RFID pallet tracking: GRAI for the pallet, SSCC for the shipment
In briefTo track a pallet you need two GS1 codes: the GRAI identifies the pallet as a returnable asset for its whole life, and the SSCC identifies the shipment and changes on every trip. Both go into a barcode or an RFID tag, which in plastic pallets can be embedded in the material.
Two different codes: GRAI for the pallet, SSCC for the shipment
For RFID pallet tracking on a loaded pallet you need to identify two things: the pallet and the goods it carries. GS1 standards use two different codes, which you can put in a barcode or in an RFID tag.
| GRAI | SSCC | |
|---|---|---|
| What it identifies | the returnable asset: pallet, tray, drum [1] | the logistic unit: goods packed together for transport or storage [2] |
| Length | 14 digits + optional serial of up to 16 characters [1] | 18 digits [2][3] |
| GS1 application identifier | (8003) [1] | (00) [3] |
| Lifespan | the pallet's whole life | one shipment; can be reused after one year [2][3] |
| Data carrier | GS1-128, GS1 DataMatrix, RFID [1] | GS1-128, RFID [2][3] |
The GRAI matters to whoever owns the pallets: a closed loop, a pool, a company that lends them to customers. The SSCC matters to anyone shipping to a receiver that works with GS1 standards.
The GRAI: how it is built and when to serialise it
The GRAI has 14 digits. The first is a zero, followed by the GS1 company prefix and the asset type, which together take up 12 digits, and finally the check digit [1]. The asset type distinguishes, for example, one pallet model from another.
The serial component is optional: up to 16 alphanumeric characters, one for each individual pallet [1]. You need it if you want to track the exact pallet and not just the model. You also need it for RFID: only a GRAI with a serial has an EPC encoding for tags [1].
RFID on plastic pallets: where the tag goes
In a plastic pallet the transponder can be embedded in the material. Some manufacturers do this to protect it from dirt and damage; the tag reads without line of sight and can be rewritten [6]. Here plastic has an advantage over wood: the tag stays inside the pallet for every cycle, including washing. You ask for an embedded tag when you order, along with logo and colour: see custom plastic pallets.
The alternative is a label or tag applied afterwards. It costs less at the start but stays exposed to impacts and forks.
For plastic pallets we found no specific GS1 rule on the number of tags. In 2010 a GS1 EPCglobal guideline, reported by the trade press, recommended two tags with a GRAI in diagonally opposite corners of wooden pallets [9]. The logic is simple: with two tags, whichever side the pallet arrives from, at least one stays readable. Ask the supplier how they positioned theirs and with which readers they tested them.
Liquids and metal: the limits of reading
GS1 explains the two difficult cases [5]:
- metal reflects and diffracts radio waves, although there are now tags designed to be mounted on metal;
- water and liquids absorb the waves and detune the tag; a RAIN tag surrounded by water can lose a lot of read range, which dedicated antennas can only partly recover.
For a pallet of drinks, detergents or sheet metal, what counts is the position of the tag in the pallet, away from the load, and the read test with the real goods.
The GS1 logistics label: where it goes
The shipping label carries the SSCC in a GS1-128 barcode. GS1 UK gives these placement rules [4]:
| Rule | Value |
|---|---|
| Height from the base of the pallet | 400 to 800 mm |
| Number of labels | 2 identical, one on the short side and one on the long side |
| Distance of the barcode from the vertical edge | at least 50 mm, quiet zones included |
| Minimum bar height | 32 mm |
| Position of the SSCC | in the lowest barcode |
Most companies use an A5 label (148×210 mm), but the GS1 specifications do not set a size [3]. The label has three sections: name or logo at the top, human-readable data in the middle, barcodes at the bottom [3].
Barcode or RFID
A barcode costs little and any scanner can read it, but you read one pallet at a time, with line of sight. RFID reads without seeing the tag and on many pallets at once, for example at a gate [6]. It costs more and needs readers and field tests.
In practice the two live side by side. The SSCC travels on the barcode label because receivers ask for it. A GRAI on an RFID tag serves whoever manages a pallet fleet and wants to know where the pallets are, how many come back and how many cycles they have done.
Pooling and closed loops: who already uses it
Pools are the first users (how pooling works is explained in the guide to plastic pallet rental). One European pool offers RFID on all the pallets and pallet boxes in its loop, to manage data in real time [7]. In the United States, a plastic pallet pool states that it embeds RFID tags and barcodes in every pallet [8]. The list of European and American pools is in the guide to plastic pallet manufacturers.
In an automated warehouse, RFID is also used to withdraw pallets that have done too many cycles, as explained in the guide to pallets for automated warehouses. For AGVs and shuttles, see pallets, AGVs and pallet trucks.
What to ask the pallet supplier
- Tag embedded during moulding or applied afterwards?
- Tag frequency and the readers it was tested with.
- How many tags per pallet and in what position.
- Encoding: serialised GRAI with your GS1 prefix, or the supplier's number [1].
- Flat space on the side of the pallet or the load for the GS1 label between 400 and 800 mm [4].
- Read test with your load, especially if you carry liquids or metal [5].
Frequently asked questions
What is the difference between SSCC and GRAI?
The SSCC is an 18-digit GS1 code that identifies a logistic unit, meaning goods packed together for one shipment, and is read with application identifier (00). The GRAI identifies the pallet, tray or drum as a returnable asset and is read with application identifier (8003). The SSCC changes with every shipment; the GRAI stays on the pallet for its whole life.
Where does the logistics label go on a pallet?
According to GS1 UK, the label goes between 400 and 800 mm from the base of the pallet, in two identical copies, one on the short side and one on the long side. The barcode must be at least 50 mm from the vertical edge and the bars must be at least 32 mm high. If there are several barcodes, the SSCC is the lowest one.
Can I add an RFID tag to an existing plastic pallet?
Yes, with a label or an applied tag, but it stays exposed to impacts, washing and dirt. Manufacturers can instead embed the transponder in the plastic during moulding, where it stays protected. If the tag needs to carry a GRAI in EPC format, the GRAI must include the serial component.
Does RFID work on pallets loaded with liquids or metal?
It works less well. According to GS1, water and liquids absorb radio waves and detune the tag, and a RAIN tag surrounded by water can lose a lot of read range. Metal reflects the waves, but there are now tags designed to be mounted on metal. Before a project, run a read test with your actual load.
Do I need RFID or is a barcode enough?
For the shipping label, a GS1-128 barcode with the SSCC is enough, and it is the standard most receivers generally ask for. RFID is useful when you want to read many pallets without seeing them, for example at a gate, or to track returnable pallets in a closed loop or a pool.
Sources
- GS1 US, An Introduction to the Global Returnable Asset Identifier (GRAI), Release 2.0 (September 2017)
- GS1 Australia, Serial Shipping Container Code (SSCC)
- GS1 UK, Logistics labels and SSCCs
- GS1 UK, Where should pallet labels be placed?
- GS1 Support, Does RFID work around metal and water? (updated 30/8/2024)
- Materialfluss, personalised Cabka-IPS load carriers with RFID transponders (24/5/2016)
- Craemer, Pooling (RFID on pallets and pallet boxes)
- iGPS, all-plastic pallet pooling
- SC Digest, GS1 EPCglobal guideline on tagging pallets with RFID (30/9/2010)
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