gp30. equipment for cargo

SUPERINTENDENT’s MANUAL “Super-Man”

Part II - Technical Part

Main Group 3 - Equipment for Cargo

Gp 30 - Hatches and Ports

“Super-Man”/Basic Edition/Part II Copyright NSA

SUPERINTENDENT’s MANUAL PART II - TECHNICAL PART Table of Contents Page

30 HATCHES AND PORTS 1

300 GENERAL 1 300.0 General Guidelines 1 300.01 Abbreviations 2 300.1 Installation General - Check Points 2 300.2 Testing 2

301 CARGO HATCH COVERS ON WEATHER DECK 2 301.0 General Guidelines 2 301.1 Types of Hatches 3 301.10 General 3 301.11 Hatch arrangements 3 301.12 Hatch cover design/construction 4 301.2 Bearing Pads 5 301.20 General 5 301.21 Special check points for bearing pads 7 301.3 Hatch Coamings 7 301.30 General 7 301.4 Hatch Cover Packings 7 301.40 General 7 301.41 Testing of tightness 8 301.42 Special check points 9 301.5 Hatch Cover Locking Devices/Cleating 9 301.50 General 9 301.51 Special check points 11 301.6 Hatch Cover Hinges 11 301.60 General 11 301.7 Opening / Closing Arrangements and Equipment 12 301.70 General 12 301.8 Manoeuvre Stations 12 301.80 General 12 301.9 Important Check Points 13

302 CARGO HATCH COVERS ON 'TWEEN DECKS 14 302.0 General Guidelines 14

303 CARGO TANK ACCESS HATCHES 15 303.0 General Guidelines 15 303.1 Arrangement and Size 15 303.10 General 15 303.11 Packings 16 303.12 Closing system/device 16 303.13 Top of coaming 17 303.2 Installation 17


303.20 General 17 303.3 Maintenance 17 303.30 General 17

304 SMALLER HATCHES 17 304.0 General Guidelines 17 304.1 Cargo Tank Cleaning Hatches 18 304.10 General 18 304.11 Arrangement and size 18 304.12 Packings 18 304.13 Closing system 19 304.14 Top of coaming 19 304.15 Installation 19 304.16 Maintenance 19 304.2 Access and Emergency Escape Hatches 19 304.20 General 19 304.21 Arrangement and size 20 304.22 Installation 20 304.23 Maintenance 20

305 BOW PORTS/DOORS WITH ACCESS RAMPS 21 305.0 General Guidelines 21 305.1 Packing System 23 305.10 General 23 305.2 Cleating System 23 305.20 General 23 305.3 Access Ramp 23 305.30 General 23 305.4 Inner Door (Collision Bulkhead) 24 305.40 General 24 305.5 Important Check Points 24

306 STERN PORTS/DOORS WITH ACCESS RAMPS 25 306.0 General Guidelines 25 306.1 Types of Ramps 26 306.10 General 26 306.11 Straight ramp 26 306.12 Quarter ramp 27 306.13 Slewing ramp 28 306.1 Packing System 29 306.2 Cleating System 29

307 SIDE PORTS/DOORS 29 307.0 General Guidelines 29

308 CARGO DOORS IN BULKHEADS 30 308.0 General Guidelines 30 308.1 Hinged Cargo Doors 30 308.10 General 30 308.2 Sliding Doors 31


308.20 General 31

309 HYDRAULIC SYSTEMS 33 309.0 General Guidelines 33 309.1 Piping System 33 309.10 General 33 309.2 Hydraulic Pumps 34 309.20 General 34 309.21 Pump types 34 309.3 Hydraulic Cylinders 35 309.30 General 35 309.31 Maintenance 35 309.4 Hydraulic Motors 36 309.40 General 36 309.41 Motor types 36 309.5 Hydraulic Valves 37 309.50 General 37 309.6 Reservoirs 37 309.60 General 37 309.7 Hydraulic Fluids 37 309.70 General 37 309.8 Commissioning of Hydraulic Systems 38 309.80 General 38 List of Figures Fig. No. Title Page 301.12 A Weather Deck Hatch – Single Plate Panels 39 301.12 B Weather Deck Hatch –Double Plate Panels 40 The above-mentioned figures and the majority of the sketches inserted directly in the text have been provided by MacGREGOR AS (Norway).


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30 HATCHES AND PORTS 300 GENERAL 300.0 General Guidelines Group (Gp) 30 contains the following Sub-Groups (SGps): * 300 - General * 301 - Cargo hatch covers on weather deck * 302 - Cargo hatch covers on 'tween decks * 303 - Cargo tank access hatches * 304 - Smaller hatches * 305 - Bow ports/doors with access ramps * 306 - Stern ports/doors with access ramps * 307 - Side ports/doors * 308 - Cargo doors in bulkheads * 309 - Hydraulic systems SGp 300 contains general guidelines and items, not naturally belonging to other Sub-Groups in the applied “SFI Group System”. Figures and sketches are either inserted directly in the text where relevant or located at the end of Gp 30. Several equipment and components such as drive units; manoeuvre consoles, locking devices, etc. are similar or equal for the various types of outfit described under the different Sub-Groups. To avoid repetition, such equipment/components are mainly described under the Sub-Group in which they initially occur, i.e. in the above regard under SGp 301. It is emphasized that proper design, correct operation and maintenance as well as sensible navigation of the vessel must be observed to prevent leakage through hatch covers and ports in heavy weather and subsequent danger of damage to vessel and cargo. In extreme cases, excessive leakage and breakdown of hatch covers or cargo ports/doors with following flooding of compartments have resulted in loss of lives and total loss of the vessel. Hatches and ports are normally built with large dimensions and strict tolerances, with emphasis on structural strength to ensure tightness. Deformation of structural members and wear down of hinges and locking devices should therefore be corrected without delay. Cracks in the steel structure should be attended to at first opportunity and wear down of steel contact surfaces and resting pads adjusted in time, in order to keep prescribed tolerances for packing compression. Packing systems must be kept in order at all times and tightness confirmed through regular inspections and testing. Note: The above guidelines concern the vessel’s seaworthiness; hence defects may constitute

a condition of Class and possible loss of insurance coverage.


