From tank release to vessel loading — mapped against IMDG Code Amendment 42-24
Getting an ISO tank from the operator’s depot to a vessel’s stow correctly is a shared responsibility, not a handover. Under the IMDG Code, the shipper does not get to lean on the tank operator’s paperwork, and the operator does not get to assume the shipper has classified and filled the cargo correctly. Both parties carry independent, overlapping duties, and where either assumes the other has it covered, the result is usually a port detention, a rejected booking, or worse.
This flowchart traces that full sequence in five phases: enquiry and pre-release checks, tank certificate verification, filling at the shipper’s facility, documentation and gate-in, and final documents at destination. Each step is set out across three columns — what the tank operator does, what the process step or shipper action requires, and the specific IMDG Code compliance gate that governs it. Particular attention is paid to the points where errors most often occur: confirming a T-code actually appears against the substance in column 13 of the Dangerous Goods List, verifying tank certificates and the ‘S’ symbol before accepting any fill-limit calculation, applying the correct degree-of-filling formula under 4.2.1.9.2–9.4, and sequencing the Dangerous Goods Declaration correctly under 5.4.1.4.1.
This is a reference tool, not a substitute for the IMDG Code itself. Shippers must work from a current edition of the Code and consult the Dangerous Goods List for the specific substance being shipped, and all personnel involved in classification, tank selection, filling, marking, placarding, or DGD preparation must be trained commensurate with their duties before any step below is carried out (1.3.1).
Note: This flowchart does not substitute for the IMDG Code. Shippers must hold a current edition of the IMDG Code and consult the Dangerous Goods List for each substance. Training of all relevant personnel is mandatory before any step in this process is carried out (1.3.1).
The three columns show: Tank Operator actions (left), Process Step or Shipper Action (centre), and the applicable IMDG Code compliance gate (right).
PHASE 1 — ENQUIRY AND TANK OPERATOR PRE-RELEASE CHECKS
Tank OperatorAwaits shipper enquiry with SDS.
1. Shipper submits enquiry with Safety Data Sheet (SDS)
SDS must be prepared as per latest amendment of IMDG Code, GHS and final destination country specific rules.Shipper’s obligation — Training (1.3)Training prerequisite: all shipper personnel responsible for classification, tank selection, filling, marking, placarding and DGD preparation must be trained commensurate with their duties (1.3.1). Training records must be maintained.
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Tank OperatorReviews SDS. Selects tank type (T-code) from operator fleet. Checks substance permitted in tanks (column 13 of DGL — T-code must be present).
2. Correct Classification by Shipper
Shipper confirms: UN number, proper shipping name, hazard class/division, packing group, subsidiary hazards, marine pollutant status.Shipper must verify this independently — not rely solely on the SDS.
3.2 Dangerous Goods List — column 13If no T-code appears in column 13: substance may NOT be transported in a portable tank without competent authority approval (6.7.1.3).
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Tank OperatorChecks T-code against substance. Confirms tank in fleet meets minimum T-code or higher. Checks 4.2.5.2.5 for permitted upward substitutions.
3. Selection of Appropriate Tank — Shipper’s Duty
The shipper — not only the operator — is responsible for selecting an appropriate tank (4.2.1.9.1). Verify:
- T-code assigned in DGL column 13
- TP special provisions in column 14
- 4.2.5.2.5 substitution table for permitted alternatives
4.2.1.9.1 | 4.2.5.2.5 | 4.2.5.2.6Shipper must not assume operator’s tank is correct. Shipper and operator BOTH carry responsibility for using the correct tank type. A wrong tank can result in port detention and cargo transfer.
PHASE 2 — TANK CERTIFICATE VERIFICATION (BEFORE FILLING)
Tank OperatorProvides test certificate to shipper. Certificate shows: T-code, MAWP, test pressure, shell capacity (‘S’ symbol if surge-plated), design temperature range, last inspection date.
