【2026 Mechanical Equipment】Troubleshooting logic and solutions for reciprocating compressors with insufficient discharge volume

1. Deviations between the intake conditions and the design standards: Whether the intake conditions meet the design requirements directly determines the suction efficiency of the compressor, which in turn affects the final exhaust volume. The main types of such deviations are as follows: Low intake pressure: Factors such as high installation altitude of the equipment, clogged intake filters, overly long intake pipelines, improperly selected pipe diameters, or intake valves that are not fully opened can all lead to increased pressure losses during the intake process. Based on the flow calculation principle of positive-displacement compressors, insufficient intake pressure will directly lead to a corresponding decrease in exhaust volume. High intake air temperature: When the temperature in the machine room is too high, the intake air ducts are affected by external heat sources, or the heat exchange efficiency of the preceding cooler declines, the density of the gas drawn into the cylinders decreases. As a result, the mass flow rate of gas drawn in per unit time also drops, leading to insufficient exhaust volume. High inlet humidity: The water vapor contained in the inhaled gas occupies part of the available volume, reducing the actual mass flow rate of the dry gas and thereby indirectly affecting the compressor’s exhaust capacity.

2. The compressor speed does not meet the specified requirements. The displacement of a reciprocating compressor is directly proportional to the crankshaft speed; if the speed fails to reach the designed value, the displacement will inevitably decrease as well. Common causes of insufficient rotational speed include a low frequency of the power supply grid, excessive slip during motor operation, belt slippage, and faults in the speed control system. All these issues can result in the actual rotational speed of the crankshaft being below the design specifications, thereby affecting exhaust efficiency.

3. Abnormally increased internal leakage in the cylinder: As the core compression component of a compressor, the sealing performance of the cylinder directly affects gas leakage. Once internal leakage increases, the exhaust volume drops significantly. The main sources of leakage and their causes are as follows: Wear or breakage of the piston rings, or an opening gap that exceeds the standard range, leading to a loss of sealing performance； Scratches on the cylinder surface and a roundness deviation exceeding the allowable limits have compromised the sealing fit between the cylinder and the piston ；

The clearance between the piston and the cylinder is too large; for pistons made of cast iron, this clearance is usually around 0.06% to 0.09% of the cylinder diameter, while for aluminum alloy pistons it is 0.12% to 0.18% of the cylinder diameter. A clearance exceeding these ranges can lead to serious air leakage； Failure of the stuffing box sealing components, wear of the piston rod, or misalignment during installation can cause axial gas leakage ；

Wear of the valve disc and seat, or the presence of foreign objects trapped inside the valve assembly, can prevent the valve disc from closing tightly, resulting in backflow of high-pressure gas to the low-pressure stage or the suction side (i.e., internal leakage).

4. Abnormal operating condition of the air valve. The air valve is a key control component for air intake and exhaust in compressors; its proper functioning directly affects the efficiency of gas flow and the sealing performance. Common abnormalities include: improper selection of the spring – excessive spring tension can cause the valve flap to open slowly, while insufficient tension can result in delayed closure of the valve flap. In both cases, the effective flow area for gases is reduced, affecting the efficiency of air intake and exhaust； The lift of the valve disc does not meet the design requirements (it is either too large or too small), or the disc is warped, resulting in poor sealing and impaired flow ；

Damage to the valve seat sealing surface and the accumulation of carbon deposits undermine the sealing performance of the valve, leading to gas leakage； Insufficient or excessive gland tightening force causes the valve cover to deform, indirectly affecting the proper opening and closing of the valve.

5. Impact of factors on the system side: In addition to failures in the compressor’s own components, abnormalities on the system side can also result in an insufficient exhaust volume. This is manifested in the following three aspects: An insufficient opening degree of the check valve at the final stage of exhaust, valves in the process pipelines not being opened enough, or an excessively high exhaust backpressure – all of these can lead to a pressure buildup, thereby increasing the compressor’s cycling effort and reducing its volumetric efficiency, and as a result, decreasing the exhaust volume； Scaling on the heat exchange tubes of the intercooler and aftercooler reduces the heat exchange efficiency, which leads to an increase in the inlet temperature at the second and third stages. As a result, the volumetric efficiency at each stage decreases, ultimately affecting the total exhaust volume ；

The bypass valves and safety valves in the process circuit have internal leakage issues, or the start-up vent valve is not fully closed, resulting in some of the compressed gas taking a short circuit and failing to enter the normal process piping network, which leads to a loss in exhaust volume.

6. System troubleshooting process and targeted countermeasures: To address the factors that may lead to insufficient exhaust volume, troubleshooting can be carried out following the steps below, along with appropriate corrective actions, in order to quickly restore the equipment to its designed performance. Priority should be given to checking the three key parameters: measure the intake pressure, intake temperature, and compressor speed respectively, compare them with the design values to determine the extent of deviation from the normal operating conditions, and thereby get an initial idea of where the problem lies； Conduct a leakage test: After shutting down the machine, fill the cylinder with dry nitrogen and maintain that pressure for 10 minutes; if the pressure drop exceeds 5%, it indicates a severe leak inside the cylinder ；