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300.01 Abbreviations * OMM: Operating and Maintenance Manual 300.1 Installation General - Check Points Following guidelines should be adhered to: ∗ Prior to installation, Owner’s representative(s) should thoroughly study arrangement and

detail drawings. ∗ Check that all hatch covers are straight and even. This may be carried out at a plane

“bed” by optical equipment, laser or piano wire. ∗ Prior to mounting of hatch covers, all welding on coamings and in deck in hatch areas to

be completed. If not, alignment/straightening of the covers after installation may prove necessary. Same apply to bow- and side ports.

∗ Check that piping, cables etc. to be fitted at/alongside coamings do not interfere with access to or operation of locking devises.

∗ Check that hatch covers and ports are safely secured in open and stowed position, and with proper drainage in open and in closed position.

∗ Check all welding on covers and coamings, in particular in corners. Same for ports and doors.

∗ Check that brackets on coamings rest on supported deck area. ∗ All grease nipples should be of same dimension and type to facilitate lubrication. ∗ Check that lubrication borings extend to the sliding surfaces. ∗ For safety reasons, good overview of the hatch area during operation of hatch covers is

needed. Same for ports. 300.2 Testing * New or repaired hatch covers and ports to be operated and tested prior to acceptance,

also including equipment for emergency operation. * For testing of tightness see 301.4. * For further details, see the respective Sub-Groups. 301 CARGO HATCH COVERS ON WEATHER DECK 301.0 General Guidelines SGp 301 includes all types of hatch covers with coamings, moving and closing arrangements, locking devices, packings, separate hydraulic systems, as well as equipment for stowing the hatch covers. In this Manual only steel hatch covers of recent designs are dealt with. Earlier days’ hatch covers consisting of wooden, manually liftable pontoons covered with tarpaulins secured to the hatch coamings by flat bars and wooden wedges are not commented on.


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Requirements regarding design, construction and operation of cargo hatch covers are given in the International Loadline Convention as well as in Class rules. Cargo hatch covers on weather deck on dry cargo vessels to be weathertight, implying that they shall prevent water from penetrating into cargo holds in any sea condition. Hatch covers for cargo holds also intended for ballast water shall be weathertight. Hatch covers for liquid cargo (e.g. OBO carriers) shall be oiltight. The hatch covers shall also comply with strength requirements for a certain inside overpressure (DNV rules: Min. 25 kN/m2). Weathertightness is achieved as a combination of several different elements, which one by one seldom gives full integrity without the full support of the others. These elements generally are: * Vessel's hatch arrangement. * Hull movements and corresponding coaming deflections. * Arrangement of locators (keeping the hatch cover panels in position as well as guiding

them during operation). * Hatch cover structure. * Bearing pad system. * Rubber sealing system. * Cleating arrangement and design as well as proper battening down. 301.1 Types of Hatches 301.10 General A large variety of different hatch arrangements and panel types are in use. Some of the most commonly used makes and types are described in the following. 301.11 Hatch arrangements Below are shown typical hatch arrangements and panel types: “Single pull”, longitudinal

Longitudinal folding


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“Piggy-back”, rolling w. stationary lifting cylinders Hatch covers lifted by crane (“Lift-away type”) Hatch covers with hydraulic hinges Transverse rolling hatch covers (“Side-rolling type”) 301.12 Hatch cover design/construction (1) General Hatch cover panels are often designed with sufficient strength to carry deck cargo, e.g. containers or lumber. Fixed container fittings at container corners to have adequate reinforcement underneath. Eye plates for lashings are required (IMO regulations) in case of timber cargo. For details, see Gp 31. In addition to the static forces acting on hatch covers and coamings, dynamic forces will be added while the vessel is at sea. Reaction forces are occurring both vertically and horizontally/ athwartships. The athwartships forces are transferred to the hatch coamings through locators (side supports). The hatch cover locking devices have practically no effect in transferring these forces. Hatch cover panels are built as single plate - or double plate panels: (2) Single plate panels Main advantage is that panel strength members are accessible from the underside for inspection and maintenance and that the panel is flexible enough to follow ship’s movement. Disadvantages are the increased maintenance area represented by stiffeners and additional work during hold cleaning to remove cargo residues from the flanges of the panel stiffeners.


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Further, water accumulated on the stiffeners (rain and from water cleaning) may be released when closing the hatch and thus cause damage to cargo. For details, see Fig. 301.12 A. The covers have manual cleating and wedge securing of cross-joints. (3) Double plate/pontoon type panels Provide a completely closed construction with the advantage of having an even, external surface for easy cleaning and maintenance. Pontoon type panels are much stiffer against torsion than single plate panels. Disadvantages are that access to inside strength members for inspection requires access openings in the pontoon. Note: Never enter a box type hatch cover for inspection without ensuring proper ventilation or without checking the oxygen level inside. The hatch construction is generally gas tight and oxygen is removed to avoid corrosion (the pontoons are some times filled with an inhibitor e.g. inert gas). In case of cracks in plating and subsequent water penetration into the pontoon (water is difficult to drain out) corrosion may develop inside. Double plate pontoon type hatch covers are normally not applied to OBO carriers since cracks in the plating and oil penetrating into the pontoon would represent an explosion hazard. Figs. 301.12 B shows compact double plate covers with automatic cleating. 301.2 Bearing Pads 301.20 General Hatch covers rest on the hatch coamings with steel-to-steel contact, either by continuous contact between the cover “skirt” and the coaming, or on bearing pads located at certain intervals around the cover. The below sketches show traditional hatch cover supports, where the skirt rests directly on the coaming top plate. Figure on the right shows a bearing pad, see also next page. Continuous contact Local insert plate Local insert plate Bearing pad


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(Note: When the skirt rests directly on the coaming top plate, some ship officers seem to believe that steel-to-steel contact is not correct, and therefore let the packing take the weight of the hatch cover, with damaging results). The relative movement between hatch cover and bearing pads in a seaway, in combination with the exerted loads, results in wear down of the pads (or of the hatch coaming top plate if bearing pads are not installed). In order to reduce the rate of wear it is important to keep the contact surfaces clean. The wear down of steel support pads may vary from 1 to 7 mm per year. This implies that such pads may have to be restored at every drydocking, sometimes more often. (Recent development is renewable pads in either hard steel or plastic friction material). The below sketch shows a design with renewable shims between the pads and the hatch coaming top plate:

From a tightness point of view, the main function of the bearing pads is to keep the rubber packing from being over-compressed, which would damage the packing. It is further important that the type of gasket and gasket geometry ensure sufficient and correct compression to cater for the distortion of hatches and hatch coaming in a seaway. Pads with low friction will have less wear, hence low friction (plastic) or easily replaceable types are recommended. Below, some alternative pad designs are shown:

