Tanker Ship Parts & Equipment: Everything You Need to Know

by | Last updated Nov 24, 2023 | Maritime Dictionary, Ship Parts, Vessel Information | 0 comments

Tanker ships, commonly known as “tankers” in the maritime world, are special kinds of vessels designed to carry liquid cargo in bulk.

Anything of liquid form can be transported through these ships. Since there are thousands of various liquid goods out there, there are also many types of tankers built.

But with the diversity of the liquids they carry, all tankers share a common set of parts and equipment. These parts are essential for the safe and efficient transportation of liquid cargo.

You may have encountered them in school or some of your tanker training courses or even on board if you’re already a seafarer.

Let’s dive into a little more knowledge of them here.

Cargo Mains

1. Cargo Tanks

This is the area where cargo is stored. You can easily spot this on a tanker ship as this is much of the deck area that you see.

Since there could be as many as 50 tanks in a single tanker, naming the tanks is in alphanumerical form and whether it is at the center or on the sides (wings).

Starting from the forward part, cargo tanks are labeled as 1P, 1S, 1C, 2P, 2S, 2C, etc. They are pronounced 1 Port, 1 Starboard, 1 Center, etc.

The whole number one cargo tanks (port, starboard, center, center port, center starboard, etc.), is named ”across”. So 1 across are all the number 1 tanks.

Inside of a cargo tank. We can see here the cargo pump, heating coils, tank cleaning machine, and two crew working inside.
Inside of a cargo tank.

2. Cargo Pumps

Generally, cargo pumps are used to drive the liquid cargo out of the ship’s tanks during discharging operation. But they can also be used to drive tank washing machines.

Depending on the kind of ship, some uses submerged centrifugal pump while others use the old conventional models.

For submerge pumps, the most commonly used are the Framo Pumping System which is hydraulic driven, and the Marflex System which is electric driven.

On other types of oil tankers like the VLCCs, centrifugal pumps are used.

Other types of pumps used in the market are reciprocating pumps, gear pumps, and screw pumps.

3. Cargo Lines

Cargo lines serve as the pathways to which the liquid cargo passes during loading and discharging operations.

Its direction is controlled by cargo valves which are operated by the officer of the watch.

4. Cargo Valves

Cargo valves allow and disallow the flow of liquid when the pump is running. It also serves to control the direction of the cargo as well as its rate of flow inside the tank.

Some cargo tanks share a common line with others. You can control which tanks to use by opening or closing the right valves.

Cargo pumps, lines, and valves are some of the most basic features of a tanker ship.

5. Cargo Control Room (CCR)

Is an office inside the ship where the Chief Officer and Officers of the Watch monitor everything.

Cargo level, tank pressure, list, trim, bending moments, cargo rate, temperature, ballasting and counter ballast, checklist, and many others are watched closely.

The CCR also establishes a connection to the shore terminal.

6. Main Cargo Hatch

A small opening where the crew can go in and out of the tank. Equipment can also be lowered here with a rope.

A crew fixing the fixed washing machine on deck near the 3P cargo tank.
Tank dome or main cargo hatch

Venting Systems

7. P/V Valves (Pressure/ Vacuum Valves)

Various pressures of immense force are present during liquid transfers. For this reason, a venting system is installed on tanker ships.

When there is too much pressure inside the tank, P/V Valve automatically opens its pressure valve. But if the pressure reaches a certain negative number, its vacuum valve opens up.

This system prevents pressurization which may lead to explosion and under pressurization or implosion.

8. Mast Riser

Another venting system for tankers is the mast riser.

If you have a homogenous cargo and the terminal allows you to vent into an open atmosphere, using the mast riser is one way to do it.

You can control the rate of flow of venting by adjusting the Mast Riser valve.

9. P/V Breaker

Another secondary venting system is a P/V Breaker which you can find on deck.

This is a cylindrical piece of equipment that is filled with water and is connected to the IG line.

Over-pressurization causes its water to spill outside whereas under-pressurization sucks the water into the IG Line.

10. Deck Water Seal

Before the inert gas is delivered into cargo tanks, it must pass first in a deck water seal.

Deck seal, as most commonly referred to, is the equipment used to purify or wash the inert gas (I.G.) before being delivered into the tank.

