MARPOL Annex II Reg 11: cargo tank arrangement

Background: 2007 reorganisation under MEPC.119(52)

Regulation 11 sits inside the chemical-tanker annex of MARPOL, the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978. The cargo-tank-arrangement obligation in the 1987 Annex II text used a different category set and a different ship-type system from the one in force today. Where the 1987 text spoke of Type I, Type II, and Type III ships carrying Category A, B, C, D noxious liquid substances under a different protective-siting calculation, the present text uses Type 1, Type 2, Type 3 ships carrying Category X, Y, Z, OS substances under a recalibrated protective-siting set.

The reorganisation came in two parallel resolutions adopted in October 2004 and entering into force on 1 January 2007. Resolution MEPC.118(52) revised MARPOL Annex II to adopt the X-Y-Z-OS structure and to renumber the regulations into the present sequence. Resolution MEPC.119(52) revised the International Bulk Chemical Code to align Chapter 17 (the NLS list) and Chapter 2 (the cargo-tank arrangement) with the new categorisation and to recalibrate the ship-type assignments accordingly.

The reorganisation was driven by three pressures. First, the GESAMP hazard-profile work of the late 1990s and early 2000s produced a recalibrated dataset for the marine-environment hazard, the human-health hazard, and the bioaccumulation potential of bulk chemicals, and the four-tier A-B-C-D structure was no longer the best fit for the underlying science. Second, the operational experience under the 1987 text showed that some Category B substances were being carried in arrangements that the recalibrated hazard profile would assign to a more stringent class, and that some Category D substances were being subjected to operational restrictions that the new science did not justify. Third, the IMO sought to harmonise the chemical-tanker arrangement requirements with parallel work on the IGC Code for gas carriers and on the IBC Code internal-equipment chapters, producing a single coherent ruleset across the bulk-liquid-cargo fleet.

The 2025 consolidated edition of MARPOL is the working reference for class-society plan approval and for PSC inspection. Operators should always work from the consolidated edition current to the date of any audit, with the latest MEPC session resolutions checked for amendments adopted but not yet incorporated into the printed consolidation. The IBC Code is reissued by IMO as a stand-alone publication, with the most recent edition incorporating the amendments adopted up to the cut-off date set by the publisher.

NLS category mapping: X / Y / Z / OS to ship Type

Regulation 11 cannot be applied without first determining the category of the cargo. Annex II Regulation 6 sets out the four categories and the listing methodology, with the actual cargo list maintained in IBC Code Chapter 17 and BCH Code Chapter VI.

Category X is the most stringent. A Category X NLS is one that, if discharged into the sea from cargo-tank cleaning or deballasting operations, is deemed to present a major hazard to either marine resources or human health. Examples include acrylonitrile, certain biocidal compounds, and a defined set of persistent or bioaccumulative chemicals. A cargo classified as Category X is usually assigned to Type 1 under IBC Code Chapter 17, although a small number of Category X substances are assigned to Type 2 where the carriage hazard rather than the discharge hazard is the dominant concern.

Category Y is the second tier. A Category Y NLS presents a hazard to either marine resources or human health, or causes harm to amenities or other legitimate uses of the sea. The Category Y list is the largest of the four. Most Category Y substances are assigned to Type 2, with high-hazard subsets such as sulphuric acid and certain phosphoric-acid grades assigned to Type 1 because of the carriage and reactivity hazard, and lower-hazard subsets assigned to Type 3 where the protective-siting requirements of Type 2 are not justified by the hazard profile.

Category Z is the third tier, presenting minor hazards to marine resources or human health. Most Category Z substances are assigned to Type 3, with the cargo-tank arrangement permitting the cargo close to the side shell behind only the double-bottom requirement. Some Category Z substances are assigned to higher Types because of carriage-side hazards (corrosivity, reactivity, vapour pressure) and appear in Chapter 17 with the more stringent assignment.

Other Substances (OS) is the residual class. OS substances are not classified as NLS for Annex II discharge-restriction purposes but may still be subject to ship-type carriage requirements where Chapter 18 of the IBC Code prescribes them, typically for hazardous-but-non-polluting cargoes.

The decision-tree for the cargo officer at fixture stage is therefore:

1. Look up the cargo in IBC Code Chapter 17 (or Chapter 18 for OS substances).
2. Read the category column (X / Y / Z / OS) and the ship type column (1 / 2 / 3).
3. Cross-check the certificate of fitness annex to confirm that the ship is certified for the cargo and the tanks nominated.
4. Confirm that the Regulation 13 prewash duty triggered by the category is operationally feasible at the unloading port.

Reference table: category to ship type assignments

Type 1 ship: double bottom + double sides + protective siting

A Type 1 chemical tanker is the most stringent class. It is built to carry the products that the IBC Code Chapter 17 list assigns to Type 1, and the cargo-tank arrangement is built around three layered structural defences:

• A double bottom: the cargo tanks are separated from the moulded baseline by an inner-bottom plating with a defined minimum vertical distance from the keel, with the void space between the inner bottom and the outer bottom available as ballast or as a dedicated void.
• Double sides: the cargo tanks are separated from the side shell by an inner-hull plating with a defined minimum horizontal distance from the moulded line, with the void space between the inner hull and the outer hull available as ballast or as a dedicated void.
• Protective siting: the cargo tanks are positioned inboard of an additional protective distance from the side shell and above an additional protective distance from the moulded baseline. The protective-siting requirement is the additional inset that distinguishes Type 1 from Type 2.

The protective-siting distances are calculated against the IBC Code Chapter 2 formulae, which combine a fixed minimum distance with a deadweight-dependent term. For a typical Type 1 newbuild of 30,000 to 40,000 deadweight tonnes, the protective-siting distance from the side shell is on the order of 760 mm above the IBC Code Type 2 inner-hull line, with an additional vertical inset above the inner-bottom line.

The Type 1 cargo-tank arrangement is the working platform for the most demanding bulk-chemical trades: high-hazard organic chemicals, certain halogenated compounds, and the small subset of Category Y cargoes (sulphuric acid, certain phosphoric grades) where the carriage hazard places the cargo in Type 1 despite the discharge category. Operators of Type 1 tonnage include Stolt-Nielsen, Odfjell, MOL Chemical Tankers, Navig8 Chemical Tankers, and a defined set of specialised owners with deepsea Type 1 fleets.

