MODULE 1 -TYPES OF CARGO
Brief description on types of cargoes carried onboard merchant ships are as follows:
-General Cargo
The modern term for these types of cargoes is breakbulk cargoes. It consists of individual items, e.g. pieces of machinery, bags, bales, and small quantities of liquids e.g. latex in deep tanks etc. Heavy items may be lifted onboard using ships gear or shore cranes.
Grain
Grain comprises of wheat, corn, rye, barley, oats, rice etc. Grains are liable to heat and/or sweat, especially if damp, when they may germinate or rot, therefore requiring careful pre-loading inspection, carriage and ventilation. In major grain ports, handling equipment’s are sophisticated, grain elevators being equipped to unload railway wagons, lorries, barges or coastal craft and to reload from storage silos at high speed into ocean going ships. For discharging grains, the pneumatic sucker system, evacuators and grabs may be utilised.
Timber
Includes timber and its by product - e.g. hardwood and softwood logs, sawn timber, wooden products, wood chips wood pulp and paper products. Where practicable, timber as it is, is carried on deck. The securing and proper stowage of deck timber has the effect of increasing a ships freeboard and because of this timber carrier may be allotted lumber loadlines in addition to the usual load lines. Timber loadlines allow ships to load more cargo as compared to the ordinary load lines as it has the following effects:
a. Reserve buoyancy of vessel is increased by compact mass of buoyant timber above the freeboard deck.
b. Effective freeboard is increased with beneficial effect on the range stability.
c. Weather deck hatches are protected.
Coal
Coal is a mineralized fossil fuel widely utilised as a source of domestic and industrial power. As a sea borne product, it is always carried in bulk. It varies from soft bituminous type to hard anthracite through to manufactured coal products.
Despite the carriage of coal being an established trade, it remains as a difficult and dangerous cargo to transport due to dangers of gas explosion, spontaneous combustion, and cargo shifting during passage and corrosion to ships hold.
Fertiliser
May be carried in bulk, bags or liquid forms. Most fertilizers are harmless, especially in bags but a few can be explosive and/or corrosive. The IMO Dangerous goods Code should be consulted when carrying these cargoes.
Cement
It may be subdivided mainly into bagged or bulk cargo in either finished cement or clinkers. It should be kept scrupulously dry so as to avoid solidifying.
It is often preferred to load bagged cement into the tweendecks of general cargo ships having the facility of reducing the height of stow which in the case of excessive tier heights in single deck ships may cause splitting of lower stowed bags. The handling of clinker is not so critical as it is normally carried in bulk; it can however be extremely dusty and is therefore subjected to shore-based anti pollution regulations.
Livestock
Normally carried on the weatherdeck in tiers of specially constructed pens. Includes sheep, goats, cattle and buffaloes. On this type of trade it is not unusual for ships to carry up to 100,000 animals and thus the provision of adequate of fodder and drinking water is a major problem.
Metals
These covers the whole range from raw base materials to metal articles e.g. steel products to scrap metal. All steel products are liable to shift at sea and need careful stowage, not only to prevent any movement, but also to avoid seriously damaging the ship.
Rust will seriously affect the value of steel products and every effort should thus be made to avoid its occurrence.
Unitised Cargo
Any two or more cargo joined together is said to be unitised - strapping together, pre-slinging, palletisation, containerization, etc. Although unitisation may increase costs to some extent (extra packaging cost), it enhances cargo handling operations, reduce pilferages simplify tallying, reduce the number of people per gang. In another words it contributes greatly to a faster turn around time for the ship. Example of unitised cargo is of soft drinks packed on pallet.
Containers
Containers are basically just a box in which cargoes are placed and the box itself is transported. Majority of general purpose containers are boxes constructed with walls of aluminium or thin steel sheeting, corrugated to provide strength and rigidity, reinforced corner posts with double watertight doors at one end. Used to carry various types of cargo e.g. tobacco, electronic components, clothing etc.
Reefer
These are mainly concerned with the carriage of fruits and vegetables and are seasonal, relying on the harvesting of crops around the world. Other reefer cargoes include frozen fruit juices, flowers and bulbs, dairy products, meat, poultry and fish, pharmaceuticals, x-ray films etc. They are handled either as a break bulk, in pallets or in containers. They require scrupulously clean and odorless cargo compartments to avoid contamination and the carriage temperature is absolutely critical.
Liquids
Sea borne liquids range from drums of products such as bitumen capable of carriage in conventional tween deck ships, to parcels of edible oils transported in specially coated and heated tanks and to huge homogenous cargo of crude mineral oil carried by VLCC’s.
Most of these products are inflammable with a low flash point and many are dangerous in other ways, either emitting toxic gases or possessing corrosive qualities or both.
Gases
Consists mainly of liquefied petroleum gas - LPG and liquefied natural gas - LNG. LPG consists mainly of propane and butane and are carried either under pressure at ambient temperature, fully refrigerated (-30° to 48°C) or semi refrigerated under a combination of pressure and reduced temperature. Any gas that vaporises during handling and carriage will be reliquefied and circulated back to the tanks. LNG is mainly ethane with propane and butane making up the balance. It is carried at or near its boiling point temperature of - 164°C at atmospheric pressure. One of the particular features of LNG is that cargo boil off is used as fuel by the ship. However, given the high value of natural gas, the use of boil off for such purpose is becoming uneconomic and efforts are being made to reduce the daily rate of boil off to below 0.25% of cargo quantity.
Dangerous Cargo
Under the auspices of IMO, a Dangerous Goods Code has evolved encompassing recommendations as to stowage, carriage, packaging, documentation and labeling of most dangerous commodities. Bulk carriers are likely to be affected by the carriage by one homogenous dangerous cargo at a time e.g. sulphur in bulk or a chemical tanker is likely to carry several lots of dangerous bulk liquids at any one time.
However, it is the general cargo ships or container ships, which can be expected to carry several classes of dangerous goods at any one time, the relative effect of which in
relation to stowage and reaction between cargoes can be somewhat complicated.
IMDG code covers carriage of dangerous
goods in packaged from or in solid form in bulk.
The IMDG code comes in 4 volumes plus a supplement. Another publication dealing with carriage of dangerous goods in UK is known as “Blue Book”.
NOTE - Detail description of specific cargoes
will be given in the subsequent modules where appropriate.
Bale Capacity
This is the cubic capacity of a cargo compartment when the breadth is taken from the inside of the cargo battens or from the inner edges of the frames, and the height from the tank top to the lower edge of the beams and the length from inside of the bulkhead stiffeners or sparring where fitted.
Grain Capacity
This is the total internal volume of a cargo compartment measured from shell plating to shell plating and from tank top to under deck and an allowance is given for the volume occupied by frames and beams. This space is not only associated with the carriage of grain, as such, but with any form of bulk cargo, which would stow similarly, that is to say completely filling the space.
