What are common locations of pressure loss in compressed air systems?

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pressure loss compressed air systemsA small fiberglass manufacturer had a problem.  There tools were not performing adequately; they would stall when production workers tried to really work them, reducing production throughput.  A compressed air auditor was called in to investigate, he found that the air compressors were running at 140 psi, as high as they could go, but the pressure at the tool was only 44 psi when it was working.  This facility is an example of what not to do when trying to reduce pressure loss in a plant.

Here are some of the most common locations of pressure loss:

  • End use components—In almost all cases, the biggest pressure loss in a compressed air system occurs between the down drop from the main distribution header pipe and the compressed air powered tool or machine. The connectors, hoses, filters, regulators and lubricators in this supply must be properly sized to avoid excessive pressure loss.  In the case of the fiberglass plant there was 75 feet of undersized ¼-in. hose and five small quick connect couplers, causing 66 psi of pressure drop when the tool operated.  The tool consumed enough compressed air to require larger 3/8-in. components. The application actually needed only two quick connect couplers.
  • Compressor room components—Very often, the compressor room is where the next larger pressure drop occurs. Components within the compressors (air/oil separators, coolers, piping), the air dryer, main system filters, piping often contribute to 10 or more psi pressure loss due to being poorly maintained or undersized when installed. Careful selection of these components for low pressure drop (even during worst case peak flows) will ensure low pressure drop during average flows. In the case of the fiberglass plant, an undersized air cooler and a malfunctioning pressure/flow controller caused a 30 psi pressure loss in the compressor room.
  • System piping—Although not as common, significant pressure loss can be experienced across undersized distribution piping within the plant. This is especially a problem where a plant has grown significantly over time, but the distribution piping has not been upgraded to match higher compressor capacity. Piping should be sized so that there is less than 2 psi pressure loss across the complete system (not including the compressor room dryer and filter) during peak production. This was not a problem at the fiberglass factory, they had an excellent 3-in. piping loop with almost no pressure loss from one end to the other.
  • Machine internals—Often the manufacturers of production machinery try to cut costs by installing less expensive pneumatic components within the machines. Smaller and lower quality components (filters, regulators, connectors, tubing, actuators) will have higher internal losses, requiring higher compressed air pressures. And often machine operators will not realize the components have compressed air filters that must be regularly maintained within filter/regulator assemblies. This design philosophy saves the manufacturer’s money, but costs the end user in higher compressed air generation costs.

The story has a happy ending, the plant fixed their compressor room pressure losses, and upgraded connectors and hoses supplying the tools. The air compressors now run at 100 psi, saving energy, and the tool receives slightly above 90 psi when it operates, increasing productivity. The production personnel are very happy with their more powerful pneumatic hand tools.

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