What is the reason for the large pressure loss in compressed air pipelines

Excessive pressure loss in compressed air systems is a common problem that directly affects equipment performance, increases energy consumption, and reduces production efficiency. The following are the main reasons and detailed analysis for the large pressure loss in compressed air pipelines:

1、 Unreasonable pipeline design

Improper selection of pipe diameter

Small pipe diameter is a common cause of pressure loss. When the compressed air flow exceeds the design capacity of the pipeline, the flow velocity increases sharply and the frictional resistance increases in a square relationship. According to the Darcy Weisbach formula, pressure loss is proportional to the square of flow velocity.

Rule of thumb: The air flow velocity in the main pipeline should be controlled between 6-9m/s, and in the branch pipeline, it should not exceed 15m/s. For example, a flow rate of 40m ³/min requires a pipeline of at least DN125. If a DN80 pipeline is mistakenly selected, the pressure loss may increase by more than 5 times.

Pipeline layout defects

Unnecessary long-distance transportation: For every additional 100 meters of straight pipe section, the pressure loss is about 0.1-0.3 bar (depending on the pipe diameter and flow rate)

Excessive right angle elbows: A 90 ° standard elbow is equivalent to 12-15 times the pipe diameter in equivalent length, and using two right angle elbows results in 40% higher pressure loss than a 135 ° gentle bend

Unreasonable pipeline routing: the presence of "air pockets" (high-level water accumulation points) or "liquid pockets" (low-level water accumulation points) will increase flow resistance

Pipeline structure issues

Using an unreasonable dendritic pipe network instead of a circular pipe network results in insufficient end pressure

The main pipeline does not adopt a gradual reduction design, and the same diameter is used throughout the entire process, resulting in energy waste

2、 Pipeline accessories and connection issues

Improper valve selection

The pressure loss is 4 times higher when using a gate valve (with a resistance coefficient of 0.2 when fully open) than a ball valve (with a resistance coefficient of 0.05)

Insufficient opening of regulating valve: When the valve opening is 50%, the flow coefficient may only be 30% of when it is fully open

Insufficient diameter of quick couplings: Some 1/2 "quick couplings have an actual diameter of only 6-8mm, resulting in severe throttling

Filter clogging

The initial pressure drop of the standard filter is about 0.1 bar, and it can reach 0.5-1 bar after blockage

Failure to replace the filter element in a timely manner: When the pressure difference exceeds 0.3 bar, the filtration efficiency drops sharply, and it should be forcibly replaced at 0.5 bar

Selection too small: When the processing capacity is less than 70% of the rated flow rate, the lifespan of the filter element is shortened by 50%

Irregular pipeline connections

Improper handling of pipe ends during threaded connections can result in burrs or reduced diameter

Incorrect flange connection causes turbulence

Incorrect installation angle of quick connector leads to additional resistance

3、 Abnormal internal state of the pipeline

Accumulation of moisture

Liquid water occupies the cross-sectional area of the pipeline: a 1mm thick water film can reduce the effective cross-sectional area of a DN100 pipeline by 6%

Formation of water hammer effect: Sudden changes in airflow can cause local pressure fluctuations to reach 2-3 times the working pressure

Corrosion products increase roughness: After 5 years of use, the roughness of carbon steel pipes can increase from 0.05mm to 0.2mm

Oil pollution deposition

Oil mist forms a viscous boundary layer on the inner wall of the pipeline, and actual measurements show that a 0.1mm oil film can increase pressure drop by 15%

Oil water mixture forms emulsion, with flow resistance 3-5 times higher than pure water

Corrosion and impurities

The annual corrosion rate of carbon steel pipes can reach 0.1-0.3mm, increasing the inner surface roughness by 10 times

Local blockage caused by foreign objects such as welding slag and sealing material fragments

4、 System operation management issues

Traffic exceeds the design value

Newly added gas equipment without corresponding pipeline expansion

High simultaneous utilization rate: When the actual flow exceeds the design flow by 30%, the pressure loss increases by about 50%

Unreasonable pressure setting

Excessive inlet pressure leads to an increase in flow rate (for every 1 bar increase in pressure, the air density increases by approximately 8%)

Improper setting of pressure reducing valve causes throttling loss

Insufficient maintenance

Unplanned drainage: When the accumulated water reaches 10% of the pipe diameter, the pressure loss increases by 25-40%

Lack of pipeline cleaning: professional blowing should be carried out every 2-3 years

Leakage not promptly addressed: A 3mm small hole leaks approximately 30000m ³ per year under a pressure of 7 bar

5、 Improper material selection

The influence of pipeline material

Galvanized steel pipes have a roughness 2-3 times higher than stainless steel pipes

Improper use of hose: 5-meter-long DN25 rubber hose has a pressure drop 0.2-0.3 bar higher than steel pipes of the same specification

Sealing material issue

Improper use of sealing tape leads to reduced diameter

O-ring and other sealing components protrude into the flow channel

Solution suggestions

Optimization design phase

Using professional pressure loss calculation software (such as PipeFlow, etc.)

Circular pipeline network+gradual reduction design

Bend curvature radius ≥ 1.5 times the pipe diameter

Improve installation quality

Perform pipeline inner wall treatment before installation

Using welding instead of threaded connection (main pipeline)

Set a drainage slope of 0.5-1%

Strengthen operation and maintenance

Establish a pressure monitoring system (key point differential pressure monitoring)

Implement graded filtering (main pipeline, branch pipeline, terminal)

Develop regular drainage and pipeline cleaning plans

technical transformation

Local expansion of high resistance pipe section

Replace high-efficiency and low resistance valves

Install an automatic flow control device

By systematically analyzing the causes of pressure loss and taking targeted measures, the system pressure drop can usually be reduced by 30-50%, with significant energy-saving effects. The renovation case of a certain automobile factory shows that after optimization, the annual electricity cost savings reached 850000 yuan, and the investment payback period was only 11 months.