It is obvious that a solid cargo can be stowed only up to the limits of the frames and beams whereas bulk cargo will flow around such members. Therefore when measuring for general cargo, it is the bale capacity, which is taken into consideration.
Although both grain and bale capacities are normally used to show the volume or capacity of a ship to carry cargo, other units of measurement are more appropriate for specific trades, e.g. TEUs for container ships, lane-metres for Ro-Ro ships, etc.
Stowage Factor
For successful loading, a vessel must utilize every cubic meter of space to the best
advantage, with due regard to the necessary care and attention to conditions of stowage. Thus, the freight earning capability of the vessel is kept at a maximum. To do this it is necessary to know the amount of space, which each tonne of a commodity will occupy. STOWAGE FACTOR is defined as the volume in cubic meters a tonne of that cargo will occupy.
The figure does not express the actual measurement of a tonne of the cargo but takes into consideration the necessary for dunnage and the form and design of the packages. Examples of stowage factors are: -Coal 1.18/1.33 cu.m./tonne.
Maize 1.37 cu.m./tonne.
Rubber in bales. 1.81/1.87 cu.m./tonne
An intelligent knowledge of the use of stowage factors is necessary to all cargo officers in order that they may make economic use of each available space unit.
Broken Stowage
This is defined as that space in a loaded cargo compartment that is not filled with cargo. It is the space occupied by dunnage, the space between packages and the space that is left over the last tier placed in stowage. Broken stowage is expressed as a percentage of the total space of the compartment. The percentage that has to be allowed varies with the type of cargo and with the space of the compartment. It is greatest when large cases have to be stowed in an end hold due to the shape of the compartment. Broken stowage in an end hold due to the shape of the compartment. Broken stowage on uniform packaged commodities will average about 10% that on general cargo will average about 25%. For example:
a) A consignment of apples packed in boxes having stowage factor 1.31cu. m/ton to be loaded in a cargo space having bale capacity equals to 1000cu m. Calculate the total amount in weight that can be loaded.
Given cargo hold space = 1000 cu m cargo stowage factor = 1.31
∴ cargo loaded = stowagevolumefactor = 31 . 1 1000 = 763.36 Tons #
b) Using the above question (1)
Calculate the total amount of cargo to be loaded if 10% broken stowage is allowed. Nett volume occupied by cargo allowing for 10% broken stowage = 1.1 m cu 1000 = 909.09 cu m ∴ cargo loaded = m/ton cu 1.31 m cu 09 . 909 = 693.96 Tons
Deadweight Cargo
Is cargo on which freight is usually charged on its weight. Cargoes which measures 1.22cu.m./tonne (s.f) or less is classed as deadweight cargo.
Measurement Cargo
Is cargo on which freight is usually charged on the volume occupied by the cargo and this cargo is usually light, bulky cargo having a stowage factor of more than 1.22 cu.m./tonne.
It has been the custom to set two standards by which cargo is measured and freight is charged. This is in order to avoid excessive freight charges, which might be out of proportion to the space occupied by a particular consignment, and to protect the ship from loss of freight commensurate with the amount of space used.
Ad Valorem Cargo
Freight for certain expensive cargoes, e.g. precious stones, fold bars, etc. is not levied based on weight or measurement but on the value of the cargo.
Cargo Documentations
a)
Mate’s Receipt (M/R) - is a document ofreceipt given by the ship’s chief officer (the Mate) for goods actually received on board. It
is carefully drawn up to show the identification, description and quantity of the goods (as verified from the ship’s tally sheets). Any damage to the cargo noticed before loading on board is entered on the M/R and the receipt is then said to be ‘claused’. All particulars from the M/R are transferred to the ‘Bill of Lading’.
b)
Bill of Lading (B/L) - is properly preparedby the ship-owner (or his agent) from details in the Mate’s Receipt, and delivered to the shipper - freight being usually paid at this stage. It is a legal document, which provides evidence of a ‘contract of carriage’ between the shipper and the ship owner (the carrier). It also acts as a document of title to the goods described therein i.e. the holder of the B/L is regarded as the rightful owner of the cargo.
c)
Cargo Manifest - is a document containinga detailed and complete list of cargo ‘as loaded’, compiled by the ship owner (or his agent) from the Bill of Lading. Copies of the manifest are delivered to the ship, the stevedores at the discharging ports and to Customs authorities at the discharging ports. As it is a comprehensive record of all cargo in the vessel, it permits the checking of cargo during discharge thereby avoiding overcarriage/short landing. Government Authorities may use it as material for compilation of the national trade statistics viz. the nation’s imports/exports.
d)
Cargo Plan - is a plan drawn up by theship’s cargo officer showing the stowage of all cargo on board the vessel. Copies of the plan are sent in advance to the discharge ports so that preparations for her unloading can be made before arrival at the port. Along with the summary of the cargo on board, a well drawn up cargo plan greatly assists in facilitating discharge and avoidance of overcarraige/short landing of cargo.
e)
Dangerous Cargo List - a shipper isobligated to declare to the Master full details of any dangerous/hazardous cargo shipped by him and covered under the “International Maritime Dangerous Goods Code’ (the I.M.D.G. Code). The Master is required to prepare a list of all dangerous/hazardous cargo
shipped on board. It should show the correct technical name of the commodity, its ‘class’ as per the I.M.D.G. Code, its quantity and weight, position of stowage on board, port of loading and the port of discharge.
Preparation Of Hold Prior
To Loading General Cargo
As temporary custodians of the cargo, it is the duty of the ship’s officers to ensure that cargo is delivered in the same condition as it was received on board. Besides ensuring that damage to cargo does not occur during handling (slinging, lifting by derricks/cranes, working forklifts etc), it is also important to prevent damage as a result of the condition of the hold itself.
1.0 Cleaning the Hold
1.1
The method and amount of cleaning required will depend upon the type of cargo previously carried in the hold. Generally speaking, a hold which is ready to receive cargo should be swept clean, dry, well ventilated and free from odour of the previous cargo(es).1.2
The hold should be cleaned prior to loading. The degree of cleanliness required will depend on the nature of the cargo to be loaded. Cargoes such as grain, sugar etc. will need a scrupulously clean hold (and usually surveyed) before loading can commence, whilst cargoes such as coal, steel etc. may not require the same level of cleanliness. 2.0 Inspecting the Hold for damages,testing bilge and fire systems
After cleaning the hold the following inspections/tests are normally carried out: 2.1 Inspection of the hold for internal damages - e.g. pipe guard, ladder rungs, leaking pipes, bilge sounding striker plates, leaking rivets/welding seams etc.
