What are Tanker Ships?

Tankers have been one of the oldest types of merchant ships; the need for these vessels arising due to heterogeneous distribution of natural oil reserves and liquid chemicals around the globe.The most common types of tankers operating at sea are oil tankers. While it may seem that oil tankers generally carry oil, the fact has quite more to it, if understood in detail. Which brings us to the need to understand that since there are different grades of oil (depending on the levels of purification), oil tankers have been designed separately and specifically to carry different oil types.It is important to have a brief look into the history of oil tankers, especially to understand the dynamics of the oil market and relate its influence on the sizes of oil tankers used in different eras.The size of oil tankers had seen a rapid increase in the mid-seventies due to abundance in oil trade, and as a result, for the first time, tankers of deadweight in the ranges of 100000-200000 lakh metric tonnes were constructed in Japan to be able to carry more quantity of oil in a single voyage, and hence reduce the freight costs for more profits.

But in the late nineties, due to the skyrocketing of oil prices, the quantity of oil being traded by sea had considerably reduced, hence almost putting an end to building of ULCC (Ultra Large Crude Carrier) and VLCC (Very Large Crude Carrier).

Based on size, oil tankers have been categorised into the following types:

Small Range (Product) Tanker: 10,000 to 60,000 tons DWT.
Panamax Tanker: 60,000 to 78,000 tons DWT.
Aframax (Average Freight Rate Assessment) Tanker: 80,000 to 1,20,000 tons DWT.
Suezmax Tanker: 1,20,000 to 2,00,000 tons DWT.
VLCC (Very Large Crude Carrier): 2,00,000 to 3,20,000 DWT.
ULCC (Ultra Large Crude Carrier): 3,20,000 to 5,50,000 DWT.

The classification of oil tankers based on type of cargo is not a clear and fixed classification, because these are terms used by different nations and organizations based on their ease of nomenclature.

Some of the most commonly used types of tankers are listed below. We will also understand, how different types of tankers are designed to carry a specific type of cargo

Product Tankers:

These tankers are designed to carry hydrocarbon products like kerosene, gasoline, paraffin, etc., chemical products like ammonia, monomers, etc., wines, molasses, etc. Though, now, chemical tankers, LPG and LNG carriers are classified differently due to significant uniqueness in their designs as compared to petroleum product tankers. Product tankers are usually short range coastal tankers, hence are smaller in capacity. They carry products from processing plants to distribution units.

Crude Oil Carriers:

Crude oil carriers are designed to transport crude oil from rigs to processing units (refineries). Since the amount of crude oil extracted from offshore drilling platforms is considerably larger than the amount of products extracted from it, crude oil tankers are required to be of sizes larger than product tankers. Sizes like that of VLCCs and ULCCs are only used for crude oil tankers, and these are usually ships that ply on long range voyages.

Chemical Tankers:

Chemical products like ammonia, palm oil, vegetable oils, monomers, caustic soda, methanol, etc. These ships have considerable uniqueness in their design, owing to the special requirements depending on the type of cargo. We will discuss these aspects in a later part of this article when we discuss design of different tankers. Chemical tankers are usually categorised into three types:

Type 1: These tankers are designed to carry products that are associated with severe environmental and safety related hazards. Such products require maximum prevention of spill.

Type 2: They are also designed for hazardous products, but the extent of severity for these products is lesser as compared to Type 1.

Type 3: These are designed to carry chemical cargo that requires moderate standards of containment and pose moderate environmental and safety hazards.

LNG and LPG Carriers:

These ships actually fall under the category of liquefied gas carriers, and a large number of them are in service to carry liquefied gases in bulk. The number of ships that carry Liquefied Petroleum Gas (LPG) is however, much more than the number of ships carrying Liquefied Natural Gas (LNG). We shall look into some of their design aspects in another article to understand what makes them very unique from other types of tankers.

