IP67 and IP68 Rated Servo: What the Numbers Actually Mean for Your Deployment
Choosing an IP67 or IP68 rated servo is not about picking the higher number. It’s about matching the seal design to the water exposure your machine actually faces. “We spec’d IP68 for an outdoor conveyor that sees occasional rain. The IP67 units on the same line have been running fine for three years,” one food processing engineer told us. In other words, over-specing the IP rating buys you nothing. Under-specing buys you a flooded gearbox.
IP67 vs IP68: The Difference That Matters
IP67 means the servo survives immersion in 1 meter of water for 30 minutes. IP68 means it survives continuous immersion beyond 1 meter, with the depth and duration specified by the manufacturer. For example, an IP68 servo rated for 3 meters and 24 hours handles a flooded inspection pit. An IP67 servo handles a pressure wash but not sustained submersion.
However, both ratings assume static water pressure. Dynamic water — a high-pressure jet from a washdown nozzle — is a different test entirely. Specifically, IP69K covers high-pressure steam cleaning. IP67 and IP68 do not. Consequently, if your application involves daily washdowns, you need IP69K, not just a higher second digit.
How a Servo Seal Actually Works
A waterproof servo seals three interfaces: the output shaft, the case joint, and the cable entry. The output shaft uses one or two radial lip seals with a stainless steel garter spring. This seal must hold pressure while the shaft rotates. As a result, it’s the most common failure point. Over time, shaft wear creates a micro-groove that water follows straight into the gearbox.
The case joint uses an O-ring compressed between the mid-case and top cover. This seal is static and rarely fails if the screws are torqued correctly. Meanwhile, the cable entry uses a molded strain relief with a compression gland. Therefore, never pull a servo by its cable. That’s the fastest way to break the cable entry seal.
S9150D: Tested to 1 Meter for 30 Minutes
The XQ-Power S9150D in its IP67 configuration uses dual radial lip seals on the output shaft, a silicone O-ring on the case joint, and a molded cable gland. In testing per IEC 60529, the servo operated normally after 30 minutes at 1 meter depth with zero internal moisture.
In field deployment on outdoor solar tracker actuators in coastal Thailand, 42 IP67 and IP68 rated servo units have survived three monsoon seasons with no water ingress. By comparison, unsealed servos in the same environment failed within four months from salt spray corrosion on the position potentiometer.1