Choosing the Right Compressor: Avoid Oversizing

Learn which factors are important when sizing a compressor and how to choose the right compressor

Anyone selecting a compressor will eventually face the same question: What size compressor do I need? As a precaution, many users choose a larger model than necessary. After all, the compressed air supply should remain reliable even if additional equipment is added or operating requirements change in the future.

A reasonable performance reserve is advisable. However, the right compressor size should be based on the actual operating profile rather than the maximum theoretical demand.

Compressor Size Should Be Based on the Application

Several factors need to be considered when selecting a compressor. In addition to the required operating pressure, the required flow rate is one of the most important criteria – in other words, the volume of compressed air the compressor must deliver within a given period of time.

It is equally important to determine whether compressed air is required continuously or only intermittently. The number of consumers operating simultaneously, the required air quality and any planned future expansion should also be taken into account during the sizing process. Only by considering all of these factors together can the correct compressor size be determined.

Actual Operating Conditions Matter More Than Theoretical Peak Demand

When planning a compressed air system, it is common practice to add together the air consumption of every connected device. In reality, however, many tools, pneumatic cylinders and valves do not operate simultaneously. Individual processes often run at different times or require compressed air only for short periods.

For this reason, it is not the theoretical maximum demand that matters most, but the application's actual operating profile. Understanding which consumers operate simultaneously and how long they require compressed air makes it possible to determine the required flow rate far more accurately.

What Information Is Required for Correct Compressor Sizing?

Before selecting a compressor, the following questions should be answered:

• What flow rate is required?
• What operating pressure is required?
• Which consumers operate simultaneously?
• Will the compressor operate continuously or only intermittently?
• What air quality is required?
• Are any future system expansions already planned?

The more accurately these questions can be answered, the easier it becomes to determine the correct compressor size.

A Performance Reserve Can Be Beneficial

A performance reserve is often included to allow for future expansion or occasional peak demand. However, there is no universal rule for determining how large this reserve should be. The appropriate capacity margin depends on the specific application and any realistic plans for future growth.

An excessively large safety margin does not automatically result in a better compressed air supply. At the same time, the compressor should provide sufficient reserve capacity to ensure reliable operation as requirements evolve.

The Compressor Is Only One Part of the System

An efficient compressed air supply depends on more than just the compressor itself. Air receivers, pipework, filters and dryers also have a significant influence on the overall performance of the system.

Likewise, increasing the operating pressure cannot compensate for insufficient flow rate. For this reason, the entire compressed air system should be considered rather than focusing solely on compressor performance.

The Right Compressor Size Reduces Long-Term Costs

A compressor that is too small may reach its performance limits and compromise the compressed air supply. On the other hand, an oversized compressor often leads to unnecessary investment costs and occupies more installation space than required.

The correct compressor size is therefore determined not by an excessive safety margin, but by carefully assessing the actual requirements of the application.

For decades, Dürr Technik has been developing oil-free compressors and compressor systems for applications where clean compressed air, exceptional reliability and continuous operation are essential. The portfolio ranges from compact compressor units for laboratory and OEM applications to powerful compressors and complete compressor systems for industrial, energy and other demanding continuous-duty applications.

A wide range of product series and system configurations is available for different applications and performance requirements. The Dürr Technik Product Finder allows users to quickly filter and compare compressors and compressor systems by flow rate, pressure or supply voltage, making it easy to identify the solution that best matches their application.