Pumps, valves, probes, fittings, tubing and sensing components for precise sample preparation, reagent handling and instrument fluidics.
Dual Valveless Pumps for Proportional Liquid Preparation
Application guide · Proportioning
Two valveless pump heads can prepare a continuous or repeated mixture when each stream has an independently defined displacement and speed. The target ratio must be verified from the collected mixture because density, pressure and slip can make two theoretical flow calculations diverge.
Engineering example: a 1:9 mixture at 10 mL/min total requires 1 mL/min concentrate and 9 mL/min diluent. If the concentrate channel is actually 1.05 mL/min and diluent remains 9 mL/min, the concentrate fraction becomes about 10.45%, not 10.00%.[1][2]
01Define the liquid, receiver and complete duty before selecting the component
Translate the analytical task into an engineering duty
Use case
Inputs to define
Decision supported
Buffer concentrate + water
Target ratio, total flow and acceptable composition
Select each head near a stable work point
Two-reagent working solution
Compatibility before mixing and usable lifetime
Mix only when the method permits
Gradient or changing ratio
Time profile and transition volume
Independent drives and feedback may be required
02Calculate the working point and the margin the instrument really needs
Calculations to complete before prototype selection
Quantity
How to define it
Why it matters
Channel targets
total flow × each volume fraction
Select displacement and rpm separately
Ratio error
actual channel flow ÷ actual total flow
Measure both or analyse mixed concentration
Mixer volume
volume ÷ total flow
Sets delay between command and composition
Use minimum, routine and maximum conditions rather than one nominal point. Include the first cycle after priming or idle, the lowest source level, the highest expected restriction and the actual receiving geometry. A nominal capacity, free-flow value or theoretical command increment is not an acceptance result.
03Map the task to a FOREACH configuration and the rest of the fluid path
04Program the full liquid cycle, including prime, wash and recovery
Prime channels separately→Establish each flow→Combine at defined junction→Mix through known volume→Verify composition→Flush incompatible residues
A complete method cycle is more than the active delivery step
The exact physical order and parallel actions depend on the instrument. Retain each state in the control and verification plan.
Record valve states, motion, dwell, sensor windows and rejected recovery cycles. This makes throughput and liquid consumption auditable and prevents a fast component movement from being reported as the complete analyzer cycle.
05Design abnormal-state diagnosis before the fault occurs
Observed result, likely mechanism and useful next action
Observed condition
Likely mechanism
Engineering response
Ratio changes with pressure
Unequal downstream loads
Balance restrictions or control channels independently
Correct outlet flows, wrong assay
Incomplete mixing or chemical interaction
Change mixer/contact time
Start-up slug off ratio
Channels reach steady state at different times
Divert to waste until stable
The controller should distinguish a recoverable event from a result-invalidating event. A retry is useful only after the original cause has been removed and the liquid path has returned to a verified state.
06Accept performance where the liquid is actually used
Minimum qualification plan for the integrated channel
Result
Where or how to measure
Acceptance question
Individual flow
Collect each channel before mixer
Matches channel target
Mixed composition
Conductivity, tracer or applicable assay
Meets ratio across run
Transition
Start, ratio change and stop
Off-spec volume is known and diverted
Test the exact liquid and complete wetted path at minimum, routine and maximum conditions.
Separate first-cycle, steady-state and post-idle results; do not average away recovery behavior.
Challenge the relevant fault and confirm the controller prevents an invalid result from being accepted.
Retain the configuration, software sequence, consumables and receiving-position result together as the qualification record.
