LPG customer using RFID tag

Malaysian liquid propane gas (LPG) supplier Elpiji is using radio frequency identification to automate the process of filling gas cylinders, attaching low-frequency (LF) passive RFID tags to several hundred such cylinders at its Penang plant. The technology has enabled the company to reduce the time required for workers to process cylinders from 30 seconds down to two.

To implement the RFID system, Elpiji enlisted the help of New Zealand RFID reader developer EDiT iD, which believes it has created the world's first RFID interrogator certified for use within an explosive environment.

Elpiji provides gas cylinders to domestic customers for use in household kitchens, says Geoffrey Lee, special assistant to the company's executive director. When a cylinder is returned to Elpiji, two critical pieces of information must be determined before it can be refilled. The first is the tare weight, or weight of the empty cylinder. Some cylinders are returned containing residual gas, and if the tare weight is inaccurate, the system will overfill the cylinders, thus wasting gas, or underfill them and distribute a partially filled cylinder to customers.

The second piece of required information is the cylinder's date of manufacture. Most countries have a requirement for cylinders to be tested 10 years after manufacture, and some gas companies also require cylinders to be refurbished every five years.

Previously, when an empty cylinder arrived at the refilling plant, an operator manually read and keyed in the cylinder's tare weight, then visually verified it was within the requirements for testing or refurbishment. If the cylinder had passed its use-by date, it was manually removed from the conveyor. The process could take an average of 30 seconds per cylinder, thereby creating bottlenecks on the filling line.

"We wanted to develop a system that did not require staff to manually input information such as the tare weight," Lee says. "RFID is more accurate when reading information and, unlike bar codes, will not be damaged as easily."

EDiT iD's first task was to develop an RFID interrogator that could be safely used within the hazardous area of an LPG filling plant. To that end, the company developed the Model 0205 reader, certified for compliance with IECEx standards for electronic equipment used in explosive environments.

The system also utilizes 125 kHz LF tags from German company Tectus that comply with the ISO-IEC 18000-2 standards, and also meet the ATEX hazardous environment requirements established by the European Union.

Because of the potential danger inherent in operating RFID within an explosive environment, Lee says, the development and approval process took more than five years. "Ensuring the readers, tags and antennas were explosion-proof was the biggest challenge," he states, "as was ensuring there was no interference because of the amount of steel in the plant. So it is important to continue fine-tuning the system."

The tag is matched to a database record that includes the tare weight and manufacture date, says EDiT iD's general manager, Mark Powell. Now, when a cylinder is placed on the conveyor belt, two fixed-position readers identify each cylinder and verify its eligibility to be refilled and reissued.

If no tag is attached to the cylinder, it is automatically pushed to a side conveyor for rejected cylinders. Likewise, if the manufacturing date exceeds regulations, the gas cylinder is rejected.

Each cylinder meeting all necessary requirements is forwarded to the next stage, where a dispenser pumps in the exact amount of gas required to fill that cylinder. The cylinders are then automatically routed to inspection, cleaning and other stations. The whole process takes two seconds, requiring no human intervention.

Elpiji uses production control software from Kosel Industries, which modified its system to accept the RFID information.

By using radio frequency identification, Powell says, Elpiji will eventually be able to process as many as 700 cylinders an hour at its small processing plants, and up to 3,600 cylinders per hour at its larger factories. "Without RFID," he says, "that is not possible because of the human intervention, such as reading the date of manufacture, and reading and manually keying in the tare weight of cylinders."

According to Powell, there is significant potential to expand the RFID system at Elpiji's factories throughout the Asia Pacific region. "At the moment, Elpiji has no way of knowing where its gas cylinders are once they leave the filling plant," he explains. "In some countries, gas cylinders can be stolen by other gas companies, or stolen and sold for scrap metal."