Start with the mechanism
An air-operated double-diaphragm pump uses compressed air to move diaphragms that displace liquid through check valves. A pressure-vessel system instead pressurizes a batch of liquid in a vessel and switches process valves to fill and discharge it. An airlift arrangement injects gas into a rising liquid column, using the density difference to promote flow. These mechanisms have different installation requirements, flow characteristics and control strategies.
Why naming matters in procurement
A request that only says air pump may lead suppliers toward the wrong equipment. Specify pneumatic pressure-vessel liquid transfer system when asking about the SINOSEN package. State whether a complete skid is required, including product valves, control cabinet, air treatment, receiver interfaces and commissioning support. Dry-powder pneumatic conveying is another field and should not be inferred from the word pneumatic.
Compare utilities on the same basis
Do not compare the electrical load of a control cabinet with the motor rating of a complete mechanical pump. The compressor energy supplying the pneumatic system belongs in the comparison. Similarly, a diaphragm-pump flow curve is not a capacity curve for a pressure-vessel system. A vessel arrangement needs a cycle calculation using usable liquid volume, fill time, transfer time and transitions.
A useful specification sentence
Describe the required outcome in measurable terms: transfer a named liquid from an identified source tank to an identified receiver, at an agreed average rate and acceptable flow variation, under stated temperature and pressure conditions. Then ask each supplier to identify its mechanism and battery limits. This makes commercial comparisons much clearer and reduces the chance of purchasing a pump without the surrounding equipment needed to operate it.
General engineering guidance. Numerical examples are illustrative; project specifications and acceptance criteria are agreed for the actual duty.