THE VADAKAYIL LOADING CURRY - PARCEL CHEMICAL TANKER STOWAGE PLANNING - CAPT AJIT VADAKAYIL
( This post is on special request from one of my readers Haris from Pakistan.)
THUMB RULE: A Master must never get rushed by his IGNORANT commercial operator, into giving a fast stow by telephone .
Some of the charterers are stupid and they can see only from their point of view, and they have NO dang idea what goes on in a Captain's mind.
If a Captain gets arm twisted by such a stupid guy , he is shortchanging himself, his ship , his owners, his technical managers, his Chief Officer and his crew..
He is bound to create a lot of heart ache for himself. And his crew is gonna work their butts of for no reason. Worse you can fail the Wall wash test or the first foot sample.
A good stow is like a work of art. Everything is considered-- as you can see that I have put 65 items here for consideration.
A good stow is like making a good Sambhar curry - which I call the VADAKAYIL LOADING CURRY.
Lot of vegetables got to go in -- not at the same time-- but at different times or they get over cooked or under cooked.
The real "Vadakayil loading curry" has 130 items-- double .
This post has just 65, and this is good enough-.
No chemical planners brains on this planet earth will go beyond 50-- and let me leave something aside, only for my chelas..
When working out a stow for parcel chemical cargoes , the checks to be carried out, include—
1. Check the ship’s Certificate of Fitness if the cargo can be carried. If the cargo is not in the list , inform the Chemical operator who will take remedial action. Permission can be obtained from the flag administration for the new chemical based on a tripartite agreement between shipping country , receiving country and flag state of the carrier, and attached to the COF as an addendum. Since new chemicals are being invented and re-evaluated for carriage almost every day it is possible that many cargoes may not be in the COF.
2.Even if the cargo can be carried as per the COF, the tank lining resistance tables must still be consulted, or the cargo cannot be carried. The notes about the previous cargo carried in the tanks, forms part of this important check.
3.Check the Compatibility Chart A . It is a must to check the exceptions.
4.If the cargo is edible, check the FOSFA lists. Both banned and acceptable lists must be checked. It is not enough to check just one of them. But if the terms of cargo carriage require consultation of NIOP or EU lists , instead of FOSFA, do so. It goes without mentioning that the Master must aim that ships tanks are always FOSFA ready for better future employment prospects.
5.Check the load density of the tanks. It is possible for heavy cargoes like sulphuric acid, the load density may not permit a full load of 98%.
6.Toxic cargoes must never be loaded next to edible cargoes.
7.Water reactive chemical cargoes like Sulphuric acid must not be loaded next to SBT ballast tanks which require ballast for trim or list correction for proper execution of voyage at sea and at berth.
8.Do not heat one tank of chemical to within 10 degrees of the BP on the chemical in the other adjacent tank. Set the tank high temperature alarm in CCR accordingly.
9.Check the P&A manual for sloshing considerations. Loading say between 20% to 80% may be banned depending on the length of the cargo tank or its length with respect to the LOA of ship.
10.Check the intact stability, trim and list-- the amount of SBT ballast required, without cooling heated cargo tanks .
11.To prevent tanks from getting cubed out, it is important to know the SG at load temperature. Many chemicals are loaded in a hot condition.
12.As certain Category Y chemicals may have to be prewashed if there is excess of clingage on tank bulkheads after completion of discharge, it is important to plan ballasting which may introduce a cold interface. Check if your loadicator has Harbour condition for SF/ BM.
13.Certain cargoes have to be recirculated at sea for successful discharge . It may not be a requirement of the shippers or charterers. A cemented deepwell pump impeller can cause delays in start of discharge or severe pump damage. Ensure that such cargoes are loaded in tanks whose drops can be fitted with diffuser nozzles. Certain cargoes like molasses can have excessive debris , in which case there must be a prefilter before the ships manifold.
14.Know the Deepwell pumps whose cofferdam leaks. Purging records must be consulted to check if it exceeds permissible limits. Do not stow polymerising cargoes in such tanks. Sufficient cargo seals must be held on board. Chief engineer must be absolutely familiar in replacing leaky seals and with tool kits used .
15.When high MP cargoes are loaded in winter, ensure that the cargo does not get frozen in pipelines. The pipeline line configuration must be considered for instant draining by gravity or steam/ air/ nitrogen blow. Personal attention must be paid to this scenario by both master and chief officer. Frozen pipeline and cargo delays mean that the ship’s management has not studied the pipeline 3D configuration and planned in advance.
16.To avoid prewash of Cat Y cargoes the AH, VH and DH values must be monitored. Sometimes shippers put a limit on VH and DH purely due to quality concerns in which case it may not be possible to heat more that 10 degrees of BP during dischg.
17.If tanks without steam inlet pipe thermal lagging on deck have to be heated excessively in winter seas with continuous cold spray from forecastle, it makes energy conservation sense to ensure that only short lengths of aft tanks are involved.