Steel-to-steel pad Low friction sliding pad Non-sliding flexible pad


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Steel/steel pads may be applied on most ships, however, max. surface pressure and hardness difference between the two steel surfaces are to be taken into account. For larger covers with increased relative movements or excessive loading, low friction or non-sliding pads are recommended. 301.21 Special check points for bearing pads * Check that the hatch cover side plate/skirt is not touching the coaming top plate. * Check that there are no sharp edges on the wear track of the mating plate that could

block the horizontal movement of the pad. * Check that the total wear down is less than 4 mm. * Check that there are no cracks in the adjacent steel structure (hatch cover/coaming). * In case of replaceable low friction bearing pads, check:

- That there are no mechanical damages - That the low friction sliding surface is intact - Condition of the mating plate

301.3 Hatch Coamings 301.30 General Design as well as accuracy in manufacturing and fitting of hatch coamings are deciding factors to attain good performance over time. The corners in the deck openings are exposed to stress concentrations, hence due consideration should be given as to correct design, fitting and welding, in accordance with Class rules. Top of hatch coaming with packing bar to be given particular attention with regard to alignment and correct fitting of hatch covers. Efficient drainage to be arranged for all hatch coamings. Drain pipes of at least 30 mm diameter with check valve (non-return device) or similar, to be fitted at each corner of the hatch coaming top, between the packing and hatch coaming plating. The pipes leading to open deck will drain away water accidentally collected on the inside of the packing. 301.4 Hatch Cover Packings 301.40 General As previously mentioned, cargo hatch covers on weather deck on dry cargo vessels to be weathertight, implying that they shall prevent water from penetrating into cargo holds in any sea condition. In a seaway, due to rolling motions, static and dynamic forces of considerable magnitude will act on the hatch covers and on locking devices/packings from the inside. On dry cargo vessels, in particular when carrying deck cargo, similar forces will act on the hatch covers from the outside.


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The resulting relative movement between the hatch cover with packing and the coaming top plate or compression bar, will normally be decisive for the choice of packing arrangement. Standard packing arrangements are: * The sliding type, tightening directly against the coaming top plate (see sketches page 6) * The traditional type, tightening against a compression bar (usually of stainless steel) The latter type is illustrated in 301.20/page 5 and in below sketches:

“FlexSeal” (MacGREGOR) Conventional seal The compression bar forces the sides of the FlexSeal against the walls of the retaining channel. The seal will remain in place when the cover and coaming move in relation to each other at sea. This also protects the retaining channel from corrosion. The rubber packing should be of a flexible type, rather than the conventional type, see sketch. It is important to consider the movements of the hatch cover and thereby the rubber packing, in particular at the joints. As a rule of thumb, a max. transverse movement of 22 mm or less, should be applied. On many ships this may be exceeded, thus favoring the sliding type. Good chemical properties such as resistance against oil, outdoor ageing and heat as well as low temperature resistance are important factors. 301.41 Testing of tightness Depending on condition, regulations/Class rules and company policy, packings to be tested for tightness at certain intervals. The traditional method is by hose testing, i.e. water under a defined pressure is directed successively on the packing area from the outside around each hatch cover, with simultaneous checking if any water penetrates to the inside. However, the exact position of any leakage may be difficult to determine.


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Ultrasonic testing (a sound generating unit is placed in the cargo hold and a sound detecting instrument is carried by the inspector around the outside of the packing) is a recommended alternative to hose testing. A third method is chalk testing by applying chalk to all compression bars, and then closing and securing the hatch covers and opening up again. If lack of chalk marks on the packing, there is not sufficient contact with the compression bars and thus a potential leaking area. However, this is generally only done if it is not possible to verify tightness in any other way, e.g. because of low temperature. When carrying cargo sensitive to water contamination, it is recommended that packing tightness is confirmed prior to every voyage, and the result entered into the log book. Hatch cover packings are designed for compression within certain working tolerances. This is influenced by the geometry of the arrangement as well as such factors as wear down of bushings of hinged type panels and the contact between panels and hatch coamings or wear (bearing) pads. An even compression of packings as well as even and clean packing bars are conditions for tight hatch covers. 301.42 Special check points * Check that packings are delivered in accordance with specifications. * The compression bar resting against the packing should in addition to exerting an even

pressure/compression, be located at the centre of the packing (chalk test). * The steel channel for the packing/gasket retaining bar should be grit blasted and coated

with a paint to which the packing glue will fix properly. * When covers are being painted, rubber packings must be covered by tape, grease or

similar. Possible spillage of paint on packing to be removed prior to drying. * Packings with deep, permanent impressions should be replaced. 301.5 Hatch Cover Locking Devices/Cleating 301.50 General The hatch cover panels are battened down to the hatch coaming with cleats in order to secure the panels in closed position and to prevent them from lifting from the coaming at sea. Compression of the rubber packing for weather- or watertight sealing is generally achieved through the weight of the panels. Note: Watertight hatch covers are generally not required by the Load Line Convention. The function of the cleats is quite often misunderstood, leading to an over-tightening of these (to achieve tightness) with possible damage to packings. However, the main reason for packing damage is wear in the steel-to-steel contact.


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As previously pointed out, relative movements between the panels and the coaming occur in a seaway, due to elastic deformation of the hatch opening. These movements lead to wear down of the hatch coaming top plate or the alternative bearing pads, see 301.2. Also the cleating system has to accommodate these movements. Operation of the cleating system may be manually or hydraulically. Hydraulic systems provide easy operation but require increased maintenance over time and represent a risk of oil leakage and operational problems. Manual systems are simple and reliable with reduced and simpler maintenance, but require more time for operation. Non-corrosive material (e.g. stainless steel) should be applied in dog bolts to reduce maintenance requirements. To maintain weathertightness, it is essential that the cleats: * Are sufficiently flexible to absorb imposed movements * Have sufficient strength to withstand the inflicted forces * Are adjustable Due to simplicity and flexibility, “quick acting”, manual cleats are often chosen. The flexibility may be further improved by using longer bolts. Alternative types are of hydraulic and/or automatic types, but these may have less flexibility. Below are shown two types of manual, quick acting cleats:

Hydraulically operated cleats are visualized below (unlocked and locked positions):


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301.51 Special check points Following guidelines should be adhered to: * Check that hydraulic cleats open and close in parallel over the entire hatch. * Instructions for fitting and operation are supplied by the hatch manufacturer and are to

be followed closely. * Check that all cleats are easily moved and without obstacles. 301.6 Hatch Cover Hinges 301.60 General Folding covers are equipped with hinges. Design and details to be based on strength analysis and to comprise adequate dimensions and local reinforcement of panels.


