A speed chain conveyor is usually specified for one reason: products have to stop at a station without stopping the line. Everything else — the chain, the carrier, the rail, the drive — exists to make that possible. Understanding the geometry explains most of the specification decisions that follow.
Key takeaways
- The chain runs continuously; carriers stop and accumulate above it through friction, a stop pin or a lift-and-shift unit.
- A 2.5× ratio between chain speed and carrier speed is the common standard, not a marketing number. It comes from the roller and sprocket geometry.
- Station pitch, carrier width and accumulation length decide the line length long before the drive does.
- Speed chain lines lose their advantage when products are heavy, dusty or need washdown. Roller or chain plate conveyors are usually better there.
How a speed chain line is built
The line has four mechanical layers. The chain runs in an aluminium or steel track and is driven by a sprocket at one end, with a take-up at the other. The carrier — sometimes called a pallet or fixture plate — sits above the chain on rollers. The rail carries the carrier's weight and keeps it aligned. The drive is a geared motor, usually with a variable-frequency drive so the line speed can be matched to takt time.
The important detail is that the chain does not pull the carrier directly. It pushes a dog, a friction block or a pin, and the carrier moves because of that contact. When the carrier reaches a stop, the contact slips or disengages, and the chain continues underneath. That is accumulation, and it is the reason a speed chain line can serve stations with different cycle times.
Where the 2.5× ratio comes from
The ratio is geometric. The carrier runs on rollers whose diameter is larger than the chain sprocket pitch circle, so for every metre of chain travel the carrier advances roughly 2.5 metres. A chain speed of 8 m/min therefore gives a carrier speed of about 20 m/min. The exact ratio depends on the roller diameter and the chain pitch used by the manufacturer, and it should be confirmed on the drawing rather than assumed.
| Chain speed | Carrier speed at 2.5× | Typical use |
|---|---|---|
| 4 m/min | 10 m/min | Long dwell stations, heavy fixtures, manual assembly |
| 6 m/min | 15 m/min | General electronics and appliance assembly |
| 8 m/min | 20 m/min | Short cycle times, high station density |
| 10 m/min | 25 m/min | Testing and inspection lines with light carriers |
The ratio matters because it decouples two numbers that are often confused. The chain speed sets the mechanical wear rate and the noise level. The carrier speed sets the transfer time between stations. A line can have a fast carrier and a slow chain, which is exactly what a 12-second takt with short transfers needs.
Free accumulation versus controlled accumulation
Free accumulation lets carriers queue against each other with a low contact force. It is simple and cheap, but the queue pressure adds up: ten carriers pushing on the first stop can create enough force to mark soft products or overload a light fixture. Controlled accumulation uses individual stops, usually pneumatic, with a sensor at each zone. The carrier stops at its own stop and never touches the one behind it.
For electronics, controlled accumulation is usually the right choice because the carriers often carry exposed assemblies. For metal parts or empty pallets, free accumulation is adequate and costs less. A mixed line can use controlled accumulation at critical stations and free accumulation in buffer sections.
Station pitch and carrier size
Station pitch is the distance between carrier centres at rest. It is set by the largest fixture, the operator's working envelope and the number of stations. A common mistake is to size the pitch from the product and forget the fixture: a 300 mm product may sit on a 500 mm carrier with a 100 mm gap, giving a 600 mm pitch. Multiply that by 14 stations and the line is 8.4 metres before the infeed and outfeed are added.
Carrier width should leave room for the fixture, the product, any test probe and the operator's hands. A carrier that is too narrow forces the fixture to overhang, which increases vibration and makes the line noisier. A carrier that is too wide wastes floor space and increases the moving mass, which in turn requires a larger drive.
Drive and tensioning
Most lines use a geared motor with a VFD. The drive must be sized for the starting torque of a fully loaded line, not the running torque. A line with 30 loaded carriers can need two to three times the running torque to start after a stop. If the drive is sized only from the running load, it will trip or stall on restart.
The take-up at the far end keeps the chain tension stable. A spring or weight take-up is preferable to a fixed adjustment because it compensates for thermal expansion and chain wear. Check the take-up travel at commissioning and mark the current position on the frame, so maintenance can see how much adjustment remains.
When a speed chain line is the wrong choice
Speed chain lines are poor at handling heavy products, abrasive dust, wet or oily environments and washdown areas. The chain track collects debris, and the accumulation mechanism relies on sliding contact that wears faster in those conditions. For pallets above roughly 100 kg, a powered roller line is usually more economical. For hot parts or parts that must drain, a chain plate conveyor is better. For cleanrooms, a belt or a covered roller line avoids the exposed chain entirely.
Frequently asked questions
Can a speed chain line run in both directions?
Yes, with a reversible drive and a symmetric stop arrangement. Reversing is common on lines that return empty carriers, but the accumulation logic has to be designed for it; a standard free-accumulation line will not reverse reliably without additional guides.
What is the maximum length of a single drive?
It depends on chain size and load, but as a working rule a single drive is comfortable up to about 30 metres of chain run. Beyond that, the chain tension and the starting torque become difficult to manage, and a second drive or a split line is usually cheaper than a heavy chain.
How much accumulation should a line have?
Enough to cover the longest station stoppage without starving the next station. A practical starting point is two to three carriers per station for a manual line, and one to two for a fully automatic line with short cycle times.
If you are comparing a speed chain line with a roller line, send the product drawing and the target rate to our engineers through the contact page. We will tell you which configuration fits, and which one does not.
