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How to Prevent Pressure Spikes in a Pneumatic System
Pressure spikes, also called pressure overshoot, occur when the pressure in a pneumatic system temporarily rises above the desired setpoint. They often happen when downstream flow changes suddenly, such as when a valve opens or a pneumatic device begins consuming air.
While the pressure regulator may appear to be the source of the problem, pressure spikes are often caused by the interaction between the regulator, inlet pressure, flow demand, tubing, valves and downstream volume.
For applications requiring especially stable and accurate pressure control, selecting the right precision pressure regulator and properly designing the pneumatic system can significantly reduce pressure fluctuations.
What Causes a Pressure Spike in a Pneumatic System?
A pressure regulator continuously responds to changes in downstream pressure and flow demand. When a downstream valve suddenly opens, pressure begins to fall and the regulator responds by opening its internal valve to supply additional flow.
If the regulator responds faster than the downstream system can absorb that flow, the outlet pressure can briefly rise above the setpoint before settling back to the desired pressure.
This pressure overshoot can be influenced by several factors:
- High inlet-to-outlet pressure differential
- Rapid changes in downstream flow
- An oversized regulator
- Undersized tubing or restrictive fittings
- Small downstream volume
- Long pneumatic lines
- Improper regulator selection
- Contamination or mechanical problems inside the regulator
Understanding the complete pneumatic system is usually the first step toward correcting the problem.
1. Select the Correct Size Pressure Regulator
Bigger is not always better when selecting a pressure regulator.
An oversized regulator may have a large valve and high flow capacity compared with the actual requirements of the application. A relatively small movement of the valve can therefore introduce a significant amount of air into the downstream system.
This becomes particularly important when controlling very low pressures or low flow rates.
Regulator selection should consider:
- Normal inlet pressure
- Required outlet pressure
- Minimum and maximum flow
- Acceptable pressure droop
- Required sensitivity
- Port and tubing size
- Expected changes in flow demand
ControlAir offers a range of precision pressure regulators designed for applications requiring accurate and repeatable pneumatic pressure control.
2. Avoid Excessive Supply Pressure
A regulator should have adequate supply pressure to provide the required downstream pressure and flow, but more pressure is not necessarily better.
Consider an application requiring only 1 psi outlet pressure while operating from a 100 psi supply. The regulator is controlling across a very large pressure differential. When downstream demand suddenly increases, even a small change in valve position can introduce a relatively large amount of energy into the system.
If the application does not require the full supply pressure, reducing the inlet pressure may improve dynamic stability.
Consider Two-Stage Pressure Regulation
For applications with a very large pressure reduction, two-stage regulation may be beneficial.
For example:
100 psi supply → First regulator at 20–30 psi → Precision regulator at 1 psi → Application
The first regulator reduces the major pressure differential, while the second regulator provides the final precision control.
3. Control How Quickly Flow Starts
A rapidly opening downstream valve can create a sudden change in demand.
The regulator responds to the pressure drop by increasing flow. If that response is too aggressive for the downstream system, pressure can temporarily overshoot the setpoint.
Depending on the application, consider:
- A soft-start valve
- A proportional valve
- A controlled-opening valve
- A flow control device
- Slowing the rate at which the process is pressurized
Reducing abrupt changes in flow demand can improve overall system stability.
4. Check Tubing, Fittings and Other Restrictions
The regulator is only one component of the pneumatic system.
Tubing, fittings, filters, solenoid valves, quick disconnects and other components can create pressure drops when flow increases. The regulator may react to this pressure drop by opening further.
As the downstream system catches up, this can contribute to temporary pressure overshoot.
Check for:
- Undersized tubing
- Long tubing runs
- Small fittings
- Restrictive valves
- Plugged or undersized filters
- Excessive elbows or connections
Reducing unnecessary restrictions can improve the regulator’s ability to respond smoothly to changes in demand.
5. Consider Downstream Volume
Downstream volume can have a significant effect on how quickly system pressure changes.
A very small downstream volume can experience a rapid pressure increase from a relatively small amount of incoming air. Adding additional downstream volume can sometimes damp short pressure disturbances.