Type 2 ship: double bottom + double sides (no protective siting)

A Type 2 chemical tanker is the middle class. It is built to carry the products that the IBC Code Chapter 17 list assigns to Type 2, and the cargo-tank arrangement is built around two layered structural defences:

• A double bottom, equivalent in effect to the Type 1 double bottom, with the inner-bottom plating separating the cargo tanks from the moulded baseline.
• Double sides, equivalent in effect to the Type 1 double sides, with the inner-hull plating separating the cargo tanks from the side shell.

The Type 2 arrangement does not include the additional protective-siting inset. The cargo tanks may extend to the inner-hull line and to the inner-bottom line, with the void spaces between inner and outer plating sized to the minimum distances prescribed in IBC Code Chapter 2.

Type 2 is the workhorse of the chemical-tanker fleet. The bulk of Category Y NLS is carried in Type 2 tonnage, including most petrochemicals (styrene monomer, methyl tert-butyl ether, certain alcohols), most vegetable oils carried under Annex II discipline, and a substantial share of the biofuel commodity set following the 2007 reclassification of palm-derived products. Operators of Type 2 tonnage include the Odfjell core fleet, the Stolt product fleet, the MOL Chemical Tankers core fleet, Iino Kaiun, Nordic Tankers, and the larger pool of mid-deepsea chemical-tanker owners.

The minimum distances under IBC Code Chapter 2 for Type 2 are calibrated to provide an adequate margin against side and bottom damage in the standard collision and grounding scenarios, with the damage-stability calculations described in the dedicated section below.

Type 3 ship: double bottom only

A Type 3 chemical tanker is the least stringent class. It is built to carry the products that the IBC Code Chapter 17 list assigns to Type 3, and the cargo-tank arrangement is built around a single layered structural defence:

• A double bottom, with the inner-bottom plating separating the cargo tanks from the moulded baseline.

A Type 3 ship is not required to provide double sides. The cargo tanks may extend outboard to the side shell, subject to the IBC Code Chapter 2 limits on tank size and on the in-tank cargo arrangement. The Type 3 arrangement is therefore a single-skin side construction with the double-bottom inner-bottom plating providing the bottom protection.

Type 3 is the carriage class for the lower-hazard Category Y and Category Z NLS, including many of the lower-toxicity vegetable oils, certain dilute aqueous solutions, molasses, and a defined set of low-hazard petrochemical specialties. The Type 3 cargo-tank arrangement is also used for the parcel-tanker fleet operating in regional trades where the cargo mix is dominated by Z-category and lower-hazard Y-category products.

The cost saving relative to Type 2 is material because the side-shell construction does not require the inner-hull plating, the framing structure is simpler, and the tank coatings can extend to the side shell without the segregation required by the inner-hull arrangement. The carriage limitation is correspondingly real: a Type 3 ship cannot accept a fixture for a Category X cargo, cannot accept a fixture for any cargo assigned to Type 1 or Type 2 in IBC Code Chapter 17, and is restricted to the Category Y / Z subset of the cargo list.

IBC Code Chapter 2: tank arrangement requirements

The IBC Code, Resolution MSC.4(48) as amended, is mandatory under SOLAS Chapter VII Part B and under MARPOL Annex II Regulation 11. Chapter 2 of the IBC Code contains the cargo-tank-arrangement requirements that translate the Type 1 / 2 / 3 framework into structural specifications.

Chapter 2 covers:

• Tank location: the protective-siting requirements for Type 1 ships, the inner-hull and inner-bottom requirements for Type 2 ships, and the inner-bottom requirement for Type 3 ships.
• Tank size: maximum cargo-tank volumes by ship Type and by deadweight, with the maximum size for Type 1 most restrictive and the maximum size for Type 3 most permissive.
• Tank shape: the limits on tank length-to-breadth ratios, on tank height, and on the in-tank baffle and bulkhead arrangement.
• Pump room location: the requirement that the cargo pump room be located within the cargo area, with the pump-room boundary forming part of the cargo-segregation set.
• Slop tank arrangement: the slop-tank capacity, location, and segregation from cargo tanks and from machinery spaces.
• Tank coatings: the compatibility requirements for coatings against the cargo list, with class-society approval for each coating in each tank.
• Cargo piping: the segregation requirements for cargo lines, ballast lines, and bunker lines, with specific arrangements for Type 1 cargoes requiring dedicated pipework runs.

Chapter 2 is supported by Chapter 3 (ship arrangements), Chapter 4 (cargo containment), Chapter 5 (cargo transfer), Chapter 6 (materials of construction), Chapter 7 (cargo temperature control), Chapter 8 (cargo tank venting and gas-freeing), Chapter 9 (environmental control), Chapter 10 (electrical installations), Chapter 11 (fire protection), and Chapter 12 (mechanical ventilation). The cargo-tank arrangement under Chapter 2 is the structural platform on which all subsequent chapters depend.

IBC Code Chapter 17: NLS Categorisation list

Chapter 17 of the IBC Code is the cargo list that maps each NLS to its category, its ship Type, and its carriage requirements. The chapter is laid out as a multi-column table with one row per cargo, and the columns include:

• Cargo name (with synonyms cross-referenced).
• Pollution category (X / Y / Z / OS).
• Hazards (S for safety, P for pollution, S/P for both).
• Ship Type (1 / 2 / 3).
• Tank type (1G / 2G integral / independent).
• Tank vents (controlled / open).
• Tank environmental control (inert, padding, dry, ventilation).
• Electrical equipment (temperature class, group, flash-point reference).
• Gauging (closed / restricted / open).
• Vapour detection (toxicity / flammability).
• Fire protection (alcohol-resistant foam, regular foam, dry chemical, water spray).
• Materials of construction restrictions (no aluminium, no copper, no zinc).
• Emergency equipment (PPE specifications).
• Special requirements (cross-reference to Chapter 15 for product-specific requirements).

The cargo officer at fixture stage relies on Chapter 17 as the single point of reference for the structural and operational requirements that the ship must satisfy to carry the cargo. The certificate of fitness issued under the IBC Code lists the cargoes that the ship is certified to carry, with the certificate cargo annex referencing Chapter 17 row-by-row.

Chapter 18 of the IBC Code lists the OS substances and the non-IBC-Code cargoes that may be carried under flag-administration discretion. Chapter 19 contains an alphabetic index. The annual MEPC and MSC sessions consider proposed amendments to Chapters 17, 18, and 19 against new GESAMP hazard profiles, and the amendments are adopted through the MEPC and MSC resolution series.

