The air compressor will stop if the exhaust pressure is low.

Shutdown protection may be triggered when the air compressor exhaust pressure is as low as 0.2-0.5MPa (about 2-5bar), the specific value varies with the model and design. The following analysis is carried out from two dimensions of conventional and water-lubricated models:

typical shutdown pressure range of 1. conventional air compressor

1. basic protection logic
   the air compressor monitors the exhaust pressure through the pressure switch or pressure sensor. When the pressure is lower than the set value, the control system will determine that it is "no-load too long" or "system pressure is insufficient", triggering the shutdown protection. For example:
   • unload pressure setting: Engineers usually set the unloading air pressure at 0.82-0.83MPa to ensure that the exhaust pressure is stable near the rated value (such as 0.8MPa). If the pressure is continuously lower than 0.77MPa for more than the set time (such as 0-30 minutes adjustable), the system will be determined as no-load too long and shut down.
   • Minimum pressure valve function: The valve maintains the minimum exhaust pressure of the system (usually 0.4-0.5MPa) and prevents backflow of gas from the gas tank. If the pressure is lower than this value, the valve may close, causing the air compressor to stop because it cannot maintain the lubricating oil circulation.
2. Actual Case Reference
   • setting of a certain type of air compressor: when the exhaust pressure is lower than 0.5MPa, the pressure switch is automatically connected to start the main engine; If the pressure is continuously lower than 0.235MPa (primary exhaust pressure) or 0.75MPa (secondary exhaust pressure), a fault shutdown may be triggered.
   • Marine air compressor: if the outlet pressure exceeds the normal shutdown pressure (such as 30bar) and does not stop, it will be forced to stop when the pressure rises to the high-pressure shutdown set value (such as higher pressure); However, in the reverse logic, if the pressure is too low (such as the oil pressure is lower than 1bar), it will stop directly.

Special Shutdown Pressure Logic of 2. Water Lubricated Air Compressor

the water-lubricated air compressor realizes sealing and cooling by replacing lubricating oil with water film, and its shutdown pressure setting needs to take into account the stability of water circulation and system protection:

1. low pressure series (0.3-0.6MPa)
   these models are mostly used in scenarios with low pressure requirements (such as pneumatic tools). If the exhaust pressure is continuously lower than 0.3MPa, the system may determine that the water circulation pressure is insufficient (water film cannot be formed) and trigger shutdown to avoid mechanical wear.
2. Medium pressure series (2.0-4.0MPa)
   high pressure water lubricated models need to maintain higher water pressure to ensure sealing effect. If the exhaust pressure is lower than 2.0MPa, the seal may fail due to insufficient water pressure, and the system will automatically shut down and give an alarm.
3. Protection mechanism of water lubrication system
   • water pressure monitoring: Monitor the water circulation pressure in real time through the pressure sensor. If the pressure is lower than the set value (such as 0.2MPa), stop the machine immediately and empty the gas in the compression chamber to prevent dry friction.
   • Temperature linkage: Water lubricated models are sensitive to temperature. If the exhaust temperature is too high and causes water vaporization (pressure drop), the system will stop synchronously to protect the equipment.

Core Principles of 3. Shutdown Pressure Setting

1. prevent mechanical damage
   low-pressure shutdown can prevent the air compressor from running under no load or insufficient lubrication/cooling, reducing the risk of bearing wear and cylinder deformation.
2. Maintain system stability
   by setting a reasonable shutdown pressure, it is ensured that the pressure of the gas tank is always higher than the minimum demand of the gas-using equipment to avoid production interruption.
3. Energy saving and life balance
   frequent start and stop will aggravate the fatigue of valve springs and seals, so the shutdown pressure setting needs to take into account the energy saving requirements and equipment life. For example, by extending the no-load operation time (e. g., 30 minutes) before stopping, the number of start-stops can be reduced.