Collared tubing is described in shorthand that makes perfect sense once someone explains it, and absolutely none before that. Here's the whole system.
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What the collars actually do
The collars (also called stops or bridges) sit at fixed distances along the tube and lock it into the pump cassette or tension arm. They stop the tubing from creeping through the rollers as it's compressed, which keeps flow rate stable over hours of operation. No collars, no positional control, and your flow rate drifts as the tube walks.
The pump design fixes the collar spacing. That is why tubing isn't interchangeable between pump families, even at the same I.D.
2-bridge vs 3-bridge
Two bridges means two collars, one on either side of the pump head. This is the common configuration for single-channel and analytical pump heads, including most ICP autosampler pumps.
Three bridges means an additional centre collar. Cassette-style multichannel pumps require three-bridge tubing, where the centre stop registers the tube in the cassette body. If your pump takes 3-bridge and you fit 2-bridge, the tube will not seat, and if you force it, you'll get inconsistent occlusion and a flow rate that means nothing.
Check your pump head, not your last order. Both configurations are stocked across the range.
The colour code
The bridge colours are an industry-standard identification system for internal diameter. They are not decorative, and they are not manufacturer-specific: orange/black is 0.13mm on any brand of collared tubing, and violet/white is 2.79mm.
The full sequence runs from orange/black (0.13mm) at the fine end, through orange/orange (0.89mm), red/red (1.14mm) and blue/blue (1.65mm), up to black/white (3.18mm). Three-bridge tubing repeats the outer colour on both ends: orange/yellow/orange is the 3-bridge equivalent of 2-bridge orange/yellow at 0.51mm.
The practical upshot: you can identify any tube in your lab by looking at the collars. Which means you can reorder correctly without hunting for a part number, and you can spot a wrong tube fitted to a channel from across the bench.
Choosing the I.D.
Flow rate through a peristaltic pump depends on bore and roller speed. Bigger bore, more volume per revolution. In practice:
- 0.13mm to 0.38mm for low-flow nebuliser feeds and micro-sampling
- 0.51mm to 1.02mm for standard ICP-OES and ICP-MS sample uptake
- 1.14mm to 1.85mm for drain lines, autoanalyser reagent delivery and general transfer
- 2.06mm to 3.18mm for waste, high-volume transfer and bulk reagent lines
A common mistake is over-sizing the drain line on an ICP spray chamber. Too much bore and the chamber doesn't drain smoothly, which shows up as a noisy signal. The drain tube is usually the wider one for a reason, but wider is not always better.
Flared ends and length options
Some grades come with flared ends, which provide a more secure connection to rigid 1/16" and 1/8" O.D. lines and reduce the chance of a tube pulling off a barb mid-run. Long-length options exist where the pump sits further from the sample tray than standard tubing allows. Both are worth knowing about before you improvise with cable ties.
Ordering without guesswork
You need three pieces of information: material, bridge count, and I.D. (or the bridge colours, which tell you the I.D.). That's it. Every product in the collared tubing range can be filtered by those three attributes.
If you're unsure what your pump takes, please tell us the pump model, and we'll tell you the tubing. We've been supplying chromatography and ICP consumables for over 25 years, so it's a short conversation.
Filter the range by material, bridge count and I.D., or call the technical team on +44 (0)1925 599070.
Browse the full collared tubing range or request a free sample.