What Happens During IP68 Certification Testing

2026-01-19

What Happens During IP68 Certification Testing—And Why Some “Rated” Actuators Still Fail?

You’ve specified an IP68-rated electric actuator for your underwater ROV, subsea valve, or washdown food processing line. The datasheet says “protected against continuous immersion.” So why did it leak during commissioning?

The truth is: an IP68 rating is not a universal guarantee—it’s a conditional promise, shaped by test parameters, design margins, real-world dynamics, and sometimes, marketing optimism. To trust an IP rating, you must understand what the test actually measures—and what it doesn’t. Let’s dive beneath the surface.

What Do the “6” and “8” in IP68 Actually Mean?

The IP (Ingress Protection) code, defined by IEC 60529, uses two digits:

First digit (6): Solid particle protection
- 6 = “Dust-tight”—no ingress of dust; complete protection against contact.
Second digit (8): Liquid ingress protection
- 8 = “Protected against continuous immersion in water under conditions specified by the manufacturer.”

Crucially, IP68 is not standardized for depth or duration. Unlike IP67 (which mandates 30 minutes at 1 meter), IP68 leaves the test conditions entirely up to the manufacturer—as long as they’re “more severe than IP67” and documented.

This ambiguity is the root of many field failures.

What Exactly Happens During an Official IP68 Test?

A legitimate IP68 test—conducted in an accredited lab—follows this protocol:

1. Preconditioning

The actuator is mounted in its intended orientation (e.g., rod horizontal, vertical, or angled).
All ports, connectors, and service interfaces are installed as in real use (not sealed with blanking plugs unless that’s how the customer receives it).
The unit may undergo thermal cycling (e.g., -25°C to +70°C) to simulate real-world expansion/contraction.

2. Dust Test (IP6X)

The unit is placed in a dust chamber with talcum powder (≤75 µm particle size).
A vacuum is applied to create a 2 kPa pressure differential, simulating suction from internal cooling or pressure changes.
After 8 hours, zero dust ingress is allowed—verified by internal inspection or functional testing.

3. Immersion Test (IPX8)

The actuator is submerged in freshwater (sometimes with additives to simulate conductivity) at a depth and duration defined by the manufacturer—commonly 1–3 meters for 24–72 hours, but could be 10m for 1 hour or 0.5m for 30 days.
Critical: The test is performed while the actuator is powered and cycled—extending and retracting repeatedly—to simulate dynamic seal stress.
Post-test, the unit is disassembled or inspected via borescope. No water may reach live electrical parts, bearings, or internal mechanisms.

Only if it passes both tests can it claim IP68.

So Why Do Some IP68 “Rated” Actuators Still Leak in the Field?

Because passing a lab test ≠ surviving real-world conditions. Here’s where the gaps emerge:

1. Test Conditions ≠ Application Conditions

A manufacturer might certify at 1m for 48 hours—but your application runs at 5m for 6 months.
The test uses static, clean, room-temperature freshwater—but your environment has saltwater, high pressure, abrasives, or wide thermal swings.
Dynamic pressure spikes (e.g., from water hammer or rapid actuator movement) create transient forces far beyond static head pressure.

Example: An actuator rated for 3m static may see >10m equivalent pressure during fast extension in deep water due to hydraulic ram effects.

2. Static vs. Dynamic Sealing

Many tests submerge a stationary actuator. But real actuators move. Each stroke:

Stretches and compresses rod seals
Creates micro-gaps during direction reversal
Wears sealing lips over time

A seal that holds when idle may leak under millions of cycles—especially if lubrication degrades or contaminants embed in the lip.

3. Poor Sealing Philosophy

Cheap designs rely on single-point sealing (e.g., one lip seal on the rod). Better designs use:

Multi-stage sealing: Primary seal + wiper + secondary backup
Labyrinth paths: Tortuous internal channels that trap moisture before it reaches electronics
Pressure-equalization vents: GORE®-style membranes that let air pass but block liquid—unless submerged too deep, where hydrostatic pressure forces water through

If the vent is omitted or undersized, internal pressure differentials can suck water past seals during cooldown.

4. Material Degradation Over Time

IP tests are short-term. But in service:

NBR (nitrile) seals harden in cold or degrade in ozone
FKM (Viton) swells in certain brake fluids or amines
Polyurethane cracks under UV or hydrolysis
Stainless steel housings can still suffer crevice corrosion in stagnant seawater

A seal that passes a 72-hour test may fail after 12 months of chemical exposure.

5. Uncontrolled Manufacturing Variability

IP performance is highly sensitive to tolerances:

Rod surface finish must be 0.2–0.4 µm Ra—rougher surfaces tear seals
Housing O-ring grooves require precise compression (15–30%)
Improper assembly (e.g., nicked seal during install) creates instant leak paths

Without statistical process control (SPC) and 100% leak testing, batch-to-batch variation can render “IP68” meaningless.

How Do Reputable Manufacturers Go Beyond the Standard?

Leading actuator builders treat IP68 not as a checkbox—but as a systems engineering challenge. Their practices include:

Defining realistic test conditions: e.g., “IP68: 10m continuous immersion, 25°C, with 10,000 actuation cycles”
Testing in application-relevant fluids: seawater, glycol, cleaning agents
Accelerated life testing: thermal cycling + salt spray + dynamic operation over 1,000+ hours
100% production leak testing: using pressure-decay or mass-flow methods on every unit
Designing for serviceability: modular seals that can be replaced in the field without full disassembly

Some even publish test videos or third-party certificates—a strong signal of confidence.

What Should You Ask Before Trusting an IP68 Claim?

Don’t just look at the rating. Ask:

“What are the exact test conditions? (Depth? Duration? Temperature? Cycled or static?)”
“Was the test performed on a production-representative unit—with all ports installed?”
“Do you perform 100% leak testing in production—or just sample testing?”
“What seal materials are used, and are they compatible with my fluid/environment?”
“Can you provide a test report from an accredited lab (e.g., TÜV, SGS, UL)?”

If the answer is vague or refers only to “compliance with IEC 60529,” proceed with caution.

IP68 Is a Starting Point—Not a Warranty

An IP68 rating tells you what a manufacturer claims under specific lab conditions—not what your actuator will endure in the field. True reliability comes from:

Conservative design margins
Application-aware testing
Robust materials and processes
Transparency in specifications

In mission-critical applications—subsea, medical, food safety—never assume. Demand data, verify test protocols, and when in doubt, overspecify. Because when water finds its way into an electric actuator, the failure isn’t just a leak—it’s downtime, contamination, safety risk, and lost trust.

And that’s a risk no IP rating alone can eliminate.

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