IPxx testing, or ingress protection testing, offers a globally recognized standard by which to test and rate any sealed device for its dust and moisture leak resistance. It is a leak standard that must be tested for in a growing number of industries, including medical, military, consumer products, and more.
One of the most common IPxx ratings is IP67. Devices that meet this rating are considered dust tight and withstand up to 30 minutes of submersion in water up to 40 inches (or one meter) in depth.
Manufacturers must test these products on the manufacturing line to make sure the device performs to these standards in the field. One of the most difficult tasks for manufacturers doing this testing is to identify a proper leak rate to meet their required standard. Below, we discuss how to identify the proper leak rate to meet these standards and considerations to ensure a reliable test.
Consider the function and context of the part/device
To begin, it is important to understand that everything will leak to a certain extent, under the right conditions. Either in terms of ingress – penetration by dust or moisture – or egress – the loss of some internal state of equilibrium.
The question then is what is an acceptable leak rate for a sealed device or component (as measured in standard cubic centimeters per minute, or scc/m)? And how does it translate to a leak test to meet the appropriate standard?
The answer? It depends.
It depends on the intended function of the part, expected operating conditions, and the consequences of any penetration by dust or moisture.
For example, enclosures with sight windows or used in certain environments may require water vapor leak rate ranges 0.5 to 3.0 scc/m. In these cases, a sealed device is being used under conditions where temperature, pressure, and exposure to water fluctuate in ways that can force dust or moisture through a leak path.
On the other hand, enclosures that are thick walled, large, and that don’t see altitude changes, or that are subject only to low-pressure spray or drips, may be able to accommodate a higher leak rate, such as 3.0 –10.0 scc/m. That’s because these factors make it less likely that unwanted moisture or dust will be able to find its way through a leak path.
Leak rate formula as a function of the Ideal Gas Law
In all scenarios and usage contexts, we are governed by the Ideal Gas Law. We know that pressure, volume, and temperature are all related in a closed system (which a leak test is). If the temperature of a part is changed during a test, the pressure within the part will change.
Thanks to the linear relationship between flow and pressure – the higher the pressure, the greater the likelihood of a flow across a leak path – we can directly correlate water flow under pressure with air flow under pressure.
For example:
- 1 meter of water equals 1.44 psi of water pressure
- 10 meters (~33 ft) equals 14.4 psig of water pressure
These pressures are then used to ascertain a leak test to IP67 standards, for example.
Ideal approaches to leak testing to meet IP standards
While some manufacturers have enacted dunk testing, or bubble testing, using water to test their devices for leaks, it is a less than ideal solution, which can be unreliable and destructive to the part, leading to unnecessary waste of resources.
In our experience with manufacturers, the ideal approach for devices to meet IP standards is to leak test with air (or an inert gas). This approach is non-destructive, measurable, and quicker to keep pace with production as compared to alternatives like dunk testing.
Depending on the acceptable leak rate for your desired IP standard and the usage scenario of your device, we suggest one of three non-destructive testing options:
- Testing with pressure
- Testing with vacuum
- Trace gas testing
Learn more about each leak test method and how to identify which is best for your IP testing application in our e-book, “How to leak test sealed parts to meet IPxx ratings”.
Looking to discuss leak testing to IP standards? Contact us today.
Last Post