Before replacing CIJ fluid tubing, confirm the installed reference, outside and inside diameters, material, fluid service, fitting interface and required length. A tube that looks the same or fits into a connector is not automatically suitable for the printer's ink, make-up fluid or operating conditions.
This guide helps maintenance buyers prepare a replacement request for continuous inkjet (CIJ) equipment. It is general procurement guidance, not an installation procedure or confirmation of compatibility.
Identify the line, not just the loose tube
Record where both ends connect and what the line carries. Distinguish ink supply, make-up supply, return and other circuits using the equipment documentation. Colour alone is not a reliable identifier. Take an overview photograph before collecting close-ups of the ends, supports and any printed markings.
If leakage prompted the request, record its observed location and the recent service history. Fluid on a tube does not establish that the tube wall is the source; an adjacent fitting or component may need investigation. Follow the applicable shutdown, isolation and fluid-handling procedure before access. Do not disconnect a pressurized line to identify its size.
OD and ID answer different questions
Outside diameter (OD) describes the tube's external size. Inside diameter (ID) describes the bore. Wall thickness links the two, but a single diameter does not fully specify a replacement. Confirm the dimensional convention and units on the drawing or supplier quotation rather than assuming which number comes first.
| Item to confirm | Evidence to send | Ordering mistake to avoid |
|---|---|---|
| OD, ID and units | Installed reference, approved drawing or measurements taken safely by a qualified person | Rounding an inch size to a nearby metric size |
| Material and grade | Equipment specification and tube markings where available | Identifying a polymer from colour or transparency |
| Fluid service | Exact ink, make-up and cleaning-fluid references relevant to the line | Assuming a material is suitable for every solvent |
| End connections | Photographs and references for each fitting and retained component | Ordering by thread appearance or tube diameter alone |
| Length and routing | Documented length, route and support arrangement | Using a shorter route that changes the intended installation |
Keep material and operating requirements together
Ask the supplier to confirm the specified tube material for the actual fluid combination and equipment application. A generic description such as clear plastic or solvent-resistant is insufficient. The required temperature range and pressure or vacuum service also belong in the compatibility review; this guide does not assign universal limits.
Do not choose a substitute solely because it is more flexible or has a familiar material name. Confirm that it meets the equipment's documented requirements and works with the specified fittings. Unknown material should remain an open verification item, not become an assumed match on the purchase order.
Check what the fitting actually requires
A replacement request should identify the connection design at both ends and whether sleeves, ferrules, seals or other components are included. Not every connection uses the same components. Ask which items may be retained and which must be replaced under the applicable service instructions.
If a threaded adapter is also required, confirm its thread designation and sealing arrangement separately. Do not force together similar-looking connections or add sealant on the basis of this guide. Assembly method, tightening and any specified leak test belong to the approved procedure.
Receive the correct scope before installation
Specify whether you need bulk tubing, a cut length or a complete prepared assembly. Record included fittings and quantities explicitly. At receipt, compare the supplied label and dimensions with the approved order, check visible condition and keep the ends protected from contamination. Escalate mismatches before installation.
After authorized service, record the fitted reference and follow the equipment's acceptance checks. A dry connection observed briefly at idle is not a substitute for the specified verification under the required operating conditions.
Frequently asked questions
Can I identify tube material from a photograph?
No. A photograph helps show routing, markings and connection geometry, but it does not establish polymer grade or fluid compatibility.
Is the same outside diameter enough?
No. Confirm the bore, material, operating requirements and fitting compatibility as well as OD.
What if the old tube has no readable reference?
Send the printer and fluid-system revision, both connection points, photographs and known fluid references. Ask for a documented identification before accepting a substitute.
Request a tubing compatibility review with the installed reference, line function, OD and ID with units, material evidence, fitting photographs and required quantity. Use the compatibility and ordering guide to organize missing information.