2.2 Testing the Bilge pumping system - This is done if it has not been carried out earlier during washing of the hold etc. Particular attention is paid to ensure that the bilge suction non-return valve is working and
‘backlash’ does not occur when the bilge pump is stopped.
2.3 Checking the hold fire detection / extinguishing systems - most ships are fitted with the CO2 extinguishing system and the CO2 lines to the hold are cleared by passing compressed air. Using artificial smoke usually checks the detection system.
2.4 Checking oil/water tightness of the Double Bottom tank top and its manhole covers - this is done by pressing up the tank to a head of oil/water and checking for leaks.
3.0 Making the Hold vermin free
Vermin such as rats, cockroaches, silver fish etc, in the holds, can cause extensive damage to cargo on board resulting in huge damage claims from shippers/consignees.
It is a requirement by law that every ship must be in possession of a valid Derating Certificate. The Port Medical Officer issues this certificate after fumigation by the burning of sulphur or the release of cyanide gas has been carried out. The certificate is valid for six months, after which a Derating Exemption certificate will be issued if no diseased rats or a large number of rats are found on board. The rat population may be kept to a minimum by the use of anti-coagulant bait, such as sodium fluoracetate. Cockroach bait, pesticides and insecticides may be used to exterminate cockroaches and other insects. Cleanliness is the most important factor in keeping a ship vermin free. When certain cargoes such as rice, are loaded, the holds are fumigated after loading to rid the cargo of weevils.
Assignment
Please submit the following assignment to ALAM
1) A hold, bale capacity 2000 cu m contains, 1200 tonnes of bagged flour, (stowage factor 1.15 cu m/tonnes). Calculate the broken stowage.
2) Describe a cargo hold preparation in your last ship and state the cargo loaded. State the preparation of hold prior to load general cargo.
MODULE 2 - FACTORS TO CONSIDER FOR
GENERAL CARGO STOWAGE
The following must be borne in mind when loading general cargo:
-1) Cargoes should be well distributed in all hatches to increase the Port speed.
2) Foodstuffs and other cargoes liable to tainting - need proper separation /segregation to avoid tainting damage.
3) Heavier cargo should be placed on deck/tank top whilst lighter cargo on top of these cargoes to prevent crushing damage. 4) It is a general rule that fragile and light packages are stowed in tween deck(s) to avoid the effects of roll and pitch of vessels. 5) Ensure packages stowed evenly (not tilting), for example near turn of bilge, end holds by the proper use of dunnage to achieve compactness of cargo stowage. 6) Light packages (cartons, etc.) stowed away from cargo hold obstructions such as - frames, deck beams, stiffeners.
7) Valuable cargo should be stowed in strong rooms or in Chief Officer’s office. 8) To avoid cargoes being crushed during slinging use proper gears like pallet, spreader.
9) Proper securing of cargoes and lashing are essential. Extra pad eyes may have to be welded to have more securing points for lashing cargoes.
Port Speed
Each day that a ship remains unnecessarily in port results in a reduction of the ship’s earning capacity. An unnecessary delay in port increase the port dues allied costs and encroaches on the time that she would have been steaming on her next voyage.
Ships officers should aim for increasing ‘port speed’ by efficient distribution of cargo, readiness of cargo spaces etc. This ‘speed of
turn round’ is also dependent on port facilities for clearing the cargo etc.
General Cargo Stowage
The following points must be borne in mind when planning loading of General Cargo by Chief Mate or officer in charge of loading. a) Safety of the ship
stability considerations proper trim/list/draught avoiding structural stresses
avoiding physical damage from cargo
b) Safety of the crew and port workers
preventing unstable cargo blocks
avoiding blocking of escape routes /safety
appliances
protection from toxic fumes/fire hazards
c) Avoiding damage to cargo
avoiding condensation/water damage
protection from taint / contamination /
interaction
preventing physical damage to cargo preventing pilferage
d) Maximum use of available space on board
minimizing ‘broken stowage using ‘filler’ cargo
e) Rapid and systematic discharging and loading
providing maximum number of working
hatches/even distribution
preventing over stowed cargo
preventing over carried/short landed cargo
(proper segregation/marking).
enhancing ‘port speed’
Cargo Plans
A cargo plan is a plan showing the disposition and distribution of cargo throughout the vessel, in as much detail as is possible.
A cargo plan for a general cargo ship will usually be drawn up at the last port of loading from information derived from the deck officers cargo workbooks, from mates receipt and from
loading plans produced by shore personnel at the loading ports. Copies of the plan will usually be sent ahead of the ship to the discharge ports.
Whilst the plan is not a scale drawing, it should show with some accuracy the location of specific parcels of cargoes in the locker doors, hatchways so that the order of discharge may be planned Whilst the format of the plan will vary from company to company, most plans will show the lower holds in elevation (side view) and other compartments such as tween decks and deck lockers, in plan view. Where possible, each parcel of cargo should be identified separately, but this is not always possible when many small parcels are involved (in which case they are grouped together).
A typical entry on the plan could be as follows:
- L’POOL/PNG
400 CASES CORNED BEEF “SPAR” 23t.
i.e. 400 cases of corned beef, loaded at Liverpool for discharge at Penang, all cases marked “SPAR” for identification and the total weight of the parcel is 23 tones.
It is usual to colour the plan according to the port of discharge, so that the likelihood of overlooking a parcel of cargo and carrying it to the next port (i.e. overcarriage) is reduced. In the case of cargo having optional ports of discharge it is coloured in both port’s colours. Where there is unused space adjacent to stowed cargo, it is measured up, and the calculated volume measured, and entered on the plan. Various symbols and conventions may be used: - for example, parcels separated by a diagonal line on a side elevation, are side by side in the hold.
In addition to the actual drawing, other useful information is shown in the plan. The name of the ship, master’s name, the voyage number, cargo loaded ON DECK, in masthouses, and in various other extraneous places such as the mate’s office and the draft at the last loading port are shown in the cargo plan. It is good practice to append a statement of dangerous cargo on board for quick
reference. A summary of total tonnages loaded in each hold and other information regarding dead light, as fuel, stores and water; means of separation used between particular parcels and the total space remaining are also appended to the plan.
Note: The typical cargo plan of a general cargo ship is shown on the opposite page.
The cargo plan has a number of functions:
- it helps to avert overcarriage and short
delivery.
the discharge sequence can be planned in
advantage.
the necessary cargo handling gear
can be rigged in advance.
discharge time can be estimated.
transport arrangement for a particular
parcel of cargo can be made.
proper decisions can be made on ventilation can be arranged with the aid of the cargo plan.
in the event of a fire breaking out in the
compartment, the cargo plan is invaluable in fighting the fire, particularly if dangerous cargoes are in the compartment.
should any cargo shift while the vessel is at
sea, prompt action can be taken with the aid of the plan.
the plan, enables the shipowner to
assess the position regarding to diverting the vessel enroute to load further parcels of cargo.
