IP68: What the Rating Actually Means

IP68 is defined by IEC 60529 as protection against "continuous immersion in water under conditions specified by the manufacturer." Unlike IP67 (which specifies 30 minutes at 1 m), IP68 has no standardised depth or time -- these are set by each manufacturer. This means two IP68 connectors from different manufacturers may have completely different actual immersion capabilities.

When reading IP68 specifications, always check the manufacturer's supplementary data:

• Specified depth (e.g., "IP68 to 200 m" is very different from "IP68 to 7,000 m")
• Test duration at that depth
• Whether tested mated or unmated
• Test medium (freshwater vs. seawater -- seawater is more demanding)

RV POWER GROUP connectors rated IP68 are tested to 7,000 m equivalent pressure (700 bar) for 24 hours, in a mated configuration, in synthetic seawater solution.

Hydrostatic Pressure Testing Protocol

Factory hydrostatic testing is the most reliable depth certification method. The test procedure:

1. Assemble and mate: Connector is fully assembled with cable overmold (if applicable) and mated pair assembled.
2. Pressurize to test pressure: Immersed in pressure vessel filled with water or oil; pressure raised to 600 psig (41 bar, equivalent to approximately 400 m depth) over 5 minutes.
3. Hold: Maintain 600 psig for 15 minutes.
4. Electrical test under pressure: Insulation resistance and continuity checked at full test pressure.
5. Depressurize and inspect: Connector disassembled (or re-tested electrically) to confirm no water ingress.
6. Certificate issued: Each serial number receives a signed pressure test certificate with test date, pressure, duration, and technician ID.

Note that 600 psig factory test pressure corresponds to a safety factor of approximately 1.8x at 3,000 m depth. For deployments at the rated 7,000 m, a higher-pressure acceptance test (>1,400 psig) would be required -- available as a custom qualification option.

Depth Rating vs. Pressure Rating: Key Conversions

Common Misconceptions About Depth Ratings

Misconception 1: "IP68 means the connector is waterproof at any depth."

False. IP68 specifies protection against continuous immersion, but the specific depth is manufacturer-defined and can be as shallow as 1.5 m for some consumer products. Always check the depth figure in the detailed specification, not just the IP code.

Misconception 2: "A 7,000 m rated connector can be connected and disconnected at 7,000 m."

Depth rating describes the maximum hydrostatic pressure the connector can withstand when mated. Wet-mating at extreme depth is a separate performance parameter and must be specified explicitly. Most subsea connectors rated for 6,000+ m are designed for connection in a pressure-balanced, ROV-assisted environment, not direct hand-mating.

Misconception 3: "Higher test pressure always means better in-service reliability."

Excessive factory test pressure can plastically deform O-ring grooves or cold-work contact pins, actually reducing reliability. Reputable manufacturers qualify their designs with finite element pressure analysis and use test pressures that produce meaningful safety margins without damaging the assembly.

Certification Documents to Request

When sourcing subsea connectors for critical applications, request the following documentation:

• Factory hydrostatic test certificate (per unit or per batch, depending on volume)
• Material certifications for shell (aluminium alloy grade, titanium grade) and O-ring compound
• Dimensional inspection report confirming compatibility with mating connector series
• Qualification test report for thermal cycling and pressure cycling life tests

RV POWER GROUP provides factory test certificates with all orders as standard. Material certs and dimensional reports are available on request. Contact [email protected].