Rotary Valve Selection Guide: From Fluid Paths to System Validation
Start rotary valve selection with the fluidic task and connections at each position. Check media, pressure, bore, fittings and control, then validate liquid replacement and operation in the complete system. Equal port counts do not imply equal functions, and normal valve movement does not establish acceptable outlet liquid or analytical results.
An unsuitable valve in automated reagent, sample or wash-liquid switching may cause too few connections, slower aspiration, longer replacement cycles or unstable first results after cleaning. The following development sequence converts these problems into selection criteria that can be checked.
01Step 1: define the function through flow-path states
Determine where liquid comes from, where it goes and which steps must occur simultaneously. Several bottles feeding one common path sequentially usually require selection. One supply feeding successive destinations requires checking distribution direction. Switching between complete circuits requires an appropriate multiport connection diagram.
| Process stage | Required source connection | Liquid destination | Program condition |
|---|---|---|---|
| Dispense A | A connected to COM | Target vessel | Meter after confirming selection |
| Clean the shared path | Wash solution connected to COM | Waste position | Confirm destination before pumping |
| Displace with B | B connected to COM | Waste position | Remove wash solution from the shared path |
| Dispense B | Maintain the B path | Target vessel | Meter after replacement criteria are met |
Count reagents, wash solution, calibration liquid and reserve connections together, and confirm whether COM is included in the nominal count. Independent simultaneous delivery requires additional system channels or valve assemblies; adding selection positions to one valve is insufficient.
For example, 8 working liquids, 1 wash solution and 1 calibration liquid require 10 selection ports. Adding 2 independent sources requires more than 10. A 16- or 24-channel option may be considered, but bore, fittings, space and actual replacement time must also be checked. This is a connection-count design example, not a validated instrument result.
A valve that dead-ends unselected streams may be unsuitable when those streams must keep flowing. Whether they close, converge into another common outlet or remain separately flowing is a selection criterion independent of position count. Include these states in the fluidic diagram.
02Step 2: define media and pressure limits
List working, wash, disinfecting and storage liquids with composition, concentration, temperature and contact time. A general acid/alkali resistance description cannot establish reagent compatibility. Samples with particles, crystallization or adhesion also require assessment of blockage, wear and residue.
Assess pressure at the valve's actual location. Pump-inlet installation requires consideration of suction pressure and air ingress; outlet installation requires consideration of downstream resistance and backpressure. Switching and blockages may produce pressure states different from steady delivery. A positive-pressure rating does not establish vacuum sealing capability.
Confirm allowable operating pressure and switching conditions before deciding whether to stop the pump, relieve pressure or use another sequence. A pressure test does not define continuous service limits, and similar fittings do not qualify a reagent selector for high-pressure injection. Ask the supplier if dynamic switching conditions are unspecified.
03Step 3: compare bore, internal volume and replacement time together
Bore influences flow resistance; internal volume describes the liquid held by a particular passage. Smaller passages may retain less liquid but increase resistance. Selecting solely for minimum volume may reduce aspiration at the target flow or lengthen liquid replacement.
| Configuration | Selection channels | Bore | Valve internal volume | Threaded connection |
|---|---|---|---|---|
| MRV3-D10 | 10 | 1.2 mm | 15.8 μL | 1/4-28 UNF |
| MRV3-D16 | 16 | 1.0 mm | 10 μL | 1/4-28 UNF |
| MRV3-D24 | 24 | 0.5 mm | 2.9 μL | 6-40 UNF |
Moving from 10 to 16 channels increases connections but also changes bore and internal volume. The 24-channel configuration uses a different thread. A higher-channel model cannot therefore be assumed to be a drop-in replacement; recheck fittings, tubing and actual delivery performance.
Theoretical straight-tube volume V = π × internal diameter² × length ÷ 4
A circular tube with 0.8 mm internal diameter and 300 mm length has a theoretical volume of approximately 151 μL; 1 mm³ = 1 μL. This geometric example excludes the valve, pump chamber, fittings and needle.
Long shared tubing may hold more liquid than the valve itself. Account for the entire shared path before determining cleaning volume with actual-liquid tests. Theoretical volume divided by flow is only an ideal starting estimate, not the time needed to eliminate mixing, adsorption or carryover.
04Step 4: check fittings, installation and control timing
Check threads, flat or tapered sealing details, matching fittings, tube diameter and insertion depth. A thread that engages does not prove a compatible seal. Allow room for tube bends, maintenance and head replacement, and avoid sustained tubing loads on the ports.
Confirm power supply, communication protocol, included driver, homing method and channel numbering. MRV3 documentation lists RS232/RS485 interfaces, but commands, returned status and fault handling must match the chosen driver protocol. The interface name alone does not establish direct compatibility.
- Establish conditionsManage pump and pressure as specified
- Select the pathCommand the target channel
- Confirm positionCheck homing and arrival status
- Displace and meterVerify delivery before routine operation
System cycle time includes valve movement, status confirmation, washing, displacement and metering. Adjacent-port switching time does not describe every channel pair or the complete replacement process. After power or communication loss, re-establish a trustworthy connection state to avoid pumping into the wrong channel.
05Step 5: validate suitability with a prototype
| Validation item | Suggested observations or measurements | Question to resolve |
|---|---|---|
| Connections and positioning | Actual liquid destination for each channel, after homing and restart | Does software numbering consistently identify the correct connection? |
| Sealing and delivery | External leakage, cross-port leakage, inlet bubbles, target flow and pressure | Is the required delivery maintained under installed conditions? |
| Replacement and residue | First result after switching, successive results and blanks | Do washing and displacement meet the allowable residue level? |
| Operational stability | Actual switching cycles and restart after shutdown | Do wear, crystallization, sticking or result drift occur? |
Acceptance thresholds, such as residue, volume error and cycle time, should follow the instrument's purpose and analytical method rather than a universal pass-cycle count. Record the exact model, wetted materials, liquid batch, tubing and operating conditions so that validity can be reassessed when the configuration changes.
06What information should a selection request include?
- Fluidic diagram and state table: sources, destinations, connections at each step and simultaneous-operation needs.
- Media list: composition, concentration, temperature, contact time and particles for reagents, samples, cleaning and storage liquids.
- Delivery conditions: flow, dispense volume, aspiration, backpressure, tube diameter and length, and allowable residue.
- Integration needs: reserve channels, fittings, space, power and communication, switching frequency, operating duration and fault states.
FOREACH can use these conditions to assess candidate MRV3 configurations. The links compare available channels, bores and fittings. Confirm head materials, drivers and nonstandard combinations against the actual order; validate performance in the installed system.
07Rotary valve selection FAQs
Are more channels always better?
Meet actual connection needs and necessary reserves first, then compare bore, fittings, space and control. More channels may change internal passages and connections. They do not automatically increase throughput or enable independent simultaneous metering.
Does smaller internal volume always mean less carryover?
Smaller internal volume only means less liquid in a specified internal path. System carryover also depends on shared tubing, adsorption, wash liquid, displacement and the analytical method. Measure it with actual liquids.
Can an existing valve be replaced by checking port count alone?
Compare connection diagrams, bore, pressure and switching conditions, wetted materials, sealing details, installation, power and control protocol. Validate numbering and the complete replacement process. Equal port counts do not establish direct interchangeability.