Wednesday, December 15, 2010



Read this PRACTICAL points carefully, so that you may save your company from financial claims and embarassment.

Encourage every crew member to talk about their mistakes, so all can learn from them. This is the way to build a winning team. Cargo work involves team work dynamics and is not a one man show.

Shipboard losses can be from--
Evaporation via PV vents.
Deliberate retention for ulterior motives.
Excessive ROB due to high pour-point of cargo or pumping problems.

‘On Paper Only ’ virtual losses : –
In many shortage claims no actual loss has taken place but the amount of cargo has been overstated when loading and/or
understated when discharging.
To avoid large vapour losses, is the Reid vapour pressure (RVP) of the cargo within the ship’s PV capacity?

Company policy often dictates the filling limit. 98% of a tank’s capacity generally allows for cargo temperature to increase by 20°C - but the difference in temperature between northern Europe and the tropics often exceeds this figure. Imagine a cargo  of Pentane loaded from LeHavre to US gulf.

Ullages exceeding limits set out in the ship’s stability book can lead to excessive free surface. This can cause sloshing, making pressure/vacuum valves ‘breathe’ and resulting in vapour losses or ‘boil off’ of the lighter fractions of the cargo. This dynamic sloshing stress can cause structural failure and endanger the crew/ ship.

Stowing volatile cargo next to heated cargo causes evaporation losses. Charterers should specify maximum adjacent temperatures.  AH  is an important spec on chemical tankers.

Chief officer must find out:--
Number of shore tanks to be loaded from,  the quantity, temperature and SG of cargo in each.
Whether there are any planned loading stops for shore tank changes.
Whether density is being expressed ‘in air’ or ‘in vacuum’
Whether shore pipelines are full or empty, and details of any pipeline displacements planned.
Whether loading by gravity or shore pumps.
Whether pumps are displacement ( screw ) or non- displacement ( centrifugal ) . Topping up is easy with gravity loading and centrifugal pump loading as valves can be throttled. Only a non-displacement pump can tolerate the ship shutting valves while it is pumping.

While in some trades the discharge port’s out turn figures alone determine the amount of cargo delivered, in others they are still compared to the bill of lading figures provided by the loadport.

Even if both terminals carry out their measurements diligently, each will (quite legally) round off temperature and ullage readings in its favour, so differences are only to be expected. In the absence of a like-for-like comparison, the ship is the only common factor - and therefore the measurements taken on board are critical. The inspector must be accompanied at all times and his ullage measurements actively verified.

Measurement errors often result from commercial pressures. Remembering that, long after the immediate pressure has been forgotten, the ship will remain responsible for having ensured that the measurements were carried out correctly. Some owners employ cargo superintendents ( supercargo ) to relieve the pressure. If, in spite of all measures taken, an early departure procedure, for example, exposes the ship to any unwarranted liability, she must protest.

Use of defective equipment-- frequently maintaining and checking ship’s equipment - and arranging for regular calibration of electronic measuring devices by an agent approved by the manufacturer improper measurement technique--- doing homework, sharing experience around and encouraging everyone to talk about their mistakes, so all can learn from them.

Never permit the use of the terminal’s measuring equipment on board. If measurements taken with the inspector’s equipment differ from those taken with the ship’s, propose that all measurements be taken with each, and both be sent for verification ashore afterwards.

If the retro-fitted vapour lock valves required by electronic gauging equipment have changed the height and/or position of the ullage point, measurements taken through such valves must be corrected before use. This Vapor lock reference measurement ( can be found in P@A manual ) should be posted in CCR bulkhead prominently.

If the ship is pitching or rolling, five measurements should be taken, withdrawing the tape as soon as it penetrates the surface of the cargo. The highest and lowest should be ignored and the middle three averaged. Weather and sea conditions should be logged.

In the same conditions on inerted ships, or where electronic, closed gauging equipment is used, the probe should be withdrawn and lowered until three readings differ by no more than 5mm.

Taking cargo temperature: The temperature of every cargo tank should be recorded separately.