Damage stability: 1m side / 1.5m bottom damage extents

The cargo-tank-arrangement requirements under Regulation 11 and IBC Code Chapter 2 are calibrated against a defined damage-stability standard. The standard combines a side-damage extent and a bottom-damage extent, with the ship required to remain afloat and within the IBC Code Chapter 2 stability criteria after the damage scenario.

The side-damage extent is:

with the longitudinal extent and vertical extent set out in detail in Chapter 2 paragraphs 2.5 and 2.6. The 1.0 m horizontal penetration is measured inboard from the moulded line of the side shell, with the longitudinal extent on the order of one-third of the ship length to a defined maximum and the vertical extent from the moulded baseline up to the bulkhead deck.

The bottom-damage extent is:

with the longitudinal and transverse extents set out in detail in Chapter 2 paragraph 2.6. The 1.5 m vertical penetration is measured upward from the moulded baseline, with the longitudinal extent on the order of one-third of the ship length and the transverse extent on the order of the ship breadth or a defined maximum.

The damage-stability calculation considers the cargo-tank loading condition combined with the ballast condition, with the ship loaded to the assigned summer load line. The intact stability criteria of the IBC Code combine with the damage-stability criteria to give the full design envelope, and the calculations are performed at plan-approval stage by the classification society on behalf of the flag administration.

The damage-stability standard for chemical tankers is more stringent than the comparable standard under Annex I Regulation 28 for oil tankers, reflecting the additional hazard severity of bulk-chemical cargoes and the additional segregation that the IBC Code imposes on the cargo-tank layout.

Certificate of fitness (IBC Code certificate) issuance

The Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk (commonly the IBC Code certificate, or the certificate of fitness) is the statutory document issued by the flag administration or its recognised classification society to attest that the ship complies with the IBC Code as a whole. The certificate is mandatory for any ship carrying NLS cargoes listed in IBC Code Chapter 17.

The certificate has three operative parts:

• The certificate page, recording the ship name, IMO number, gross tonnage, deadweight, ship type (1, 2, or 3), the IBC Code edition against which the ship is certified, the issue date, the expiry date, and the issuing administration or class society.
• The cargo annex, listing each cargo that the ship is certified to carry, with the tank or tanks in which each cargo may be loaded, the carriage temperature limit, the inert-gas or padding requirement, and any product-specific restriction.
• The endorsement page, recording the annual, intermediate, and renewal surveys carried out, the surveyor name, the survey date, and the verification of compliance.

The certificate is issued for a maximum of five years in line with the SOLAS / MARPOL convention cycle. Annual surveys are required at each anniversary of the issue date, with intermediate survey at the second or third anniversary depending on the survey scheme, and renewal survey before the expiry date. The certificate cargo annex may be amended through the survey cycle to add or remove cargoes, subject to the necessary plan approval and to the tank-coating compatibility set.

The certificate of fitness is the single document that the cargo charterer, the cargo surveyor, the port reception facility, the PSC inspector, and the cargo terminal will all rely on to verify the ship’s eligibility for the fixture. A discrepancy between the certificate cargo annex and the cargo nominated on the bill of lading is a high-severity finding that escalates rapidly under the Tokyo MoU and Paris MoU regimes.

Flag-state Type 1/2/3 marking on certificate

The ship Type is marked on the certificate of fitness page as a single-character or numeric field (Type 1, Type 2, or Type 3). The marking is the flag-administration attestation that the ship satisfies the IBC Code Chapter 2 cargo-tank-arrangement requirements for the marked Type, and the cargo annex is consistent with the marking.

A ship may be assigned a single Type that applies to all cargo tanks, or it may be assigned a mixed-Type arrangement where different cargo tanks satisfy different requirements. A common mixed-Type arrangement on parcel tankers is Type 2 for the wing tanks and Type 3 for the centre tanks, reflecting the inboard-protection effect of the wing-tank arrangement on the centre-tank cargo and allowing a wider cargo mix in the same hull. The certificate cargo annex in such cases lists the tanks individually with the carriage permission per tank.

The flag-administration marking practice varies by administration. Major flags (Panama, Liberia, Marshall Islands, Singapore, Hong Kong, Greece, Norway, Cyprus, Malta, Bahamas) issue certificates with the standardised Type marking and the standard cargo-annex format derived from the IMO Model Course materials. Smaller flag administrations may issue certificates in a national format, with the same substantive content but with locally specific layout.

The PSC inspector at the port of unloading will:

1. Read the Type from the certificate page.
2. Cross-check the cargo nominated on the bill of lading against the cargo annex.
3. Verify that the tank into which the cargo was loaded is marked in the cargo annex for that cargo.
4. Cross-check the Type marking against the IBC Code Chapter 17 row for the cargo.
5. Verify that the certificate is current and that the most recent annual or intermediate survey is endorsed on the endorsement page.

A discrepancy at any of these five points triggers an inspection finding, with a severity escalation curve from observation to detention depending on the magnitude of the discrepancy and on the safety implications.

Class society implementation: DNV, LR, ABS, BV, NK, RINA, KR, CCS, RS, IRS

The IACS member societies implement Annex II Regulation 11 and IBC Code Chapter 2 through their statutory rule sets, harmonised by IACS Unified Interpretations on the cargo-tank arrangement, the protective-siting calculation, and the damage-stability standard.