Cargo Plan On Tankers
Like the cargo ships, the tanker cargo plan is particularly useful when a number of diverse cargoes are to be loaded. Unlike the cargo ship, it is only necessary to show the disposition of the tanker cargoes in plan view, at one level. It is sometime the practice to overprint the comparable importance. Most of the functions of the plan are similar to that of the general cargo plan. It is particularly useful to deck officers when loading or discharging to the chief officer for planning tank cleaning and to the chief engineer for maintaining cargo temperature. The cargo plan enables a visual record to be kept of previous cargoes, which is of significant importance to the chief officer when planning the disposition of future cargoes.
DUTIES AND RESPONSIBILITIES OF
CARGO OFFICERS
Cargo Officers
The term ‘Cargo Officers’ implies the person responsible for the safe and efficient handling and stowage of cargo on board. This responsibility also includes the proper preparation of the hold prior to loading, correct supervision during the working of cargoes proper to the preservation of cargo whilst in transit and the co-operation/co-ordination with relevant port authorities whilst in port/harbour. The Master to the senior most deck officer i.e. the Chief Officer generally delegates the responsibilities of the Cargo Officer. The 2nd and 3rd Officers, who are called the ‘Junior Cargo Officers’, assist the Chief Officer in carrying out these duties.
Duties And Responsibilities
The main duties and responsibilities of the Cargo Officer are listed below:
1) To ensure the proper preparation of all cargo spaces for the types of cargo to be carried.
2) To inspect the ship’s cargo gear to ensure that it is in good working condition and in accordance with the statutory requirements. 3) To ensure that all holds, accesses and parts of the ship comply with the requirements of the Dock Safety Regulations.
4) To ensure proper status of guardrails, manhole covers, side ports, stern doors, container fittings etc.
5) To plan and supervise the proper stowage of cargo on board ensuring the safety of life and property, and avoiding excessive ship stresses whilst having adequate stability during loading and discharging and at all stages of the voyage.
6) To achieve proper stowage of cargo not in such a manner as to prevent correct and speedy discharge, taking into account the
proper rotation of ports and also ensure that no cargo is over stowed.
7) To undertake measures to prevent the out-break of fire on board and to ensure that fire fighting equipment is in readiness all the time. 8) To ensure the safe operation of all ship’s cargo handling gears.
9) To avoid damage to the cargo - to ensure the proper handling, slinging, discharging, separation, ventilation, slinging, distribution of cargo. In the case of refrigerated cargoes - The proper control of temperature.
10) To take adequate measures to prevent the pilferage of cargo.
11) To maintain a daily check and record of cargo loaded or discharged including the vessel’s draught.
12) To make proper and correct entries into the Mate’s Log Book, issue relevant Mate’s Receipts for cargo loaded, drawing up of cargo plans, hatch lists, cargo summaries, dangerous cargo lists etc. To maintain the Dangerous Cargo Register.
13) To attempt a good distribution of cargo at loading and discharge ports, so as to obtain the fastest turn round of the vessel and minimise port stay.
14) To ensure that all cargo is properly secured, hatches well battened down and cargo gears secured before the vessel proceeds to sea.
15)
To ensures that proper ventilation of cargo spaces is carried out to prevent cargo damage due to condensation/sweat. To check and record temperatures and CO2 concentrationsin refrigerated cargo spaces.
16) In the event of bad or adverse weather conditions, to ensure the water tightness of
compartments, proper trimming of ventilators and the lashings of cargo etc.
17) To ensure that all work on board is carried out in accordance with the “Code of Safe Working Practices”.
18) To properly delegate duties to Junior Cargo Officers with adequate instructions for the proper loading/discharging and stowage of cargo and the overall safety of the vessel.
Packaging Of General Cargo
General cargo may be presented for shipment with various forms of packaging, such as:
Bags - made from natural fibres like
jute/cotton or from synthetic fibres and paper. Used for cement, grain, sugar etc. They are liable to bursting at their seams.
Cartons - made from cardboard. Used for
finished goods like condensed milk, shoes, or for carrying fruits etc. They are very fragile and liable to be crushed.
Chests - rectangular/square boxes made
from plywood. Used for carrying tea. They are fragile and liable to be crushed.
Cases - rectangular boxes made from
wooden planks nailed and banded. Can be strong or fragile depending on quality of wood & construction of case. Used for heavier goods like spare parts etc. or to protect fragile goods.
Crates - rectangular, made from wooden
planks with ‘grated’ design. Not as strong as cases and sides are fragile. Used for machinery parts etc.
Bales - formed when commodities such as
natural fibre, cloth etc. are pressed tightly into a rectangular bundle and then strapped firmly with metal bands or cord. Lifting by hooking onto bands should be avoided.
Barrels - made from shaped wooden
planks called ‘staves’ and held by metal hoops. The weakest part is the rounded middle called the ‘bilge’ and the strongest is at the quarter hoop’. The opening for filling the contents is called the ‘bung’. Ideally placed on wedges, called ‘quoins’ placed below the quarter hoops keeping the ‘bilge off the
ground and the ‘bung’ upwards (i.e. ‘Bung up and bilge free’). Used for carriage of wine etc. and similar produce.
Slinging Of General Cargoes
Loading and discharging of cargo is facilitated by the use of proper cargo handling gears namely, derricks/cranes (the lifting machines) and slings. Slings facilitate the ‘grouping’ of unit packages of cargo conveniently for connecting to derricks / cranes. Various types of slings, for use with different types of general cargo, are available and are designed to minimise damage to the cargo during the lifting process.
Some of the principle types of slings, available are clearly explained in various textbook.
Unitization/Palletization
To further facilitate quicker dispatch of cargo into/out of the ship, and to allow it to be handled mechanically by machines such as forklift trucks, small packages of cargo (unit packages) of uniform size are sometimes consolidated into ‘unit loads’ on ‘pallets’ (double-layered wooden platforms of standard dimensions capable of being lifted conveniently by fork lift trucks). Special ‘pallet slings’ make the slinging of pallets, onto derrick/cranes, faster and easier. The concept being to assist the process of cargo handling by reducing the number of occasions when a piece of cargo has to be manually handled thereby increasing cargo throughout.
‘Pre-slinging’ of cargo, where slings are left on after loading so as to facilitate quicker discharge at the other end (by avoiding the building up of sling loads again) is a form of unitization and is used on some trades.
‘Containerisation” is a special form of unitization and will be discussed later.
