Start hereRules checked 20 October 2026
A few litres of seawater through a hatch cover joint will not sink a ship, but they can turn a hold of grain, steel coils or paper into a cargo claim. IACS says it plainly in its guidance to owners: loss of weathertight integrity “continues to be a constant factor leading to cargo damage”, and class and load line survey reports contain “frequent references” to poorly maintained hatch covers. In 2025 Paris MoU inspectors recorded 2,637 deficiencies under the Load Line Convention, the regime that covers hatchways and their covers.
The hatch cover is also structure. On bulk carriers the forward covers take green seas, and a cover that lifts or leaks can flood a forward hold. That is why every special survey requires the sealing of all hatch covers to be proved, by hose test or an equivalent such as an ultrasonic test, and why the firms doing ultrasonic tests for class must be approved. Walk the hatch below and tick what is wrong.
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In this lesson
- Ultrasonic tightness test of No. 1 hatch cover, bulk carrier
- In plain words
- In detail
- What the rules say
- Flag and class notes
- Key numbers
- What inspectors find
- Quiz: 6 questions
Try it
Ultrasonic tightness test of No. 1 hatch cover, bulk carrier
In plain words
A steel hatch cover does not stay dry because it is heavy. It stays dry because a continuous rubber gasket on the cover is pressed down onto a steel compression bar on the coaming or the next panel, all the way round and across every joint. Cleats or other securing devices pull the cover down to keep that pressure on. Behind the gasket line, drain channels take away any water that gets past, through non-return valves that stop the sea coming back in.
When the ship works in a seaway, the hull and the covers flex. A gasket that is only just touching the bar lifts off and lets water in. A gasket that has been squashed flat for years has lost its spring and cannot follow the movement. So a good seal needs the right amount of compression, not just contact.
There are three ways to test it.
- Chalk test: chalk on the compression bars, close the cover, open it again and look for a continuous line on the gasket. Done when new covers are fitted.
- Hose test: a powerful jet of water along every joint while someone in the hold looks for leaks. Simple, but it wets the hold and only shows whether there is contact at that moment.
- Ultrasonic test: a transmitter in the empty hold fills it with high-frequency sound. Outside, the operator runs a receiver along every joint. Where the seal is good, almost no sound gets through. Where compression is lost, sound leaks out and the receiver shows how much, as a percentage of the signal measured with the hatch open. No water is used, and the test finds weak compression before it becomes a leak.
In detail
What the rules require, and when
| When | What | Source |
|---|---|---|
| New covers, after installation | Chalk test, then hose test at 200 kN/m² or more; alternatives may be considered | IACS Rec 14, 6.1 to 6.3 |
| Every annual survey | Hatch covers, coamings, seals, cleats, drains, hydraulics examined; random operation of mechanically operated covers | UR Z7 3.2.3 |
| Annual survey, bulk carriers | Covers in the forward 25% of length plus at least one other set surveyed open, closed and in operation, so every set is seen at least once in 5 years; hose or chalk test where considered necessary | UR Z10.2 3.2.3.2, 3.2.3.7 |
| Every special survey | All hatch covers: operation checked, and sealing proved “by hose testing or equivalent” | UR Z7 2.2.10.3; UR Z10.2 2.2.4.3 |
| Special survey No. 3 onwards | Thickness measurement of all cargo hold hatch covers and coamings | UR Z7 Table 1 |
The annual hatch cover inspection also fulfils the load line annual survey, which IACS Rec 15 links to Article 14 of the 1966 Load Line Convention.
The hose test (guidance values)
IACS Rec 14 gives a water pressure of not less than 200 kN/m² (about 2 bar), with guidance values of a nozzle of at least 12 mm, pressure enough for a free vertical jet of up to 10 m, and the nozzle not more than 1.5 m from the joint. The hose test shows whether the gasket is in contact at that moment. It cannot measure compression, it needs an empty and inspectable hold, and it is impractical with cargo that must stay dry or in freezing weather.
The ultrasonic test, step by step
- Prepare. Hold empty enough to place the transmitter; covers cleaned at the bearing surfaces; drains clear.
- Open hatch value (OHV). With the hatch open, the receiver measures the transmitter’s signal directly. This is the 100% reference.
- Close and secure as for sea. All panels closed, all peripheral and cross-joint cleats fastened, hydraulic cleats locked.
- Scan. The operator moves the receiver slowly along the full perimeter and every cross-joint, outside the gasket line.
- Record. Readings as a percentage of the OHV, with locations marked on a sketch of the cover.
