing of the COW system before use, the observation arrangements for early detection of leakage, the use of the inert gas system including the oxygen-content and pressure-maintenance requirements and the actions following an IGS failure, and the per-tank wash programmes that the crew must follow.
Resolution MEPC.81(43), adopted on 1 July 1999, amended Section 9 of the standard format. This is the same MEPC session and date that revised the COW Specifications themselves, so the Reg 33 equipment side and the Reg 35 manual side were updated together. The amendment to Section 9 reflected practical experience proposed by member governments since 1979. The 1999 revision is why a manual approved to the current standard reads differently in its Section 9 from a manual approved in the early 1980s, and why class plan-approval against the current format checks for the MEPC.81(43) Section 9 content.
The objective of writing every operating procedure into the manual is to reproduce the conditions under which the ship’s COW system was tested and approved. The commissioning trial establishes that the system, run at the stated pressures, machine speeds, and cycle durations, achieves the required coverage at acceptable oxygen levels. The manual then locks those tested conditions into the daily operating instructions, so that every wash on every voyage repeats the approved test rather than improvising. A crew that follows the manual is, by construction, reproducing the approved configuration.
The inert-gas precondition: oxygen at or below 8 percent by volume
The hardest operational control in Regulation 35 is the oxygen ceiling, and it is the control most often probed at inspection. No tank may be crude oil washed unless the inert gas system is in proper operation. That is the absolute precondition: the inert gas system is not a parallel option, it is the enabling safety plant without which a wash cannot lawfully begin. The Specifications cross-reference the inert gas requirement that applies to the ship, and SOLAS Chapter II-2 carries the parallel fire-safety provisions for the IGS itself.
The oxygen verification is specific in location and value. Before each tank is crude oil washed, the oxygen level is determined at a point 1 meter below the deck and at the middle region of the ullage space, and neither of these determinations may exceed 8 percent by volume. The two-point check exists because the inert atmosphere is not perfectly mixed: a reading near the deck and a reading in the body of the ullage can differ, and both must be below the ceiling before the wash starts. Where a tank has complete or partial wash bulkheads (swash bulkheads), the readings are taken from similar levels in each section of the tank, both sides, because each compartment can hold a different atmosphere.
The 8 percent by volume figure is the lean-side limit below which a hydrocarbon, air, and inert-gas mixture cannot ignite. It is not a target oxygen level; it is a ceiling that must not be reached or exceeded. The inert gas being delivered to the tanks is far leaner than this, typically below 5 percent oxygen at the main line, so the 8 percent figure is a margin that triggers a stop, not a normal operating point. During the wash the oxygen level of the inert gas being delivered is continuously monitored, so the control is not just a pre-wash snapshot but a running condition.
Two failure conditions stop the operation. If during crude oil washing the oxygen level of the inert gas being delivered exceeds 8 percent by volume, washing stops until the inert gas atmosphere is restored. If the pressure of the atmosphere in the tanks is no longer positive, washing stops until positive pressure is re-established. The positive-pressure requirement is the second leg of the inert-gas control: a tank at or below atmospheric pressure can draw air inward through hatch seals, pressure/vacuum valves, or vent risers, and an in-leakage of air raises the oxygen content toward the flammable range. Positive pressure throughout the wash keeps the leak direction outward, so any leak vents inert gas rather than admitting air. The two conditions, oxygen below 8 percent and pressure positive, are checked together and either one breaching halts the wash.
The reason the control is this strict is the physics of the wash itself. A crude-oil jet leaving a fixed machine at high pressure produces a fine mist of hydrocarbon droplets in the ullage space and deposits an electrostatic charge of several thousand volts on the droplets and on the surfaces they strike. In air, that mist sits inside the flammable range for most crudes and condensates, and a static discharge would ignite it. The inert atmosphere removes the oxygen that the flammable mixture needs. Lose the inert atmosphere mid-wash and the tank becomes an electrostatically charged, flammable, mist-filled space, which is why Regulation 35 stops the operation the moment either oxygen or pressure leaves its limit.
The washing programme: tanks washed, frequency, single-stage and multi-stage
Regulation 35 requires the wash to follow the programme in the approved manual, and the manual carries the per-tank programmes that satisfy the coverage and frequency rules in the Specifications. The operating side of those rules divides into two purposes that drive different washing frequencies: washing for sludge control and washing of tanks that are to be used for ballast.