BASIC CARGO HANDLING
EQUIPMENT AND CARE OF
CARGO
Chain Sling
Consists of a length of chain with a large ring at one end and a hook on smaller ring at the other end. It is used for lifting heavy logs, bundles of iron and most steel work. Care must always be taken that no kinks are allowed to form in the chain when goods are being lifted.
Can Hooks
The hook slips under the lip of the drum or barrel. There are frequently four or five sets of hooks on a ring, which enables drums and barrels to be handled very rapidly. They are not to be recommended for handling heavy barrels as there is a possibility that the staves will be pulled out.
Snotter
May be made of either rope or wire by forming an eye at each end of a 16mm - 20mm wire (2” - 2.5 “) or 50mm - 60mm rope (6” - 7”) 4 to 6 metres (2-3 fathoms) in length. It is used for slinging cases, bales, wet hides and timber.
Plate Clamps
There are various type o plate clamps, but the principle is that the plate is gripped when the weight is taken, so that there is no chance of plate slipping as it could do if a chain sling was used.
Rope Sling
This is formed by joining the ends of a piece of 25mm - 30mm rope 3” - 3.5“) about 10 to 12 metres (5 to 7 fathoms) in length with a short splice. The sling is in very common use. Bags, baled goods, barrels and cases may all be along with this.
Boxes
Similar to the tray by a wooden side is fixed around it. Used for handling explosives.
Trays
May be square, rectangular or round. They are slung by pieces of rope called legs, attached to the corners. Used for small cases and drums.
Canvas Sling
This is formed by sewing a piece of canvas between the parts of a rope sling. It is used for bagged grain, rice, coffee and similar cargoes where the contents of the bag are small. Any spillage is retained in the canvas and is not wasted. The stress on the outside bags is spread more evenly and thus the chance of splitting is reduced.
DAMAGE DUE TO IMPROPER
USE OF CARGO HANDLING
EQUIPMENT
Much cargo damage results from careless or improper handling during the loading and discharging processes, the following being the principal sources of such damage:
-Careless Winch Work
Lowering heavy slings or drafts of cargo too fast on to cargo already in stowage not infrequently is responsible for damage which, often goes undetected until discharge.
Cargo Hooks
The use of these implements is indispensable in the handling of a large variety of commodities, but with bag cargo, fine bale goods, hides, fire rolls of paper and matting, etc., light packages, liquid containers, crates and like packages whose contents are exposed or unprotected, the use of cargo hooks should be strictly prohibited.
Crow and Pinch Bars
These also are indispensable to the sound stowage of many classes of heavy packages, but their use should never be permitted when stowing barrels, or other liquid containers, or with any packages which are not substantial enough to withstand damage from their use.
Crushing against Ship’s
Sides
Hatch coamings, beam sockets, etc., should be safeguarded against by the use of overside skids, the correct plumbing and guying of derricks, and careful winch driving, especially when swinging booms are in use.
Dragging Cargo
Dragging Cargo by winches along the deck to save trucking, from remote ends and wings of holds and ‘tween decks instead of making up the “draft” or “sling” near the hatch, is a prolific source of damage to, and loss of contents of the lighter class of packages, as well as to the cargo in stowage over which such is dragged.
Dropping Packages
Dropping packages from trays, trucks, railway cars, top tiers of lighters, etc., by which their contents are broken or exposed, the packages splintered, deformed or loosened in their fastenings and rendered unfit for the subsequent handling they are subjected to. To avoid this, suitable skids should be used for packages, which are too heavy to be handed down.
Improper Appliances
The use of special appliances tends to be expeditious and economical in handling of cargo, but damage is frequently caused by the improper use of such appliances.
Net slings are most useful with many kinds of small packages, but if used with bagstuff, light cases, etc., a great deal of damage results. Similarly chain slings are indispensable for certain types of packages and useful for most classes of iron goods, but the use of such with light cases, sheet iron, coils of lead or copper piping, sawn logs of valuable timber and other goods liable to buckling, fraying or marking by chain is productive of damage and claims. Canvas or web slings should be used for slinging bag flour, coffee and like cargo, while the use of trays for certain classes of goods is much to be preferred to slinging by net or rope.
Improper Slinging
Too much weight in a draft endangers the safety of packages situated at the outside edge of bottom and top tiers into which the sling is liable to be drawn by weight below and compression above.
A draft composed of many packages should taper off on top to prevent springing or
crushing the outside upper packages by compression of the sling. Light or fragile packages should not be slung along with heavy packages.
Lack of Walking Boards
Lack of Walking Boards and landing platforms. Where these are not provided and used, damage is caused to packages, in towage, over which other cargo has to be worked into the position where it is to be stowed.
Packages, which are damaged after they are at “ship’s risk”, should be carefully re-coopered or repaired before stowing away.
SWEAT AND VENTILATION
1) SWEATa) “Sweat” is condensation, which forms on all surfaces in a cargo compartment due to the inability of the cooled air in the compartment, to hold water vapour in suspension (warm air can hold much more water vapour than cool air).
i) Ship’s Sweat - exists when water droplets are deposited onto the ship’s structure in the compartment (e.g. deckheads, beams, frames, shipside, stringers etc.) and then fall onto or come in contact with the cargo.
It occurs when the dew point of the air in the cargo compartment is more than the temperature of the outside air/structural parts of the compartment.
It is usually found on voyages from warm places to colder places.
ii) Cargo Sweat - arises when condensation forms directly on the body of cargo itself.
It occurs when the temperature of the air in the compartment (or the cargo itself) is lower than the dew point of the incoming air.
It is likely to be found on voyages from cold to warmer places.
c) Prevention of Damage by Sweat
Although intelligent use of dunnage can minimise damage from sweat, it is more prudent to consider the prevention of damage by the elimination/minimisation of sweat by efficient ventilation.
The controlling factor for the formation sweat is the relationship between the temperature and humidity of the air in/outside the compartment. Air having 100% humidity is said to be “saturated the temperature at which this occurs is called its dew point.
i)
When the dew point of the outside air is lower than or equal to the dew point of the air in the compartment - VENTILATE.)ii
When the dew point of the outside air is greater than the dew point of the air in the compartment - DO NOT VENTILATE.2) VENTILATION
a) Ventilation has the main objectives of:
preventing moisture damage to cargo
originating from condensation (sweat) within the cargo compartment.
removing fumes and odours
emanating from cargoes stowed in the compartment to prevent ‘taint’ or other damage.
thus preventing fire.
b) Ventilation may be described as either:
)i
Through Ventilation - with the flow of airoccurring through the body of the cargo assisted by proper ‘trimming’ of ventilators and the judicious use of dunnage.