18.Tanks with deepwell pump suctions protruding into ballast tank at the bottom can have a frozen pump impeller. Such a cold frozen pocket can remain so even if the entire cargo tank of high MP cargo is well heated . The level of cold ballast underneath such a pocket must be monitored by chief officer.
19.Cargo stow history of last 3 cargoes must also include the ullage levels, especially if the cargoes have been non-water soluble , high BP, high MP , strong odour insensitive ones. Cancelling out effects of a subsequent cargo depends on ullages.
20.Avoid loading sensitive wallwash cargoes in non-water soluble , high BP previous cargo tanks.
21.Very high viscous cargoes like high brix molasses or clay slurries must be loaded in tanks with big pumps and big dia dischg risers. It is immaterial if the discharge port claims to have a booster pump on quay to assist discharge. This is more important if ship does not have her own screw booster pump at the manifold.
22.There are certain cargoes like MEG FG where the preload inspection by surveyor does not allow water condensation on bulkheads. If the adjacent tank contains a cold interface cargo like Styrene Monomer, it becomes a impossible task. Avoid such a scenario by giving an alternate stow. Warm moist air will always condense on a cold surface , as a thumb rule.
23.Avoid loading odour sensitive cargoes ( edibles, glycerines, spirit, MEG FG after strong odour cargoes ( MTBE, Phenol, Acrylate, Fish oil, Molasses ).
24.Heat expansion due to AH or ambient voyage temperatures.
25.High VP cargo PV vents must never get rimed. Riming due to cold sea spray from forecastle is usual in Bering sea.
26.Bad steam coils can cause water contamination or worse boiler explosion.
27.Toxic heated tanks like Phenol must be sufficiently away from the accommodation.
28.If ballast pumps derive the power from the Main Framo Power pack, this means all ballasting, deballasting operations for trimming/ listing at berth will affect the cargo discharge rate. Plan cargo in such a way that dischg time is not lost at berth.
29.Cargoes like Sulphuric acid ( exothermic reaction while tankcleaning with water which damages tank lining ) and Annex 1 lubes ( expensive oil in slop quantity ) must be properly superstripped at completion of discharge. Check superstripping hardware facilities before you plan the stow. Some ships have aft tank delivery decklines with a natural tilt towards the manifold, to avoid smaller superstrip lines .
30.Use minimum number of tanks which have to be squeegeed, recirculated or flushing framo pump cofferdams while running .
31.Where Nitrogen has to be padded at sea ( especially from Nitrogen bottle bank , when ship does not have a fixed plant ) , keep the cargo tanks full , to reduce the effort and money.
32.For drying and Semi-drying veg oils ensure there is no AH. This will reduce the tankcleaning time and consumption of tankcleaning chemicals.
33.Allow for tank lining recovery time. For example , stainless steel after carriage of Wet or Green Fertiliser grade Phosphoric acid. Epoxy tank after carriage of Benzene.
34.In case of WWT , a spare set of tanks must be ready. In case of WWT failure, certain ports like Jubail or Terminals like DOW do not permit extra cleaning at berth , and ship has to cast off and anchor in designated area.
35.When certain cargoes like Sulphuric acid has to be surrounded by empty tanks , keep such tanks of low volume to avoid losing cargo space.
36.When you get long ocean crossings with partly empty ship, allow for a chance to do passivation and epoxy lining touch with sufficient curing time up by shipstaff.
37.After one aggressive cargo like Caustic Soda, do not plan another aggressive cargo like Wet Phosphoric acid before the SS tanklining can recover.
38.To desorb a solvent cargo like Benzene from swollen epoxy lining, it may be necessary to apply adjacent heat to speed up evaporation. Absorbed chemical in epoxy can cause huge contamination claims and failure of coating while impinging with watercleaning jets.
39.Offset bad effects of previous cargo with new cargo. Keep tanks always FOSFA ready and WWT ready. Example –loading gasoline or Phosphoric acid after Palm oil fatty acids. Tankcleaning time and tankcleaning chemicals can be saved.
40.If you are using same manifold flexible hose for discharging many grades , gives the best grades first.
41.With drying veg oils or polymerising cargoes in tank , it may not be possible to use steam for cleaning or reducing chlorides in the adjacent tanks. Polymerisation can take place even at cruciform weld corners.
42.Have a record of shipboard PV valve pressure / vacuum tests, done with on board test kits. Use the best PV valves for high VP volatile cargoes.
43.While discharging Annex 1 CPP at submarine terminals, it must be noted that no airblow will be allowed as per terminal rules to prevent damage to submerged hose. Ensure that internal stripping can be carried out with proper line configuration.
44.Know your tankcleaning chemical ROB and the possibility of replenishment.
45.Avoid methanol manual spray to get a tank ready for WWT cargo. Check out the last 3 cargoes well and plan.
46.If ship has loaded colour dyed cargoes in zinc tanks, avoid using the same tanks for WWT cargoes.
