How pinch valves work.
Central-pinch geometry, tubing selection, and where ARTēVA® belongs in single-use bioprocess against a diaphragm valve.
A pinch valve never touches the product. The flow path is a length of tubing, and the valve closes it from the outside. That makes the wetted path a consumable and the valve a piece of capital equipment.
The mechanism
A pinch valve closes flexible tubing by compressing it until the bore collapses on itself. In a central-pinch design the tubing is squeezed at one point from opposing sides, so the wall folds inward symmetrically and meets in the middle.
Because the closing force is applied to the outside of the tube, nothing in the valve is wetted. The product sees tubing and nothing else. Replace the tubing and you have replaced the entire flow path, with no cleaning and no cleaning validation.
ARTēVA® uses a reusable 316L stainless steel encapsulated pinch head. The head is the durable part and is rated for well over 10,000 cycles. The tubing is the disposable part.
Tubing selection is the whole decision
With a diaphragm valve the manufacturer controls the sealing element. With a pinch valve the sealing element is tubing that you specify and that a tubing vendor validates. Get it wrong and the valve does not close.
ARTēVA® takes unbraided silicone or TPE as the standard specification, in inside diameters from ⅛″ to 1″.
A braid or reinforcing layer exists to stop the tube collapsing under pressure. Collapsing the tube is exactly what a pinch valve does for a living, so the two are working against each other. That is a real tension, and it is why reinforced tubing is a conversation rather than a checkbox.
It is not a blanket no. Whether a given tube closes reliably depends on the construction, not on the word braided, so the useful answer is to test the specific tubing rather than reason from the category. Send a sample. Double-braid is the one that has given us trouble.
Worth being honest about the alternative: if the line pressure is high enough to need heavy reinforcement, a diaphragm valve is usually the better tool, and a supplier who sells you a pinch valve without saying so is not doing you a favour.
Wall thickness follows from the inside and outside diameters, which is why the ARTēVA® order code carries both. The four digits either side of the X are the tube inside and outside diameter in thousandths of an inch.
The tubing is validated by its vendor, not by whoever made the valve. Before a pinch valve goes into a GMP line you want four things on file from the tubing manufacturer: USP Class VI status, an ISO 10993 biological evaluation where the application calls for one, extractables and leachables data against your actual process fluid, and the validated gamma dose if the assembly is irradiated. A valve supplier can tell you what the valve will close on. Only the tubing maker can tell you what the tube does to your product.
Actuation
| Code | Actuation | Typical use |
|---|---|---|
| 16 | Manual | Bench work, manual sampling, low cycle counts |
| 19 | Pneumatic | Skid-mounted, interlocked with plant air |
| 19E | eMaxion™ electric | Automated skids needing position control |
The three heads look nothing alike in service, which matters when someone is identifying a valve on a skid from a photograph rather than a part number.
Pinch or diaphragm?
They are not competing for the same job. The question is whether the flow path is a consumable.
| Diaphragm | Pinch | |
|---|---|---|
| Wetted path | 316L body plus diaphragm | Tubing only |
| Changeover | Clean and validate in place | Replace the tubing |
| Consumable | Diaphragm | The whole flow path |
| Pressure capability | Set by body and diaphragm | Set by the tubing |
| Best suited to | Multi-use, CIP and SIP lines | Single-use, frequent product changeover |
In practice: if the line is cleaned and reused, a diaphragm valve is almost always right. If the line is a single-use assembly that gets discarded between batches, a pinch valve removes the cleaning step entirely, and the cleaning step is usually the expensive part.
What to give engineering
A pinch valve enquiry is short, but two things are load-bearing.
- Tube inside and outside diameter. Not nominal size. The wall thickness determines the closing force.
- Tubing material, silicone or TPE, and confirmation that it is unbraided.
Everything else, actuation and any interlocking, follows from the skid design.
Build an ARTēVA® pinch valve
Tube inside and outside diameter, actuation, and tubing material. Three steps and a part number.
Open the configurator →