Cargo temperature may vary by 5 °C at different levels in the tank, so must be averaged from at least three readings -
top, middle and bottom. Some digital probes can measure at more frequent intervals A measurement error of 1°C can distort the volume calculation by +/-0.1%, depending on cargo density.
Checking cargo density
Checking cargo density. Despite practical difficulties, it is best practice to make sure the density of the cargo is measured and compared with the figures supplied by the terminal. If the loading terminal measures densities in vacuum and the discharge port in air, the figures must be corrected to avoid an apparent loss . A difference of 0.0100 Kg/litre in cargo density can alter a VLCC’s tonnage calculation by some 3,000 metric tonnes

Allowing for trim/ list:  Many loadport cargo measurement errors are caused by failing to make due allowance for trim and list. These should be based on draft readings whenever possible.

Free water:  The quantity of any free water detected must also be corrected for trim and list. Protest even small amounts, as there is likely to be more in suspension.

Cargo calculations: Make sure all parties are using the same edition of the ASTM Petroleum Measurement tables for mineral cargoes. Make sure ASTM tables are NOT used for organic chemicals. If the surveyor insists , then make a remark . Ensure disport also uses the same tables.

Make sure the contents of the ship’s pipelines are included in the calculations.

Sign the inspector’s quantity report ‘for ullages and temperatures only’.

Apply the vessel experience factor (VEF).

If the ship’s figures differ from the shore’s, review the calculations.  If the difference is confirmed, initiate the owner’s standard procedure.

Cargo surveyor:  Accompany the inspector at all times, ensuring that he measures temperatures, ullages, densities, list and trim

Ullaging active tanks regularly and comparing results with hourly shore discharge rates helps ensure that cargo is not being misdirected / diverted in the receiving terminal.

Monitoring air and sea temperature and sea state can provide valuable evidence in case of a subsequent dispute about the pumpability of the cargo. Most shore pipelines are not heated or lagged.

Stripping  The best way to avoid losses resulting from charter party freight retention clauses is to make sure the ship can demonstrate it did everything possible to discharge all the cargo. Provided it is within the ship’s stress limits, the greater the trim aft, the better the drainage, especially with high MP and viscous cargoes.

When stripping high pour-point cargo: Maintain cargo at the recommended discharge temperature until the heating coils are about to be exposed start stripping as soon as cargo pumping stops. Protest any request from the shore to stop. If the stop is essential, continue stripping to an accumulation tank and resume cargo heating as soon as possible.

When stripping high vapour pressure cargoes: Avoid operating pumps at excessive speed which increases vaporisation, causes cavitation and reduces suction. Increasing the pressure of inert gas in the cargo tank or increasing the back pressure on the pump can improve pumping performance.

Re-inspect ‘empty’ tanks before declaring a grade finished.

ROB determination:
Additional cargo may have accumulated due to:
Changes in list and trim
Bulkhead, pipeline or valve leaks difficulty of calibrating bottom levels of tanks
Blocked limber holes, on inner frame tanks
Unmeasurable tank side clingage
Uncertainty about the liquidity of bottom residues

It is always important to observe and log precisely how the inspector measures ROB. Ensure he surveys all the cargo tanks.   Make sure he takes great care reading sounding rods or bobs, to avoid the common mistake of overstating the liquid element of bottom residues because it has run down over the sediment as the rod is raised.
Ask him to take samples of the bottom residue, from more than one point in each tank if possible.

If you suspect that the samples may be unrepresentative because of the tendency of less viscous material to flow more easily into the sampling device, ask the inspector to sample the more viscous material found in the pump mud box or the manifold when it is disconnected.

Urge that the wedge formula be applied only to the liquid element of the ROB, since it can be argued that there must be as much sediment under the liquid as there is in the dry parts of the tank.

Ensure that the tank dry certificate states that  All pipelines are stripped dry. Do not allow the shore hoses to be disconnected until the inspector has signed a dry tank certificate, or a statement of ROB, that you agree with. If you dispute the inspector’s figures, initiate company standard procedure.