Tanks washed for sludge control keep the waxy and asphaltenic deposits from building up over successive cargoes. The Specifications require that a portion of the cargo tanks be crude oil washed for sludge control during each loaded voyage, with the programme rotating through the tanks across voyages so that each tank receives a sludge-control wash at a defined frequency rather than every voyage. The intent is to hold residue at a steady low level across the fleet’s trading pattern, not to wash every tank to a polished state every time.
Tanks that are to be used for ballast are washed before ballast water is admitted, so that the ballast taken into a cargo tank goes into a tank already cleaned by crude rather than a tank holding cargo residue. This is the discharge-control purpose: clean tanks before ballasting means the ballast water leaves the tank far cleaner and the Regulation 34 discharge calculation is far easier to satisfy. A vessel with segregated ballast tanks does not ballast its cargo tanks in normal service, so this category bites mainly in heavy-weather departure ballast conditions where additional ballast in a cargo tank is needed for the safety of the ship.
The single-stage versus multi-stage distinction describes how a given tank is washed within one discharge. A single-stage wash runs the machines through one programmed pattern, usually a bottom wash, sufficient for routine sludge control on a tank that is staying in the crude trade. A multi-stage wash runs more than one pattern in sequence, a top wash directing jets up to the deckhead and upper structure followed by a bottom wash to the lower bulkheads and tank floor, used when fuller coverage is needed, for example before a tank is to be ballasted or to contribute to the cumulative coverage programme. The manual specifies which tanks get single-stage and which get multi-stage washing on a given voyage, and the duration of each machine cycle, so that the operating officer runs the approved sequence rather than choosing one ad hoc.
The duration and coverage are not left to judgment. The manual states the machine cycle durations and the number of cycles per tank that the commissioning trial proved would achieve the required coverage. The operating officer’s task is to run those durations and counts, and to record that they were run. Cutting a cycle short to save time, or skipping a stage, defeats the tested coverage and shows up as a mismatch between the manual and the record book.
On-board quantity, remaining on board, and the role of measurement
The effectiveness of a wash is judged by how little oil remains in the tank after it, and Regulation 35 operations are bracketed by two measurements: the on-board quantity (OBQ) before loading and the remaining on board (ROB) after discharge. OBQ is the quantity of oil, water, and residue measured in the cargo tanks before the next cargo is loaded, the leftover from the previous discharge and wash. ROB is the quantity measured in the tanks after the cargo has been discharged and the wash completed, before the vessel departs the discharge berth. Both are measured by gauging the liquid and clingage in each tank and converting to volume.
These quantities are commercial and regulatory at once. Commercially, a low ROB means more of the loaded cargo was delivered to the receiver and less was left clinging to the ship, so the cargo outturn (the delivered quantity) is closer to the loaded quantity, and the apparent loss is smaller. A well-run COW operation is the principal lever on ROB for a crude carrier, because crude washing strips the clingage that water washing would have sent to the slop tank. Regulatorily, the measured ROB confirms that the wash achieved its purpose, and a high ROB after a wash that the record book says was completed is a flag that the wash was deficient or the record is wrong.
The measurement is taken against the wash, not separately from it. The manual’s wash programme is designed so that, run as written, it brings the ROB to the low figure proved at the commissioning trial. The operating officer confirms the wash was run and then confirms the ROB, and the two together evidence that Regulation 35 was satisfied for that voyage. The OBQ at the next load port, in turn, confirms the tank was left in the expected state for loading. Crude carriers carry these figures in the cargo documentation and, where relevant, in the record book, and surveyors read them as a check on COW effectiveness.
Line and machine testing before the wash
Regulation 35 operations begin with testing, not washing. Before the COW system is used on a voyage, the COW main and the associated piping are pressure tested and observed for leakage. The Specifications require system observation to provide early detection of leakage, because the COW main carries crude at high pressure across the open cargo deck, and a leak from a pressurized crude line onto a deck during cargo operations is a serious fire and pollution hazard. The pre-use pressure test confirms the line holds before crude is admitted to it.
The washing machines are checked for proper functioning before and during the wash. The manual specifies the methods of checking the operation of the tank washing machines: confirming each machine is rotating, that the nozzle is delivering at the stated pressure, and that the programmed pattern is being followed. A machine that has seized, that is delivering below pressure, or whose nozzle has worn does not achieve the approved coverage, and the check exists to catch that before the wash is credited.
One crew member is assigned at the start of the operation to walk the pipeline system and check for leakage as soon as the wash begins, to check the COW equipment for proper functioning, and to monitor the inert gas values, the tank pressure & the oxygen reading, throughout. This is the running observation that the Specifications require, and it is the human side of the continuous oxygen monitoring: a person on deck watching the line and the gauges while the wash runs, ready to stop the operation if the line leaks or the inert-gas condition fails.