• DNV: Pt. 5 Ch. 7 Chemical and Product Tankers, with sub-chapters on cargo-tank arrangement, double-hull construction, and protective siting. The DNV TANKER (CHEMICAL) class notation extends to certificate-of-fitness issuance under flag delegation. DNV’s Type 1 plan-approval workflow is the deepsea-fleet standard for many Stolt and Odfjell newbuilds.
• Lloyd’s Register: Rules and Regulations for the Classification of Ships, Part 7 Chapter 1 (Chemical Tankers), with Lloyd’s plan-approval procedures for the cargo-tank arrangement, the protective-siting calculation, and the supporting damage-stability work. Lloyd’s tonnage in the chemical-tanker market is concentrated in the European deepsea fleets and the Korean newbuild yards.
• ABS: Steel Vessel Rules Part 5, Chapter 8 (Vessels Intended for the Carriage of Chemicals), with the ABS Chemical Carrier notation. ABS is the classification society of choice for many US-flag and Liberia-flag chemical tankers, with the supporting tank-arrangement and protective-siting review aligned with USCG inspection practice.
• Bureau Veritas: NR 482 (Chemical Tankers), with BV’s plan-approval workflow for the cargo-tank arrangement and the protective-siting calculation. BV tonnage is strong in the French, Italian, and West African chemical-tanker fleets.
• Nippon Kaiji Kyokai (NK / ClassNK): Rules for the Survey and Construction of Steel Ships, Part R (Chemical Tankers), with NK’s plan-approval workflow for the cargo-tank arrangement. NK is the classification society for the Japanese chemical-tanker fleet (MOL Chemical Tankers, Iino Kaiun, NYK chemical tonnage).
• RINA: Rules for the Classification of Ships, Part E Chapter 8 (Chemical Tankers), serving the Italian and southern-European fleets.
• Korean Register (KR): Rules for the Classification of Steel Ships, Part 7 (Tankers), serving the Korean owners (Sinokor, KSS Line) and the Korean newbuild yards.
• China Classification Society (CCS): Rules for Classification of Sea-going Steel Ships, Part 8 (Chemical Tankers), serving the Chinese coastal and deepsea chemical-tanker fleets.
• Russian Maritime Register of Shipping (RS): Rules for the Classification and Construction of Sea-Going Ships, with the chemical-tanker chapter aligning with MARPOL Annex II requirements for the Russian-flag chemical-tanker fleet.
• Indian Register of Shipping (IRS): Rules and Regulations for the Construction and Classification of Steel Ships, Part 5 (Chemical Tankers), with IRS’s plan-approval workflow integrated into the classification survey cycle and serving the Indian-flag chemical-tanker fleet.

The IACS Unified Interpretation set on the IBC Code ensures that a cargo-tank arrangement approved by one society is recognised on transfer to another society without re-doing the underlying engineering review, subject to flag-administration confirmation. The transfer-of-class workflow under the IACS Procedural Requirements PR 1A includes a review of the certificate of fitness and the cargo annex, with the receiving society endorsing the certificate against its own rule set after confirming structural equivalence.

PSC inspection focus: manifold ID + P&A Manual cross-check

Port State Control inspection of chemical tankers under the Tokyo MoU, the Paris MoU, the USCG, and parallel MoU regimes focuses on three documentary and operational tests under Annex II Regulation 11 and the IBC Code.

The first test is certificate currency and Type-marking consistency. The inspector reads the Type from the certificate of fitness page, cross-checks the cargo nominated on the bill of lading against the cargo annex, and verifies that the tank into which the cargo was loaded is listed in the annex for that cargo. The inspector also confirms that the certificate is in the current period, that the most recent annual or intermediate survey is endorsed, and that the issuing administration is recognised.

The second test is the cargo manifold ID. The inspector walks the cargo deck, identifies the manifold flange that was used for loading or unloading, reads the tank-side stencilling that links the manifold to the cargo tank, and traces the line through the cargo system to the tank. The inspector then cross-checks the manifold-to-tank linkage against the cargo annex on the certificate of fitness. A mismatch where the cargo was loaded into a tank not certified for the cargo is a detention-grade finding.

The third test is the P&A Manual cross-check with the certificate of fitness cargo annex. The cargo annex on the certificate must reference the same cargoes as the P&A Manual cargo annex, with the same tank assignments, the same carriage temperature limits, and the same inert-gas or padding requirements. A mismatch where the P&A Manual lists a cargo that the certificate cargo annex does not list, or vice versa, is a P&A Manual currency finding that escalates depending on whether the cargo is in fact on board.

PSC databases at the parismou.org and tokyo-mou.org portals show that chemical-tanker findings under MARPOL Annex II are dominated by the certificate-currency category and the cargo-annex consistency category, with structural-arrangement findings concentrated on older tonnage where the inner-hull plating or the inner-bottom plating has degraded below the IBC Code Chapter 2 minimum.

Relationship to Reg 13 prewash (cross-link)

Regulation 11 and Regulation 13 are the two operational pillars of Annex II. Regulation 11 is the structural rule that determines what the ship can carry; Regulation 13 is the operational rule that determines how the residue is managed when the cargo is unloaded.

The two rules interact at three points:

• Cargo selection: a cargo officer accepting a fixture nomination first verifies that the ship is the right Type (Regulation 11) before considering the prewash duty (Regulation 13). A Type 3 ship cannot accept a Category X fixture irrespective of the operational feasibility of the prewash, because the structural arrangement does not satisfy Regulation 11 for that cargo.
• Tank assignment: the certificate cargo annex (Regulation 11) specifies which tanks may carry which cargoes. The P&A Manual (Regulation 13) specifies the prewash route, the slop-tank route, and the reception-facility manifold for each tank-cargo combination. The two annexes must be consistent or the PSC inspector will find the discrepancy at the next port.
• Voyage planning: the structural arrangement (Type) defines the cargo-mix flexibility, and the prewash duty defines the operational sequence at each unloading port. A Type 1 ship loading a Category X cargo at the loading port will need a reception facility at the unloading port, and the voyage plan must verify both the structural eligibility and the operational feasibility together.

The cross-reference between Regulation 11 and Regulation 13 is therefore a daily operational discipline for the cargo officer, with the certificate of fitness cargo annex and the P&A Manual cargo annex used in tandem at every fixture review.

Trade-name examples: Stolt, Odfjell, MOL Chemical Tankers fleet mix

The chemical-tanker market is structured around a small set of deepsea operators with substantial Type 1 and Type 2 tonnage, and a wider population of regional operators with Type 2 and Type 3 tonnage in coastal and intra-regional trades.

Stolt-Nielsen operates a deepsea fleet centred on Type 1 and Type 2 tonnage, with the Type 1 fleet carrying the most stringent NLS and the Type 2 fleet covering the broader Category Y mix. Stolt’s deepsea coverage spans the Houston-Rotterdam-Singapore triangle, with the European Stolt-Botlek terminal cluster providing the reception and segregation infrastructure for the Type 1 cargoes that the fleet carries.

Odfjell operates a comparable deepsea fleet with a substantial Type 1 + Type 2 mix. Odfjell’s tonnage is concentrated in the parcel-tanker class, with multiple cargoes loaded simultaneously into segregated tanks and the cargo annex on each ship covering several hundred IBC Code Chapter 17 entries. The Odfjell terminals at Rotterdam, Houston, and Singapore mirror the deepsea voyage circuit.