Calculate the ROB independently, compare results with the inspector’s and log any differences.


In the contest against claims, as in today’s competitive market place, only the best informed will win.

Approximately 45% of alleged shipboard contamination problems are, on investigation, found to be shore related.

Residues of previous contents of storage tanks, lines and hoses.
Tank and line cleaning media, including water.
Other products, because of valve leakage or mis-operation or poor in-line blending.
Fresh water or impurities carried over from the manufacturing process.
Fresh water from leaking heating coils or tank roofs.
Salt water from leaking sub-sea pipelines.

Residues of previous contents of ship’s tanks, lines, pumps and hoses.
Dirty sounding and ullaging equipment.
Tank coating deficiencies.
Tank and line cleaning media, including water.
Other part cargoes, because of valve leakage, valve mis-operation or tank structural deficiency (e.g. bulkhead cracks).
Other part cargoes’ vapour via common inert gas systems.
Salt water from leaking tank hatch domes, butterworth ports , sounding pipes and vents.
Fresh water from leaking heating coils.
Copper leaching from alloys used to manufacture heating coils on CPP ships (e.g. alloy brass contamination of jet fuel).

Is the tank coating suitable for the cargo? For example white wine needs stainless steel; epoxy is preferred for vegetable oils.

Some cargoes can permanently damage certain coatings, others make coatings soft for a while, during which time the range of cargoes they can tolerate is restricted. Refer to the coating manufacturer’s resistance lists.

For multi-grade loadings, plan the use of pumps and pipelines to avoid or minimise commingling or downgrading. Ensure line displacements are calculated such as to avoid cross-contamination.

If ullages are insufficient, cargo from one tank can slosh through a common vent line to contaminate non-compatible cargo in an adjacent tank, if the ship rolls or pounds.

The vapours of one grade can put another grade out of specification, e.g. gasoline and kerosene or diesel, if the VRS spools are not disconnected.

Heat reduces the effectiveness of inhibitors, so avoid stowing inhibited cargoes adjacent to heated tanks.

The Chief Officer must ascertain the following from the terminal representatives- 
whether the shore pipeline is dedicated--details of any shore pipeline displacements planned number of shore tanks to be loaded from,   and the quantity, temperature and density of cargo in each.  Whether any loading stops are planned for shore tank changes,   whether ship or shore is responsible - and how to stop in an emergency.

If changes are to take place without stops, that the ship receive notification of every change for sampling purposes.

Whether the ship will be receiving two sets of samples from the shore tanks: one for the receiver, one for the shipowner
(if not, log that the request was made and refused)

Cargo surveyor:--
Remember, an ‘independent inspector’ is independent in name only - expect him to give the ship’s interests low priority, and make sure he is accompanied by an officer at all times.

An experienced officer may well be more expert than the inspector, who is usually a non-marine person or even a ex-junior officer.

Tanks cannot be entered where local regulations insist on constant operation of the inert gas system but, whenever possible, make sure that the inspector checks every tank thoroughly.

If the ship’s pipelines have been drained, demonstrate this to him and ensure it appears on the inspection certificate.

Outside the chemical trade, tank inspections are often subjective so, if you do not agree with the inspector, try to reach a commercial solution – always faster and cheaper than a legal one.

As soon as it becomes apparent that you cannot agree, protest.

Sampling: Adopt a sampling procedure that satisfies the relevant authorities.

Make sure the ship has the right equipment, including clean bottles, seals and labels.

Label samples with the following information:
Ship’s name, date and time
Location, cargo name
Operational status (e.g. ‘after loading’)
Sample source (e.g. ‘tank number...’)
Sample type (e.g. ‘top’; ‘composite’)
Identity of sampler
Seal number

Make sure each sample is signed and sealed, preferably by the independent inspector. Note the particulars of every sample taken for the ship’s purposes in a sampling log. Present the inspector with a list of samples drawn and retained by the ship for acknowledgement and signature. Require any party to whom a sample is handed over to sign a receipt for it.