4. Shipper Verifies Tank Certificates Prior to Filling
Shipper must verify the validity of test certificates before the tank is filled (4.2.1.9.1):
- Confirm T-code on plate matches DGL column 13 requirement
- Confirm 5-year or 2.5-year inspection is not expired
- Confirm design temperature range covers cargo filling temperature
- Confirm tank capacity matches planned cargo quantity
- Verify ‘S’ symbol on the physical data plate (6.7.2.20.1(g)) before accepting any fill limit calculation: the ‘S’ after the tank water capacity figure confirms the shell is divided into sections of not more than 7,500 L by surge plates. Visually match the ‘S’ on the physical plate with the booking declaration. No ‘S’ on the plate means a single undivided section and the 80/20 rule applies if the liquid viscosity is less than 2,680 mm²/s at 20°C.
6.7.2.19.6 — Inspection currencyAn expired tank may NOT be filled. If filled before expiry, transport within 3 months of expiry is permitted. If inspection window is missed without exemption, a full new 5-year periodic test is required before the tank can be refilled.
Check ‘S’ symbol: 6.7.2.20.1(g) — confirms surge-plate sections ≤7,500 L.
Check ‘S’ symbol: 6.7.2.20.1(g) — confirms surge-plate sections ≤7,500 L.
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Tank OperatorConfirms special requirements. Communicates any heating, nitrogen blanketing, cleaning, or lining requirements.
5. Special Tank Preparation — Shipper Communicates
Shipper must communicate well in advance any requirements for:
- Heating/temperature control (TP3, TP33)
- Nitrogen blanketing (TP7 — air elimination from vapour space)
- Compatibility with shell material, gaskets, linings
- Dedicated tank requirements for reactive substances
4.2.1.9.1 — Compatibility checkShipper shall ensure substance is compatible with shell materials, gaskets, service equipment and any protective linings — not likely to react dangerously or appreciably weaken materials. If in doubt, consult substance manufacturer and competent authority.
PHASE 3 — FILLING AT SHIPPER’S FACILITY
Tank OperatorConfirms clean, serviceable tank released to shipper. Pre-fill check: service equipment in good working order, no residue on outside of shell or service equipment.
6. Pre-fill Inspection by Shipper (4.2.1.9.6)
Ensure a valid Tank Cleaning Certificate is available.Before and after filling, shipper confirms tank is NOT in any prohibited condition:
- No residue of previously transported substances adhering to the outside of shell or service equipment (4.2.1.9.6.2)
- Tank is not leaking or damaged affecting integrity or lifting/securing arrangements (4.2.1.9.6.3)
- Service equipment examined and in good working order (4.2.1.9.6.4)
- Forklift pockets closed off before filling (4.2.1.9.7)
4.2.1.9.6 — Prohibited conditions for transportA tank in any of these conditions shall NOT be offered for transport. This obligation rests on the shipper as consignor.
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Tank Operator
7. Calculate Maximum and Minimum Degree of Filling
Calculate the applicable degree of filling formula per DGL column 14 TP code:
- TP1 (general): 97 / [1 + α(tr − tf)] — maximum ~97%
- TP2 (class 6.1/8 PG I–II, VP >1.75 bar at 65°C, marine pollutants): 95 / [1 + α(tr − tf)] — max ~95%
- TP3 (elevated temp / molten solids): 95 × dr / df
For heated substances, the viscosity threshold of 2,680 mm²/s must be evaluated at the maximum temperature of the substance during transport, not just at 20°C (4.2.1.9.6.1).
Use calculator: shashikallada.com/iso-tank-and-ibc-calculator
4.2.1.9.2 (TP1) | 4.2.1.9.3 (TP2) | 4.2.1.9.5.1 (TP3)Overfilling creates risk of over-pressurization and rupture as liquid expands with temperature during transport.
80/20 rule: fill either >80% or <20% to avoid destabilizing liquid surge — unless shell sections ≤7,500 L (4.2.1.9.6.1).
