How Much Compressed Air Do You Really Need?
A Compressed Air System Sizing Guide
Many facilities don’t know how much compressed air they really need, which results in over- or undersizing their compressors. Selecting the right size air compressor for the needs of your facility is critical to performance, efficiency and cost-effective operation.
This industrial air compressor sizing guide will help you understand how to size your compressor to match your facility’s actual air demand so you can avoid unnecessary costs and ensure optimal performance and air compressor efficiency.
Size Matters! Why Choosing the Right Size Air Compressor is Critical
Compressed air is not free. It takes, on average, 1hp to generate 4.5 CFM of air, and 80% of that energy usage is lost to the heat of compression, making compressed air a crucial, but very expensive, plant utility.
Energy costs become even higher and performance is hindered when your air compressor is under- or oversized due to poor air compressor capacity planning.
The Hidden Costs of Undersized Compressors
When a compressor is undersized, air demand will exceed the ability of the compressor, resulting in declining plant pressure and possible equipment alarms and malfunctions, which can damage production equipment or disrupt processes, potentially causing costly downtime, repairs, and the production of faulty or low-quality products.
Undersized compressors may also experience premature failure. Reciprocating compressors may overheat, while rotary screw compressors are subject to damaging oil carryover due to low pressure.
The Hidden Costs of Oversized Compressors
Bigger is not always better. Not only will you pay more upfront for an oversized compressor, but when your unit is too big, it may result in costly maintenance and performance issues.
For example, oversized fixed-speed compressors will run at partial load, triggering short cycling – frequent starting and stopping – and causing electricity spikes, equipment wear and tear and premature failure.
Oversized variable speed compressors may experience degraded efficiency, short cycling, condensation issues, and heavy oil carryover in the compression chamber, increasing electricity and maintenance costs.
How to Size an Air Compressor Using a Compressed Air Demand Calculation
Accurate industrial air compressor sizing relies on a careful compressed air demand calculation. This means you’ll need to determine the air volume (CFM) and pressure (PSI) requirements for your facility.
Understanding CFM and PSI Air Compressor Ratings
- CFM, or cubic feet per minute, is the volume of air that an air compressor can provide at a given pressure.
- PSI, or pounds per square inch, measures air pressure, or the force that air is delivered.
CFM and PSI are not independent ratings. Together, CFM and PSI values determine how much air flows and at what force. This is why air compressors are always rated by the CFM output at a specific PSI, such as 100 CFM at 125 PSI.
How to Determine Your Actual Air Demand
When determining your actual air demand, it’s important to first differentiate between actual/average demand and peak demand. Actual demand is the volume of air (CFM) that is required during a normal, long-term operating cycle. Peak demand is the volume of air required during the busiest production time.
The following formula will help you determine what size compressor you need to satisfy your actual demand while still providing a cushion to cover peak demand periods.
Step 1: Calculate your CFM requirements.
- Identify equipment requirements: Find the manufacturer CFM specifications for each tool that will operate at the same time. (CFM requirements should be included in equipment manuals.)
- Total the CFM: Add the CFM of all the tools that will be used at the same time. This is your minimum CFM.
- Apply a safety margin: To account for leaks/pressure drops, peak air demand periods and future growth, multiply your minimum CFM by 1.5.
The CFM calculation for three tools with a 20 CFM rating looks like this:
(20 CFM + 20 CFM + 20 CFM) x 1.5 = 90 CFM
Step 2: Determine your PSI requirement.
- Find the equipment with the highest PSI requirement: No calculations are needed. Simply identify the tool or machine with the highest PSI requirement in the facility. This is your PSI requirement.
So, if your facility has a CFM requirement of 90 CFM and the highest PSI requirement is 150, the common practice is to specify an air compressor that offers 90 CFM at 150 PSI. However, this can lead to higher energy costs, so if you don’t want to run the entire plant at an elevated level to accommodate the highest PSI rating, alternative solutions, such as a small booster or dedicated equipment, are recommended.
How Compressed Air System Design Impacts Sizing
Selecting the right size air compressor for your facility is only one part of the equation. Plant air system design is also a critical factor to efficient and effective performance. Key considerations and air system components include:
Air Receiver Tanks:
These store treated air to accommodate peak demand periods without overworking the compressor.
Dryers and Filtration:
Moisture and contaminants can degrade the quality of your compressed air, cause blockages that reduce system efficiency and performance, and damage system components and tools. Filtration prevents contaminants from entering the system and dryers remove moisture. Both are critical to the performance and energy efficiency of the compressed air system, as well as the quality of your compressed air.
Piping Layout:
The air delivery system should contain as few bends and long runs as possible to avoid friction, which causes pressure drops and inefficiencies. Piping choice matters, too. Common pipe materials include aluminum and stainless steel. It should be noted that PVC and CPVC piping should NEVER be used and are not permissible under Occupational Safety & Health Administration (OSHA) regulations due to potential safety hazards.
Leak Management:
Compressed air leaks cause pressure drops and waste energy! Leaks can waste 20% to 30% of a compressor’s output, costing thousands of dollars each year. Common culprits include loose fittings and connections, worn seals and gaskets, damaged hoses and piping and malfunctioning valves. A leak management program that regularly inspects these components to detect and address leaks is essential to optimal performance and efficiency of the system.
Plan for Emergencies:
Even well-designed and maintained air compression systems can experience downtime. Make sure you have a reliable service provider and a plan in place for an air compressor rental to avoid unplanned downtime or handle unexpected demand peaks. Contact Tavoron’s rental services. We can help you create an emergency rental plan.
Let Tavoron Help You Get It Right
As part of an overall well-designed air compression system, the correct size air compressor will provide enough capacity to deliver stable and effective air flow and pressure, even during periods of peak demand.
Taking the time to evaluate your air demand, right-size your compressor, and optimize your compressed air system design will lower your energy costs, improve system performance and reliability, extend the life of your equipment, and provide long-term scalability.
Tavoron knows that industrial air system optimization isn’t just about selecting the right size air compressor; it’s about proper design of the entire system.
