When choosing between piston‑type compressors and diaphragm compressors, there is often debate over which is better. While manufacturers of oil‑free piston compressors claim their products are superior, diaphragm compressor manufacturers argue that their technology offers a better solution. The reality, however, is that there is no clear‑cut answer.

The right selection depends on a range of factors, including: ‑ The gas to be compressed; ‑ Required operating pressure; ‑ Required volumetric capacity; ‑ Clean‑liness requirements for the compressed gas (acceptability of oil / oil vapor).

In this article, we will take an in‑depth look at these factors to help you determine which compressor is best suited for your requirements.

Fig. 1 illustrates the application suitability of compressors in terms of operating pressure and capacity according to their types.

The figure above shows that a wide range of capacities and operating pressures can be covered. Nevertheless, piston‑type compressors are the preferred choice for high operating pressures above 15 bar and high‑capacity applications above 15 bar, whereas diaphragm compressors represent the only option for certain higher operating pressures. The overlapping area in the diagram of Fig. 1 indicates the range where both types are applicable, and more specific selection factors come into play within this zone.

The main similarity between diaphragm compressors and piston‑type compressors is that both feature an oil‑filled crankcase housing the crank‑linkage mechanism (CKM). In addition, the number of rods and pistons in both compressors corresponds to the number of compression stages of the compressor. Apart from these common features, however, the two compressor types differ in design and operation. Their further differences are summarized in the table below.

This additional information is also essential for your selection.

Diaphragm compressors are well‑suited for compressing clean / ultra‑pure / toxic gases, where even the slightest contact with oil vapor inside the compression chamber is unacceptable.

Diaphragm compressors can handle any inlet pressure, while piston‑type compressors have limitations in this respect.

For diaphragm compressors, the gas to be compressed must be dry and moisture‑free to prevent accelerated wear and premature failure.

Diaphragm compressors are larger and more costly than reciprocating compressors of comparable characteristics.

Diaphragm compressors are recommended for compressing expensive, rare and pure gases, so as to avoid substantial losses caused by contaminants and oil vapor.