Note: filling cannot take place on board ship (4.2.1.9.8).
80/20 rule: fill either >80% or <20% to avoid destabilizing liquid surge — unless shell sections ≤7,500 L (4.2.1.9.6.1).
Note: filling cannot take place on board ship (4.2.1.9.8).
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Tank Operator
8. Marking and Placarding Before Gate-in
Shipper applies to all four sides of tank:
- UN number in black digits ≥65 mm high
- Hazard class placard(s) — primary and subsidiary risk
- Marine pollutant mark (if applicable, 250×250 mm)
5.3.1.1.4.1 | 5.3.2.1.1 | 5.3.2.1.3Memory rule: 4–2–4–4 (columns 1,2,3 and 4 of dangerous goods list in chapter 3.2 of IMDG Code).
(UN No. on 4 sides; PSN on 2 sides; placards on 4 sides; marine pollutant mark on 4 sides).
(UN No. on 4 sides; PSN on 2 sides; placards on 4 sides; marine pollutant mark on 4 sides).
PHASE 4 — DOCUMENTATION AND GATE-IN
Operator / Freight ForwarderCollects documents. Booking confirmed, slot booked, VGM submitted.
9. Dangerous Goods Declaration (DGD) — Shipper’s Document
Shipper prepares and signs the DGD. Mandatory sequence in Box 14 (5.4.1.4.1):
- (1) UN number preceded by ‘UN’
- (2) Proper shipping name (+ technical name if SP 274 or 318 applies)
- (3) Primary hazard class/division (+ compatibility group for Class 1)
- (4) Subsidiary hazard(s) in parentheses
- (5) Packing group (where assigned)
5.4.1.4.1 — Mandatory DGD sequenceDGD must be signed and dated by the shipper (5.4.1.4.2). The carrier is entitled to rely on the information given by the consignor. Shipper and carrier each retain copies for a minimum of 3 months (5.4.6).
Additional information (flashpoint, marine pollutant designation, EMS) goes AFTER the 5-element description.
Additional information (flashpoint, marine pollutant designation, EMS) goes AFTER the 5-element description.
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Carrier / Shipping LineIssues BL. Operator follows up on: SI, DGD copy, VGM, gate-in confirmation. HBL and MBL issued.
10. Gate-in and Vessel Loading
Tank offered at port gate. Terminal verifies marks and placards are in place.Terminal / vessel checks: IMDG Code stowage category, segregation requirements met.
Vessel sails — operator sends loading confirmation and HBL to shipper.
Chapter 7 — Stowage and SegregationThe carrier must stow the portable tank in accordance with the stowage category (column 16a of DGL) and segregation table (7.2.4). Tank must not be offered while leaking or with expired inspection.
PHASE 5 — FINAL DOCUMENTS AND DESTINATION
Final Documents IssuedHBL / MBL. Dangerous Goods Declaration. VGM. HBL sent to consignee.
11. At Destination
ISO tank unloaded at destination port.Operator follows up on: tank return, cleaning confirmation, any customs holds.
If tank is to be returned empty uncleaned: transport document must state ‘EMPTY UNCLEANED’ or ‘RESIDUE LAST CONTAINED’ plus the last cargo description.
5.4.1.1.7 — Empty uncleaned tanksEmpty uncleaned portable tanks must comply with the same requirements as filled tanks (4.2.1.5). The transport document must include the words ‘EMPTY UNCLEANED’ or ‘RESIDUE LAST CONTAINED’ before or after the dangerous goods description.
▼ END OF PROCESS
Need the fill-limit numbers fast? Use the ISO Tank & IBC Degree-of-Filling Calculator to run TP1 and TP2 calculations against your cargo’s densities.
This flowchart is a working reference only and does not replace the current edition of the IMDG Code. Always verify against the Dangerous Goods List entry for your specific substance.
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