Most wet cargo claims start at a hatch cover joint that looked fine from the deck. Hardened rubber, a worn landing pad or a blocked drain lets seawater in, and the claim lands months later. This guide gives the measurable limits for seals, compression bars, cleats and drainage, the acceptance numbers for hose and ultrasonic tests, and how to keep every hatch check on record in Marine Inspection.
Ship hatch cover maintenance and weathertightness testing: four numbers decide whether the seal works
A hatch cover stays tight only while the rubber packing is squeezed by the right amount: not too little, not too much. Wear on the steel, set in the rubber or a sagging cross-joint changes that amount, and the test results follow.
Why hatch cover maintenance decides cargo wetting claims and PSC detention
Hatch covers sit at the meeting point of three exposures: cargo claims, load line compliance and port state control. Under the Load Line Convention they must be weathertight, so a leaking cover is a statutory finding as well as a commercial one. Fleets that want to see hatch defects across every bulk carrier can ask for a demo.
Tokyo MOU figure: 273 covers and hatchways plus 554 protection of openings, out of 2,929 campaign deficiencies. For how codes and action codes work, see our PSC deficiency codes guide.
Hatch cover components that make the weathertight seal
Weathertightness is a chain of parts, and the weakest one sets the result. Each component below has its own failure mode and its own check. Our earlier hatch cover testing article explains the test methods; this guide is about keeping each part inside its limits, which you can track part by part for free.
Rubber packing
Fails by: hardening, cracking, permanent set, paint on the rubber.
Check: set depth, elasticity, joints, retaining channel.
Compression bar
Fails by: bending, corrosion, sharp edges, coating build-up.
Check: straightness, rounded contact edge, chalk line.
Landing pads, steel contact
Fails by: wear that lets the cover sink and crush the rubber.
Check: pad height against drawing, level top plates.
Cleats and wedges
Fails by: wastage, perished washers, uneven tension.
Check: setting, washers, hydraulic lock, cross-joint wedges.
Drain channels and NRVs
Fails by: scale and cargo residue, missing non-return balls.
Check: clean channels, free-moving valves.
Wheels, rails, hydraulics
Fails by: worn axles, damaged trackways, leaking cylinders.
Check: wheel alignment, grease, oil condition and filters.
Hatch rubber packing: permanent set limits and replacement
Rubber that has been squeezed for years stops springing back. The groove the compression bar leaves is the permanent set, and once it eats up enough of the design compression the seal cannot close the gap any more. Renew when the set reaches the maker’s limit. Published guidance ranges from 50% of design compression (Gard, citing makers’ manuals) to 75% (a Class Ltd master’s guide), so the manual for your covers decides. See set readings logged against each joint.
Illustrative check
Verdict: above a 50% maker limit, so renew; under a 75% limit, keep it and trend it. Same rubber, different answer: this is why the manual figure goes in the checklist.
Before renewing: check the steel-to-steel contact and landing pads. New rubber on worn pads is crushed within weeks.
Renew properly: whole lengths with glued joints, original-spec rubber, clean retaining channel, and never paint over packing.
Compression bars, landing pads and steel-to-steel contact
Most hatch covers carry their load through landing pads or continuous steel contact, not through the rubber. That steel sets how far the cover sinks onto the packing, so wear on it quietly changes the compression. These figures come from the Class Ltd hatch cover maintenance guide; use them as triggers, with the maker’s drawing as the reference. Record pad heights with photos at each check.
Pad or coaming top wear
Raises pressure on the gasket and damages it. Repair is essential.
Cross-joint sag
Opens a large gap between compression bar and packing along the joint.
Adjacent top plates
Panels should sit level when closed for sea; a step means pad wear or distortion.
Compression bar
Rounded where it meets the rubber, corrosion-resistant, straight and clean (IACS Rec. 14).
Restore pads to their original design height only with the ship out of service, using the maker’s drawings. Cassette-type pads can be swapped as a unit.
Put the maker’s set limit and pad heights in every hatch checklist
Crews log readings per joint, the app compares them with your covers’ limits, and anything over becomes a work order.
Hatch cleat adjustment without overtightening
Overtightened cleats are a common way crews try to cure a leak, and they make it worse. Tightening past the correct setting crushes the packing, damages the landing pads and does nothing for weathertightness. The method below follows the Class Ltd guide; Gard gives the same warning. Ask us to show a cleat-by-cleat inspection form.
Close and secure the cover. Engage the cleat cam without locking it.
Run the locking nut down until the compression washer just touches the coaming underside or steel washer.
Tighten one full turn, no more. Protect the thread afterwards.
Set all cleats along a skirt together, so each carries a similar load.
Securing-device figures from IACS Recommendation 14.
Hatch drainage checks: channels and non-return valves
The packing is the first barrier; drainage is the second. Water that gets past the outer seal should run along a channel and out through a non-return valve, never into the hold. IACS Recommendation 14 calls for drainage inside the gasket line, channels under cross-joints, and protection against backflow on every drain outlet. For the hydraulic side of opening and closing, see the deck machinery hydraulics guide. You can also make drain checks part of the pre-closing routine.
