The QBY pneumatic diaphragm pump is driven by compressed air and uses the reciprocating motion of the diaphragm within the sealed chamber to transport fluids. It has no rotating seals, no packing boxes, and no risk of electrical sparks, making it ideal for transporting chemicals, sludge, solvents, and even shear-sensitive liquids – the latter can often render centrifugal pumps unusable within just a few weeks.

Working principle

The pump body consists of two flexible diaphragms connected by a connecting rod. Compressed air pushes one diaphragm forward, discharging the liquid; at the same time, the other diaphragm moves backward, drawing in the liquid. The air valve switches the direction of the airflow, creating a stable reciprocating cycle. The flow rate can be easily controlled by adjusting the pressure of the air source: reducing the air volume lowers the pump speed, and increasing the air volume increases the output. Even if the outlet valve is closed, the pump will smoothly stop running without damage. Once the valve is opened, it will automatically resume operation.

Material Matching

The key to the material selection for the QBY pump lies in its compatibility with the liquid. Common diaphragm materials: chloroprene rubber (suitable for water-based liquids and mild chemicals), nitrile rubber (resistant to oil and petroleum-based liquids), fluororubber (resistant to strong solvents and high temperatures), polytetrafluoroethylene composite membrane (nearly completely resistant to chemical corrosion, with the backing layer ensuring flexibility). The pump body material includes cast iron, aluminum alloy, stainless steel, and engineering plastics. Choosing the right material can prevent diaphragm swelling, hardening, or delamination, and also prevent fluid contamination.

Typical Applications

Chemical transportation: Transporting acids, bases, and solvents from barrels and tanks to reaction vessels, without requiring the power source to be close to the wet end.

Wastewater and sump pit cleaning: Dealing with dirty water and slurry containing solids, without causing blockage or wear and tear.

Coating and ink circulation: Low shear transfer of solvent-based or water-based coatings without disrupting pigment dispersion

Ceramic glaze supply: Conveys abrasive slurry without rotational seal wear, and can be shut down and restarted at any time.

Oil and fuel transportation: Safely transport diesel, lubricating oil, etc., avoiding the risk of electrical pump ignition.

Printing and packaging: Stable supply of low and medium viscosity adhesives and varnish.

In addition, this pump can run without load for a short period without being damaged, and it can be shut down under pressure. It can also meet intermittent process requirements.

Selection and Installation

If the pump type is too large, it will waste the air source and increase pipeline pulsation; if it is too small, it will operate at high speed all day long, shortening the lifespan of the diaphragm. The selection should be based on the required flow rate and total head. The exhaust pressure can usually reach 8 bar. The intake needs to be equipped with a filter and an oil-water separator to prevent dirty and wet air from causing the air valve to get stuck. The inlet pipeline should not be too thin or bent to avoid cavitation on the suction side – during cavitation, the pump chamber emits a gravel-like sound, which will quickly damage the diaphragm. If the process requires pulsation-free transportation, a pulse damping device can be added at the outlet.

Maintenance Points

Most of the shutdown failures originate from the air valve part. Dust or condensate water in the compressed air will contaminate the valve core, causing abnormal pump operation. Just add a filter and separator upstream of the air source and drain regularly to avoid this. The diaphragm replacement cycle depends on the medium, temperature and operating speed. Prepare a set of diaphragm maintenance kit and schedule planned shutdowns for replacement. During replacement, check the torque of the diaphragm bolt and the wear of the inner wall of the chamber. In addition, wear of the ball valve and valve seat can lead to internal leakage and a decrease in flow – if the pump operates normally but the output decreases, check the check valve first.

Summary

The QBY pneumatic diaphragm pump lies between the simple hand pump and the complex metering pump. It is suitable for non-potable liquids, allows idle running, has no risk of electric sparks, does not cause damage under pressure, and does not require priming or restart with introduction of water. For fluids that would damage seals, jam the impeller, or generate dangerous steam, this pump is often the most suitable solution.