Procedure for Maintenance of Hatch Covers:
The watertightness of hatch covers is imperative to protect the cargo and avoid large cargo claims. The vessel’s maintenance program for testing & maintenance of hatch covers should also include recommended instructions from hatch cover manufacturers. Due to frequent operation of the hatch cover requires constant maintenance of various moving and non-moving parts including renewals as listed below:
Rust removal from steel work:- The top & sides of the hatch covers, coamings & stays must be thoroughly checked for signs of corrosion and reduction in plate thickness. Areas particularly liable to corrosion include welded seams on the hatch top, edges of pontoons, drain channels, circumference of lightning holes in stays, edges of flanges or brackets, shadow areas such as behind accentric wheels where chipping devices cannot reach underside of the trackway, retaining channel for rubber packing, etc.
Cleaning:- Dirt & Cargo residues or the trackway and rubber packing will prevent watertightness.
Compression Bars:- Compression bars must be of an even height, with a rounded profile and no sharp edges due to corrosion as this could damage the rubber packing. If uneven, they must be built up by welding or ground to an even height. Extremely bad lengths are to cropped & renewed. Compression bars are often made of stainless steel for long life to avoid the problems mentioned above.
Rubber Packing:- The rubber packing all around the hatch cover and across each panel should be in good condition, elastic & not hardened. The point is t have gaskets of sufficient residence to achieve tightness when resting against compression bars of adjoining panels and hatch coamings. Rubber packing should be protected from paint and chemicals. The retaining channels in which the packing sits should be free of corrosion. Rubber packing is to be replaced if damaged or compressed to less than 80% of original size. Rubber packing cannot be repaired in bits & pieces as uneven compression will result. The entire length must be replaced. The retaining channel must be chipped & painted prior to renewal of rubber packing.
Eccentric Wheels & Balancing Wheels:- Eccentric wheels should freely rotate even by hand. They should be greased atleast once a month especially after a long voyage. Every six months depending on their use they should be opened up, cleaned greased and the bearings renewed if necessary. Wheel bush wheel pin must be replaced if there is more than 1 mm of wear down.
Towing Chains:- Towing chains are susceptible to elongation as they bear a lot of stress when pulling the covers. If elongated a gap will appear between adjoining panels when closing. However any elongation means deformation and weaking and loss of strength. If elongation exceeds 5 % of its original length that particular length of chain must be replaced.
Quick acting cleats:- Quick acting cleats and screw bolt cleats pull the hatch cover down tight over the coaming. Thus, compressing the rubber packing. The length of the cleat should be adjusted by a nut so as to produce just the right amount of compression. On old cleats the rubber washer often hardens & the threads should be protected from corrosion by greasing.
Resting Pads:- The full weight of the hatch covers is not supposed to be borne by gaskets alone, only to the extent that the correct design compression of the gasket is achieved and then limited by the hatch cover resting steel to steel on coaming top on designed resting pads. Wear and corrosion of the resting pads or where these are not fitted, reduction of the lower edges of hatch covers and the corrosion of contact area of the hatch coaming top should be avoided by proper maintenance.
Guttes & Drain pipes:- Cross over joints between panels will have gutters fitted underneath the packing to accumulate small amounts of water penetrating. These gutters will drain the water to the hatch coaming gutters and it is important to check that they are not fractured or damaged at the ends so water drains down the inside of the coamings instead. The hatch coaming gutters will drain the water aft to drain pipes. They should be kept clean of all remains of cargo before battering down. Non-return valve of the drain pipes should be checked for clogging by duster cargo residues and tested for efficient functioning.
Pull Wire:- The pull wire for the covers should be in good condition & greased. Blocks through which it is led must be regularly checked & maintained.
Planned Maintenance System for Hatch Covers:
Bulk carrier hatch cover maintenance standards:
As per IMO /MSC/Circ.1071 Ship owners and operators are recommended to maintain a record of maintenance, and component replacement, to facilitate statutory surveys by the Administration.
All major repairs should be undertaken only after consultation with the hatch cover manufacturer and with the approval of the Administration. Hatch cover maintenance plans should form part of a ships safety management system as referred to in the ISM Code.
Although the PMS has an ongoing system both for renewals and maintenance regime, it is recommended that vessels maintain a simple checklist as per makers instructions is advisable to be maintained on board and the checklist should cover the below items.
After Each cargo operation:
- Clean the coaming tops and remove any debris or equipment.
- Clear drain line holes and valves of debris.
- Drain valve caps should be attached by chain, but not screwed on. They must be ready in case of a fire in the hold or when carrying out fumigation operations.
- Grooves and worn landing pads can be built up with welding and ground down, as required, giving a permanent repair.
- Check and clean the surface of the seals and take special care if the cargo is dusty or gritty.
- After discharge check hold internals, including ladders, sounding pipes, backetrs and inner coaming surface for mechanical damage.
- Check hydraulic system for leaks, especially coupling, valve blocks and flexible hoses.
- Check forrust streaks on the inside of the coaming which would indicate a leaking hatch cover, then take any necessery remedial action. Clean off the old rust streaks and stains.
Routine Maintenance – Three monthly:
- Grease wheel spindles, cleat spindles, hinge pins and hydraulic cylinder protective sheaths.
- Check hinge pins for wear and repair as necessary. Worn hinge pins can casue slewing of panels and leaking cross joint cleats.
- Grease cleat wedges, drive chain sprockets, toothed racks and cylinder spherical bearings.
- Check and adjust drive and towing chain adjusters.
- Check rubber seals for elasticity, mechanical damage or permanent deformation
- Hatch covers usually make steel ¨Cto steel contact when a compression bar indents rubber seals by 12-16 mm, check makers manual for exact compression.
- When the hatch covers are opened the rubber should almost retain its original shape, although new rubber will invariable suffer a 1-2 mm permanent set after the first operation.
- Once the permanent indentation reaches 70% of the designed compression the hatch cover is likely to leak.
- Do not grease the rubber packing or seals unless proceeding into cold wetaher when glycerine based grease can be used.
9 Monthly or Annual checks:
- Check quantity and condition of spares carried on board
- The rubber packings and adhesive have a limited shelf life and normally should be date stamped when purchased
- Check hydraulic system oil by analysis
- Check safety locking devices and hydraulic system cutouts
Dos and Donts:
- Always rectify steel to steel faults first
- Keep chains and cleats correctly adjusted
- Attach locking pins and chains to doors and hatch covers in open position
- Keep coaming tops and double drainage channels in good order
- Keep hatch covers and clean coaming tops and double drainage channels after loading bulk cargo through the grain or cement hatches
- Always keep wheels, hinges and chain tension equipment well greased
- Do not enter a hold with suspect atmosphere
- Do not remove ball valve from drain valves
- Do not allow grooves to form in coaming tops in way of the side panels
- Do not leave loose cleats when proceeding to sea
- Do not screw down cleats beyond normal tension