When power is lost, your valve’s default setting becomes critical.
That’s where fail open and fail close actuators come in. These are designed to either stop or continue flow automatically when the power cuts out. The choice between them depends on what you’re protecting — your system, your product, or the people working around it.
Below, we’ll break down the real difference between fail open and fail close valve actuators, what causes them to switch, and how to choose the right one for your setup.
What Triggers a Fail-Safe Response?
Fail-safe doesn’t mean the valve breaks.
It means the system has lost the power source that drives the actuator. That could be electricity, air, hydraulic fluid, or gas.
In each case, the actuator is designed to return to a safe position when the signal disappears.
That signal can fail because of:
- Power outages during storms
- Low upstream pressure
- Frozen lines or equipment failure
If your process can’t afford unplanned flow, you’ll need to decide whether flow should stop or continue when that happens.
How a Fail Open Valve Responds
A fail open valve opens when the power goes out.
These are usually spring-loaded to stay open unless pressurized air (or power) keeps them shut. That’s why they’re also called air to close valves.
Fail open setups are used when it’s safer to let media through than block it during failure.
Typical examples:
- Cooling water lines to prevent overheating
- Fire suppression systems where water needs to flow without delay
When power returns, the actuator re-closes the valve if that’s what the process requires.
So if your priority is to relieve pressure or keep coolant flowing, a fail open valve setup fits that goal.
What a Fail Closed Valve Does
A fail closed valve shuts when power is lost.
Also called air to open valves, these require a constant power or pressure source to stay open. When the power drops, the valve springs shut automatically.
This helps prevent:
- Leaks of hazardous material
- Equipment damage due to overflow
- Media flowing into unwanted areas
You’ll often find fail closed valves in:
- Wastewater systems
- Chemical holding tanks
- Pressure-sensitive vessel outlets
A close fail scenario is ideal when your process must stop instantly during an emergency.
Fail Open vs Fail Close — Which One Fits?
The decision comes down to your application.
Ask: What’s the risk if the valve stays open when it shouldn’t? What’s the damage if it closes and interrupts the flow?
Use a fail open valve when:
- Blocking flow during a power outage would cause overheating or buildup
- Safety relies on media continuing to flow (e.g., fire protection systems)
Use a fail closed valve when:
- You need to contain media immediately during signal loss
- Uncontrolled flow can damage downstream equipment or safety zones
Each has its own use case. It’s not about which is better — it’s about what you need to protect.
For a deeper understanding of how actuators help manage flow in these situations, check out The Basics of Valve Control Using Electric Valve Actuators.
The Open Closed Valve Relationship
Some systems use both fail open and fail closed valves.
That’s especially true in large industrial setups where flow must be directed or blocked based on different emergency outcomes. It’s not uncommon to see valves fail open on inlet lines while outlet lines fail closed.
That level of control depends on the actuator type and setup logic.
Using electric valve actuators, you can program sequences that align with your fail-safe goals.
If your actuator seems sluggish or unresponsive, here’s a good place to start: What Are Signs That My Actuator Valve Is Not Working?
Don’t Let Power Loss Decide the Outcome
Power cuts happen. Whether caused by nature, system faults, or routine maintenance — it’s going to affect your valve actuator at some point.
The question is: what happens next?
Fail open vs fail close isn’t a small setting. It could save you from downtime, safety hazards, or legal problems.
Choose the one that supports your system goals.
You can explore actuator types that offer both fail open and fail closed functionality in our electric actuator catalog.
Need guidance? Our team can help walk through your application and choose the safest route.