With an overview of the different types of tankers and each of their functionality, we will now look into the important design aspects of each of them. It is important for you to keep in mind from now, to observe how every design decision that is made, is directly or indirectly related to a functional aspect of the ship. We will relate every design aspect with the inter-related functional or market-based reason that governs it

Very Large Crude Carrier and Ultra Large Crude Carrier

A Very large crude carrier and an ultra large crude carrier are two examples of the different types of oil tankers. These oil tankers are extremely important in the shipping industry for they help to transport huge quantities of crude oil across the oceans and seas.

Dead Weight Tonnage (DWT) is the measure of weight when it comes to tankers. In terms of oil tankers like a very large crude carrier or an ultra large crude carrier, the DWT represent the maximum quantity of DWT that can be carried. The terms ‘very large’ and ‘ultra large’ are in fact categorisations of the oil tankers which are included in the category of being ‘large.’

It has to be noted that tankers are basically divided into two types: the product tanker and the crude tanker. The product tanker is designed to ferry cargo like petroleum and other refined products that are produced from crude oil, from the industrial plants to the final markets for selling.

This being the case, product tankers are generally smaller and compact as compared to the crude tankers which are bulkier and huger. The bulk and the hugeness of a crude tanker help to carry more containers and barrels of crude oil. However it has to be noted that there are six main classifications of crude tankers:

Tankers that are classified as being under General Range
Tankers that are classified as being under Medium Range
Tankers that are classified as being under Large Range 1
Large Range 2 Tankers
Very Large Crude Carrier
Ultra Large Crude Carrier

A very large crude carrier (VLCC) has a dead weight tonnage or cargo carrying capacity ranking up to 2,50,000 tons. On the other hand, an ultra large crude carrier (ULCC) has a DWT of anything between 2, 50,000 to 5, 00,000 tons. In simple terms, it can be said that these two types of oil tankers ferry about two billion oil containers and barrels.

Carrying such a heavy weight would not only ensure that many oil containers are being transported, but it would also ensure that limited number of trips are taken to ferry a specified number of containers. A very large crude carrier and an ultra large crude carrier are also known as ‘supertankers’ because of their mammoth weight carrying capacity.

The Shell Oil Company first designed the weighing system that brought into use the terminology of ‘very large crude carrier’ and ‘ultra large crude carrier.’ As per the Average Freight Rate Assessment system, the denominations of oil tankers were based on the concept of DWT and the above listed oil tankers classification was introduced. The method adopted was very successful as tankers could be specified more easily on the basis of their cargo-carrying capacity and thereby reduce accidents that could be caused due to excessive cargo.

Tankers and more specifically oil tankers are built for a very important purpose. With the help of oil tankers like a very large crude carrier or an ultra large crude carrier, the role and scope of oil tankers becomes far more feasible. Development is a major factor in today’s times. In order to facilitate better development of the human civilization, it is relevant that very large crude carriers and ultra large crude carriers are used appropriately and successfully.

15 Important Points To Consider For Efficient Tanker Ship Operations

Though tanker practice is a very specialised subject, whose training is disseminated through Basic and Advanced training modules supported with intensive onboard training, it has been observed that even after adequate experience negligence occurs at various levels, leading to challenges in ports for loading or discharging.

It is not only the duty of the Chief Officer or Master to look after various deck operations on board, but very tanker man including, the cadet, must be aware of some basic practices at different stages and support the senior management by bringing any non-conformity to their notice. To do this they must be aware of best practices performed on board.

We have enumerated a few things here which have come to the notice by during the career of a deck officer at sea. This by no means an exhaustive list, but surprisingly very commonsensical.

1. Take Charge Immediately: Even if it is your first day on a tanker, or the company or even the first day in rank; the ship will not give you any discount on that account. The problems will emerge almost immediately when you are least suspecting them. In fact, this may happen even if the ship is straight out of the shipyard. So just behave as if it is your first day at sea and get cracking on learning the essentials of that vessel. Some companies provide sufficient overlap for senior officers for this purpose; hence it is left to the senior officers to ensure that all the support staff is adequately familiarised with the shipboard operations.

