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Start with the chemical and the complete duty
An AODD pump can be a strong fit for chemical transfer because it is a compressed-air-driven positive-displacement pump with no rotating shaft seal in the liquid path. That does not make every AODD configuration suitable for every chemical. Start with the actual fluid identity, concentration, operating and cleaning temperatures, viscosity, solids, required flow, discharge pressure and suction conditions. If the fluid is a blend, provide the full composition or SDS information rather than checking each ingredient independently. The selection should be based on the worst credible operating condition, not only the normal batch condition.
Check every wetted material, not just the pump body
Chemical compatibility must be reviewed across the complete wetted path. For an AODD pump this commonly includes liquid chambers and manifolds, diaphragms, valve balls, valve seats and sealing elements. Wilden's chemical compatibility guide explicitly notes that chart ratings are an information source rather than a guarantee, and that diaphragm life also depends on process conditions such as temperature, abrasiveness, media and lift conditions. Record any unknown material as an item to confirm before quotation. Cleaning or flushing chemicals must be included because they can be more aggressive than the process liquid.
Select flow and pressure from the real operating point
Do not size the pump from a maximum flow number alone. The required flow must be considered together with discharge pressure, available air pressure and available air volume. Wilden's AODD operating principle explains that both air pressure and air volume are needed to produce the required liquid flow. Line losses, filters, valves, elevation changes and downstream equipment all affect the duty. A practical selection should leave operating margin and should be checked against the performance curve for the exact pump configuration rather than against a family-level maximum.
Treat suction conditions and viscosity as part of the sizing problem
AODD pumps can self-prime, but suction performance still depends on the actual installation. Long suction lines, small pipe diameters, restrictions, high viscosity, low tank level and vapor pressure can reduce filling of the liquid chambers. For viscous chemicals, the pump may need to run more slowly so the chambers can fill completely. For solids or crystals, provide particle size, concentration and whether the solids are hard, abrasive or prone to settling. Suction piping should be reviewed for air leaks because even a small leak can reduce delivered flow without showing an external liquid leak.
Avoid the common selection shortcuts
Common mistakes include choosing only by port size, copying the body material from an old pump, assuming PTFE automatically solves every compatibility problem, or selecting the smallest pump that can reach the target flow at its published maximum. Another mistake is omitting the compressed-air system from the review. A pump can be correctly sized hydraulically but still underperform if the air line, regulator, filter or compressor cannot provide the required air volume at pressure. For a replacement, send the old pump's full model and item number, but also explain why it is being replaced so the same failure mode is not repeated.
Frequently asked questions
What information should I send for a chemical-transfer AODD pump selection?
Send the fluid name or SDS, concentration, process and cleaning temperatures, viscosity, solids, required flow, discharge pressure, suction conditions, connection standard, air supply and installation details.
Is a chemical compatibility chart enough to approve the pump materials?
No. It is a screening tool. The final review should consider concentration, temperature, exposure time, abrasiveness, cleaning chemistry and every wetted component in the actual configuration.
Should I choose an AODD pump by maximum flow?
No. Use the required operating point and check it against the exact pump curve together with air pressure, air volume and system losses. Maximum catalog values are not a recommended continuous operating point.
Can DFIN help match a WILDEN configuration to an existing pump?
Yes. Send the complete WILDEN item number and model, nameplate photos, the current duty and any repeated failure or maintenance history so the replacement can be reviewed against the actual service.
Related DFIN pages
Technical references
Prepared by the DFIN editorial team as practical identification, selection and maintenance guidance. Confirm the exact product configuration and service procedure before ordering or maintenance.