Understanding Bulk Liquid Transport Equipment

  • Posted by: miamiseo

The freight industry trasports three types of goods: gases, liquids, and solids or dry goods. All these three categories of goods have their own specialized type of equipment required for their safe and efficient transportation.

Gaseous substances require specialized reinforced and cylindrical tanks for transportation while solid goods can be transported in standard shipping containers.

The transportation of liquid cargo on the other hand can be made in a standard ISO tank or in a flexitank.

The ISO tank

The ISO tank has for a long time been the standard way of bulk liquid transportation. This container consists of a hull made of stainless steel with the inner layer constituted of protective layers of materials to preserve the stainless steel hull from corrosion.

The protective inner layers and the strong steel container enable it to transport both hazardous and non-hazardous bulk liquids and this includes flammable materials such as fuels and dangerous chemicals.

The ISO tank derives its name from the International Organization for Standardization or (ISO) that sets the parameters of what is considered an ISO tank container.

The typical shape of the ISO tank leans more towards cylindrical for strength and has a man hole-like hole at the top and at least one valve at the end of the container for offloading.

The ISO tank is very versatile and is used for transporting consumable liquids such as milk, juices, alcohol, molasses, and vegetable oils as well as non-edible and even hazardous liquid such as gasoline, diesel, industrial chemicals, and liquid petroleum gas or LPG.

The ISO tank has a large capacity ranging from 5,000 to 11,000 gallons and for a long time has been the ideal way of bulk liquid transportation.


A flexitank is a collapsible bulk liquid transportation container that is made of multiple layers of polyethylene with an outer reinforced wall composed of interwoven polyethylene material.

Its collapsible nature means that it is ideal for use in an already existing 20-foot container where it is placed and used for the transportation of non-hazardous liquids. It is used for transporting consumable liquids such as milk, juices, alcohol, molasses, and vegetable oils as well as non-edible ones like non-hazardous industrial liquids.

The flexitank fits very well in the standard shipping container where it is placed while empty and filled up from there.

The flexitank was an evolution that came about from the needs of the logistics industry where it became necessary to use existing infrastructure to transport liquids rather than relying on the more expensive ISO containers.

The beauty of using flexitanks as a bulk liquid transportation method is that the walls of the shipping container provide additional reinforcement without having to do any additional and expensive modifications to the mode of transportation other than adding bulkheads.

Flexitanks are available in sizes ranging from 16 to 24,000 liters or 4,000 gallons to 6,300 gallons making them a very ideal way of bulk liquid transportation.

Equipment required

Containers to be used for the transportation of flexitanks are 20-foot containers with a minimum gross weight of 30,000 kilograms or around 14,000 pounds. The container must meet the shipping line condition criteria UCIRC (Unified Container Inspection and Repair Criteria) or IICL (Institute of International Container Lessors).

The flexibag

The internal layers are manufactured out of virgin, high-quality, food grade approved materials. The material out of which the flexitanks are made must also meet the requirements of the COA.

The materials

The common material used in manufacturing flexitanks is polyethylene but other materials such as polyvinyl chloride (PVC) can be used and the technique and mixture of ingredients is a secret that top manufacturers keep close to their chests.


Non-wooden bulkheads can be used as long as they are of adequate strength and rigidity and this is actually recommended to prevent pressure on the doors of the container.

Handling procedures

It is recommended that the shipping container be less than five years old and should be visually inspected to ensure that it is structurally undamaged. The container should have operational locking bars on the doors that can be operated and secured as intended.

The container should be rust free and free from sharp edges that might compromise the integrity of the flexitank.

Installing the flexitank

The inner walls of the container should be covered with cardboard to prevent it from abrading against the container material. Protective shoes should be worn during the installation of the flexitank to avoid damage to the protection material lining the container.

The flexitank should only be fitted and position inside the container by specially trained personnel.


Once the flexitank and bulkhead system is installed, close the left door of the container and begin connecting your hoses. The valve attached to the flexitank should be supported at the level of the valve to prevent it from damaging the valve.

It is important to start the filling at a lower filling rate such as 200 liters (52 Gallons) per minute and increase the rate gradually as you progress. The feeling rate should not exceed 1000 liters (264 Gallons) per minute.

The temperature of the loaded product should not exceed the specifications of the flexitank manufacturer.


The container should display a label warning that a container has a loaded flexitank.


The right-hand door of the container should be opened carefully while the left door is kept closed at least until the flexitank is substantially empty.

Disposal of the flexitank

After fully discharging the flexitank, the liners of the container should be removed and safely disposed or recycled and this is usually as agreed between the shipper and consignee.

We hope this article has been useful and provided information on bulk liquid transportation. At Techno Group USA we offer top quality flexitanks, solutions and services. We provide our customers with complete manuals, videos and online support for the loading and discharging of their flexitanks.

Author: miamiseo