2. Be Aware of the Cargo Plan: It is very important to be aware of the cargo stowage and details in each tank before the loading operation. The plan may change while actual loading, still it should be discussed during a preloading meeting with as many ship staff as possible and definitely with the entire deck crew, C/E and Second or First Engineer.

3. Display The Cargo Stowage in CCR: A very common but serious incident onboard is the shifting of cargo from one tank to another due to valves not holding. A whiteboard display in CCR will cost less than $20. Design it to display the Ullage and Mean Temperature and Tank I.G.Pressures. Write down the final loading temperatures and ullages on it after or before departure as per the final Bill of Lading. A daily glance and comparison of the CCR displays will immediately alert the vessel management team of a breach. This will save a lot of tension and running around if everyone visiting the CCR for more than 5 minutes could check the Console display of Ullage with the whiteboard display.

4. Display the Cargo MSDS in the Cargo Control Room: This is not just the mandatory requirement but also a necessity for the crew to be aware of what they are carrying and how dangerous it is.

5. Check the I.G.Pressures: It is mandatory to have remote pressure indication from each tank in the CCR. However, this will be of no use if the support staff did not know the importance of it and simply pressed the Low-Pressure alarm acknowledgement. If the vessel is loaded fully to 98 %, it is normal to have a daily fluctuation from High to Low -Low Pressure depending upon the ambient temperature. Still, a mean reading will enable you to plan topping up of the tanks with IG.

6. Do not shut off the Inert Gas Inlet valves to isolate the tanks from mainline: I know this may sound crazy, because who will shut off the valves since this may subject the tank to vacuum to overpressure or vacuum in case of malfunction of the PV valves. However, you will be surprised how many times this has been done in order to prevent intermixing of cargoes.

7. Check the Cargo Heating Lines seriously: If your tanker has cargo heating lines, you must test them as per PMS or earlier even if there is no plan to carry heated cargo. With uncertainty in the oil market, you can never be sure what cargo is being planned next. It will be very embarrassing if a loading port is planned a few hours away with heated cargo and the vessel is not sure of its heating lines.

8. Do not switch off the OVERFILL Alarms: When the vessel is 98% loaded, it is quite common to have frequent Overfill (also known as Hi-Hi Level alarms) alarms in case of rough weather. It is strongly advised never to turn them off. Few alarms are designed not to be disabled, but it has been noted that the ship staff switches off the electrical supply to these alarms. However, even if the alarm has been isolated, ensure all alarms are tested prior to arrival to port.

9. Check Oxygen Content of tanks regularly and well before arrival: There is nothing to elaborate on this for any tanker man. However, this is common neglect. The equipment used to check Oxygen and H2S must be calibrated and have a certificate. Any other special check required must also be carried out.

10. Pressure Testing of all Cargo Lines and Pre discharge tests: It is important to carry out the pre Arrival Cargo checks as per the company SMS. It is surprising how many Chief Officers and Masters do not carry out the pressure testing of lines (even though the nature of cargo permits it). Most of the pre-discharge tests start and end with the remote stopping of the cargo pumps. In case of crossing the Atlantic or the vessel having faced bad weather during the voyage, it is advisable to carry out pressure testing of lines at least 72 hours in advance. This will give the vessel staff sufficient time to rectify any leakages of Dressor Couplings or any other defects in the pumps or pipelines.

11. Reset All Cargo Pumps after trying out Remote Emergency Stop: This is a common mistake that is made. As the last part of the operation, the pumps are tripped from remote and the entire plant is shut down. This is not the correct thing to do. Whether the prime mover for the cargo pumps is steam, electrical or hydraulic, ensure that the trip is reset and the pumps can be started again. Depending upon the system on board, this will vary, but whatever the system be, please ensure that it will start normally during a Cargo discharge. If the system is steam-based, ensure that the COP speed was reduced to a minimum before trying out remote trips, otherwise, the pump will race or start at a higher runaway RPM next time when the pumps are started. This has caused serious accidents in the past due to governors getting stuck at higher RPMs.