However, additional volume will also increase filling and exhausting time.
The correct solution depends on whether the application requires extremely fast response, extremely stable pressure, or a balance between the two.
6. Measure Pressure Where It Matters
Pressure at the regulator outlet may not be the same as pressure at the actual process.
For example:
Regulator → 10 feet of tubing → Solenoid valve → Application
A pressure sensor installed immediately after the regulator may see a different transient than a sensor installed at the application.
When troubleshooting pressure spikes, determine:
- Where the pressure is being measured
- Where the pressure spike matters to the process
- What restrictions exist between those two locations
For critical applications, measuring pressure close to the point of use can provide a much better picture of actual system performance.
7. Use a Precision Regulator for Low-Pressure Applications
Very low-pressure applications can be particularly sensitive to pressure variations.
A general-purpose regulator that performs well at 40, 60 or 80 psi may not provide the sensitivity required to accurately control pressures of only a few psi or fractions of a psi.
Precision regulators are designed to provide improved sensitivity, repeatability and pressure control for demanding pneumatic applications.
ControlAir’s precision pressure regulator family includes models for low-pressure, miniature, high-flow and other precision applications.
For applications requiring higher flow capacity combined with precision control, the ControlAir Type 700 Precision Air Pressure Regulator is one available option.
8. Check for Mechanical or Contamination Problems
If a pneumatic system operated correctly in the past and pressure spikes suddenly appear, inspect the regulator and air supply.
Possible causes include:
- Dirt or contamination on the valve seat
- A damaged valve seat
- A sticking valve or pintle
- Diaphragm damage
- Internal friction
- Oil or water contamination
Clean, properly filtered air can help maintain regulator performance and extend operating life.
How Do You Troubleshoot a Pneumatic Pressure Spike?
When investigating pressure overshoot, gather as much information about the system as possible.
Start with these questions:
- What is the normal inlet pressure?
- What is the desired outlet pressure?
- How high does the pressure spike?
- How long does the spike last?
- What is the normal and maximum flow rate?
- What causes flow to begin?
- What size and length tubing is being used?
- What valves or restrictions are downstream?
- Where is pressure being measured?
- Did the system always behave this way, or is the problem new?
One useful troubleshooting test is to temporarily reduce the inlet pressure, provided sufficient pressure remains available to achieve the required flow.
If lowering the supply pressure significantly reduces the pressure spike, the high inlet-to-outlet pressure differential may be contributing to the problem.
Pressure Spikes Are Often a System Problem
When pressure overshoot occurs, replacing the regulator should not automatically be the first step.
Pneumatic pressure control is affected by the complete system. Regulator size, inlet pressure, downstream flow, tubing, valves, volume and measurement location all influence how the system responds.
Proper regulator selection and good pneumatic system design can improve pressure stability and help prevent unwanted pressure spikes.
If your application requires particularly accurate pressure control, review ControlAir’s Precision Pressure Regulators or review our guide on How to Determine the Appropriate Regulator.
Frequently Asked Questions
What causes pressure spikes after a pneumatic valve opens?
A sudden increase in flow demand can cause a regulator to open rapidly. Depending on supply pressure, regulator size, downstream volume and restrictions, the outlet pressure may temporarily overshoot before settling at the desired setpoint.
Can high inlet pressure cause pressure overshoot?
A large difference between inlet and outlet pressure can contribute to difficult dynamic control, particularly in very low-pressure applications. Reducing inlet pressure or using two-stage pressure regulation may improve stability.
Can a pressure regulator be too large?
Yes. A regulator with substantially more flow capacity than the application requires may be more difficult to control at very low flow rates or pressures. Proper regulator sizing is important for stable performance.
Will a precision pressure regulator eliminate pressure spikes?
A properly selected precision regulator can improve sensitivity and pressure stability, but the entire pneumatic system must be considered. Tubing, valves, flow demand, supply pressure and downstream volume can all contribute to pressure overshoot.
Where should pressure be measured in a pneumatic system?
For critical applications, pressure should generally be measured as close as practical to the point where pressure control matters. Long tubing runs and restrictive components can cause pressure at the regulator outlet to differ from pressure at the process.