MOL Chemical Tankers operates a fleet weighted toward Type 2 with a Type 3 component for the regional fleet. The fleet is concentrated in the Asian and trans-Pacific deepsea trades, with the Japanese owner relationships supporting the petrochemical commodity flows from the Persian Gulf and the US Gulf to Asian discharge ports. The MOL Chemical Tankers fleet is classed predominantly with NK with smaller portions classed with DNV and Lloyd’s.

Navig8 Chemical Tankers, Iino Kaiun, Berlian Laju Tanker, Sinokor, KSS Line, Maersk Tankers (chemical-trading division), Nordic Tankers, Wisby Tankers, and a long tail of regional operators round out the global chemical-tanker fleet, with the Type-mix on each fleet reflecting the trade pattern and the cargo-mix focus.

The fleet-mix decision for an owner ordering a newbuild is a commercial calculation: a Type 1 ship costs more to build but carries everything in the IBC Code Chapter 17 list; a Type 2 ship costs less but cannot accept Type 1 cargoes; a Type 3 ship costs least but is restricted to the Category Y / Z subset. The deepsea operators with broad cargo-mix exposure tend to a Type 1 + Type 2 blend; the regional operators with focused cargo-mix exposure tend to a Type 2 + Type 3 blend.

Newbuild cost premium: Type 1 vs Type 3

The newbuild cost premium for a Type 1 ship over a Type 3 ship of comparable deadweight is in the range:

The premium reflects the structural and outfit cost adders associated with the Type 1 arrangement:

• Inner-hull plating: the inner-hull plates and the supporting framing add steel weight and fabrication labour. The inner-hull addition alone is on the order of 5 to 8 percent of the deadweight-tonne steel cost.
• Protective siting inset: the additional inboard distance reduces cargo-tank volume for a given hull breadth, requiring a larger hull for equivalent cargo capacity. The inset alone adds on the order of 3 to 5 percent of the steel cost through the hull-up-sizing effect.
• Tank coatings: the Type 1 cargo mix typically requires the most demanding tank coatings (zinc silicate, phenolic epoxy, or stainless-steel tank cladding), with the coating cost rising sharply across the coating-grade range.
• Cargo piping segregation: the dedicated pipework runs for high-hazard cargoes add piping length, valve count, and pump-room complexity.
• Cargo-handling instrumentation: the closed-gauging, vapour-detection, and leak-detection requirements for Type 1 cargoes add instrumentation cost.

The 15 to 25 percent premium is observed in newbuild contract pricing across the major Korean and Japanese yards (Hyundai Mipo, Daewoo, Imabari, Hyundai Heavy Industries), with smaller premiums on stainless-steel parcel tankers where the coating-cost effect is partly absorbed in the materials specification.

The cost premium is recovered over the operating life of the ship through the access to higher-margin cargoes that the Type 1 arrangement enables. A Type 1 ship can fix on a Category X freight rate that a Type 2 ship cannot, and the freight-rate spread on the high-hazard cargoes is sufficient to recoup the additional capex over a typical 15 to 20 year operating life. The commercial decision to order Type 1 versus Type 2 is therefore a function of the owner’s expected cargo mix and the freight-rate spread between the cargo classes.

Cargo flexibility trade-off

The structural decision encoded in the ship Type is a cargo-flexibility trade-off:

• A Type 1 ship can carry everything that a Type 2 ship carries, plus the most-stringent NLS that the Type 2 ship cannot. The cargo-annex coverage on a Type 1 newbuild is typically the broadest in the IBC Code Chapter 17 list, subject to coating compatibility and tank-coating exclusions.
• A Type 2 ship can carry most of the Category Y NLS, all of the Category Z NLS, and a wide subset of OS substances. The cargo-annex coverage on a Type 2 newbuild is broad but excludes the Type 1 cargoes.
• A Type 3 ship is restricted to the Category Y and Z subsets assigned to Type 3 in IBC Code Chapter 17 and to the OS substances. The cargo-annex coverage on a Type 3 newbuild is the most restricted, with the cargo officer working a smaller fixture pool.

The trade-off works in two directions. Upward flexibility (a Type 1 ship doing a Type 2 cargo) is always operationally feasible, but it underutilises the structural premium that the Type 1 ship represents. The Type 1 ship doing a Type 2 cargo is delivering more protective siting and more inner-hull margin than the cargo requires, with the extra capex effectively idle for the duration of the fixture. Downward flexibility (a Type 3 ship doing a Type 1 cargo) is not feasible: the structural arrangement does not support the carriage, and the certificate of fitness cargo annex will not list the cargo.

The fleet-mix decision is therefore the cargo officer’s single largest structural commitment, and the Type-marking on the certificate of fitness is the gating constraint on every fixture nomination. The chartering desk maintains a Type-by-Type fleet schedule and matches each fixture nomination to the right Type ship, with the deepsea Type 1 capacity reserved for the high-margin Category X and high-hazard Category Y trades.

IGC Code parallel for gas carriers (Type 1G/2G/2PG/3G)

The IBC Code Type 1 / 2 / 3 framework has a direct parallel in the IGC Code for liquefied-gas carriers, the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, Resolution MSC.5(48) as amended.

The IGC Code defines four ship types:

• Type 1G: the most stringent ship type, for gases considered to present the greatest overall hazard. Comparable in stringency to IBC Code Type 1, with double bottom, double sides, and protective siting.
• Type 2G: for gases of intermediate hazard, with double bottom and double sides, comparable to IBC Code Type 2.
• Type 2PG: a sub-type of 2G with independent pressure tanks rather than membrane or prismatic containment, used for smaller LPG and certain chemical-gas trades.
• Type 3G: the least stringent type, for the lowest-hazard gases, comparable to IBC Code Type 3.

The IGC Code Chapter 17 cargo list maps each gas to the type, in parallel with the IBC Code Chapter 17 mapping for liquid chemicals. The certificate of fitness for a gas carrier is the Certificate of Fitness for the Carriage of Liquefied Gases in Bulk issued under the IGC Code, parallel in form and effect to the IBC Code certificate of fitness.

The structural and operational discipline on a gas carrier is more stringent in some respects than on a chemical tanker, reflecting the additional hazards of cryogenic and pressurised cargo containment, but the underlying ship-type framework is the same: the most stringent type carries the most hazardous cargoes, and the cargo annex on the certificate is the gating document at every fixture and at every PSC inspection. Owners with mixed chemical and gas-carrier fleets (Stolt, Odfjell, MOL through subsidiaries) maintain separate IBC and IGC certificate sets for each ship and apply parallel disciplines on the two fleets.

