Overview of Electronic Seal (eSeal)
Electronic Seal (eSeal), being one of the most promising applications of the RFID technology, is an electronic device which is composed of traditional supply chain seal as well as RFID tag. The main function of it is to act as barriers against pilferage, smuggling, and sabotage of cargo within containers and trailers and route to their destination. When the container is loaded at the point of origin and the doors closed, an eSeal is fixed to the container and is read by a handheld reader which determines that the eSeal is activated and working. If desired, additional data can be programmed into the eSeal such as the container number, routing information or contents. The container then departs for either container consolidation centre or a port facility where fixed or hand-held readers poll the eSeal. If the eSeal has been tampered with, it will indicate the event and the container can be segregated for inspection.
Basic Components of eSeal
As mentioned before, one of the main components of eSeal is traditional supply chain seal. Basically, it can be classified in three groups which are held on the bar, on the handle and on the hock. Examples of those traditional supply chain seals are shown in Table 2a, 2b and 2c.
Table 2a: Examples of the seals which are held on the bar
Table 2b: Examples of the seals which are held on the handle
Table 2c: Examples of the seals which are held on the hook
Types of eSeal
When integrating different traditional supply chain seal with RFID tag, different eSeal will be produced. In general, they are active eSeal and passive eSeal. Table 3a and 3b shows the examples of different eSeal.
Active eSeal is made use of active RFID tag. Similar to RFID tag, Active eSeal has its own data storage capacity and can automatically communicate with the readers stayed around 3 hundred feet. It can even detect tampering when it occurs and add it to a time log of events. However, the stability of the active eSeal is not high as they have to rely on battery power source to function. The cost of active eSeal is much higher than passive eSeal due to the presence of battery. The active eSeal can range from USD $20 to $400 per unit, while passive eSeal can be USD $20 dollars or less per unit.
Table 3a: Examples of Active eSeal
For passive eSeal, passive RFID tag will be used. Without battery, it can only communicate when being triggered by readers and the range of readability is around 30 feet. Since the passive seal uses the absorbed energy to reflect its information back to the reader, the interference to environment is smaller when comparing with active seal. However, it has limited data storage capacity and no continuous power. It cannot measure the condition of the seal. For instances, it cannot detect and record tampering at the time of the event. It can simply report whether it is intact or not when interrogated by a reader. Data might lose if the data storage of passive seal is used up or not being triggered.
Table 3b: Examples of Passive eSeal
RFID-based eSeal vs. Traditional Supply Chain Seal
Due to the presence of traditional supply chain seal, eSeal can provide mechanical function like a lock. Moreover, eSeal can contain identification data which are important to record and manipulate containers and shipment information by using RFID technology. Apart from guaranteeing the authenticity and integrity of freight containers, the visibility of the supply chain can be enhanced. With the significant benefit of eSeal, there is increasing trend of eSeal development and deployment. One of the early users of eSeal is the Mexican government. They used eSeal for in-bond container shipments between Los Angeles/Long Beach, southwest U.S. border crossings, and destinations in Mexico.