By David Walker, Staff Writer at Go2marine.com
When purchasing a new hatch, whether for replacement or a new application, there are three main factors to consider. First, determine both the material the hatch is cast in and the gasket material. Second, consider the desired location, orientation, design and use requirements of the hatch.
Hatch safety features must be a priority when being used in locations where a person may need to open it from either side or when the hatch could potentially serve as an escape route from below decks. Finally, determine the lifetime performance of the hatch, which is dependent on materials used, construction and maintenance routine.
Hatch Choice: Materials, Considerations and Location
Commercial hatches are cast in steel, aluminum, and ductile iron. Gaskets may be neoprene or buna-n.
- Steel Hatch — Fitted to steel vessels, welded easily to decks and cabins, requires painting or galvanizing to prevent rust. Affordable and strong.
- Aluminum Hatch — Fitted to aluminum composite (fiberglass) or wood vessels. Lightweight, rust free, can be brittle in subfreezing weather. May be anodized or powder coated.
- Ductile Iron Hatch — Fitted to steel vessels. Stronger, more flexible and harder than cast iron, cheaper than steel. Requires galvanizing or painting.
- Other Hatch Materials — Cast bronze or stainless steel used for special applications. Expensive, usually available only by special order.
- Neoprene Gasket — Seals very well, flexible in most weather, suitable for a wide variety of environments.
- Buna-n Gasket — Standard Nitrile, excellent resistance to petroleum-based oils and fuels, water and alcohols with good resistance to acids and bases.
The location of a hatch and its use will dictate the type of hinges and opening orientation, or the ability to use a removable hatch cover. Hatches are round, square or oval, with common sizes from 14 to 24 inches. For applications where the vessel owner often needs to have access below, hatches in a deck may be either fitted with flush hinges or be a lift-out hatch. Bolt-down manhole hatches are an affordable option often used where a hatch is required to equal the strength of the deck it is fitted to and only needs occasional access. To open the hinged or lift-out hatch from the working side, a removable handle or T-handle is required. All opening hatches must be able to be opened from the backside without tools.
Hatch safety considerations, features, design, and operation
Determine the use of the hatch. There are hatches you can dog down from the outside only. Take into consideration the location, deck or bulkhead, or whether personnel on the other side may, for any reason, need to open the hatch. Hatches need to be secure when closed. A properly constructed hatch does not depend on the hatch cover or door for its strength. Design-wise, a hatch should have the ability to be opened from both sides and be able to function as designed for its service life.
Designer considerations
Mitchell Hinds, naval designer for Guido Perla & Associates adds the following comments about hatches installed on a vessel:
- Use hatches built to ABS standards — the design cut-off for a steel vessel is 90 meters and under — vessels over this length require a designed hatch.
- The structural integrity of a deck, bulkhead surface must be retained with the installation of the hatch ring or coaming (without the hatch or door).
Inspection and Hatch Maintenance
The key to long service life of a hatch is lubrication and maintenance. Hatch life will be adversely affected by damage, as well as corrosion. Hinges, dogs and other moving parts must be kept in good order, lubricated and able to move as freely as the design allows.
Hatches need painting or protection from the marine environment. Galvanized steel hatches tend to self-heal with scratches to the surface, offering a surface protection that lasts 20 to 40 years in maritime conditions. Any part of the hatch that is painted must not restrict the moving parts from functioning as designed. Do a regular inspection to ensure the hatch functions as designed.
What does the U.S. Coast Guard look for when they check the hatches on a commercial fishing vessel?
An interview with Dan Hardin — USCG commercial fishing vessel coordinator, 13th District (Oregon, Washington and Southern Alaskan fishing fleets) — offered the following answers:
What is checked when inspecting hatches?
- Watertight integrity of the vessel is essential; a hatch or door is an opening that reduces the watertight integrity.
- When a commercial fishing vessel is inspected, the primary concern is maintaining the watertight integrity of the hull, weather deck and deck.
The USCG will check:
- Hinges on hatches and doors, they need to have lubricated hinges, be able to move freely, opening to the maximum they can — no “overpaint” on hinges.
- Hatch coaming must be watertight to the deck and not lifted by rust. Straight hatch coaming with no damage.
- Hatch coaming gasket/seal condition must be intact and never painted.