The Procedures and Arrangements Manual

Regulation 11 does not stop at the structural arrangement. It carries the measures of control that turn the cargo-tank layout into a working pollution-prevention regime, and the central document is the Procedures and Arrangements Manual (P&A Manual). Every ship certified to carry Category X, Y, or Z noxious liquid substances in bulk must carry an approved P&A Manual on board. The manual is approved by the flag administration or its recognised class society, and the standard format is set out in the appendix to MARPOL Annex II as revised under MEPC.118(52).

The manual identifies, ship-specific and tank-specific, the physical arrangements and the operational procedures the crew must follow so that no NLS or NLS-contaminated water is discharged in breach of the Annex II limits. Its mandatory contents run to a defined set of sections. It describes the cargo-piping and pumping arrangement, the stripping system and the design-test stripping quantities for each tank, the cargo-tank ventilation arrangement where ventilation is the chosen residue-removal method, the ballast-handling arrangement, the slop-tank arrangement, and the location and dimensions of the underwater discharge outlets. It then sets out the operational procedures: cargo unloading, tank stripping, the Regulation 13 prewash sequence by category, ventilation procedures, ballast and slops handling, and the discharge-to-sea procedure under the speed, depth, and distance conditions of Annex II Regulation 13.

The P&A Manual cargo annex must match the certificate of fitness cargo annex tank-for-tank. A PSC inspector who finds the manual listing a cargo the certificate does not, or a tank assignment the certificate contradicts, records a currency finding that escalates if the cargo is on board. The manual is the single operational reference the cargo officer reads before each discharge, and it is the document the surveyor checks against the as-built pumping and stripping arrangement at the periodic survey.

Slop-tank arrangement under the P&A Manual

The slop-tank arrangement is one of the defined sections in the P&A Manual and a required structural element of the IBC Code-compliant ship. Each ship certified to carry NLS must have at least one dedicated slop tank within the cargo area, segregated from cargo tanks and from machinery spaces by cofferdam or an approved equivalent. The slop tank collects the prewash effluent and any NLS-contaminated water before transfer to a port reception facility or, for Z-category residues meeting the Regulation 13 conditions, before discharge to sea under the controlled-discharge procedure.

The capacity of the slop tank must accommodate the anticipated prewash volume for the largest single-cargo tank on the ship, calculated at the P&A Manual cycle count and the wash-water rate specified for the cargo group. For a Category X cargo in a 1,500 m³ tank, the prewash cycle typically runs three to five passes, and the slop-tank capacity must be set so the full prewash volume fits without exceeding 90 percent of the slop-tank capacity. On deepsea parcel tankers with multiple Category X tanks, the slop-tank arrangement is sequenced so the tank discharges to the reception facility before the next Category X prewash cycle starts, and the P&A Manual records that sequencing explicitly.

Regulation 12: the efficient stripping standard and build-date tiers

Regulation 12 of MARPOL Annex II (as revised under MEPC.118(52)) sets the pumping, piping, and unloading-arrangement requirements that complement the structural arrangement of Regulation 11. The key output of Regulation 12 is the efficient stripping standard: the maximum quantity of residue that a cargo tank and its associated piping may retain after unloading and stripping.

The standard is tiered by build date, reflecting the tightening of the requirement over successive Annex II editions. The three tiers, based on the keel-laying or equivalent date, are:

For ships built before 1 July 1986, the tier is the most lenient: 300 liters for Category X and Y and 900 liters for Category Z, reflecting the stripping-pump technology available before the 1986 cutoff. Ships built from 1 July 1986 to 31 December 2006 tighten to 100 liters for Category X and Y and 300 liters for Category Z. The 2007 revision under MEPC.118(52) consolidated the tiers into a single 75-liter ceiling for Category X, Y, and Z alike, regardless of category, because modern deep-well pump and educator-stripper technology reliably achieves that threshold across the full cargo range. The figures tighten in step across the three tiers: the Category Z ceiling alone falls from 900 liters to 300 liters to 75 liters as the build date crosses the 1986 and 2007 boundaries.

The residue figure is not a paper assumption. It is verified by a stripping test at the construction stage, with the result entered in the P&A Manual. The verification compares the measured residue against the standard:

where $V_{\text{residue}}$ is the residual quantity measured in the cargo tank and its piping after the stripping run, and $V_{\text{max}}$ is the Regulation 12 ceiling for the ship’s build date. On a post-2007 newbuild, where the ceiling is 75 liters for every category, a tank that strips to a measured 60 liters passes; a tank that strips to 90 liters fails and the arrangement must be modified before the manual is approved. The stripping-quantity calculation for an operating tank can be checked with the tanker stripping calculator, and the venting side of the residue-removal procedure with the cargo venting velocity check.

The stripping test at the construction stage is witnessed by the class surveyor and by a representative of the flag administration where required. The measured residue for each tank is entered into the P&A Manual as a tested figure, and the manual approval is conditional on every tested figure meeting the build-date ceiling. A ship that cannot demonstrate its build-date standard on a tank (75 liters on a post-2007 newbuild) does not receive manual approval for that tank, and the certificate of fitness cargo annex cannot list a Category X or high-hazard Y cargo for that tank until the arrangement is corrected.

Piping arrangement and line-clearing requirements

Regulation 12 also governs the piping arrangement from a residue-control perspective. The cargo discharge piping must be arranged so that the line from the tank to the manifold can be fully cleared into the tank or into the stripping receiver, leaving no cargo trapped in the line after the stripping run. A line-clearing test, similar to the tank-stripping test, is part of the P&A Manual approval process for each cargo-piping leg.

The requirement to clear the lines is the source of the educator (jet pump) fitting that is standard on most chemical tankers. The deep-well pump discharges the bulk of the cargo; the educator uses the pump discharge as motive fluid to strip the last residue from the tank bottom and from the piping legs, clearing the line below the deep-well pump cut-off level. The educator capacity, the pump suction geometry, and the stripping line bore are all specified in the P&A Manual against the measured residue figure for each tank.

Residual-quantity verification and the Cargo Record Book

The stripping test result is the figure that the flag administration and the PSC inspector rely on when auditing the Cargo Record Book Part II entry for cargo unloading. Code C in the CRB Part II records the quantity of cargo unloaded and the residue remaining; the residue figure logged by the officer must be consistent with the P&A Manual tested figure for the tank and with the physical reading taken at the end of the stripping run.