)ii
Surface Ventilation - with the flow ofair occurring only at the upper surface of the cargo and not being forced into the body of the cargo.
c) Ventilation may be provided by two major means:
i)
Natural Ventilation - this is achievedby ‘trimming’ the ship’s ventilators and obtaining a natural flow of air caused by the vessels movement or outside wind.
Trimming the leeward ventilation into the wind and trimming the winward vents away from the wind can effect ‘Through natural Ventilation’. The air in the compartment will then move in a direction contrary to the flow of outside air.
ii)
Mechanical or Forced Draught Ventilation - The simplest of such systemsconsists of a fan of appropriate size and design which delivers outside air into the compartment, and the used air from the compartment is discharged to the atmosphere via the natural exhaust ventilator.
Sometimes such an arrangement does not prove satisfactory and hence the exhausting is also done mechanically by means of a suitable exhaust fan. The delivery and exhaust is properly balanced to provided good airflow.
3) DUNNAGE
Dunnage’ may be referred to as the wood that is used to protect cargo. It may be in the form of wooden planks, or slats, bamboo, bamboo or rush mats.
Many general cargo ships have permanent dunnage, called ‘spar ceiling’ or ‘cargo battens’, fitted over the side frames in the hold (and sometimes over the bulkhead stiffeners). It consists of 150mm x 50mm (6” x 2”) timber usually fitted horizontally into cleats over the
side frames with the distance between the ‘battens’ of about 230mm (9”).
Cargo battens are sometimes fitted vertically and in such cases the initial expense is generally greater. However there tends to be less subsequent damage to the battens and better protection is afforded to the cargo.
The tank top is usually covered with a double layer of non-permanent dunnage called ‘portable dunnage’. The bottom layer consists of 50mm x 50mm (2” x 2”) timber spaced about 0.7 to 1.0 metre (2-3 feet) apart and laid athwartships - if the ship has conventional side bilges (otherwise laid fore-and-aft in case of ‘bilge wells’) to allow free drainage. The upper layer consists of 150mm x 25mm (6” x 1”) boards laid across the lower layer, about 230mm (9”) apart.
In some ships the tank top, in way of the hatch, is protected from impact damage by cargo by a permanent wooden sheating called the ‘tank top ceiling’. This does not replace dunnage and the portable dunnage should be laid over this and it should also extend over limber boards.
Similar dunnage arrangements will be found in the tween decks, however the lower layer of portable dunnage may also consist of 150mm x 25mm boards (sometimes only a single layer is used). Particular attention should be paid at the shipside stringer, where a thicker layer of portable dunnage may be prudent, as water tends to accumulate here.
Timber used for dunnage should be clean, dry, stain free, odour free and free from nails and large splinters. New timber should be free from resin and the strong smell of new wood.
With some cargoes such as bagged rice etc, the hold pillars should be lagged with bamboo mats. When battens are not fitted on bulkhead stiffeners, a lattice of bamboos may have to be erected as a temporary measure.
It must be noted that dunnage need not be laid if the cargo does not require ventilation. For example, when coal is loaded in bulk, the cargo battens are removed and no portable dunnage is laid.
The use of dunnage may be summarised as:
Preventing cargo coming into contact with
free moisture/water on the tween deck or tank top.
Preventing cargo from coming into contact with the steel boundary of the hold thus minimising damage due to ‘ship’s sweat’.
Assisting in providing ventilation, thus preventing / reducing ‘sweat’.
Preventing spontaneous heating by
affording good ventilation.
Aiding distribution of weight over a layer of
cargo thus minimising crushing damage to cargo.
Preventing chafage between cargoes. Certain types can prevent pilferage of
cargo.
Aiding in distribution of cargo weight over
tank top etc.
Can be used to separate cargoes (this is
not considered as a normal practice).
Entry Into Enclosed Spaces
There are many enclosed spaces on a ship - if in doubt about any space you may have to enter CHECK FIRST with Chief Officer.
An Enclosed Space Is
any space or compartment that has been
closed or unventilated for some time.
any space or compartment that may,
because of the cargo carried, contain noxious, flammable or harmful gases.
any space or compartment which may be
contaminated by cargo or gases leaking through a bulkhead or pipeline.
any storeroom or space containing noxious
or harmful materials
any space or compartment which may be
deficient in oxygen.
These definitions include pump rooms on tankers. There may be special instructions for routine entry into pump rooms on your ship. Make sure you know what they are.
AN ENCLOSED SPACE SHOULD NEVER BE ENTERED UNLESS AUTHORITY HAS BEEN GIVEN BY THE MASTER OR A RESPONSIBLE
OFFICER
The atmosphere in any enclosed space may be incapable of supporting human life. It may contain flammable or toxic gases or not enough oxygen.
This is why it is essential that the Master or officer in charge, who will ensure that all the necessary safety precautions have been taken before anyone is allowed to enter an enclosed space, must give instructions or permission.
Precautions Before Entering
Tanks Or Confined Spaces
1) Prior to entry into enclosed space it is essential to obtain permission first.
2) Test on tank atmosphere - should be checked by using explosimeter and oxygen analyser where appropriate for safe entry. 3) Ventilate space prior to entry and continuously during the operation so as to ensure the environment is safe.
4) Entry should be restricted to the minimum number of personnel required for the job and a record is made on the number of personnel. 5) Adequate lighting to be provided for the entry.
6) Properly attired and safety gear should be observed by all personnel involved in the entry into enclosed spaces.
7) Use only intrinsically safe equipment when the enclosed space was used to store or carry flammable cargoes prior to the entry.
8) Post signs at entrance and one competent man on standby to monitor the operation. 9) Proper and effective communication established between all parties involved in the entry.
10) Emergency procedures and evacuation should be briefed and well understood to all personnel involved.
Assignment
Please complete the assignment and return to ALAM
1) State the functions of a cargo plan in a bulk carrier.
2) Describe ship sweat and cargo sweat and the factor affecting sweat.
MODULE 3 - CONVENTIONAL DERRICK
RIGS
The Single Swinging Derrick
The single derrick rig is basically a boom supported at its base (heel) by a special pivotal arrangement called the ‘goose neck’, which allows it to be raised or lowered by means of a ‘topping lift span’ and to be swung from side to side by means of ‘slewing guys’. Near the head of the derrick boom is the ‘spider band’ onto which are attached the ‘derrick head span block’, the ‘slewing guy pendants’ and the ‘cargo head block’.
The topping lift span, downhaul (the hauling part) is led via the ‘mast head span block’ on to a ‘dolly winch’ usually fitted with its own motor for the sole purpose of raising/lowering the derrick boom (in order ships the daily winch may have no motive power of it’s own and is turned by using a ‘bull wire’ onto the side drum of the cargo winch. A safety device in the form of a ‘pawl’ is fitted to the dolly winch to prevent the accidental lowering of the derrick boom.