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Non-corrosive materials in bearing surfaces (pin and bushing) as well as correct alignment are important factors to ensure trouble-free operation. Further an axial boring in the hinge pin with a radial boring to the middle of the bearing surface for efficient and frequent lubrication of the bearing is also required. For ships in operation, slackness in hinges as a result of wear of bushings (bushes), may result in hatch covers being untight at crossover joints between panels. 301.7 Opening / Closing Arrangements and Equipment 301.70 General Drive units/systems for hatches (and ports) may be divided in four categories: * Cylinders/jacks * Electric/hydraulic motors * Jigger winches * Wire-operated by ship’s crane For chain operation by hydraulic motor, see Figs. 301.12 A and B. For hydraulic cylinders, check that piston rods are protected against paint, welding spray, etc. Check that axles and bushings needing maintenance are equipped with grease nipples. For details, see SGp 309 and MGp 8/Gp 83. 301.8 Manoeuvre Stations 301.80 General Following requirements apply: ∗ All valves etc. needed for operation of the system should be gathered and located in a

place giving the best possible visual control during opening and closing of the hatches. ∗ Signs specifying manoeuvre instructions to be easily visible during operation. ∗ The manoeuvre station should be placed in a lockable and watertight box and secured

against unintentional operation. ∗ Necessary steps, platforms and handrails should be installed to provide crewmembers

with a safe place for operating the hatch covers.


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301.9 Important Check Points ∗ Clean bearing/resting pads and top of hatch coaming and packing bar prior to closing.

Check that hatch coaming gutters are sufficiently clean to drain possible water in an efficient manner. Check that the inner edge of the drain channels are in good condition in order to avoid that possible water drains to the hold in stead of to the drain pipes.

∗ Keep packing channel (retaining channel) well preserved and free from corrosion. ∗ Keep drain pipes from hatch coaming top plate open and check that drain pipes/non-

return devices are free from dirt. ∗ Check steel structure of panels for indents and cracks, in particular in way of “hard

points” like hydraulic cylinder-, hinge-, locator- and pad attachments, panel corners etc. ∗ Check wear down of contact surfaces between hatch covers and coaming top/pads, and

keep packing compression within limits specified by maker. Check hinges for excessive play.

∗ Check packings for damage, fastening and elasticity. Replace them every 5-8 years, de-

pending on circumstances and condition. It should be noted that much more frequent replacement often are required, if tolerances for compression are not correctly maintained.

∗ Check that all crossover drains are sufficiently long to reach the drains of the hatch

coaming top, and that they are not damaged, fractured or corroded. ∗ Check proper functioning of all wheels, rollers, racks and other arrangements for opening

and closing the hatch covers, as poor functioning of these may cause damage to tightness systems.

∗ Avoid paint and grease on packings. ∗ Keep hydraulic system with cylinders, valves and pipes in good working order and

without oil leakage. Check the oil regularly and keep system free from impurities and air. * Check the hatch covers for structural strength and heavy corrosion. ∗ Check brackets on cargo hatch coamings and deck plating at hatch corners for cracks, see

MGp 2/Gp 20. ∗ Check that all hatch covers are mechanically secured (locked) when in open position. ∗ Ensure that all cleats are in place and secured before leaving port. ∗ Remember that leaking hatch covers may cause severe damage to valuable cargo.


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302 CARGO HATCH COVERS ON 'TWEEN DECKS 302.0 General Guidelines 'Tween deck hatch covers are fitted flush, secured with cleats and without rubber packing. Unless required by damage stability regulations (for ships exceeding 80 m length), ‘tween deck hatch covers are normally non-weather/non-watertight. To ensure trouble-free operation, the maintenance and inspection check points given in 301.9 should apply. Check securing of opened panels to avoid accidents. Handrails around the ‘tween deck openings may for the same reason be needed. Specialised vessels (e.g. reefers) will need ‘tween deck covers with packings and thermal insulation. As ‘tween deck hatch covers generally will carry cargo loads, they should be well maintained in order not to corrode. Structural soundness to be verified. 'Tween deck covers are mainly wire- or hydraulically operated folding type. Folding covers are arranged in one or several panels and are stowed to either end or to sides of the cargo hold. For typical 'tween deck hatch arrangement, see below photo and sketch:


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303 CARGO TANK ACCESS HATCHES 303.0 General Guidelines Cargo tank access hatches are important items, especially on chemical and product tankers, where seawater contamination of the cargo may lead to severe economical consequences and serious loss of reputation. Of equal importance is the hatches’ ability to contain the cargo. These hatches should therefore be an item ”Subject to Owner's Approval”. The number of hatchways and other openings in the tank deck are not to be larger than necessary for reasonable access to and ventilation of each tank/compartment. 303.1 Arrangement and Size 303.10 General Access hatches are available in different designs, mainly of circular or conical types, see below sketches.

Choice of type depends on the ladder system in the tank as well as on the deck arrangement, generally with an aim to optimize passage into the tank and to reduce the size of the hatch. It is also of utmost importance that the closing force is sufficient to exert an effective pressure on the seal. The distance between the longitudinal deck beams governs the form and the size of the opening in the deck plating and is therefore a key factor when selecting correct type of hatch. The cover should be symmetrical and a circular shape is preferred. The hatches generally have diameters ranging from 800 to 1000 mm, 850 to 900 mm being the most common dimensions. The coaming height has to satisfy the Load Line Convention, possible Flag State regulations and Class rules. Coaming heights of 800 - 1000 mm are most common. Typical designs are shown below (“Swing-away type”, Source: Nor-Marine AS): M

“S

aterial and strength of hatch are subject to approva

uper-Man”/Basic Edition/Part II

l by Class or national authorities.