A CRB entry showing a residue figure materially larger than the P&A Manual tested figure is a PSC finding. Two explanations apply: either the stripping system has degraded below the tested performance (a maintenance finding under IBC Code Chapter 5), or the entry was falsified (a falsification finding under Annex II and under the applicable port-state criminal law, including US 33 CFR Part 151 and EU Directive 2005/35/EC). The PSC inspector’s standard practice is to cross-check the CRB residue figure against the P&A Manual tested figure for the tank, note any discrepancy, and test the stripping system if the ship is in port.

A discrepancy between the CRB entry and the P&A Manual is also the signal that triggers the tank inspection under some MoU regimes: the inspector enters the tank space (after gas-free certification) and visually confirms whether the residue is consistent with the logged figure. This is the same physical check that the terminal surveyor performs at the discharge port before signing the tank-cleanliness certificate, and its outcome feeds into the Regulation 13 prewash decision at the next loading port.

Underwater discharge outlet

When NLS-contaminated water that meets the Annex II discharge conditions is released to the sea, it must leave through a dedicated underwater discharge outlet sized and sited so the effluent enters the water below the surface and away from seawater intakes. Regulation 11, read with the P&A Manual standard format, fixes the outlet geometry against the ship’s drag-related wake at the discharge speed.

The outlet must be located in the turn of the bilge so the effluent discharges into the boundary layer and is carried aft, and it must be a defined distance forward of the seawater inlets to avoid recirculation into the cooling and ballast systems. The maximum permissible discharge rate through the underwater outlet is set so the effluent exit velocity does not exceed the wake velocity at the hull at the point of discharge, the condition that keeps the diluted effluent inside the boundary layer rather than throwing a visible plume to the surface. The sizing condition is:

where $Q_D$ is the maximum discharge rate in cubic metres per hour through the outlet, $L_D$ is the distance in metres from the bow to the discharge outlet, and $V_D$ is the ship’s speed in knots during the discharge. The factor $L_D \cdot V_D$ encodes the residence time of a fluid element in the hull boundary layer: a longer run forward of the outlet and a higher speed both raise the dilution the wake can supply, so both raise the rate the outlet may pass.

For a 145 m parcel tanker discharging at 7 knots with the outlet 95 m abaft the bow, $Q_D \le 95 \times 7 = 665 \text{ m}^3/\text{h}$. The pump and outlet are then sized to that ceiling, and the P&A Manual records both the outlet dimensions and the speed-and-rate limit the crew must hold during any discharge to sea.

Cargo discharge piping minimum

The cargo-piping arrangement under Regulation 11 carries a related residue-control requirement. The discharge piping that drains each cargo tank must terminate above the load waterline so any remaining residue cannot siphon overboard outside the controlled discharge procedure, and the underwater-discharge line that handles the diluted slops is a separate, dedicated run. The cargo-stripping line is sized to clear the tank to the Regulation 12 residual standard within the design stripping time, which sets a practical minimum line bore for a given tank volume and stripping-pump capacity.

The minimum stripping-line cross-section follows from the stripping-pump throughput and the maximum acceptable line velocity:

where $A_{\min}$ is the minimum internal cross-sectional area of the stripping line, $Q_{\text{strip}}$ is the stripping-pump volumetric rate, and $v_{\max}$ is the maximum line velocity before entrainment and turbulence start to leave residue clinging to the pipe wall. For a stripping rate of 50 m³/h, which is $0.0139 \text{ m}^3/\text{s}$, against a maximum line velocity of 3 m/s, the line area is $A_{\min} = 0.0139 / 3 = 0.0046 \text{ m}^2$, an internal diameter of about 77 mm, so a DN80 line clears the tank within the residual standard. The P&A Manual records the as-fitted stripping-line size and the corresponding verified residue.

Type 1/2/3 protective-distance and damage-extent standards

The Type 1 / 2 / 3 cargo-tank-arrangement requirements rest on the IBC Code Chapter 2 protective-distance rules and the damage-extent standards the arrangement is checked against. The minimum side-damage extent for the design check is $d_{\text{side damage}} \ge 1.0 \text{ m}$ for Type 1 and Type 2 ships, measured inboard from the moulded line of the side shell, with the longitudinal and vertical extents set out in Chapter 2 paragraphs 2.5 and 2.6. The minimum bottom-damage extent is $d_{\text{bottom damage}} \ge 1.5 \text{ m}$ for Type 1, Type 2, and Type 3 ships, measured upward from the moulded baseline.

The protective-siting inboard distance for a Type 1 ship is calculated against IBC Code Chapter 2 paragraph 2.6 with a deadweight-dependent term and a fixed minimum:

Here $d_{\text{protective}}$ is the protective-siting inboard distance, $d_{\text{min}}$ is the absolute minimum prescribed by Chapter 2 (a fixed length on the order of 760 mm for the side-shell inset), $k_p$ is the dimensional coefficient in the Chapter 2 formula, and $DWT$ is the deadweight in tonnes. The 1.0 m and 1.5 m extents trace back to the SOLAS damage-stability work of the 1970s and 1980s, calibrated to the collision and grounding scenarios in the international fleet, and the same extent values reappear in the parallel IGC Code standard. The protective-siting formula derives from the structural work supporting MEPC.119(52), which calibrated the inboard distance against the energy-absorbing capacity of the inner-hull plating under a defined collision impulse. The formula is dimensional, not first-principles, and the coefficients are tuned to the empirical damage statistics in the chemical-tanker fleet.

Two design assumptions sit under these checks. The cargo-tank geometry follows the moulded-line rules of the IBC Code, with the inner-hull and inner-bottom plates measured from the moulded line, and the damage scenarios apply at the summer load line as the deepest assigned draught. The protective-siting calculation uses the DWT at scantling draught for the deadweight-dependent term, with the matching geometry of the cargo-tank envelope.

Worked example: protective siting and newbuild cost

A 30,000 DWT chemical tanker designed as Type 1 takes its protective-siting inboard distance from the Chapter 2 formula:

The cargo-tank outer boundary is inset about 4.66 m from the side shell, and the bottom inset against the bottom-damage extent runs on the order of 1.5 m above the moulded baseline. The cargo-tank arrangement is laid out inside these envelopes, with the wing-tank and centre-tank split chosen to keep cargo-tank volume as high as the protective envelope allows. Specify the same hull as Type 3 and the cargo-tank boundary may run out to the side shell, subject to the Chapter 2 in-tank limits, so the cargo volume per metre of breadth is larger. That deadweight-versus-volume trade is the lever the owner pulls to balance Type 1 cargo flexibility against carried volume.