More importantly, its function is to prevent the backflow of toxic gases coming from the cargo tank to the engine room.

A meme for deck seal wherein the first image shows the actual deck seal equipment of a tanker vessel on deck and the second equipment are actual seals on the deck of a yacht.

11. IG Branches

The IG line is further branched into smaller pipelines going to individual tanks.

These lines are called IG branches or IG Local and are connected to the tank using a valve.

12. Vapor Return Line

Some terminals don’t allow venting into the atmosphere. Thus, the vapor coming out of the ship’s tanks during loading operation is returned to the shore facility using a vapor return line.

The ship’s vapor line has its own manifold and is connected to individual tanks. A flexible hose is connected here that leads back to the terminal.

Production Plants

13. Inert Gas Plant (I.G. Plant)

Some tankers use inert gas to reduce the oxygen content inside the cargo tank. They use an equipment called the inert gas plant to do it.

This plant produces a low-oxygen gas which is delivered on deck via I.G. pipelines. The lower the oxygen inside the tank, the safer the ship is from fire or explosion. 

The development of the Inert Gas Plant is a game changer in the tanker industry when it comes to safety.

14. Nitrogen Plant 

Since Inert Gas is considered “dirty” and highly incompatible with other cargoes, nitrogen is used as a substitute.

Thus, some ships like Gas Carriers, Chemical Tankers, and Reefers are built with Nitrogen Generators.

Nitrogen gas or N2 is used for purging, padding, and inerting.

Midship Resources

15. Midship Store

A Midship Store is not a sari-sari store where you can buy something for retail. In fact, it is a storage area where you can find various equipment most of which are for emergency and oil spill control.

Fire extinguishers, BA sets, and Emergency Cargo Pumps are a few that you can find here.

The midship store is also called the Deck Store

16. Hose Handling Crane

This is a manifold crane used for lifting heavy objects on deck like reducers, cargo hoses, portable gangways, motors, and yes, even your luggage upon signing on or off.

Hose handling crane offers the best way to identify a tanker ship from other types of merchant ships even if it’s far on the horizon.

17. Manifold Reducers

A tanker terminal may be able to handle various sizes of tanker ships. However, its loading arm or cargo hose connection at the manifold may not fit with that of the ship.

For this reason, ships carry with them manifold reducers to be able to connect with the shore.

Remember that if the shore can not connect its loading arm/ hose with the ship, there will be no cargo operation to conduct.

18. Drip Tray

One reason why there are very strict rules around the tanker market is because of oil spills.

A drip tray is a huge and long basin built directly under the manifold to capture any drops or leaks in the connection.

The manifold area is one of the most prone to spill accidents since this is the part where connections and disconnections happen.

There would always be drops if not liters of cargo remaining in the hose or arm. The drip tray is built to capture them.

19. Portable Cargo Pump

Sometimes, the main pump fails for some reason and the ship’s crew is unable to fix it.

To discharge the remaining cargo, a portable cargo pump is lowered inside the tank. This pump is much smaller than the main ones. 

Thus, it would take longer to finish the operation once this is used. And there is only one spare available so it’s kind of a drag if two or more cargo pumps fail at the same time.

20. Manifold Area

An area on a tanker ship (port and starboard) where cargo connections to different cargo tanks can be found.

It is easily spotted as it is mostly at the center of the ship, easily reached with the hose handling crane, and built with a drip tray underneath.

21. Deck Tanks

As cargo tanks aren’t enough at times, deck tanks can also be installed on the deck. These are huge cylindrical tanks that you can see on the deck of a tanker ship.

They can be filled with cargo or dirty water too.

22. Gas-Freeing Fans

Cargo and ballast tanks are enclosed spaces. Toxic gases and low oxygen content are expected inside the tanks.

To remove these hazards, the tank is normally washed and ventilated. Ventilation is the process of introducing fresh air inside the tank to remove any toxic gases present.

This is done with the use of gas-freeing fans. They can be operated by water, hydraulic, steam, or air.

Main deck of a tanker ship and its parts labelled with arrows.
Main deck of a tanker ship and its parts.

Gauging System

23. Tank Radars

To monitor the level of cargo inside the tank, a ship is installed with a tank radar. 