Copyright NSA

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For the safety of the crew, access hatch covers should have an arrangement for securing the cover in open position. All entrance hatches should be marked with relevant tank number. 303.11 Packings Access hatches normally have a single seal system. Double sealing systems are in use, but can in some cases do more harm than good, for the reasons described in the following. The downward closing force decided by the hatch design is often just about sufficient to compress one seal properly. When two seals are used, the force on each seal will be reduced and may result in insufficient packing pressure. One should also remember that the seal often becomes buckled. Tightness is only achieved when the waveform of the seal is flattened out by the compression force. Two seals will only be effective if there is sufficient compression force to deform both seals and still have enough downward force to exert a line pressure to overcome the internal tank pressure. Note: If two seals are used, they must have different hardness in order to ensure full compression of at least one packing. To balance the above statement, it should be mentioned that some hatch makers supplying hatches with double seals, have arranged the outer seal in such way that no compression force is required to achieve protection against seawater ingress. It is very important that the packing groove/channel is uniform and that the channel walls are parallel and within ± 1-2 mm tolerance. Non-parallel walls may cause leakage. A packing size widely used is 38x38 mm and is normally in stock where packings are being purchased. It is further important that the packing joints are correctly made so that they do not come apart after having been fitted. Therefore all packings should be purchased ready-joined in a ring. Packings on oil tankers should be of a crude oil resistant neoprene (or similar) material. For chemical tankers, the packings should be suitable for the cargoes intended to be carried. 303.12 Closing system/device A conventional closing system used to be ”toggles” arranged around the circumference of the hatch. This system alone is not recommended. Non-symmetrical tightening of the toggles will give an uneven distribution of the force and can in the worst case create leakages. A better solution is a closing and tightening system where the cover is being forced down in the centre. A central force will on a symmetrical hatch coaming be evenly distributed around the circumference. This central closing force will normally be sufficient to provide full indentation of the packing and proper tightness. Toggles can then be used as additional safety, once the hatch is pre-compressed. Note that a central closing system, which only uses a centre wheel, in some cases may not give sufficient closing force by itself. Toggles should therefore be used as an extra precaution, if the hatch is not designed with an especially powerful central closing system, which makes additional toggles unnecessary.


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303.13 Top of coaming Design of the coaming top is important, especially on hatches intended for chemical and product tankers where chemical-resistant seals are being used. There are two important items to consider, i.e. the flatness of the sealing surface on the coaming, and the rigidity of the coaming top. Both the horizontal and vertical tolerances of a hatch coaming top may be deformed during installation, due to welding distortion or by being welded to a ship structure not yet completed. The top of the coaming should therefore be designed to maintain its shape within the tolerances required, also after being fitted on board. 303.2 Installation 303.20 General It is an advantage that hatches are equipped with outlets for vent pipes, steps and tank number marking as well as any brackets required by the shipyard. Excess heat should be avoided and care should be taken throughout the building period to protect the hatches from damage, in particular if the access hatches are used as support for heavy items or as a strong point for lowering equipment through the hatch opening. As a normal practise the hatches should be fitted rather late in the building period. The seals should be fitted after completion of all work on deck, including shot/grit blasting, painting etc. 303.3 Maintenance 303.30 General The access hatch should be well maintained. In particular the packings and closing arrangement must be regularly inspected to make sure that they are in good working condition at all times. The coaming top should be free from indentations. 304 SMALLER HATCHES 304.0 General Guidelines SGp 304 deals with cargo tank cleaning hatches as well as access and emergency hatches on dry cargo vessels Hatchways, openings for ventilation, ullage plugs or sighting ports etc. are not to be placed in enclosed compartments where there is a danger of accumulation of gases.


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304.1 Cargo Tank Cleaning Hatches 304.10 General As for cargo tank access hatches, cargo tank cleaning/“Butterworth” hatches should be an item “Subject to Owner’s Approval”. (For tank cleaning, see Gp 38). 304.11 Arrangement and size Small hatches of this type are always cylindrical and designed either to be welded to deck or penetrate through the deck. The inside diameter is often decided by the size of the portable tank cleaning machine, normally 300-340 mm. The coaming height depends on type of vessel, for crude oil tankers often 200 mm. For chemical and product tankers the coaming height normally varies from 250 to 600 mm. It is, however, advantageous to have the cover located above the splash zone on deck. As for access hatches, the coaming height has to satisfy the Load Line Convention, Flag State and Class rules. A typical design (with radial seal to prevent ingress of sea water) is shown below (Source: Nor-Marine):

Material and strength of the hatch are subject to approval by Class or national authorities. 304.12 Packings Tank cleaning hatches can have double or single seal system. A double seal system should only be used when adequate closing force is available from the closing mechanism(s). Lack of closing force increases the risk of leaks. See also 303.11. For hatches with double seals, the outer seal should be arranged in such a way that no compression force is required to achieve protection from seawater pressure/ingress. The packing groove/channel must be uniform with parallel sides and max. ± 1 mm tolerance. Common packing size is 25x25 mm, which normally is in stock where packings are being


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purchased. For joints and other details, see 303.11. Packings onboard oil tankers should be of a crude oil resistant neoprene (or similar) material. For chemical tankers the packings should be suitable for the cargoes intended to be carried. 304.13 Closing system As for access hatches, the conventional way of using hinges and a lid with toggles as the only means of obtaining a closing force, has several disadvantages. Non-symmetrical tightening can cause leaks, and pinching and excessive wear can occur at the hinges, even if oval hinges are used. Further, the solution does not allow for optimum design of the coaming top. A better solution is therefore generally to have a central closing system with sufficient closing force to pre-compress the seal and ensure tightness by itself. A secondary set of toggles will then provide additional safety, see sketch 304.11. 304.14 Top of coaming The top of the coaming for tank cleaning hatches should be fitted with a stainless steel roundbar, or even better, be reinforced and machined. Two important items must be considered, i.e. the flatness of the sealing surface and the rigidity of the coaming top. For chemical/product tankers it is recommended that the coaming top is reinforced and machined to given tolerances. The reinforcement will reduce the possibilities of wear and distortion during installation (welding). The machining will provide a flat surface and the closing force will exert an adequate and even seal pressure, not deforming the seal to follow the contour of an “out of flatness” coaming. 304.15 Installation Special care should be taken when welding the hatch to deck. See also 303.2. 304.16 Maintenance See 303.3. 304.2 Access and Emergency Escape Hatches 304.20 General Emergency escape hatches are to be arranged as required by SOLAS, national authorities and/or Class.