The newbuild cost premium for the Type 1 specification over an equivalent Type 3 hull runs $\frac{\text{Capex}_{\text{Type 1}}}{\text{Capex}_{\text{Type 3}}} \approx 1.15\text{-}1.25$, so the adder on this 30,000 DWT hull is on the order of $\Delta\text{Capex} \approx 0.20 \cdot \text{Capex}_{\text{Type 3}}$. The 1.15 to 1.25 range is empirical, drawn from newbuild contract pricing across the Korean, Japanese, and Chinese yards over the last twenty years, with the actual premium on a given order set by the deadweight, the coating specification, and the yard. The premium covers the inner-hull plating and framing (5 to 8 percent of the steel cost), the hull up-sizing forced by the protective inset (3 to 5 percent), the demanding Type 1 coatings, the segregated pipework, and the closed-gauging and vapour-detection instrumentation.

Limitations

The figures and formulae here describe the standard arrangement and the standard checks; several conditions move the answer, and a designer or cargo officer who treats the standard case as the only case will be wrong on real tonnage.

A parcel tanker is rarely a single Type. A common arrangement is Type 2 in the wing tanks and Type 3 in the centre tanks, where the wing tanks shield the centre cargo. The certificate of fitness cargo annex then lists each tank individually, and the cargo officer must match each cargo to a tank with adequate Type, not to a single ship-wide Type marking. The structural Type is also not the only constraint: even where the Type is adequate, the tank coating can exclude a cargo (a zinc-silicate tank against an aromatic cargo, an epoxy tank against a high-temperature cargo), and those exclusions live in the cargo annex tank-by-tank.

Legacy tonnage carries its own limitation. A ship built to an earlier Annex II standard may not meet the present damage-stability criteria or the 75-liter residual figure that applies to a post-2007 newbuild; the grandfathering provisions in the IBC Code allow continued operation under the standard at construction, with flag administrations and class societies running inspection programmes to confirm the arrangement has not degraded below the build-date minimum. A ship ordered as Type 2 can also be re-rated to Type 3 at delivery if the as-built dimensional check fails the Type 2 protective distances, and the cargo annex is cut back with commercial consequences for the owner. The discharge-outlet sizing is bounded too: the $Q_D \le L_D \cdot V_D$ rule holds for normal hull forms and steady discharge speeds and does not cover discharge while manoeuvring, at very low speed, or in confined water, where the boundary-layer dilution the formula assumes is not present and discharge to sea is not permitted regardless of the computed rate.

The stripping-standard tiers are a recurring source of error for ships operating in trades that mix old and new tonnage. A ship built before 1 July 1986 holds a P&A Manual tested figure calibrated to the most lenient tier: 300 liters for Category X and Y and 900 liters for Category Z. That ship’s tested figure is not interchangeable with the 75-liter standard applied to a 2010 newbuild, and a cargo officer chartering both into the same NLS trade must track the build-date tier for the residue entry in the CRB. Confusing the two tiers, or applying the older ship’s 300-liter figure to a post-2007 hull held to 75 liters, is a falsification risk.

Sulphuric acid is the standing reminder that the category and the Type are separate axes. It is a Category Y substance on the discharge side, yet the carriage hazard puts it in Type 1 in IBC Code Chapter 17, so the Type 1 protective-siting inset is the gating constraint even though the discharge category is Y. The most common application errors follow the same theme: confusing the 1987 Type I/II/III (Categories A/B/C/D) with the 2007 Type 1/2/3 (Categories X/Y/Z/OS), reading the Type as a ship-wide attribute when the cargo annex is tank-by-tank, leaving the cargo annex out of step after a recoating, loading a Category X cargo into a wrong-Type tank under fixture pressure, treating the Type 1 inset as optional, equating IGC Code Type 1G with IBC Code Type 1 across two separate frameworks, and reading the Type number as a quality grade rather than a hazard-specific arrangement.

See also

• MARPOL Convention
• MARPOL Annex II: Noxious Liquid Substances
• MARPOL Annex II Regulation 13: Cargo Tank Washing
• MARPOL Annex I Regulation 28: Damage Stability
• MARPOL Annex I Regulation 37: SOPEP
• HNS Convention 2010
• OPRC 1990 and HNS Protocol
• Calculator catalogue

References

• IMO, MARPOL: Articles, Protocols, Annexes, Unified Interpretations of the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 (Consolidated Edition), latest edition.
• IMO, International Bulk Chemical Code (IBC Code), latest edition with amendments through the most recent MEPC and MSC sessions.
• IMO, International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code), latest edition.
• Resolution MEPC.118(52), Amendments to the Annex of the Protocol of 1978 relating to the International Convention for the Prevention of Pollution from Ships, 1973 (2004 revision of Annex II).
• Resolution MEPC.119(52), Amendments to the IBC Code aligning Chapters 2 and 17 with the revised Annex II (2004).
• IACS, Unified Interpretations on the IBC Code and on MARPOL Annex II.
• DNV, Rules for Classification: Ships, Pt. 5 Ch. 7 Chemical and Product Tankers.
• Lloyd’s Register, Rules and Regulations for the Classification of Ships, Part 7 Chapter 1 (Chemical Tankers).
• ABS, Rules for Building and Classing Steel Vessels, Part 5 Chapter 8 (Chemical Carriers).
• Bureau Veritas, NR 482 Chemical Tankers.
• ClassNK, Rules for the Survey and Construction of Steel Ships, Part R (Chemical Tankers).
• Korean Register, Rules for the Classification of Steel Ships, Part 7 (Tankers).
• China Classification Society, Rules for Classification of Sea-going Steel Ships, Part 8 (Chemical Tankers).
• Russian Maritime Register of Shipping, Rules for the Classification and Construction of Sea-Going Ships.
• Indian Register of Shipping, Rules and Regulations for the Construction and Classification of Steel Ships, Part 5 (Chemical Tankers).
• Tokyo MoU and Paris MoU, PSC inspection databases.

Related calculators

• MARPOL Annex IV - Sewage Holding Tank Capacity
• Tanker Op - Stripping - cargo tank
• Tanker Op - Purging - cargo tank
• Cargo Tank Venting - Velocity Check
• Coating - IOPP Cargo Tank Coating
• IMO Type 9 Portable Tank
• COW - Tank Cycle per MARPOL
• MARPOL Annex V/4 - Cargo residues garbage