12. Do Not Ignore Pump Room Bilge Alarms: Depending upon the yard the Pump Room and Fore Peak Store Alarms are provided in CCR, ECR or a combination of any of these. Please identify this as soon as you board the vessel and respond to a high-level Bilge Alarm in a positive manner without ignoring it.

13. Check the quantity of feed water: Water consumption is relatively higher on Tanker vessels carrying heated cargo and having Steam Cargo plant. This is the most ignored area since depending upon the ship practice the responsibility may vary from the Engine department to Deck. Whether it is before arriving for a loading port for heated cargo, or discharge, if your Cargo plant is operated by steam you may need to know how much distilled water you have for the boiler plant. Doubly ensure this by taking actual tank sounding, rather than depending upon remote gauges.

14. Cold Weather precautions: This has to be taken into consideration for all kind of vessels, but there are a few specific areas to tankers which become critical. These include completely draining the cargo heating lines; testing steam lines for deck seal; draining the ODME pump in the pump room, tank cleaning heater etc. Any negligence on this account may have an enormously damaging effect on the vessel operation. The ODME sampling pump, in fact, should be kept drained at the casing, at all times, unless it is required. The PV breaker liquid also needs to be checked for sufficient cold weather levels.

15. OIL Record Book: It is imperative that the ORB (Oil Record Book) is filled up completely and correctly almost immediately after an operation is carried out. However, this is not done in quite a few cases. Officer in charge keeps waiting for a few days before making entries. This strategy can backfire at times if the officer forgets due to some urgency, and it has happened quite a few times.

General Procedure to Fight Fire on Tanker Ship in a Terminal

With tones of highly flammable and hazardous cargo and fuel oil on board, tanker ships are accident prone zones having high probability of fire accidents. The frequent cargo handling operations and loading/unloading procedures of hazardous materials make tanker ships highly vulnerable to accidents. Sometimes in spite of taking all safety precautions, accidents involving fire do take place on tanker ships because of unprecedented events.Tacking fire on tanker ships require strategic planning and systematic approach, along with the least response time. The approach to fight fire on board ships would differ according to the type of the fire, source of fire, and the location of the ship. Mentioned below is the general action that is taken when a fire breaks out on a tanker ship while the ship in a terminal.

Actions to be taken by ship personnel to fight fire on tanker ship in a terminal

As stated by the standard rule for emergency situations, the first thing the tanker ship personnel must do in case of fire on board is to raise the alarm by sounding the recognized alarm signal which consists of a series of long blasts from the ship’s whistle. Usually, each of this alarm blast is not less than 10 seconds. However, there is a possibility that the terminal authority might ask the ship to give a locally recognized signal in case of an emergency. In such cases, the stated emergency alarm should be raised.

As soon as the signal is sounded, all cargo, bunkering and ballasting operations, must be stopped by the ship. The main engine and the steering gear must also be brought to a stand by position. All other cargo operation equipment for tankers must also be stopped immediately if they are in use.

Once this is done, the ship’s crew will take the responsibility of fighting the fire under the leadership of the ship’s captain or any other officer appointed for the task. The procedure for fire fighting at the terminal remains the same as that when the ship is at the sea. An additional team/ group might be formed for assistance in fire fighting or for disconnecting and arranging hoses from the manifold. All resources and human efforts available are used to stop the fire as soon as possible.

If the situation requires, the master of the ship might ask assistance from the terminal authority. The ship’s fire fighting team must make a united effort with the professional fire fighters from the shore to bring the fire under control.

Actions to be taken by the terminal to fight fire on tanker ship

On hearing the emergency alarm from the tanker ship, the terminal in-charge would immediately inform the control room. The control room will sound the terminal fire alarm, inform the port authority, and commence shutting down of loading, discharging, bunkering or ballasting procedures immediately.

