How LPG is Transported
LPG exists as either a gas (vapour) or as a liquid, when it is under a modest amount of pressure in gas bottles, cylinders, tanks and larger LPG storage vessels.
Given that gaseous LPG has a volume 270x that of liquid LPG, it is almost always transported in its more compact liquid state.
LPG (propane) can be transported in a number of ways, including by ship, rail, tanker trucks, intermodal tanks, cylinder trucks, pipelines and local gas reticulation systems.
There are also some much more basic ways – LPG mule train anyone?
We’ll explore all of these and discuss the details of each…
Bulk Transport by Ship
LPG is transported across entire oceans in large tankers, typically called gas carriers.
The most common for transoceanic trips are Very Large Gas Carriers – VLGCs.
The VLGC class ships carry up to about 43,000 tonnes (84,000m3) of LPG and are usually about 230m in length.
VLGCs are fully refrigerated.
The LPG is kept at approximately -48°C, which is below the boiling point of LPG (propane), which is -42°C.
This means that there is no vapour pressure build up, remaining at about 1 atmosphere of pressure.
The structure of the ship only needs to deal with the weight of the LPG and not any extra pressure.
There are about 200 VLGCs in service around the world.
Transported in Intermodal ISO Tank Containers
ISO tank containers are LPG storage vessels mounted within a standardised framework.
The standardised framework is built to ISO (International Organisation for Standardisation) standards, just like a standard (closed steel box) shipping container.
Typical LPG ISO tank sizing is 6.05m (20ft) long, 2.4m wide and 2.55m high, although other sizes also exist, including 12.2m (40ft) versions.
Capacity of the 6m ISO LPG tank is 24,000-25,000 litres or around 12 tonnes of LPG.
A tank container is built to the ISO standards to be “intermodal”, making it suitable for different modes of transportation and stackable.
These containers can be used for transport by ship, rail or truck, being transferred between them without unloading/reloading the LPG cargo.
Transported by Rail in Bulk and ISO Tanks
Tanker rail cars are used to move large quantities of LPG in bulk.
These tankers can be anywhere from 65,000 to 127,000 litres in capacity, which is about 65 tonnes of LPG.
They are approximately 19m long and 5m high.
The limitation on bulk rail transport is that you need a loading/unloading terminal at each end.
For that reason, the use of bulk rail is typically limited to specific applications, such as transporting LPG from well sites to terminals.
However, rail can also be used to transport ISO tank containers.
Rail would be used for this, in lieu of truck transport, when the distances are long enough to justify the economics.
Pipeline Transport of LPG
LPG pipelines are typically employed between gas fields and storage terminals.
The prohibitive expense involved in building pipelines makes them rare.
Reticulated Gas Systems
There are some communities or building estates that have LPG reticulation systems.
The pipes to the homes are supplied from a central storage tank or tanks.
Each home is equipped with a meter, similar to natural gas meters.
Transported by Road Tankers
Large quantities of LPG are frequently moved between terminals and depots via large road tankers and B-doubles.
LPG road trains, with three trailers, are also occasionally used.
An LPG B-double is made up of a prime mover which pulls two large tank trailers, which are linked by a fifth wheel and can be up to 26m long.
An LPG road tanker is the same arrangement, but the prime mover is only pulling a single large tank trailer.
A single road tanker holds 19 to 23 tonnes.
Road tankers are also used for direct deliveries to high volume consumers, like petrol stations and large industrial users.
Transport by Local Bobtail Tankers
Local bulk deliveries, to end users, are done with bobtail tankers.
Unlike the road tankers, bobtail tankers are not articulated, so there is no trailer involved.
Also known as a rigid tanker, the LPG vessel is attached to the same frame as the prime mover.
Sizes vary quite a bit, from small 4 tonne tankers to larger 12 tonne versions.
The gas is dispensed using a pump and hose reel arrangement.
The use of local tankers allows for automatically scheduled deliveries without waiting for the customer to empty a cylinder completely, as is the case with exchange.
This eliminates the need to check cylinders or call for deliveries.
Cylinder Truck Delivery
Lower volume users are supplied with gas bottles on an exchange basis.
The driver delivers full cylinders and removes the empties, for refilling.
LPG can be supplied virtually anywhere, using a truck.
LPG Delivery by Beasts of Burden
But there are some places that even a truck can’t go.
In some parts of the world, they go back to time-honoured methods.
They transport LPG using pack animals.
Mules can carry 100kg or more, so 2 or 3 small LPG bottles are well within their comfort range.
The accompanying picture shows LPG being transported via a mule train.
LPG Transport via People Power
In some countries, they don’t even rely on animals for help.
Push carts and bicycle carts work just fine when delivering LPG short distances.
So, for congested inner cities, with frequent traffic jams, what better way to deliver than with pedal power?
And then there is the most basic solution, just carrying them by hand, one at a time.
However, safety practices look to be an issue for some.
One of the key advantages of LPG is its portability.
LPG can be supplied virtually anywhere people can go.
Delivery methods can range from very sophisticated to extremely basic.
From requiring considerable capital investment to virtually no investment at all.
Regardless of how it’s delivered, LPG is there when people need it.
Clean, safe and reliable energy for everyone everywhere.
Comments, questions or feedback?
The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free & may not be applicable in all circumstances.