The ‘cargo runner’ downhaul is led from the ‘cargo head block’ to the cargo winch via the ‘derrick heel block’ and usually passes through a ‘runner guide’ on the boom, which prevents the runner from sagging.
The slewing guys (fitted on each side of the boom) which have their wire pendants shackled to the spider band at the derrick head have their lower parts consisting of a cordage tackle for hauling on.
The single derrick rig can be used to lift loads to the full extent of it’s SWL (safe working load), which is marked near the heel of the boom, provided the cargo runner (or cargo purchase) is also rated to that SWL.
NOTE: When a single derrick is used in the Union Purchase rig, a ‘preventer guy’ is passed over its head on the outboard side.
A single swinging derrick which converts a single whip to a double whip and creates a mechanical advantage. Used to lift load double of the SWL of the cargo runner (The derrick must be rated higher).
YO-YO Gear
Employed using two or four single derricks. Used for loads heavier than those, which can be handled by the union purchase or single swinging derrick.
Two Derricks
The two inshore derricks are rigged with a gun tackle and their moving blocks are joined by a heavy strop supporting a floating block (YO-YO) with the cargo hook attached. Operation is carried out by swinging both derricks towards the hatch/quayside, keeping both derricks heads as close together as possible.
Four Derricks
Two pairs of derricks are rigged similar to the union purchase. The two cargo runners of the inboard derricks are passed through a floating block and shackled together; similarly the outboard derrick runners are passed through another floating block and shackled together. The floating blocks are then shackled together to form the union with the cargo hook secured below them.
DERRICK RIGS
Union Purchase System
Fig. A - Union purchase rig
(slewing guys not shown)
This is probably the most common derrick system in use on general cargo vessels. Two derricks are “coupled”, “married”, or joined by
a union hook and worked in conjunction with each other. Refer to fig. A. Each cargo boom is joined to the vertical mast or post by a swivel fitting known as a goose neck (so named because of the shape of the fitting). Then up and down, or luffing, movement as the boom is carried out by a topping lift/span tackle, and the horizontal or athwartships movement is controlled by a slewing guy attached to the outboard side of the boom head. The two booms are linked by a schooner guy which runs from the inboard side of one boom head to the other and thence to the deck via a lead block on the mast. Inboard slewing guys sometimes replace the schooner guy but the latter tend to interfere with the cargo-working operation. The schooner guy is always well clear of the cargo working area.
The guys and tackles position the derricks. One boom is positioned over the hatch and the other boom is positioned over the ship’s side. When the booms are set up in position the preventer guys are set up tight. These are single lengths of wire which lead from the outboard side of the boom to the deck and which have the function of taking the guy load during the cargo-handling operation. The preventer guy is sometimes called the standing guy as it has no moving parts whereas the slewing guy consists of a tackle (usually the only tackle on board ship rigged to advantage).
A cargo wire, or runner, from each boom is joined by a three-way swivel which is known as a union hook. In the unloading process the boom centred over the hold lifts the load by its runner. Once the loadline has been lifted to a sufficient height to clear deck obstructions, the cargo runner from the other derrick is used to move the load over the ship’s side and on the quay or into a lighter.
Precautions
The following criteria must be complied with at all times:
)a The minimum operating angle of either derrick should be not less than 15° to the horizontal, and it is recommended that the angle be not less than 30°;
)b The maximum included angle between the cargo runners must not exceed 120°;
)c The outreach beyond the midship breadth of the ship should not less than 4m.
The main advantage of this system is that it is probably the fastest method used for discharging break-bulk, non-unitized general cargo.
Disadvantages
a) It can only be used for light loads, an average of approximately 1.5 - 2 tonnes per load.
b) The winchmen must be highly skilled and experienced.
c) The derricks cannot be used for “spot loading”.
d) Re-positioning the derricks is time-consuming.
The Jumbo Derrick
This is basically a single swinging derrick with a much greater SWL (about 30 - 50 tonnes). The boom can be raised or lowered, with the
load, by the topping lift span led to a separate winch, and it can be swung from side to side (slewed) by ‘siean guys’ or either side led to separate winches.
In view of the greater SWL, the topping lift span; the cargo fall and the steam guys are all multiple-fold purchases. Further the cargo purchase and the topping lift purchase are rigged advantage (by use or additional ‘lead’ sheaves).
In view of the heavy loads involved and the size of the rig, great care is required for setting it up (which may take up to 2 - 3 hours).
PATENT DERRICKS
Basic Characteristics
i) The twin topping lift/slewing guy principle is used which gives good control of a single derrick.
ii) The capability of handling heavier loads than the union purchase system.
iii) Combined slewing and topping (luffing) tackles.
iv) Very good spot loading facilities. i.e. the load can be set down in most positions within the hatch area.
v) A high degree of centralized control with the operation being conducted by one man. vi) The derrick is rigged at all times and can quickly be brought into operation.
vii) The use of new technology reduces the stresses encountered with the union purchase system.
There are many patent derrick systems used on board ship but the best known are probably “Hallen” and “Velle” for the handling of general cargoes and “Stuelcken” for heavy lifts.
Hallen Derrick
The Hallen swinging derrick employs the twin topping principle which allows good control of a single derrick. This derrick was originally designed for loads of 5 - 8 tonnes but loads of over 100 tonnes are now unexceptional. The derrick can be mounted on all types of mast or derrick post and can make a traverse from port to starboard of 160 - 180°.
In the original design a fixed frame “outrigger” was fitted to the mast (as in fig. B) which was commonly known as a “D” frame. This had the effect of keeping the topping lifts at a sufficiently wide angle to one another to ensure the derrick remaining steady even
when swung out over the ship’s side to an angle of 80° from the fore and aft line. The D frame also helped to keep the derrick stable in all positions, even when the vessel had a list. However, under some operational conditions there were disadvantages when using the D frame:
1) When the derrick was swung outboard, the sharp angle created by the contact of the topping lift guy pennant with the frame caused excessive strain in the topping lift.
2) There was a tendency fro the single-wire pennant on the topping lift to slip above or below the frame when working at “difficult” angles, once again putting excessive strain on the topping lift.
3) The contact with the frame caused chafing on the pennant. This was reduced by fitting rollers to the frame or by protecting the wire. The D frame has been largely replaced by outrigger rods. (fig. 3) which are pivoted, and are stayed on the outboard side only so that the rod nearest the discharging side can swing towards the ship’s side, thus ensuring a wide separation angle of the topping lifts.
As with other patent derricks, such as Velle and Stuelcken, the V-shape arrangement of the topping lifts gives a broad base which is necessary for lateral holding and guiding of the derrick. In figure 3 the broad base between the topping lifts is provided by a cross-tree at the mast head. It could also be provided by derrick posts, gate masts, or V masts.