47.Chloride sensitive cargoes like MEG FG keep away from sea waves. A check can be made on routing charts for wind direction . Low freeboard chemical tankers must be aware that a butter worth port seal is effective only if there are 2 packing ring seals ( inner teflon/ outer viton) , with check nuts. SS nuts and bolts do not have friction coefficient and can slip when buffeted by waves or with normal vibration. Greasing SS threads and lowering the friction further can cause horrendous cargo claims. With exhothermic/ sputtering cargoes like sulphuric acid, the whole adventure might come under imminent peril.
48.When dischg high MP cargoes in winter, it should be possible to transfer the contents of a tank ( with frozen pipelines ) to another nearby tank having same cargo with portable framo pump.
49.Cargoes which require oxygen dependent additives , load in large tanks >3000 cum.
50.Edible high spec cargo for Coke like White Phosphoric acid has to be recirculated in empty tanks as a flush and then this flushed quantity is down graded to fertiliser grade and stowed in another tank. Ensure there is sufficient trim / list to do this effectively and fast , as in winter this flushed quantity of high MP will freeze.
51.Avoid loading phenol in tanks which carried acid as previous cargo, unless the tank is washed well and pH value is reduced in tank and appendages to minimum 6/7.
52.For special cargoes like HMD or chlorinated solvents check the list of acceptable previous cargoes.
53.If FFA and moisture content is unknown for hydrolysable cargoes avoid giving a epoxy tank stow. SS tank is best.
54.Cleaning temperature or DH must not exceed the max allowed for the tank lining .
55.In ships with centre tanks load high MP water insoluble cargoes in centre tanks to avoid shifting SBT around to prevent cold interface.
56.In case you are loading / dischg high MP cargoes in winter from barges , with frequent stoppages it is of great advantage to have a natural slope of pipeline from manifold to ships tank, assisting airblow flow by gravity, to prevent cargo freezing inside pipelines and causing delay. Phenol can kill the crew who may be trying to clear a frozen pipeline in a unplanned hurry.
57.When squeegeing high MP cargoes in winter, it is better to have a gravity slope from tank to manifold, to prevent cargo freezing in pipelines in about 20 minutes of manual squeegeing time.
58.Tanks whose deepwell pump seals require change must be planned to the emptied out first in a series of dischg ports.
59.Ship can fail NVM test of WWT, if the tank has contained high BP previous cargo or if the SS tank is unpassivated with poor chromic oxide layer.
60.Tanks which have to be recirculated at sea must have a delivery check valve which will prevent the tank cargo from travelling to manifold .
61.Make sure charterers agree with your stow. While you are keeping 60 points in mind, which can benefit your ship and crew, the charterers or shippers will have only their own narrow interests in focus, where they make more money from the voyage.
61.It must be remembered that common CRUCIFORM welds is NOT permitted between Bunker tanks and toxic chemical tank—but it IS allowed between water reactive chemical tank and Ballast tanks. For HEAT segregation to prevent polymerization/ decomposition/ evolution of dangerous gas—cruciform weld touching is NOT allowed. Touching CRUCIFORM welds NOT involving heat segregation between incompatible chemicals are allowed.
62. The stowage must be in consonance with the Damage stability requirements ( breach of empty and full compartments creating list ) --more so when all tanks are cubically full with high density cargo, and loading to tropical loadlines.
63. Do NOT allow condensation due to a cold interface bulkhead to fail the tank inspection--- and when cargo is NOT ready , the shippers get very squeamish about some water condensation on the bulkhead , even if the chemical is NOT water sensitive.
64. In case of multiple ports with load/ discharge , be aware that a cold bulkhead due to cargo interface cannot be HOT cleaned properly or even steamed properly.
65.Make sure charterers agree with your stow. While you are keeping 65 points in mind, which can benefit your ship and crew, the charterers or shippers will have only their own narrow interests in focus, where they make more money from the voyage.
You fail the Wall wash test or the first foot --and your baby is burnt..
CARGO PLANNING
The vessel shall be loaded/discharged in accordance with the conditions provided in the approved Stability and Trim Manual & P&A manual with respect to load line, trim and, intact stability and strength.
The loading computer shall be calibrated against the test condition (class approved, where applicable) before each cargo planning operation and at least quarterly in order to verify the reliability of the information.
Records of such calibration shall be maintained by the Chief Officer. If the vessel is not provided with a loading computer, checks shall be undertaken to verify actual draft conditions against conditions provided in the vessel’s trim and stability booklet & P&A manual (loading manual).
Prior to arrival loading/discharging port, the Chief Officer shall pre-calculate the cargo and prepare a Cargo plan. The Cargo Plan shall comply with ISGOTT and ICS Tanker Safety Guide – Chemical.
It shall include details of cargo loading/discharging operations and rates, and ballasting, taking into consideration the maximum allowed free surface moment, possible draft and air draft limitations, trim and stress, ullages/soundings, cargo stowage, and management of tank atmosphere.
The Cargo Plan shall be available at the ship-shore interface meeting.
CAPT AJIT VADAKAYIL
30 YEARS IN COMMAND
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