Before every closing
- Clear rust scale and cargo residue from coaming and cross-joint channels
- Sweep compression bars and packing clean of grain or ore dust
- Check no lashing gear or debris sits in the trackway
Non-return valves
- Ball or flap in place and moving freely
- Renew damaged, missing or seized valves
- Drain valves open before heavy weather
Channel condition
- Repair holed or wasted channels at once and paint them
- Check the space between steel contact and gasket drains, where fitted
- Confirm drain pipes are clear end to end
Weathertightness testing: hose test vs ultrasonic vs chalk
IACS Recommendation 14 expects covers to be tested at intervals not exceeding twelve months, and surveys under the ESP Code check sealing by hose test or an equivalent. Ultrasonic testing is the method P&I clubs prefer, because it gives a number for every point on the joint. See ultrasonic readings plotted per hold.
| Method | How it is done | Pass or fail | Limits |
|---|---|---|---|
| Ultrasonic | Transmitter in the closed hold; sensor run along every joint outside. Readings compared with the open hatch value (OHV). | Over 10% of OHV indicates a leak, unless the equipment maker says otherwise | Type-approved, calibrated kit; certified operator (service suppliers under IACS UR Z17) |
| Hose test | Water jet along joints from outside; inspector in the hold looks for ingress. | Any water in the hold | Not less than 200 kN/m² (2 bar), nozzle at least 12 mm, held no more than 1.5 m away; empty hold, not below freezing, two people |
| Chalk test | Chalk on compression bars; cover closed and reopened to read the imprint on the rubber. | Continuous, even imprint | Shows alignment and contact only; it is not a leak test |
| Light test | Crew in the dark hold look for daylight at the joints. | No light visible | Effective but hazardous; enclosed-space rules apply |
Hose figures are IACS Rec. 14 guidance values. Gard advises against relying on tape or foam sealants; if a charterer requires them, have the covers tested by an independent surveyor first and keep the results.
Hatch cover inspection and maintenance schedule
Spread the work so nothing waits for a dry dock. Tags show which items come from a rule or recommendation and which are common practice; the maker’s manual overrides where it is stricter. The deck section of our port state control inspections checklist covers the same hatchway items PSC will look at, and you can schedule all of it as recurring jobs.
| When | Task | Basis |
|---|---|---|
| Before each closing | Clean packing, bars, channels and trackways; check NRVs; set cleats one turn | Guidance |
| Before heavy weather | Drain valves open, cleats and wedges checked, cross-joints secured | Guidance |
| Monthly | Packing condition and set, cleat washers, wheels and axles, grease trackways | Practice |
| Quarterly | Landing pad and coaming wear, compression bar straightness, chalk test where doubtful | Practice |
| Every 12 months | Weathertightness test (ultrasonic preferred) | IACS Rec. 14 |
| Annual and renewal surveys | Covers, coamings and securing devices examined; sealing checked by hose or equivalent | Rule |
| Hydraulics | Filters every 12 months; oil every 5 years or after major repairs | Practice |
| After any event | Heavy weather, impact, cargo damage claim or packing renewal: retest | Guidance |
How Marine Inspection keeps every hatch cover joint on the map
A test report that says “hold 3 leaking” is hard to fix and harder to defend in a claim. Marine Inspection keeps a tightness map for each hold: every joint segment carries its latest ultrasonic reading, packing set and photos, so repairs go to the right metre and the before-and-after proof sits on one screen. The map below is an illustrative example.
Hold 3 cross-joint: landing pad wear 5 mm found under the leak. Work order raised for pad restoration before packing renewal, retest booked before next loading.
Hatch cover maintenance FAQs
How often should hatch covers be tested for weathertightness?
IACS Recommendation 14 calls for testing at intervals not exceeding twelve months, and again after repairs, packing renewal, heavy weather damage or any sign of leakage. Many operators also test before cargoes sensitive to water.
What ultrasonic reading means a hatch cover is leaking?
A reading above 10% of the open hatch value is generally taken as a leak, unless the equipment maker gives a different threshold. The test must use type-approved, calibrated equipment and a certified operator.
When should hatch rubber packing be replaced?
When the permanent set reaches the maker’s limit, usually stated as a share of the design compression: guidance ranges from 50% to 75%. Also renew rubber that is hard, cracked, torn or painted, and check landing pads before fitting new lengths.
What pressure is used for a hatch cover hose test?
IACS guidance values are a water pressure of not less than 200 kN/m² (about 2 bar) through a nozzle of at least 12 mm, held no more than 1.5 m from the joint, with an observer in the empty hold.
Does tightening the cleats harder stop a leak?
No. Cleats set beyond the correct position crush the packing and wear the landing pads without improving weathertightness. Find the cause: set rubber, pad wear, a bent compression bar or blocked drainage.
Can sealing tape be used instead of repairing covers?
Gard advises against relying on tape or expansion foam. If a charterer insists, have the covers tested by an independent surveyor first and keep the report. Marine Inspection can store that evidence with each voyage.
Tight covers, dry cargo, defensible records
Bring packing checks, pad readings, cleat settings and ultrasonic results into one hatch history for every vessel.
