There is nothing worse than making it through a technical project only to be disrupted by some critical detail that was overlooked. Pressure drop is often overlooked, misunderstood and misdiagnosed.

Pressure drop is often the cause of excessive energy consumption and poor system performance. If unaddressed before the purchase of a compressor or booster, you could be buying an improperly sized unit. If unaddressed or misdiagnosed for an existing system, it can lead to costly downtime, unexpected and even unnecessary equipment expenses.

Undersized or incorrectly sized piping is the most basic culprit is pressure drop issues. But it doesn’t end there; piping arrangements, compressor components and ancillary equipment are often part of the problem as well. There are many factors in handling pressure drop issues during the design stages of a capital equipment purchase as well as solving problems with systems currently in operation.

Pressure drop is a term used to characterize the reduction in air or gas pressure anywhere in a compression system. A properly operating system should be designed with the least amount of pressure drop that is practical. For example, it is not practical to have long runs of undersized piping, but properly sized check valves are necessary and the pressure drop associated must be taken into account.

Imagine a freeway in a large metropolitan area that has only one or two lanes, onramps that bottleneck, and numerous sharp turns. Traffic becomes congested and motorists have to slow down when using the onramps and navigating the sharp turns. Compressed air and gas systems experiencing pressure drop issues are similar to an undersized and poorly designed freeway. In this example the freeway represents the pipe sizing and arrangement, the onramps represent ancillary equipment such as filters, dryers, and gas separation equipment while the sharp turns represent components such as valves, fittings, and junctions.

What Causes Pressure Drop?

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Components such as this coalescing filter or moisture separator (top) and this pressure safety valve will cause some minor pressure drops.

Any type of obstruction, restriction, or roughness in the system will cause resistance to gas flow and cause a pressure drop. In a distribution system, the highest pressure drops are usually found at the points of use, including undersized or leaking hoses, tubes, disconnects, filters, and regulators. On the supply side of the system, aftercoolers, moisture separators, dryers, filters, and improperly sized piping are the main items causing significant pressure drops.

The maximum pressure drop from the supply side to the points of use will occur where the compressed air flow rate and temperature are the highest. System components should be selected based on these conditions and the manufacturer of each component should be requested to supply pressure drop information under these conditions. During the design phase, it is critical that occasional large flow requirements (air bursts, startup/shutdown of equipment, etc) are recognized, and the system is designed to handle the pressure drops for these occasional large flows. This is exactly why, during the quoting and compressor sizing process, Hycomp salesmen and engineers work with our customers to completely and accurately fill out the Hycomp Application Worksheet (“Application Worksheet” will be a link to our AppWork form).

The distribution piping system often is diagnosed as having a high-pressure drop because a point-of-use pressure regulator cannot sustain the required downstream pressure. If such a regulator is set at 85 psig and the regulator and/or the upstream filter has a pressure drop of 20 psi, the system upstream of the filter and regulator would have to maintain at least 105 psig. The 20 psi pressure drop may be blamed on the system piping rather than on the components at fault. The correct diagnosis requires pressure measurements at different points in the system to identify the component(s) causing the high-pressure drop. In this example, the filter/regulator size would need to be increased, not the piping.

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Minimizing Pressure Drop

Keeping pressure drop to a practical minimum requires a total systems approach in design and maintenance. Air treatment components, such as aftercoolers, moisture separators, dryers, and filters, should be selected with an acceptable pressure drop at specified maximum operating conditions. When installed, the recommended maintenance procedures should be followed and documented.

Additional ways to minimize pressure drop are:

  • Properly design the distribution system.
  • Operate and maintain air filtering and drying equipment to reduce the effects of moisture, such as pipe corrosion.
  • Select aftercoolers, separators, dryers, and filters having the least possible pressure drop for the rated conditions.
  • Reduce the distance the air travels through the distribution system. If long runs are required, properly size the pipe.
  • Use new, smooth bore, clean piping.
  • Specify pressure regulators, hoses, and connections having the best performance characteristics at the lowest pressure differential.

Hycomp Investigation & Experience

When Hycomp compressors and boosters are configured and sold, they are sized to accept a specific inlet pressure and flow. If the pressure drop of all the other installed components before the Hycomp booster is not taken into account, for example, what was thought to be 120 psig at inlet could be more like 100 psig, then the booster may not be able to achieve the desired discharge pressure. Even if the compressor works harder to provide that pressure and succeeds, flow and/or reliability may suffer.

One thing that may be blamed for pressure drop is actually pressure loss. This can occur when process demands exceed the supply capabilities. If an application requires a specific flow and then that requirement is increased, chances are that the booster may not be able to provide the increased demand. For example, an end-user runs a laser-cutting facility and purchased a Hycomp nitrogen booster that mates with their N2 generator to provide 3 laser-cutting machines with 600 psig at 45 scfm flow each. If the end-user then installs 2 more laser cutting units without upgrading their nitrogen boosting setup, they could be disappointed in the results as the single booster may not be able to handle the increased demand (pressure and flow) at the point of use.

Hycomp sales professionals and engineers have the knowledge to assist distributors and end-users in properly sizing a compression system to fit the desired application. This begins with a thorough investigation on the front end of an inquiry and continues until the compressor system arrives on location and is in operation. However, if precise conditions are not given and system pressure drops are not accounted for, a perfectly operating and brand-new compressor or booster system may not be able to meet the requirements. So much is riding on the original info that is collected using a Hycomp Application Worksheet; it is paramount this information be accurate.

Much like a cross-country road trip, if you fail to properly plan your route, you could find yourself far from your intended destination. All the information collected for sizing a compressor must be accurate or you could find yourself in a situation where the compressor just purchased can’t keep your application in operation. Trust your Hycomp sales and engineering team to help you plan and investigate each application, so your process always runs efficiently.