The terminal personnel, according to the severity of the situation, can also ask the adjacent or nearby ships to shut down all loading, discharging, bunkering or ballasting procedures. In order to maintain a level of utmost safety during emergency situations, the terminal authority might ask nearby ships to disconnect all their metal arms and hoses and keep their engines and steering gear ready.

The terminal in-charge, after discussing with the control room officials, might send professional fire fighters or fire fighting tugs to assist in the emergency process. The terminal might also ask outside assistance such as civil fire brigade, medical aids, rescue launches, police etc. if the situation requires.

Fighting fire on tankers is not an easy task especially when the fire is big and has a potent fuel source nearby. The ship and terminal personnel must work with combined team effort to bring the fire under control before it becomes a major threat to the ship and the terminal.

10 Important Points to Remember After Completing Cargo Operations on Tankers

Cargo loading/unloading operations on ships is a hazardous task that can lead to serious consequences. Ship officers must take extra precautions not only while carrying out these operations but also after completion.

Cargo handling on tanker ships involves a variety of equipment and tools which must be used properly to ensure safe operations. Mentioned below are ten important points which must be considered after completion of tanker cargo operations.

1.Check Loaded Quantity

After the completion of cargo loading, the loaded quantity of the cargo tanks should be checked and confirmed by a responsible officer and also by a representative of the shore. Any kind of discrepancy in the quantity must be informed to the master and concerned authority immediately.

2. Inform Engine Room

Notify the engine department after discharging is over and ensure that the surveyor has issued the “Dry Tank Certificate or Empty Tank Certificate” to the vessel.

3. Keep The Logbook Updated

Ensure that times of all events of the loading/discharging operation are recorded in the Cargo logbook and main points are  transferred in the Deck logbook.

4. Close All Valves

After the completion of the cargo loading / unloading operations, all cargo valves involved in the process should be closed. Shore control valves should be closed before the tanker valves.

5. Remove the Cargo Hoses By Avoiding Oil Spill

After checking that the valves are closed, cargo hoses should be taken off by ensuring that leakages from cargo left in the hoses is collected into cargo pans. This is extremely necessary to prevent any kind of oil spill.

6. Check Breather Valve

The breather valves should be checked to ensure that they are correctly set to maintain pressure inside the tank.

7. Change the Flange Position

Change the fitted position of the Spectacle Blind flange to it’s blank side to isolate the line and prevent overflowing.

8. Close Tank Openings

All appropriate tank openings should be closed by using the designated tools after the completion of the cargo loading / unloading. This operation is to be carried out by pump-man or bosun under the guidance of chief officer or other responsible officer. Also, cargo manifolds and marine arms or hoses should be securely blanked after being disconnected.

9. Remove Earth Bonding Cables

The Earth Bonding Cables should be taken off after the cargo hoses are disconnected.

10. Open Drain Cocks

The tanker manifold and shore valves should be closed and the drain cocks at the tanker’s manifold should be opened to allow draining of cargo into fixed drain tanks or portable drip trays.

Additional Points to Remember During and Towards Completing of Cargo Operation

If it is necessary to sound the tanks when approaching the completion of cargo discharge, the inert gas pressure can again be reduced to a minimum safe operational level to permit sounding through sighting ports or sounding pipes. Care should be taken to avoid the ingress of air or an excessive release of inert gas
If STS operation is being performed and there is a large difference in freeboard between the seagoing vessel and the inland tanker, the crew must make allowance for the contents of the hose on completion of the transfer

The Inert Gas System (IGS) recorder shall be switched on to record and monitor the cargo tank’s pressure. It should also be suitably marked for details of voyage number, date and time of starting and corresponding present pressure

Where possible, the completion of loading should be done by gravity. If pumps have to be used to end the process, their delivery rate during the ‘standby’ time should be regulated so that shore control valves can be closed as soon as requested by the tanker.

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