How do you control air supply from an air compressor to two separate air tanks?

I. First, clearly define the control objectives.

When a single air compressor supplies two air receivers, it is not as simple as splitting the piping into two branches; rather, the control objectives must first be clearly defined. Different objectives correspond to different valves, instruments, and control logic.

• Do the two gas cylinders need to be kept at the same pressure, or should they each maintain a different pressure?
• Do the two gas cylinders require independent automatic refilling, or is it sufficient to connect them in parallel for storage?
• Are there any priority gas supply requirements, such as ensuring that a particular gas cylinder maintains pressure first?
• Is the air compressor suitable for continuous operation, load‑unload cycling, or does it permit frequent start‑stop cycles?

II. Common Pipeline Layout Methods

A more common approach is to adoptCentralized and parallel gas supplyAfter the compressed air is discharged, it undergoes post‑cooling, oil–water separation, filtration, or drying, then enters a main header pipe. From this header, two branch lines diverge, each feeding into one of the two gas storage tanks.

• The air compressor outlet shall be equipped with the necessary filtration, separation, and drainage devices.
• It is recommended to install shut-off valves on each gas cylinder branch line to facilitate maintenance and isolation.
• Each gas cylinder shall be equipped with a pressure gauge, a safety valve, and a drain‑off device.
• If backflow is possible, a check valve may be installed on the branch line.

III. Control When Two Gas Cylinders Require Different Pressures

If the two gas cylinders operate at different pressures, it is not recommended to use a single pressure point to directly control both lines. Typically, within the allowable range of the main line pressure, the low-pressure side can be equipped with a pressure-reducing and pressure-stabilizing device.

• The high-pressure side gas cylinder can supply gas at the system’s allowable pressure.
• The low-pressure side gas cylinder can have its pressure adjusted to the desired range via a pressure-reducing valve.
• A pressure monitoring point shall be installed downstream of the pressure-reducing valve, and appropriate protective devices shall be provided.
• The set pressure of each gas cylinder must be compatible with the allowable working pressure of the cylinder, piping, and associated equipment.

IV. Automatic Air Replenishment Using a Pressure Switch and a Solenoid Valve

If two gas cylinders each require automatic refilling, independent pressure sensing and control components can be installed for each cylinder.

• Each gas cylinder is equipped with a pressure switch or pressure transmitter to monitor the internal pressure.
• An electromagnetic valve or an electric ball valve shall be installed on the inlet branch of each gas cylinder.
• When the pressure in a particular gas cylinder falls below the set lower limit, open the inlet valve for that line.
• When the pressure reaches the set upper limit, close the inlet valve for that line.

If the air compressor itself is not suitable for frequent start–stop cycles, the main pipeline pressure should be used to control the compressor’s loading, unloading, or shutdown, while the inlet valves of the two air receivers are responsible only for opening and closing their respective branch lines.

V. Priority Gas Supply and Interlock Logic

In some applications, the two gas cylinders are not refilled evenly at the same time; instead, the pressure in one cylinder must be prioritized. In such cases, a simple control logic can be implemented.

• When the priority gas cylinder pressure is insufficient, supply gas to the priority cylinder first.
• Once the priority gas cylinder reaches its set pressure, the other cylinder is then permitted to replenish its charge.
• An interlock can be installed between the two intake valves to prevent a significant pressure drop caused by simultaneous high‑flow intake.
• Sequential air supply can also be achieved via pressure differential, time delay, or a controller.

VI. Safety and Commissioning Key Points

Gas cylinders are pressure vessels, and their control system design must account not only for automation but also for safety and maintainability.

• Gas cylinders shall be equipped with approved safety valves, pressure gauges, and relief devices.
• The pressure setpoint shall not exceed the allowable working pressure of the gas cylinder, piping, and associated components.
• During system shutdown or maintenance, safe pressure relief and drainage shall be ensured.
• Before commissioning, verify the valve orientation, pneumatic circuit sealing, and electrical wiring.
• Perform manual testing first, then switch to automatic control to prevent false operations.

VII. Recommendations for Selecting a Simple Solution

If the two gas cylinders are used solely as storage buffers and have identical pressure requirements, a common header can be employed for supply, with branch lines isolated by manual valves, while the air compressor is controlled uniformly by the header pressure.

If two gas cylinders each need to maintain pressure automatically, pressure sensors and solenoid valves can be added to the branch lines of each cylinder, with the controller independently regulating gas inflow based on the pressure in each line.

If the two gas cylinders have different pressure requirements, they should be zoned and controlled in conjunction with pressure-reducing valves, pressure monitoring devices, and safety protection components.