- Evaluate. Industry practice, as described by P&I loss prevention guidance, treats readings above 10% of the OHV as loss of compression needing investigation and repair. The approval criteria actually used must be written in the firm’s procedure (UR Z17 Annex 1, 2.4).
- Look. Follow up with a visual inspection: over-compressed rubber or a knife-edged compression bar can block the sound and give a false “tight” reading.
- Repair and retest the leaking sections, then issue the report with the tester’s certificate of approval.
Class societies agreed in 2001, according to the P&I guidance, that ultrasonic testing with class type-approved equipment and qualified operators is acceptable as an alternative to hose testing for class and statutory purposes. UR Z7 2.2.10.3 itself only says “hose testing or equivalent” and does not name a method; in practice ultrasonic testing by a UR Z17 approved firm is the equivalent class accepts.
Who may test: UR Z17
“Firms engaged in tightness testing of closing appliances such as hatches, doors etc. with ultrasonic equipment” are one of the four categories that must be approved by the class society whenever the surveyor uses their results for class decisions. UR Z17 Annex 1, section 2 requires:
- operators who know the design, functioning and sealing features of hatches and doors, have experience of their operation and maintenance, and can document theoretical and practical on-board training on the specified equipment;
- a demonstration to the surveyor that the ultrasonic equipment is fit for detecting leaks in closing appliances;
- documented procedures including the equipment manual, its adjustment, maintenance, operation and approval criteria.
A ship’s own ultrasonic kit used by the crew is a useful maintenance tool, but the results count for class only when the operator is approved and the surveyor accepts them.
Structure behind the seal
Hatch covers and coamings are gauged from special survey No. 3 onwards. For covers designed to UR S21 Rev.6 (ships contracted from 1 July 2024), steel renewal is required where single-skin cover plating is below t_net + 0.5 mm; between t_net + 0.5 and t_net + 1.0 mm, coating kept in GOOD condition or annual gauging may be accepted instead. Rec 14 also sets design details worth checking in service: securing rods or bolts at least 19 mm diameter for hatchways over 5 m², resilient washers on rod cleats, and a positive mechanical lock on hydraulic cleats.
What the rules say
- UR Z7 paragraph 2.2.10.3 requires the effectiveness of the sealing of all hatch covers to be checked “by hose testing or equivalent” at each special survey.3
- UR Z7 paragraph 3.2.3.2 requires the annual survey to check gaskets, gasket lips, compression bars, drainage channels, cleats, hydraulics and safety locks of mechanically operated steel covers.3
- UR Z10.2 paragraph 3.2.3.2 requires bulk carrier hatch covers in the forward 25% of length and at least one other set to be surveyed open, closed and in operation at each annual survey, with all cleats fastened.4
- UR Z10.2 paragraph 3.2.3.7 allows the sealing to be proved by hose or chalk testing, supplemented by dimensional measurements of seal compressing components, where considered necessary.4
- IACS Recommendation 14 paragraph 6.2 sets the hose test at a water pressure of not less than 200 kN/m², and 6.3 says alternative tightness test methods will be considered.1
- IACS Recommendation 14 (guidance, not a mandatory rule) paragraph 3.1.1 calls for drain openings with effective means against water ingress, such as non-return valves, and 4.1.5 for hydraulic cleats to stay mechanically locked if hydraulics fail.1
- UR Z17 paragraph 4.2 requires firms doing ultrasonic tightness testing of hatches and doors to be approved by the society whose surveyor uses their results.5
- UR Z17 Annex 1, paragraphs 2.2 to 2.4, sets operator qualifications, a fitness-for-purpose demonstration of the equipment, and written procedures including approval criteria.5
- IACS Recommendation 15 paragraph 4.3 advises a hose test whenever the surveyor doubts weathertightness, and paragraph 6.1 makes routine checks between surveys the owner’s, master’s and crew’s responsibility.2
- UR S21 Rev.6 section 7.2 requires steel renewal where single-skin hatch cover plating is gauged below t_net + 0.5 mm.7
Flag and class notes
- Ultrasonic tightness testing is accepted by class as “equivalent” to a hose test only when done by a firm on that society’s list of approved service suppliers under UR Z17. Check the list, or ask for the firm’s certificate, before booking.5
- UR Z7 paragraph 3.2.3.1 requires confirmation at every annual survey that no unapproved changes have been made to hatch covers, coamings, securing and sealing devices. Replacing a gasket profile or cleat type with a non-original design can count as an unapproved change; consult the manufacturer and class first.3
- Rec 15 notes that some hatch covers, for example on ships carrying timber, heavy parcels or containers on the covers, deform quickly; owners should increase checks when a ship changes trade.2
Key numbers
| What | Value |
|---|---|
| Hose test water pressure | at least 200 kN/m² (about 2 bar)1 |
| Hose nozzle diameter (guidance) | at least 12 mm1 |
| Hose nozzle distance from joint (guidance) | at most 1.5 m1 |
| Ultrasonic reading needing investigation (industry practice) | above 10% of open hatch value6 |
| Bulk carrier annual survey | forward 25% of covers plus one other set; all sets within 5 years4 |
| Minimum securing rod or bolt diameter, hatchways over 5 m² | 19 mm1 |
| Hatch cover gauging | from special survey No. 33 |
| UR S21 single-skin renewal | gauged below t_net + 0.5 mm7 |
What inspectors find
- Load line deficiencies remain a major group: 2,637 recorded by Paris MoU inspectors in 2025, 5.1% of all deficiencies.8
- Gaskets with permanent set, missing sections or the wrong profile, and compression bars worn or corroded; IACS Rec 15 lists worn gaskets, corrosion and incorrect maintenance or repair among the causes of leaking covers.2
- Blocked drain channels and missing non-return valves.1
- Cleats corroded, missing rubber washers or not adjusted, so packing line pressure is lost between securing devices.2
- Ultrasonic test reports from firms not approved by the ship’s class society, or without approval criteria.5
FAQ
Is an ultrasonic test better than a hose test?