The pre-use checks tie back to the commissioning trial that approved the system. The trial that established the manual was run at stated pressures, machine speeds, & cycle durations, and it confirmed that those settings achieved the required coverage at acceptable oxygen levels. The daily pre-wash testing exists to confirm that the system still performs as it did at that trial: that the main still holds pressure, that the machines still rotate and deliver, that the analyzers still read true. A system that has drifted from its tested state, through nozzle wear, gauge drift, or valve seizure, no longer reproduces the approved trial, and the operating officer running the manual’s procedures on a drifted system is running an approved procedure on an unapproved configuration.
The timing of the wash within the cargo discharge is itself a controlled variable, because the wash draws its crude from the cargo discharge main while the tank is being emptied. A bottom wash is run late in the discharge of a tank, when the cargo level has fallen enough that the downward jets reach the lower bulkheads & the tank floor. A top wash is run earlier, while enough cargo remains for the upward jets to strike the deckhead and upper structure safely. The manual sets this sequencing per tank, integrated with the cargo discharge plan, so that the washing-machine demand is matched to the cargo pumping rate at each terminal. The operating officer cannot run the wash on a schedule of convenience; the wash phases are pinned to defined cargo levels in the discharging tank.
Post-wash draining, stripping, and the slop tank
A COW operation does not end when the machines stop. The tank, the machines, and the COW main are drained and the residual liquid is stripped to the slop tank. After the wash of a tank is complete, the cargo and the wash crude in the tank are pumped out by the cargo pumps, and the final bottoms are removed by the stripping system, which handles the small residual quantity the main cargo pumps cannot lift. The stripping line delivers these bottoms to the slop tank, where they join the small slop volume that the COW regime generates.
The COW main itself is drained and depressurized at the end of the operation, so the high-pressure crude line is not left charged across the deck between voyages. Leaving the main pressurized is both a leak risk and a hazard to anyone working on deck, and the Specifications require the system to be left in a known safe state at the end of the wash. The drained crude from the main is stripped to the slop tank or back to a cargo tank, depending on the ship’s arrangement.
The slop volume that a COW operation sends to the slop tank is small precisely because the cleaning medium is crude, not water. A tank washed with crude leaves its dissolved residue in the cargo, which goes ashore with the discharge; only the final stripping bottoms reach the slop tank. This is the link to the discharge regime: the smaller the slop volume, the smaller the load-on-top burden and the easier the Regulation 34 discharge calculation on the eventual decant of separated water from the slop tank.
Recording in the Oil Record Book Part II
Every COW operation is recorded in the Oil Record Book Part II, the cargo and ballast operations record that every oil tanker of 150 gross tonnage and above carries. The Part II book is required by the parallel oil-record-book provision of Annex I (the cargo-side record-book regulation, distinct from the machinery-space Part I), and tank cleaning, including crude oil washing, is one of the listed operational categories that must be entered. The entry for a COW operation records the identity of the tanks washed, the method (single-stage or multi-stage, top or bottom wash), the duration, the oxygen readings taken before and monitored during the wash, and the responsible officer’s involvement, with the master signing each completed page.
The record book is the evidence that Regulation 35 was followed, and it is the first thing an inspector reads. A Port State Control officer boarding a crude carrier reads the Part II entries against the approved Operations and Equipment Manual: do the tanks recorded as washed match the cargo discharged, do the oxygen readings fall below 8 percent, does the wash method match the manual’s programme for those tanks, is there a responsible officer’s confirmation. Inconsistencies, a tank recorded as washed on a voyage where no cargo was discharged, an oxygen reading above 8 percent during a wash, a wash method that departs from the manual without a recorded reason, are common deficiency findings and can lead to detention. The record book turns the operating discipline of Regulation 35 into an auditable trail.
The same operation may generate parallel obligations in other records. A crude carrier above the relevant size carrying high-vapor-pressure crude operates under a VOC Management Plan, & a discharge of separated slop water through the oil discharge monitoring equipment generates its own Part II entry under the discharge category. The COW entry is one strand of a record set, and surveyors cross-read them: a COW record that does not reconcile with the cargo record or the discharge record is a flag even if each record is internally complete.
