Hatch Cover Ultrasonic Tightness Testing: A Practical Guide

Hatch cover ultrasonic tightness testing is a non-destructive method used to identify potential leakage paths through hatch covers, access hatches and other closing appliances. It can be performed without flooding the deck, making it useful during cargo operations, short port calls and periods when hose testing is impractical. A reliable test still requires clean sealing arrangements, controlled instrument setup and a clear acceptance basis.

Ultrasonic testing does not automatically replace every statutory, class, charterer or manufacturer-required test. Confirm acceptance of the method and pass/fail criteria with the relevant party before attendance.

Why hatch cover tightness matters

Water ingress can damage cargo, destabilise sensitive bulk commodities, interrupt voyages and lead to substantial claims. Leakage often occurs through compressed or damaged rubber packing, corroded compression bars, blocked drain channels, defective non-return valves, distorted panels, worn cleats or poorly maintained cross joints.

A test should therefore be treated as part of hatch-cover condition management, not as a stand-alone certificate. The result indicates tightness under the test conditions; it does not prove structural strength or guarantee performance in every sea state.

How the ultrasonic method works

An ultrasonic transmitter is placed inside the cargo hold. With the hatch closed and secured, an operator scans the external sealing perimeter using a receiver. Sound escaping through discontinuities indicates potential leakage paths. Readings are compared with the instrument’s open-hatch reference value and the agreed acceptance criterion.

Instrument-specific procedures matter. The transmitter arrangement, receiver sensitivity, calibration check, distance, hatch geometry and background noise can influence results. Use trained personnel familiar with the test set and hatch-cover construction.

Ultrasonic testing compared with hose testing

Hose testing introduces water over the hatch perimeter while personnel inspect inside for ingress. It can demonstrate leakage visually but may be unsuitable over water-sensitive cargo, in freezing weather or where deck drainage and pollution controls are restrictive. It can also be difficult during cargo work.

Ultrasonic testing is dry, repeatable and able to identify local leakage without wetting the hold. However, it evaluates sound transmission rather than reproducing external water pressure. The choice of method should follow class, flag, charterer, P&I or contract requirements rather than convenience alone.

Preparing the vessel

1. Identify the hatch type, maker, number of panels and intended acceptance standard.
2. Review previous test reports, cargo claims and known repair areas.
3. Clean compression bars, rubber packing, channels and cross joints.
4. Remove cargo residue that prevents correct closing or creates false sound paths.
5. Check cleats, wedges, hydraulic systems and panel alignment.
6. Confirm safe access around the full hatch perimeter.
7. Control other ultrasonic sources and excessive machinery noise where possible.
8. Ensure the hold can be entered safely to place and recover transmitters.

Hatches should be closed and secured in their normal seagoing condition. Testing loosely landed panels does not assess the actual compression arrangement.

Establishing the reference value

Before scanning, the operator establishes an open-hatch value using the instrument manufacturer’s procedure. This provides the reference against which leakage readings are assessed. The reference and instrument settings should be recorded in the report.

Acceptance is often expressed as a percentage of the open-hatch value, but the applicable threshold must come from the agreed class, instrument or contractual procedure. Avoid inserting a generic threshold into a purchase order without confirming that all parties accept it.

Where leakage is commonly found

• panel corners and cross joints;
• split, hardened, permanently compressed or detached rubber packing;
• corroded, wasted or mechanically damaged compression bars;
• misadjusted cleats, wedges and eccentric wheels;
• hinges or linkages that prevent panels seating evenly;
• access-hatch covers and ventilation closures;
• drain channels, drain pipes and non-return arrangements;
• temporary repairs and areas affected by cargo-handling damage.

Interpreting and marking findings

The operator should scan systematically and mark suspect areas on the hatch and report sketch. A high reading identifies a sound path; visual examination is then needed to determine whether the cause is packing, compression, alignment, corrosion or another opening. Broad leakage can indicate poor overall compression, while isolated peaks often correspond to local defects.

If adjustments or repairs are completed during attendance, the affected area should be retested under the same setup. Record initial and final readings so the repair outcome is traceable.

What the report should contain

A useful report includes vessel and hatch identification, date, place, weather where relevant, instrument make and serial number, calibration or verification status, transmitter placement, open-hatch reference, acceptance basis and readings by location. Plans or photographs should show leakage paths and repairs. Any inaccessible or untested areas must be clearly stated.

The report should avoid declaring the entire cargo system “watertight” where only selected hatches were tested. Conclusions must match the actual scope and agreed terminology.

Common reasons tests are disputed

• No agreed acceptance criterion was established before testing.
• The open-hatch reference or instrument settings were not recorded.
• Hatches were not fully cleated in seagoing condition.
• Background noise or sound transmission between holds affected readings.
• Leak locations were not mapped clearly enough for repair.
• The service supplier’s qualification was not accepted by the requesting party.
• The report claimed more than the test could demonstrate.

Turning leakage readings into effective repairs

Replacing rubber packing is not the correct response to every high reading. First establish the mechanical cause. Packing may be serviceable but under-compressed because of panel distortion or poor cleat adjustment. New rubber fitted against a wasted compression bar may still leak. Excessive adjustment can over-compress packing, damage cleats and make panels difficult to operate.

Use chalk tests, compression measurements, visual inspection and maker tolerances alongside ultrasonic findings. Repairs may involve local packing renewal, adhesive work, compression-bar restoration, cleat adjustment, hinge or wheel correction, drain cleaning or structural steel work. Permanent repairs should preserve drainage paths and panel movement rather than sealing openings indiscriminately.

Retest after the hatch has been operated and secured normally. Where extensive repairs are completed, scan the full affected perimeter rather than only the original marked points, because adjustment can transfer compression and reveal another weak area.

Using the result for cargo and survey decisions

Different stakeholders may use the report for class survey, planned maintenance, charterer due diligence, condition survey or cargo-claim prevention. Identify the purpose on the work order. A maintenance screening report may not satisfy a class or charterparty requirement if witnessing, supplier approval or a prescribed format was omitted.

Masters should retain the test report with hatch maintenance records and ensure defects are entered into the planned-maintenance system. Before loading water-sensitive cargo, review open recommendations, temporary repairs and the condition of drains and non-return devices. Tightness testing supports the decision, but proper operation, inspection and maintenance remain necessary throughout the voyage.

Planning attendance during a port call

Provide the number and arrangement of hatches, vessel plans, test purpose, required standard and previous findings. State whether holds are empty, loaded or under cargo preparation and whether terminal operations restrict access. Allow time to adjust cleats, repair packing and conduct a final retest.

Review the hatch cover ultrasonic testing service and location guidance for Singapore, the Netherlands or Rotterdam. A complete request can be submitted through vslSafety’s quotation form.

Technical references

Use the current requirements of the vessel’s class, flag, charterparty or cargo interests together with the ultrasonic instrument manufacturer’s approved procedure. IACS guidance on service suppliers and hatch-cover tightness testing may also apply. Confirm the accepted method and criteria before testing begins.