It measures something different. A hose test shows contact at that moment; an ultrasonic test shows where compression is lost, which predicts leaks at sea, and uses no water. It can miss over-compressed seals, so a visual inspection should follow.
Can the ship's crew use their own ultrasonic kit for class?
For the ship’s own maintenance, yes. For class credit at a special survey, the test must be done by a firm approved under UR Z17 whose results the surveyor accepts.
Do we have to test before every cargo?
No rule requires it, but charterers, cargo interests and P&I clubs often ask for a recent test before water-sensitive cargoes. The class requirement is at the special survey and whenever the surveyor considers it necessary.
Can I fix a leak with tape or a tarpaulin?
Rec 15 says the master may decide to use tarpaulins or adhesive tape in extreme cases, but the use of tarpaulins on mechanically operated steel covers “must be considered an emergency temporary measure”. The real repair is the gasket, the bar or the cleats.
Quiz6 questions
Sources
- 1
IACS Recommendation No. 14, Hatch cover securing and tightness, Rev.2 Corr.1 (October 2005), paragraphs 2.2.2, 3.1.1, 3.2, 4.1.2, 4.1.4, 4.1.5, 4.2.2 and 6.1 to 6.3. https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2022/05/19141052/rec_14_pdf177.pdf
- 2
IACS Recommendation No. 15, Care and survey of hatch covers of dry cargo ships: guidance to owners, Rev.3 (August 2013), paragraphs 1.1 to 1.4, 2, 3.3, 3.4, 4.1, 4.3, 5.4, 6.1 and 6.1.5. https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2022/05/19141142/rec_15_pdf178.pdf
- 3
IACS Unified Requirement Z7, Hull Classification Surveys, Rev.29 Corr.1 (May 2024), paragraphs 2.2.10, 3.2.3 and Table 1. https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2024/05/21130428/UR-Z7Rev.29Corr.1.pdf
- 4
IACS Unified Requirement Z10.2, Hull Surveys of Bulk Carriers, Rev.37 (February 2023), paragraphs 2.2.4 and 3.2.3.2 to 3.2.3.7. https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2023/08/10152246/ur-z102rev37.pdf
- 5
IACS Unified Requirement Z17, Procedural Requirements for Service Suppliers, Rev.21 (January 2025, implemented from 1 July 2026), paragraphs 4.1.2, 4.2, 5.2.11 and Annex 1, section 2. https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2023/05/14135618/UR-Z17-Rev.21-Jan-2025-CLN.pdf
- 6
North of England P&I Association, Loss Prevention Briefing: Hatch Cover Testing (2011), sections on hose tests, ultrasonic tightness testing and comparison of methods. Industry guidance, not a rule.
- 7
IACS Unified Requirement S21, Evaluation of Scantlings of Hatch Covers and Hatch Coamings and Closing Arrangements of Cargo Holds of Ships, Rev.6 (January 2023), section 7.2. https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2023/08/10144821/ur-s21rev6.pdf
- 8
Paris MoU on Port State Control, Annual Report 2025 (published 1 July 2026), Major categories of deficiencies 2023-2025. https://parismou.org/year-report/year-report-2025/
Rules checked 20 October 2026. VSL Safety is not an approved training provider and doesn't issue certificates. These lessons don't replace STCW training, or the manufacturer's training and certification that service technicians need.