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The number of access hatches is to be kept to a minimum considering the effective and safe operation of the ship. 304.21 Arrangement and size Arrangement and strength of access and emergency escape hatches with coamings and closing devices are subject to approval by Class. Access hatches are to be operable from both sides. For opening of emergency hatches, there shall not be a need for a key to open the hatch from the escape side. Therefore, emergency exit hatches shall neither be equipped with padlocks on the outside. (However, arrangements with external locking are being used, when these can be released from the inside). Standard entrance hatches may be delivered with fittings for padlocks, which should be removed if the hatch is to be used as an emergency exit (if not equipped as mentioned above). To avoid theft, hatch covers may be secured on the inside, in a way not obstructing easy opening in case of emergency. 304.22 Installation All emergency escape hatches and access hatches should, if possible, be installed in such positions that they are protected against sea impact, see also MGp 2/Gp 23/SGp 234. Proper support of the hatches to be ensured, possibly including reinforcement of the deck. 304.23 Maintenance All access and emergency escape hatches should be maintained regularly as any other hatch. The hatches, with coaming and connection to deck as well as securing arrangement should be checked regularly for possible corrosion and/or cracks. Experience has shown that lack of maintenance on many of these hatches, particularly in the forward part of the ship, has been the cause for many bulk carrier accidents, see also MGp 2/Gp 23. Emergency escape hatches and the area around these hatches shall always be kept free from items and constructions that may hamper proper operation of the hatches in case of an emergency.


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305 BOW PORTS/DOORS WITH ACCESS RAMPS 305.0 General Guidelines Access to cargo and car decks on Ro/Ro vessels in world-wide trades and on combined cargo/passenger ferries is frequently arranged through the bow. Bow access requires, by regulation, a high degree of safety and strict operational and maintenance procedures. Class rules regarding specific design and operation criteria should therefore be studied in detail. The opening in the bow structure may be designed as double swing doors opening horizontally in parallel, one to each side, or as a visor, which opens vertically in one piece as shown in below sketches:


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A typical swing/side-hinged door is shown below:

The bow swing doors as well as the visor are watertight parts of the vessel’s hull/shell, designed to withstand sea impact and dynamic forces as defined in Class rules. Bow doors and visor are normally built as integrated parts of the hull, and then cut out and refitted when necessary accessories have been fitted. Bow ports/doors are hinged, hydraulically operated and secured with hydraulic cleating and with mechanical securing in open and closed positions. Where bow doors are leading to complete or long, forward enclosed compartments, an additional, inner watertight door is to be fitted, see also 305.4. This requirement applies to passenger vessels as well as to cargo ships.


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This requirement is also complied with when applying a bow ramp where the inner part of the ramp in closed position is acting as a watertight door, independently of the outer part of the ramp. With this solution, and provided it is positioned in compliance with Class requirements, there is no requirement for an additional inner bow door, see below sketch:

305.1 Packing System 305.10 General The watertight packing system is designed to withstand a certain “head”/water pressure. For details, see 301.4 - Hatch Cover Packings. 305.2 Cleating System 305.20 General The bow port/door being an integral part of the vessel’s hull, safe securing of the bow port in closed/locked position is of paramount importance. The cleating system is normally hydraulically operated, with mechanical securing in locked position. Indication lamps and audible alarm are required on the bridge to show when the bow port is closed and fully secured. TV and indication system for high water level are required, in order to monitor the space between the outer port and the inner door (collision bulkhead). 305.3 Access Ramp 305.30 General Forward access ramps are normally built in 2 or 3 sections folding in a storage position well inside the bow doors. The folded ramp may as mentioned, be equipped with a watertight packing system and serve as a second barrier for water ingress, however, requirements in this regard depend on trading and Class rules.


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305.4 Inner Door (Collision Bulkhead) 305.40 General When built with sufficient strength and closed and secured watertight, the inner door serves as the collision bulkhead required by Class (also statutory SOLAS requirement). With such large openings in the collision bulkhead, the racking stiffness of the vessel should be considered in order to avoid sideways deflections that may lead to leakages into the cargo space. The typical inner door is hydraulically operated, hinged at sides or alternatively at upper end (see also 305.0). The latter type is stowed horizontally beneath deck when in open position. A comprehensive packing and cleating system provides watertightness in closed position. 305.5 Important Check Points ∗ Check that coamings are correctly fitted to ensure that the port/door blade(s) is even with

shell plating when closed. ∗ Fitting of hinges requires the highest accuracy, since these are main components in the

port’s manoeuvring equipment. Check accurate fitting of bolts and holes. ∗ Check that all cleats can be mechanically secured in closed positions. ∗ Check indication for all cleats, including correct working order of indication lights for

closed door/ramp and for locking devices. ∗ Check that hydraulic piping/hoses are protected from damage by the port’s moveable

parts, or by cargo. ∗ Check alignment/straightness of coamings to ensure even packing pressure. ∗ Check securing arrangement in open position. ∗ Check sufficient drain in deck inside port/door opening, including cleaning possibilities. ∗ Check max clearances of load carrying supports designed for transfer of acting forces

from door to hull structure. These supports and surrounding structure also to be checked for signs of damage.

∗ Checks to be carried out in accordance with the Operating and Maintenance Manual

(OMM) for this type of equipment. For contents and structure of OMM, check with Class. Copy of the OMM to be filed on board.

All important maintenance and inspection items to be entered into the vessel’s PMS.


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306 STERN PORTS/DOORS WITH ACCESS RAMPS 306.0 General Guidelines Requirements to stern access on Ro/Ro vessels are as for bow access, see 305.0. For a general view of a Ro/Ro vessel, see below sketch:

Various arrangements of stern doors and stern ramps are being used: ∗ Combined stern door/ramp: The combined stern door/ramp is the common arrangement on most Ro/Ro vessels, except for some large, deep-sea vessels with a large “jumbo” ramp and a wide entrance to the Ro/Ro decks, requiring a separate stern door. The combined stern door/ramp is normally bottom hinged, in open position acting as a driving ramp and in closed and cleated condition as a watertight door. The ramp/door is operated by direct acting cylinders or wires and hydraulic winch(es). Watertightness is achieved by rubber packing arranged in the coaming, being part of the vessel’s structure and a corresponding compression bar on the ramp. ∗ Watertight stern door(s) with separate driving ramp(s): The stern door is nearly always top-hinged, arranged forward of the ramp(s) and fitted with rubber packing in contact with deck and doorframe. Where large openings are made in connection with stern ramps, racking calculations should be carried out in order to ensure proper stiffness to avoid leakages due to large transverse deflections.