The link to Regulation 34 discharge limits and load-on-top
Regulation 35 operations feed directly into the discharge regime that the adjacent regulation controls. The cargo-area discharge limits (the regulation that caps oil discharge from the cargo area, read with the discharge-control provisions) allow a tanker outside special areas to discharge separated water from the slop tank only when it is proceeding en route, more than 50 nautical miles from the nearest land, at an instantaneous rate not exceeding 30 liters per nautical mile, and with the total quantity of oil discharged not exceeding 1/30,000 of the cargo of which the residue formed a part. The oil discharge monitoring and control system (ODME) enforces these limits in real time.
Crude oil washing changes the arithmetic of that calculation by changing the inputs. Because COW cleans the tanks with crude rather than water, it produces far less slop than water washing did: a water-washing voyage historically generated slop volumes of several percent of cargo tank capacity, while a COW-equipped vessel generates slop well below 1 percent. Less slop means a smaller quantity of separated water to decant, a smaller oil content in that water, and a larger margin against the 1/30,000 total. The load-on-top procedure, retaining the slops and loading the next cargo on top of them, is correspondingly lighter: there is less to retain, less to separate, and less to decant.
The two regulations are sequential in the operating cycle. Regulation 35 governs the wash that produces (or, by using crude, avoids producing) the residue; the discharge-control regulation governs what may be done with whatever residue and slop the wash leaves. A vessel that runs COW well under Regulation 35 makes its discharge-control compliance easier, because it presents the ODME with a smaller, cleaner slop to manage. A vessel that washes poorly, or that reverts to water washing where COW was expected, presents a larger slop and a tighter discharge calculation. The operating quality under Regulation 35 is the upstream control on the discharge quality downstream.
Safety: inert gas dependence, static electricity, and the tanker safety regime
The safety architecture around Regulation 35 is built on one dependence: the operation cannot run without the inert gas system. The 8 percent oxygen ceiling and the positive-pressure requirement are both expressions of that dependence, and both are continuously verified during the wash. The Specifications make the inert gas system the gate: no tank is washed unless the IGS is in proper operation, and the wash stops the moment the delivered inert gas exceeds 8 percent oxygen or the tank pressure goes non-positive. A vessel with a degraded inert gas plant, a fouled scrubber, a failed blower, a leaking deck water seal, cannot lawfully run COW regardless of the condition of its washing machines.
The static-electricity hazard is the reason the inert atmosphere is non-negotiable rather than merely advisable. A high-pressure crude jet generates a fine charged mist in the ullage space, and the charge can reach several thousand volts on droplets & impinged surfaces. In an oxygen-bearing atmosphere that mist is flammable and a discharge would ignite it. The Specifications and the supporting industry practice impose electrostatic precautions, controlled wash pressures, machine speeds within the approved range, and the prohibition on washing into an atmosphere that is not inert, precisely to keep the charged mist from meeting both oxygen and an ignition path at the same time. The inert atmosphere removes the oxygen leg of that triangle.
Regulation 35 sits inside the wider tanker safety regime rather than standing alone. The inert gas system it depends on is required and surveyed under SOLAS Chapter II-2, the fire-safety chapter, so the same plant that enables COW under Annex I is regulated for fire safety under SOLAS. The cargo operation it forms part of is governed by the ship’s safety management system under the ISM Code, by the industry guidance in the International Safety Guide for Oil Tankers and Terminals, and by the terminal’s own requirements at the loading and discharge berths. The pollution-prevention purpose of Regulation 35, cleaner tanks and smaller slops, is therefore delivered through a safety system whose primary justification is preventing a tank explosion. The two purposes are joined: the control that makes COW clean (the inert atmosphere) is the same control that makes it safe.
US implementation under 33 CFR 157.138
The flag-State and port-State implementation of the Regulation 35 manual requirement is visible in national law. In the United States, the Coast Guard implements the COW Operations and Equipment Manual requirement at 33 CFR 157.138, within 33 CFR Part 157 Subpart D, the crude oil washing rules for tank vessels. The federal provision carries the same content as the international requirement: a tank vessel that uses a COW system must have an Operations and Equipment Manual approved as meeting the COW Specifications, the manual must describe the system and the operating procedures, and the vessel must operate the system in accordance with the manual. The US rule shows the international Regulation 35 obligation reproduced in a port State’s domestic law, which is the mechanism by which a port State enforces the manual requirement on foreign-flag vessels calling at its terminals.
