A silicone tube can meet its specified inside diameter, outside diameter and wall thickness when straight yet still flatten, fold or kink after installation. The result depends on the complete routing system: tube construction, bend geometry, connection points, nearby hardware, pressure conditions and the way operators assemble the line. A useful RFQ therefore describes the actual route instead of asking a supplier for one universal silicone tubing bend radius.
The purpose of this review is to help engineering and procurement teams provide enough evidence for a project-specific discussion. It does not replace prototype installation, flow testing or validation in the intended equipment.
Show the installed route, not only the tube dimensions
Start with a drawing or marked photograph that identifies the tube path from one connection to the other. Include the position and orientation of fittings, clamps, guides, moving parts, covers and nearby edges. State whether the route is fixed or whether it changes during assembly, cleaning, maintenance or normal machine movement.
Give the available envelope around each turn. A centerline path is useful, but the supplier also needs to know where the tube may contact a panel or component. If the route passes through a hole, slot or bulkhead, provide its size, edge treatment and alignment relative to the fittings.
Record the nominal straight length and the installed distance between connections. Excess length can create an unintended loop, while insufficient length can pull the tube sideways at a fitting and tighten a bend. State how length is measured and whether tolerances apply to the cut tube, assembled line or both.
Describe each critical bend
Identify the bends most likely to control the design. For each one, provide the approximate bend angle, available radius or envelope and distance from the nearest fitting, clamp or restraint. A scaled drawing is preferable to a single radius value because two routes with the same nominal radius may load the tube differently.
Avoid treating a catalog bend figure as an assured property for every condition. Kink behavior may change with wall thickness, diameter ratio, hardness, reinforcement, temperature, internal pressure, vacuum, aging and installation technique. The acceptable result also depends on how much change in flow area the equipment can tolerate.
If a current assembly has failed, mark the exact location and direction of the kink. Share photographs of the tube both installed and removed. Note whether the condition appears immediately, only after the equipment warms up, after repeated movement or after maintenance.
Define the tubing construction and material basis
Provide the required inside diameter, outside diameter or wall thickness, including tolerances and measurement condition. State whether the line is unreinforced, braided, fabric reinforced or another construction. If the supplier may recommend an alternative wall or construction, distinguish negotiable features from fixed interface requirements.
Specify the material family, hardness target, color and any project documents that require review. Service-fluid compatibility and market documentation should be evaluated for the particular formulation and application; the word silicone alone does not establish suitability.
Use the Silicone Tubing page to organize the dimensional and construction questions, then include the controlled drawing and application notes with the RFQ.
Explain pressure, vacuum and flow conditions
State whether the tube operates under positive pressure, vacuum, gravity flow or intermittent flow. Provide the normal and maximum project conditions, including temperature and relevant start-up or cleaning states. Under vacuum, a route that appears stable when unpressurized may flatten differently; under pressure, movement or expansion may alter how the tube contacts restraints.
Describe the conveyed fluid or gas at the level needed for material and safety review. Include viscosity, particulates or pulsing conditions when they affect flow or bending behavior. Do not ask the supplier to infer these conditions from the machine name alone.
Define the functional concern. It may be complete blockage, a permitted reduction in flow area, unstable delivery, visible folding, excessive load on a fitting or repeatability after cycling. A measurable project criterion gives the sample review a clearer basis than the instruction “must not kink.”
Include fittings, clamps and assembly method
Connection geometry can control the first bend. Provide fitting type, barb or stem dimensions, insertion depth, clamp location and the free straight length available before the tube turns. Identify swiveling or rotating connectors and whether their orientation is controlled during assembly.
Show every clip, tie, channel or sleeve that locates the tube. State its contact width and whether it grips, guides or protects the line. A restraint placed too close to a turn can concentrate deformation, while an uncontrolled guide may allow the route to shift into a smaller radius.
Describe how the line is installed: pushed over fittings before routing, routed before final connection, supplied as a preassembled set or cut and fitted at the machine. Note any tools, lubricants or temporary bending steps. Assembly variation should be considered when samples are reviewed.
Plan representative samples and checks
For a critical route, request enough tubing to build the actual assembly or a dimensionally representative fixture. Label samples by material, size, construction and lot or build reference. If alternatives are compared, keep their identifiers and installation method separate.
Record the installed shape at room condition and at the relevant project states. Depending on the application, checks may include visual folding, minimum cross-section, pressure drop, flow stability, vacuum response, connection load or movement cycles. The buyer and supplier should agree the method, equipment and acceptance basis rather than assume a universal test.
Photographs and videos can document the route, but dimensional records and controlled sample labels remain important. The approval should state which geometry, fittings, conditions and installation method were evaluated. It should not be treated as a service-life guarantee for other routing configurations.
Prepare the RFQ package
A practical package combines the tubing dimensions and tolerances, material and construction basis, route drawing, critical-bend details, fitting data, restraints, pressure or vacuum conditions, temperature range, conveyed medium, assembly method, sample quantity and proposed checks. List open questions and identify which interfaces cannot change.
If space is still being designed, provide more than one routing envelope and explain the tradeoffs available to the equipment team. The supplier can then comment on options without presenting one bend-radius number as a blanket promise.
To request a project-specific review, submit the drawing, routing photos, connection details, operating context and validation needs through the Forvard Tech RFQ form.