This is a fixed tank gauging equipment which is very useful to avoid overflowing by giving various audio-visual alarms.

This tool has sensors connected to the computer in the CCR where officers can monitor everything.

24. UTI Gauging Equipment

Sometimes, tank radars fail, become unreliable, or their accuracy lessens. To compensate for their shortcomings, a manual Hermetic or MMC Type UTI is used.

This is a gauging device that produces an audible alarm when it touches liquid cargo. The reading on its tape allows you to determine its ullage. 

This equipment also helps in detecting interface or water within your cargo.

25. Ullage Point

Is a protruding pipe found on top of every tank. It is where the sampler and UTI are connected.

Other names include sampling point or vapor lock.

26. Cargo Level Alarm System

An oil spill is one of the riskiest parts of a tanker operation. To give audible and visual warnings about the tank’s cargo levels, tanker vessels have a cargo level alarm system in place.

High-Level Alarm triggers at the tank’s 95% capacity and the Overfill Alarm is at 98%.


27. Heating coils/ Heat Exchangers

These are pipelines where steam passes through that eventually heats the cargo inside the tank.

Heating coils are found inside the tank. Meanwhile, there are other heat exchangers built on the deck.

These are used when carrying high-viscosity cargoes, vegetable oils, and animal fats.

28. Steam Line

On some tanker ships, steam is very important on deck. They can be used during tank cleaning and maintaining the temperature of the cargo.

Steam is delivered on deck via steam line which is connected to the Engine boilers where the steam is produced.

Tank Cleaning

29. Fixed Tank Cleaning Machines

Some cargoes are not compatible with the previous one and to remove their traces, the ship conducts tank cleaning operations.

Fixed tank cleaning machines are built on the deck with nozzles inside the tank.

The nozzle rotates when high-pressure water passes through hitting the bulkheads inside the tank at 360°.

30. Portable Tank Cleaning Machines

Sometimes, fixed tank cleaning machines aren’t enough as there are blind spots inside the tank.

To compensate for this inefficiency, a portable machine is lowered.

This machine is connected to a hose and is lowered at different heights via the Butterworth hole or main hatch.

Holding a bottle of vegetable oil taken after open sampling method using the Butterworth Hole of a tanker vessel.
Open sampling using the Butterworth Hole or Butterwash.

31. Butterworth Hole (Butterwash)

A much smaller opening where blowers are mounted to ventilate the tank. This is also used for open sampling and tank cleaning.

This is normally fully secured with bolts and nuts (airtight/ watertight integrity).


32. Emergency Deck Shower

Since tanker ships carry dangerous liquids, there are emergency showers installed on deck to wash them off.

These showers provide first aid relief whenever a crew member comes in contact with chemicals anywhere on his body while on duty.

Also installed together with the shower is an eyewash used for chemicals splashed in the eye.

33. Emergency Stop of Cargo Pumps

Crazy things sometimes happen on board and we immediately want to stop the cargo operation. If this happens, emergency stops come in handy.

These are push buttons installed on catwalks of tanker ships that are used in case of emergency like an oil spill, leakages, overflowing, fire, or any other emergency.

There are also emergency stops inside the CCR.


34. Retention Tank

Tanker ships carry cargoes that can be harmful to the environment like oil and other chemicals. A retention tank is a small tank used to dispose of dirty water so it doesn’t get thrown to sea.

Yes, we do have slop tanks but there are instances when slop tanks are filled with cargo. 

Thus, when we have oily water waste on deck like the spills at the drip trays, these can be pumped into the retention tank.

35. Crossover Lines

Except pure chemical tankers, oil and product tankers use crossover lines to let the cargo pass from one line to the other.

When the ship is loading or discharging at a certain port, it’s most possible out of 6 or 7 manifolds, only 1 or 2 may only be used for connection.

A crossover line enables the possibility for the other tanks to be used by interconnecting them with one another. 

To put it simply, it is a pipe bigger than the cargo line to which all tanks are connected with each other.

They are segregated from each other using valves.

This list is not exhaustive and there could be a few equipment not listed here that you can find in your respective tanker ships.

Just a quick trivia: Do you know that Greece is the largest ship-owning country with huge tankers in its fleet?

Keep safe on your jobs and

May the winds be in your favor.



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