In the Hallen system each topping lifts runs to its own winch. Hauling on both winches tops the derrick, and if one winch hauls in while the others pay out, the derrick slews to the side of the ship on which the hauling winch is located. a third winch is used for hoisting and lowering the cargo. The derrick is controlled by two levers. One lever operates the cargo, purchase and the other lever has a multi-position control for the topping and slewing operation.
Velle Derrick
The Velle swinging derrick also uses three winches. The cargo purchase is operated by a standard type winch but the topping lifts are arranged so that one of the other two winches
controls the luffing while the third winch is used solely for slewing. Each of the topping lift winches has a split or divided barrel on to which the ends of falls are secured. On the luffing winch the falls are laid on to the split barrels in the same direction. Thus both falls will hoist or lower the derrick simultaneously. On the slewing winch the falls are laid on to the split barrels in opposite directions. Thus when the barrels rotate, one fall pays out while the other heaves in and the derricks slews to port or starboard. The topping lift luffing and slewing winches are operated by a multi-position control lever which is multi-positioned adjacent to the cargo purchase control lever. The operator stands between the levers and operates the cargo purchase with his left hand and controls the derrick movements with his right hand.
Figure C shows a plan view of an early version of the Velle derrick in which a bridle bar was used to spread the topping lift spans at the derrick head. The bridle bar evolved into the “T”- shaped derrick head shown in Figure 5. Both arrangements make very wide slewing angles possible due to the good lateral stability achieved by the spread of the spans at the derrick head. The derrick can be swung outboard until it is almost perpendicular to the ship’s side, even with an adverse list.
Pendulous swinging of the load has been a major problem with derricks in which the load hangs a “single points”. Good load stabilization is achieved with the T-shaped derrick head as the spread of the cargo runner reduces pendulous swinging and load rotation. The Velle derrick is noted for its comparatively simple design, reliability, and versatility. The standard designs operate up to a capacity of approximately 35 tonnes but heavy-duty designs are capable of lifting approximately 100 tonnes.
Disadvantages of ‘D’ frame
1) When swung outboard, sharp angles created by topping guy with frame cause excess strain in topping guy.
2) At difficult angles single topping pennant to slip above or below “D” frame - excessive strain.
3) Contact with frame cause chafing. Reduce by fitting rollers.
Two Levers
1) One operates the cargo.
2) Other (multi-position) for topping & slewing position.
SHIPS CARGO DECK CRANES
Some modern ships are fitted with cranes instead of derricks. Basically they are provided with individual electrical driven motors to permit lifting of the ‘JIB’, slewing of the jib and the working of the cargo hoist.
The ‘JIB’ is a projecting hinged arm and is usually of the luffing type which allows it to ensures hat the hook carrying the weight remains at the same level.
The lifting wire rope is rigged usually as a single whip. It leads over a sheave at the head of the jib and is called the purchase. Between the purchase and the hook is a weight called the ‘ponder ball’. Its function is to help the purchase to over-haul when there is no load. The crane may be set to move on rails the ship or along the ship or may be fixed centrally with a large reach and angle of slew.
Cranes offer the following advantages:
- greater ‘spotting area’ particularly when
installed on the vessel centre line, providing greater flexibility.
faster loading/discharging rate. less time in preparing for operations.
decks clear of guys, stays and other
standing/running riggings.
self contained and easier to operate.
The main disadvantages of the crane are its higher initial cost and the possible pendulous swinging of the load when slewing is done in a fast manner.
Derrick Testing
Ship’s derricks are initially tested (initial test) with the boom at an angle of not more than 15° to the horizontal or, if this is impracticable, 30°.
During its working life, it is recommended that the derrick be retested after any repair to the derrick or permanent fittings, or after any alteration of the rig is not covered by the ship’s plan.
When carrying out a test, the Decks Regulations, form 99 should be consulted, to ascertain whether the accessory gear complies with the statutory requirements. If all is in order, the test may be carried out; otherwise, all loose gear, blocks, shackles, etc., should be sent to works for the necessary treatment in accordance with the statutory requirements laid down in form 99.
The safe working load of the derrick ‘as rigged’ should be checked by reference to the individual safe working loads of the blocks and shackles in the rig, either by direct calculation, or by the preparation of load diagrams. The strength of the wire ropes in the cargo and span purchases should also the checked for the required factor of safety.
If any items of gear are found to be of insufficient strength, either they should be replaced by gear of the appropriate size and strength, or the safe working load of the derrick reduced.
Tests are generally carried out by the use of loads (known as a ‘dead load test’); or by the use of a dynamometer (test clock). It is preferable that the ‘initial test’ be carried out by ‘dead load’.
If no particular derrick a single whip is normally used but the derrick boom and span gear are capable of supporting a cargo load greater than that which may be lifted by a single whip, a proof load may be applied with the cargo runner double up at the derrick head, provided that the ship’s blocks and shackles are used for the test. Where it is found necessary to use the doubling-up method (i.e. a gun-tackle rig), this should be stated on the certificate of test, also the safe working load that may be lifted on a single whip.
When a derrick is rigged with a cargo purchase, and the hauling part of the purchase
is parallel to the boom, the safe working load marked on the upper block in the purchase should be greater than that marked on the lower block. This takes into account the increased resultant load due to the tension in the hauling part of the purchase.
Before applying a proof load to the derrick, all permanent attachments on the mast and derrick should be carefully examined. It is also good practice to rig an adequate preventer span wire rope as a precautionary measure against any part of the span gear ‘carrying away’. This additional span wire rope should not take the mass of the mass of the derrick during test.
When proceeding with the test, the proof load should be applied steadily, and all fittings should be carefully watched for any indication of failure. Apart from watching, it is also desirable to ‘listen’ for any signs of failure. When testing heavy-lift derricks, care should be taken to ensure that the anchorage for the test clock is of adequate strength, avoiding any risk of structural damage to the ship. For derricks of 30 t safe working load and over, it is advisable to lift moving loads or use a specially designed anchorage on the vessel, and to ensure that there is sufficient stability to avoid excessive list under test. It is also important that shrouds and preventers are properly set up to give adequate support to the mast. Furthermore, slewing guys should be so placed that the angle they make with the derrick boom is not unduly narrow, so that when the vessel heels over under load, they will control the derrick without developing excessive tension.
On completion of the test, a final visual examination of all parts of the derrick rig, and of all permanent attachments on the mast and derrick, should be made before issuing the certificate of test and examination.
In all cases the winches should be carefully examined to ensure that they are in good working order, and that the controls act effectively. Information to this effect should be noted on the certificate of test and examination.