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306.1 Types of Ramps 306.10 General The driving ramp(s) may be arranged as: * Straight stern ramp parallel to vessel’s centre line. * “Quarter ramp” arranged at an angle to vessel’s centre line. * Slewing ramp, which is ideal when there is a need for changing the direction of the

ramp from port to starboard side. 306.11 Straight ramp Below is shown a typical straight stern ramp. Operation is by wires hauled by a double drum hydraulic winch.


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306.12 Quarter ramp The sketch below shows a typical quarter ramp with stern door and side ramp. The quarter ramp enables the vessel to berth at practically any quay. The ramp may be divided into several sections, with total length sufficient to cope with relevant tidal conditions and quay arrangements. The sketch also shows an inner driving ramp and bulkhead door. Due to heavy weight, the ramp is operated by wires and hydraulic winches.

Quarter Ramp


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306.13 Slewing ramp Slewing ramps are designed for loading/discharging on one side of the vessel and at the stern, or on both sides and at the stern, see below sketch:

A typical slewing ramp is visualized below:


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306.1 Packing System See 305.1 306.2 Cleating System See 305.2 307 SIDE PORTS/DOORS 307.0 General Guidelines Side doors are arranged in ship’s side for loading and discharging pallets and other types of unitized cargo, vehicles etc. as well as for passengers, pilot or bunker. Side ports/doors may be top, side or bottom hinged, with vertical or horizontal sliding. Opening can be outwards or inwards. Larger ports should always open outwards, so that the sea pressure/dynamic forces will press the door harder against the coaming in the vessel's structure and not away from it. Side doors are normally operated by direct acting hydraulic cylinders, alternatively by crane/wire in combination with hydraulic cylinders. Watertightness and cleating are in principle arranged as for bow and stern ports. For doors located just above the waterline, due care to be taken to ensure adequate coaming height when loading/unloading heavy objects, that can make the vessel heel. Important check points for side doors on cargo vessels with clear door opening larger than 6 m2 and part of the door below deepest waterline are: * Testing of system for opening and closing of the door, operation of cleats and support

devices etc. Make sure to operate in correct sequence. * Check that a signboard giving instructions that the door is to be completely closed and

all closing devices locked before leaving quayside, is fitted at the operating stand and on the bridge.

* Means for testing of indicator lights to be provided at each operating stand, indicating that the door is closed and that cleats, support and locking devices are working properly. Indication panels to be provided with lamp test facility.

* Means for testing of indicator lights and audible alarms also to be provided on the bridge.

* Check that all sensors for the indication system are properly shielded from water ingress, ice formation and mechanical damage.

* For passenger vessels, check the water leakage detection system with audible alarm and television on bridge as well as in engine control room. For cargo vessels only, audible alarms on the bridge as well as in the engine control room are required.

For details, see Gp 32. Longitudinal strength in way of side doors should be particularly checked, as large openings in the hull structure always have to be compensated for.


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308 CARGO DOORS IN BULKHEADS 308.0 General Guidelines Cargo doors are generally arranged in watertight as well as in non-watertight bulkheads. These doors are normally of hinged or sliding type. Hinged doors may be top or side hinged and normally operated by direct acting hydraulic cylinders. Sliding doors are generally wire or chain operated by a hydraulic motor. Tightness and cleating are in principle as for external doors. Doors in watertight bulkheads will need the approval of Class and Flag State. Important check points are: * Local operation from both sides * Remote operation * Indication lights and alarms 308.1 Hinged Cargo Doors 308.10 General Hinged doors may be top hinged or side hinged. Lack of sufficient stowage space favours a top-hinged design, see below sketch. The door is of watertight type, 12,5 m wide and 6,5 m high and intended for a large Ro/Ro-vessel. The door is operated by hydraulic cylinders. Cleats may be of automatic wedge type or manually operated. When space allows, side hinged doors may be found preferable as they are very suitable for closing large sill-less bulkhead openings. When using two-panel doors (rather than a single panel) the storage space for cargo is better utilised.


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308.2 Sliding Doors 308.20 General Doors with a vertical guillotine-type action is a suitable solution in confined spaces where side-sliding is not possible, see below sketch:

The shown door is about 7 m wide and 4 m high. For watertight type doors, the weight of a vertically moving sliding door, combined with specially designed roller guides in which the door moves, ensures very efficient sealing. Securing and locking in open and closed positions may be done hydraulically.


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The movement of a “vertical” sliding door need not be confined by the free deck height since the door panel often can pass through and be locked at the deck above. Below is further shown a SOLAS “Class III” door (for installation below deepest load line). Such doors are generally applied to smaller openings only, usually with sill and metal-to-metal contact.

Installation and operation is subject to strict, safety-based regulations, including: * Being capable of control from both sides of the door as well as from points above the

bulkhead deck and from the wheelhouse. * Where operation is electro-hydraulically powered, the system must have the ability to

open and close the door a specified number of times after the power supply has failed.


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309 HYDRAULIC SYSTEMS For hydraulic systems in general, see MGp 8/Gp 83, which also includes details related to application of hydraulic systems onboard ships. 309.0 General Guidelines Hydraulic power transmission equipment is widely used in ship operation. The hydraulic method of power control and transmission is often selected because of following specific features: ∗ Design simplicity ∗ Exertion of almost unlimited amount of force ∗ Power unit and controls may be located far apart ∗ Automatic control of sequential operations ∗ A wide variety of speed and force using simple controls ∗ Limited wear on moving parts. ∗ Automatic release of pressure at overload ∗ Absence of vibration ∗ Automatic lubrication The two most important requirements related to operation of any hydraulic system are: ∗ Keep the system tight ∗ Keep the system clean Most hydraulic systems applied in the operation of cargo ports and doors, hatches and ramps include following equipment/components: ∗ Piping system ∗ Hydraulic pumps ∗ --- " --- cylinders ∗ --- " --- motors ∗ --- " --- valves ∗ --- " --- reservoirs ∗ --- " --- fluids These are further dealt with in the following (as well as in more detail in Gp 83). 309.1 Piping System 309.10 General Following requirements are relevant:


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∗ All couplings of same material. ∗ Couplings of well known and recognized make. ∗ No bends to be sharper than specified by supplier. ∗ Clamping of good quality at adequate distance. Clamping must permit movement due to

temperature variations. ∗ After testing all couplings to be tightened (vibrations, temperature variations, etc.). ∗ Check protection and easy maintenance behind piping. 309.2 Hydraulic Pumps 309.20 General Manufacturers’ instructions must be followed when operating or servicing pumps. The following items should be observed as general guidelines. Before starting any pump for the first time, check to ensure that: ∗ The pump shaft rotates easily by hand. ∗ The reservoir is full of fluid. (Note: some pumps must be primed when started for the

first time). ∗ All machine controls are in neutral position. ∗ All suction valves are open. ∗ Jog the pump to ensure that it rotates in the correct direction. ∗ Check that the fluid has correct viscosity. ∗ Check all piping joints for leakage. ∗ If any indication that fluid is not being pumped, the pump should be stopped

immediately. 309.21 Pump types The following sketches show various types of hydraulic pumps. Main advantages and disadvantages of the various main types are as follows: (1) Axial piston pump (pressure-compensated with variable displacement) * Advantages: - To be used when many different oil consumers in a hydraulic system - High pressure - Large range of oil capacity * Disadvantage: High noise level (2) Gear Pump * Advantages: Low noise level * Disadvantage: Limited range of oil capacity and lower pressure


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(3) Vane Pump * Advantages: Large range of oil capacity and low noise level * Disadvantage: Lower pressure

Axial Piston Pump Vane Pump Variable Volume

External Gear Pump Internal Gear Pump

309.3 Hydraulic Cylinders 309.30 General Cylinders are used where linear motion is required. A simple cylinder consists of a piston and rod installed inside a suitably enclosed tubular housing. The rod extends out of one or both ends of the housing for connection to the mechanism to be moved. For details, see MGp 8/Gp 83. 309.31 Maintenance Following guidelines should be observed: ∗ External leakage: A typical leakage observed on exposed cylinders on board vessels is leakage around the piston rod. This may be due to: - Damage to the chromium liner or the surface of the piston rod and subsequent damage

to the rod packing. The only remedy in this case is to renew the liner as well as the piston rod packing.


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- If the piston rod is vertical and pointing upwards, the piston rod packing has a tendency of collecting salt and impurities, which in turn damage the packing and its function. Hydraulic cylinders should therefore whenever possible be placed vertically with the piston rod pointing downwards.

Hydraulic oil leakages may result in damage to cargo, crew injury due to slippery deck, overboard oil pollution and may further imply a risk of fire. ∗ Internal leakage: Internal leakage around the piston will result in loss of efficiency or sluggish movement. This may be due to worn piston packing, worn piston rings or scored cylinder walls. Scored cylinder walls are usually caused by abrasive material in the oil. ∗ Loose mounting: If the cylinders are allowed to move as a result of not being securely fastened, abnormal wear of the piston rod packing will be the result. All cylinders should be periodically checked for loose mounting bolts. ∗ Misalignment: Piston rods must be properly aligned. Misalignment causes undue strain that will result in excessive piston packing wear or piston rod packing wear. In extreme cases it may result in bending of the piston rod. 309.4 Hydraulic Motors 309.40 General A hydraulic motor may be considered as a hydraulic pump working in reverse. 309.41 Motor types The below sketches show some typical types of hydraulic motors (see also Gp 83):

Axial-Vane Motor Gear-on-Gear Motor

High torque, low speed radial piston motors are mainly used for side rolling hatch covers and winches for large stern ramps.


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309.5 Hydraulic Valves 309.50 General Valves are essential elements for controlling fluid system performance. There are numerous varieties of hydraulic valves on the market, but most of these are variations of the valves used to perform fundamental functions, i.e. pressure, volume and direction of fluid flow. Manufacturers’ maintenance instructions to be followed, observing following general guidelines: ∗ Valve re-assembly requires absolute cleanliness. ∗ Couplings must be re-assembled with correct gaskets, bushings and cups. ∗ Only proper/tailor-made tools should be used. ∗ Particular caution must be exercised when disassembling valves containing preloaded

spring. ∗ Care must be taken to ensure that valves are not installed strained/with distortion. 309.6 Reservoirs 309.60 General The primary function of a reservoir is to supply an adequate amount of fluid to the hydraulic system. It also supplies extra fluid to the system in the event of leakage or cylinder extension. In addition, most reservoirs are used to recondition the fluid by allowing the turbulent fluid returning from the hydraulic system to settle and deaerate. The reservoir may also act as a heat exchanger and cool down the returning fluid. Reservoirs represent the greatest potential of contaminating the fluid and the system. To accomplish its functions and ensure that the fluid is not contaminated, reservoirs must be designed and located with extreme care. 309.7 Hydraulic Fluids 309.70 General The primary function of a hydraulic fluid is to transmit the force that is applied at one point in a system to some other location. To accomplish this, the hydraulic fluid must be incompressible and flow freely. In addition, hydraulic fluids must perform several other functions that are extremely important, such as:


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∗ The fluid must provide adequate sealing and lubrication between the moving parts to reduce friction and to minimise wear.

∗ The fluid should protect the parts in the system from oxidation and corrosion. ∗ The fluid should carry away heat from the system. Cooler to be fitted as required. ∗ The fluid should be stable with little or no physical or chemical change during its useful

life. ∗ The fluid should permit rapid separation of air and settling of insoluble contaminants

entering the system. 309.8 Commissioning of Hydraulic Systems 309.80 General The main rule is to follow manufacturers’ instructions closely. Following general guidelines to be observed: ∗ In order to remove all dirt and impurities in the piping system after installation, a

flushing-through of the piping must be done. ∗ Before filling hydraulic fluid in the system, all components in the system must be

thoroughly checked to make sure they are clean. This must be done immediately prior to filling.

∗ Careful checking of piping and wiring as well as alignment of motors and pumps should

also be carried out prior to filling of hydraulic fluid. ∗ The hydraulic accumulators to be charged in accordance with instruction manual ∗ A filter must always be used when filling the system with hydraulic fluid. ∗ A complete testing program to be established and followed, including pressure testing of

the hydraulic system. Testing of all opening and closing functions as well as hydraulic cleating and all other maneuvering operations.

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Fig. 301.12 A Weather Deck Hatch – Single Plate Panels


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Fig. 301.12 B Weather Deck Hatch – Double Plate Panels

gp30. equipment for cargo

Documents

general guidelines

cargo hatch covers

hatch arrangements

hatch cover packings

hatch coamings

types of hatches

cargo tank access hatches

hatch cover hinges