How do hatches get tested for sealing and integrity?
- Two tests are used in testing the hatch for watertightness; these tests also confirm gasket sealing condition, coaming straightness and fit of the hatch:
- The chalk test for contact (chalk powdered on the hatch and see where it contacts the seal or vice versa) and the light test (close the hatch, see if any light comes through the edges).
What else about the hatch is checked?
- Check securing, all dogs fitted and working smoothly.
- Hatch must be solid and in good shape. Prefer that removable hatches have a chain leash.
- The USCG talks with owners about securing hatches all the time. A vessel only maintains watertight integrity when hatches are closed and sealed.
Thanks to Dan Hardin for taking the time to speak with me and offer the above information.
Hatch Failure
Hatch failure is usually an inspection failure or a critical failure. All hatches are inspected by the Coast Guard, Transport Canada, other state and federal agencies, as well as the owners and skippers of the vessels. A hatch that fails in inspection can be fixed and made serviceable. A hatch that suffers a critical or catastrophic failure can sink a vessel.
More common inspection hatch failures are
- Seizure of the hatch due to corrosion
- A leaking hatch, caused by a bent deck ring or coaming, damaged or otherwise inferior seal
- Losing the hatch because it is a removable hatch without a restraining leash
Critical hatch failure
Think of a 24-inch round hatch as a hole in your deck. Water at just 1-foot deep will allow in more than 1,400 gallons per minute through the open 24-inch hatch — a 10-second wash of a wave will allow in some 230 gallons, taking a decent pump more than 10 minutes to clear.
Critical hatch failure is regarded as the loss of a hatch. Insure that your hatch is used in accordance to manufacture design intentions. Hatches are not usually designed to contain positive water pressure in a wet hold.
In December 2007, Transport Canada published their findings of an investigation into three recent vessel sinkings caused by hatch failures.
Transport Canada’s results, in summary, are:
- Failure to correctly fasten the hatch means the hatch is either not secured at all or only partially secured. In either instance the cover may be dislodged, allowing leakage and/or downflooding.
- Problems associated with its [single crossbar hatches] incorrect operation and lack of maintenance, which may lead to leakage and major downflooding.
Transport Canada Conclusion
Owners of vessels fitted with single crossbar-type hatch covers are strongly encouraged to:
- inspect the hatches for material defects;
- contact the manufacturer for any operation and maintenance instructions and conduct the recommended maintenance;
- insure that their operation will maintain watertight integrity in all conditions of operation; and
- demonstrate to all crew members the correct operation of the hatch and point out potential problems with its operation and maintenance.
In Summary
The hatches on your vessel should see a long, safe service life. Select a hatch and hatch gasket of appropriate materials. Choose a hatch design that works for both use and location for your vessel. Conduct regular, routine maintenance and inspection on the hatch, hinges, hatch seal and securing chain. Adhere to operational and safety guidelines for use. Use caution when securing hatches closed while underway or open when used for access. Train all vessel personnel in the proper operation of the vessel’s hatches.
Thanks to Baier Hatch for their support of this article. Go2marine supplies Baier hatches and other service parts for commercial fishing vessels.
Baier hatches contain many unique features, including the patented strongback system of securing the hatch cover to the deck and a simple securing method (with only two moving parts) that is completely field serviceable. Baier manufactures hatches and coamings in steel, aluminum and ductile iron.
High-quality standards and responsiveness to marine safety issues continue to influence Baier hatch design. Baier Hatches are ABS, Canadian Department of Transportation (Transport Canada), Army Corps of Engineers and U.S. Coast Guard approved, and the hatches are a common fitment to Coast Guard and state vessels.
Glossary
ABS, the American Bureau of Shipping is a leading ship classification society.
Coaming is any vertical surface on a ship designed to deflect or prevent entry of water. It usually refers to a raised section of deck plating around an opening, such as a hatch. Coamings also provide a frame onto which to fit a hatch cover.
Hatch is a small door in large mechanical structures and vehicles, often provided for maintenance access. A narrow passageway between the decks of a ship or submarine.
Hatch dog is a tool that prevents movement or imparts movement by offering physical obstruction or engagement of some kind. It may hold another object in place by blocking it, clamping it, or otherwise obstructing its movement. When you secure a hatch, you dog it down.
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