The point of noting the national rule is the enforcement chain. A flag State approves the manual under its Annex I obligation; a port State checks the same manual against the same Specifications under its domestic rule and under its Port State Control authority. A crude carrier calling at a US crude terminal presents its flag-approved manual and is checked against 33 CFR 157.138; a carrier calling in a Paris MOU or Tokyo MOU port is checked under the equivalent regional regime. The manual that Regulation 35 mandates is the document that travels with the ship and is read by every authority in the chain.
Limitations
Regulation 35 is an operating-discipline regulation, and its boundaries follow from that. The first limitation is that the regulation governs operation, not fitting: it assumes a compliant system already installed under Regulation 33, and it has nothing to say about whether a given tanker must have COW at all. A small crude carrier outside the Regulation 33 thresholds is outside the COW fit requirement and therefore outside the Regulation 35 operating requirement too, though it remains bound by the discharge-control regulation when it cleans tanks by other means.
A second limitation is that the regulation’s controls are only as reliable as the instruments behind them. The 8 percent oxygen ceiling is meaningful only if the oxygen analyzers, the fixed analyzer on the inert gas main and the portable analyzers used at the ullage, are in calibration. An analyzer that reads low gives false assurance that the atmosphere is inert when it is not, and the regulation’s stop conditions never trigger because the breach is never seen. The operating regime assumes calibrated instruments, and a drifted analyzer quietly defeats the whole control. The same applies to the COW main pressure gauges that confirm the machines are delivering at the approved pressure.
A third limitation is that the manual binds the operation to the as-tested configuration, so a manual that has fallen out of date with the ship is a hidden non-compliance. If washing machines are changed, the COW main is re-routed, or the wash programme is altered without revising and re-approving the manual, the crew may be running an approved procedure that no longer matches the installed system, and the coverage the manual promises is no longer the coverage the system delivers. The revision-on-alteration requirement exists to close this gap, but it depends on the operator actually triggering the re-approval when the system changes.
A fourth limitation is that the record book evidences the operation, not its quality. A complete, signed set of Part II entries proves that a wash was logged; it does not prove the wash achieved its coverage. A machine that rotated but delivered below pressure, a cycle run for the logged duration but with a worn nozzle, a tank recorded as washed multi-stage but in fact washed single-stage, all produce clean record entries and deficient outcomes. The record is necessary evidence and not sufficient evidence, which is why surveyors cross-check it against ROB figures, against the cargo record, and against physical inspection of the machines.
A final limitation is one of applicability to the cargo. Crude oil washing works because cargo crude dissolves its own residue, so the regime is specific to crude oil tankers and does not transfer to refined-product cargoes or to combination carriers on a product voyage. Very heavy or high-viscosity crudes can leave residue that the same crude does not fully redissolve, in which case the approved manual must address those trades specifically and the operating officer cannot assume that the standard wash programme will reach the usual ROB. The regulation governs the operation of a system whose underlying chemistry is cargo-dependent, and the manual is where that cargo-dependence is supposed to be captured.
See also
- MARPOL Annex I: Regulations for the Prevention of Pollution by Oil
- MARPOL Annex I Regulation 33: Crude Oil Washing requirements
- Marine tank cleaning and crude oil washing
- MARPOL Annex I Regulation 12: Oil Residue (Sludge) Tanks
- MARPOL Annex I Regulation 15: Discharge Control
- MARPOL Annex I Regulation 17: Oil Record Book
- MARPOL Annex I Regulation 18: Segregated Ballast Tanks
- MARPOL Annex I Special Areas
- Marine Inert Gas Systems
- Port State Control
- MARPOL Convention
- Calculator catalogue
References
- IMO MARPOL Annex I, current consolidated text, Chapter 4, Regulation 35, Crude oil washing operations, read with Regulation 33.
- IMO Resolution MEPC.3(XII), Recommendation on the Standard Format for the Crude Oil Washing Operations and Equipment Manual, 30 November 1979.
- IMO Resolution MEPC.81(43), Amendments to Section 9 of the Standard Format for the COW Operations and Equipment Manual, 1 July 1999.
- IMO Resolution A.446(XI), Revised Specifications for the Design, Operation and Control of Crude Oil Washing Systems, 15 November 1979.
- IMO Resolution A.497(XII), Amendments to the Revised Specifications for COW Systems, 19 November 1981.
- IMO Resolution A.897(21), Further Amendments to the Revised Specifications for COW Systems, 25 November 1999.
- US Coast Guard, 33 CFR Part 157 Subpart D and 33 CFR 157.138, Crude Oil Washing Operations and Equipment Manual.
- SOLAS Chapter II-2, Inert gas systems, current consolidated text.