The history of twistlocks
Twist locks to lock down freight containers to ships, rail cars, road chassis and other carriers such as flat racks have been in use since the use of the ISO freight container started. It has always been important to know if the Twist lock is locked or unlocked.
The locking and securing of freight containers, equipped with International Standard Organization (ISO) bottom corner castings to load carriers such as a truck chassis or rail car, has been pursued for more than 30 years.
Over the years, different types of locking devices to secure freight containers have been developed. Depending on the circumstances of the security required, three main types of Twist locks have been developed and used.
Location cones
Location cones do not provide vertical locking of the container on the carrier. The disadvantage of not having vertical locking used on rail cars has been acceptable because such locks do not require labor for locking or unlocking. This is being reconsidered because empty freight containers without vertical load hold down have been blown off rail cars during exposure to side winds or passing over high bridges.
Fully automatic twistlocks
Positive locking devices provide vertical locking down of the container on the rail car. This type of lock permits the lock to unlock if a predetermined lifting force is exceeded. This device is called; fully automatic Twist locks. These types of locks are becoming more and more common and are now used in many parts of the world.
Manual twistlocks
Positive manual locking devices provide locking of the container on the rail car unless unlocked or broken. Such locks are commonly designed as a stem with a rectangular upward pointed head called a shaft.
After loading a container, the container is locked manually by turning the Twist lock shaft twist right or left 90 Degrees, hence the name Twist lock. They come in three basic designs, non-retractable, retractable and screw down and are commonly used also on road vehicles. This type of Twist lock is more time consuming to handle since they all have to be individually and manually operated.
Operating manual locking Twist locks on rail cars has been proven to be very labor intensive. For instance, a railcar fitted with 24 manual Twist locks to its rail car requires an enormous amount of time to lock these containers and is considered a major disadvantage such as poor productivity. There is a need for less time consuming systems which Celtec provide.
The number of different length containers increases the number of different load configurations that the securing system on the rail car must be capable of handling. The locks must be retractable or removable, so that the correct number of locks in the right positions to suit a certain load configuration.
