Pumps, valves, probes, fittings, tubing and sensing components for precise sample preparation, reagent handling and instrument fluidics.
Diaphragm Pumps for Thermal and Auxiliary Liquid Circulation
Application guide · Circulation
Auxiliary circulation may maintain temperature, suspend a benign working liquid or refresh a non-measurement loop. Specify the loop's required flow at installed resistance and the temperature-uniformity or suspension result; do not select from reservoir volume alone.
Engineering example: a 500 mL loop targeted at three theoretical turnovers per minute requires 1.5 L/min, outside a 300–600 mL/min pump class. The design must reduce the turnover target, split the loop or select another pump architecture rather than extrapolate free-flow data.[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
Temperature-control liquid
Heat load, allowed gradient and loop resistance
Verify thermal result, not only circulation
Suspension support
Settling time, allowable shear and particle size
Confirm diaphragm/valve suitability
Auxiliary rinse loop
Exchange frequency and idle sanitation
Avoid stagnant branches
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
Turnover rate
installed flow ÷ loop volume
Only a starting indicator for mixing
Pressure loss
tubing + heat exchanger + valves + filter
Use actual temperature and viscosity
Continuous duty
hours/day, ambient and fluid temperature
Select motor and thermal margin
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
Fill and vent loop→Ramp circulation→Reach thermal or mixing stability→Monitor pressure and level→Handle bubbles or low level→Drain and sanitize
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
Temperature gradient remains
Flow too low or exchanger limitation
Measure inlet/outlet temperature and flow
Noise/cavitation
Excess suction loss or hot liquid
Improve inlet and reduce speed
Filter loading changes flow
Growing loop resistance
Trend pressure and define service limit
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
Installed flow
At minimum/normal/maximum loop resistance
Within target range
Process result
Temperature uniformity or suspension stability
Meets instrument criterion
Long run
Worst ambient and maintenance interval
No unacceptable heat, leak or degradation
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.
