Folding Hatch Cover

Hydraulic cylinder or wire hoist

Provides the lifting force to start the fold; hydraulically operated covers are now the norm on larger hatches, with wire and winch systems still found on older or smaller vessels.

Cleats, wedges and cross-joint seals

Secure the closed cover against the coaming and seal the joints between panels; rubber gaskets compressed by the cleating system are what actually keeps the hold weathertight, not the steel-to-steel contact of the panels.

Hydraulic power pack

Drives the cylinders; often shared between several hatches on a bulk carrier, so a power pack fault can affect more than one hatch cover at once.

Selection and sizing

• Hatch opening size - larger openings need more panel pairs, increasing the number of hinge and wheel points to maintain.
• Deck load and cargo securing - cover strength must accommodate any deck cargo, lashing points or walkway loads specified for that hatch.
• Available headroom when stacked - folded panel height must clear crane reach, lashing bridges and any deck cargo stowed nearby.
• Weathertightness class - freeboard deck and superstructure deck hatches have different required standards of sealing arrangement.

Regulations and class

Hatch covers on the freeboard deck and exposed superstructure decks are covered by the International Convention on Load Lines, which sets minimum strength and weathertightness requirements, and by class rules for structural scantlings of the panels and securing arrangement. Class surveys require periodic hatch cover weathertightness testing, commonly a hose test or ultrasonic tightness test, and visual condition checks of panels, seals, cleats and drive mechanism as part of the annual and intermediate survey cycle. Class also typically requires load testing or functional verification of the hydraulic or wire operating system.

Typical faults

What to look for in a supplier

• Panel and hinge steel grade and coating specification suited to the trade, since corrosion at hinge and track surfaces is the main long-term maintenance driver.
• Gasket material compatible with the cargo carried and the climate range the ship operates in.
• Availability of individual panels, hinge pins and wheel sets as spares, rather than only complete cover replacement.

Test hatch weathertightness before loading a cargo sensitive to moisture, not after a claim - a hose or ultrasonic test takes far less time than arguing a wet-cargo survey afterward.