Store samples in a secure space which is cool, well ventilated and not exposed to light.

Since the Hague Rules allow claims to be presented up to a year after the event, samples should not be disposed of until that period of time has elapsed.

Samples showing that the condition of the cargo did not change between loading and discharge provide the best defence against unfounded contamination claims.

If the lab report is to be right, the sample must be right too - an inspector is as prone to error as the next man.

The inspector must be accompanied at all times, to ensure that the sampling procedure satisfies the relevant authorities.

If the inspector fails to do something he should, or does it wrong, point it out to him, and log anything he does not put right.
Log any faults with his equipment and any occasions when he borrows the ship’s.

As well as any samples he takes for the consignee, the receiver and his own firm, ask the inspector to take another set for the ship. If he refuses, note it in the log - and take your own.

Chief Officers should ensure they receive two sets of shore tank samples for each grade: one set for delivery to the receiver’s agent; the other to be retained by the ship.

Asking the inspector to take starting samples at the manifold is the best way to detect contamination or commingling in shore lines.

Make sure first foot samples are taken to verify that the ship’s lines are clean.

Discourage the inspector from subjecting them to visual analysis only, while loading continues.

Loading should be stopped while proper tests are carried out, particularly when the specification is critical.

If the samples are off-test, advise the charterer without delay.

Even if tests reveal no problems, the ship must retain its duplicate samples in case of any later dispute.

Carry out spot checks at the manifold whenever practicable during loading, particularly after any shore stops and
preferably accompanied by the inspector or a representative of the terminal.

Accompany the inspector when he opens the sealed unit of any composite sampler.

After-loading samples should be taken from top, middle and bottom of each cargo tank.

If the cargo is to be treated with an additive, the fact should be recorded on the bill of lading. Unless you are certain that the shipper and receiver have agreed to this taking place after loading, require any party proposing to do this to sign for receipt of a letter protesting the procedure - before he carries it out.

Make sure you receive a certificate in respect of cargoes that are inhibited.

At the discharge port, in-line samples of each grade of cargo should be taken at the manifold:
- at the start of discharging
- once during every watch that the grade is being discharged
- during stripping
- If the inspector fails to take any of these samples, the ship should take its own.
- Make sure the inspector samples any free water found, so that its source can be established.
- Sampling gas oil bunker tanks after loading and before discharging helps defend against claims that cargo has been used as

Maintain a minimum of two-valve separation throughout the discharge of multiple grade cargoes. On chemical tankers, unnecessary spols are removed and blanked.

Valves should be sealed (if they were not sealed in the loadport) and the seals pointed out to the inspector and logged.
If possible, leave seals in place until discharge is completed and ask the inspector to note the fact.

The most easily contaminated grades should be discharged first, if possible. If any grade cannot tolerate contact with residues of the grade before, strip the cargo line. If necessary, flush the line with the second grade and re-strip - it is better to lose part of the cargo through downgrading than to contaminate all of it and the shore tank besides.

A watch officer discovering contamination should:
- stop discharging the relevant cargo
- close that system’s valves
- advise the Chief Officer, who advises the Master, who contacts the owner and his local P&I correspondent.

The Master should:
- sample the remaining cargo and request testing
- await instructions from the owner

Crew must never try to conceal a operational error which may result in contamination. The sooner problems are identified, the less the owner’s potential exposure.

Remember--  on chemical tankers ( unlike oil tankers ) we take manifold sample --WITHOUT opening the manifold valve--for obvious reasons..  

CAPT AJIT VADAKAYIL ( 28 years in command )


  1. Indebted sir. I wish you were on the Facebook, there are so many of us, who would wish to be enriched by your knowledge, on / off the marine industry and/or chemical tankers.


  2. Dear Capt. Ajit, Quite an informative blog. As stated in your blog, I am a non-marine Cargo Inspector having almost 35 years of experience in Marine Cargo Surveying.Please get in touch with me at : Regards T S Shrinivaasan