A pneumatic manifold must do more than physically provide enough ports. The internal supply passages, valves, fittings, and upstream compressed-air system also have to deliver the airflow required by the connected equipment.
A manifold that is too restrictive may appear to operate correctly at low demand while producing slow cylinders or pressure loss when several actuators operate together.
Air Consumption
Determine Pneumatic Air Demand
Pneumatic cylinders consume compressed air each time their internal chambers are filled. Larger cylinders and higher operating pressures generally require more air per movement.
Systems using air cylinders should consider bore size, stroke, operating pressure, cycle frequency, and the number of actuators operating at the same time.
Individual actuator demand is only part of the calculation. The manifold and supply network must support the combined demand occurring during peak portions of the machine cycle.
Restrictions
Pressure Drop Through Pneumatic Systems
Compressed air loses pressure as it moves through restrictive passages, valves, fittings, filters, regulators, and tubing.
If the supply pressure falls too much before reaching an actuator, available force and speed can be reduced.
A well-sized manifold helps limit unnecessary restrictions between the main air supply and the devices using the compressed air.
Supply Capacity
Compressor and Upstream Air Supply
Increasing manifold passage size cannot compensate for an air supply that is unable to provide the required flow.
The capacity of air compressors, receivers, filters, regulators, main piping, and branch lines all affect the air available at the manifold.
Sizing should therefore consider the manifold as one part of the complete compressed-air system.
Valve Capacity
Selecting Valves for Required Airflow
A large manifold passage can still be restricted by a valve with insufficient flow capacity. Valve selection should match the actuator demand and desired response time.
Supply and exhaust capacity both matter because an actuator cannot move rapidly if air enters freely but cannot exhaust efficiently.
Tubing diameter and fitting geometry downstream of the valve should also be considered.
Engineering
Pneumatic Manifold Sizing Factors
Troubleshooting
Symptoms of an Undersized Pneumatic System
Slow actuator movement, inconsistent cycle time, pressure dropping during simultaneous operation, or a machine that performs differently when other pneumatic devices operate can indicate inadequate airflow.
The restriction may exist in the manifold, but it may also be located in tubing, fittings, valves, filters, regulators, or the upstream compressed-air supply.
Pneumatic Troubleshooting Guide →