Temperature Effects on Part Testing in the Medical Device Sector

Leak testing is a vital step in the manufacturing and validation of medical devices, particularly those involving sealed components, sterile barriers, or fluid pathways. While there are many factors to consider when preparing to leak test a new part, one that can lead to both false positives and negatives is temperature. Understanding and controlling temperature during leak testing is essential for accurate, repeatable results.

Why Temperature Matters in Leak Testing

Leak testing methods such as pressure decay, vacuum decay, and mass flow often rely on the assumption that pressure changes are due to leaks alone. However, according to the Ideal Gas Law (PV = nRT), temperature and pressure are inherently linked. This is particularly relevant for parts that have recently undergone sterilization, ultrasonic welding, molding, or high-speed filling as these processes that can leave components significantly warmer than room temperature. As the part is tested, it cools, which reduces the sensed pressure and can register as a leak. It’s not just parts though, the environmental temperature changes also need to be considered when testing parts. When it comes to temperature, there are two types of temperature effect that need to be considered: Adiabatic and Ambient. Depending on the part and the situation, one or both effects could cause inconsistent leak test results leading to incorrectly passing/failing parts.

Adiabatic Effects: Temperature Changes During the Test

Most gases and liquids expand when they get warmer, so if you heat a gas that's trapped in a sealed space, for example, if the part is still warm, the pressure will go up. Similarly, there is also the concern of filling or compressing the gas too quickly during the test which can result in a temperature swing that affects the test results.

Reducing Adiabatic Errors in Leak Testing

In both cases, there are a few simple solutions to help minimize this effect. In really sensitive leak tests, it might help to fill the part using a pressure-regulated source, rather than a fast blast of air. This stabilizes the adiabatic temperature rise by limiting the pressure rise. It is also recommended to test at the lowest pressure that will meet the requirements for the testing part. Finally, after the filling cycle, allowing the proper time for stabilization of temperature to occur will lead to less false positives and negative.

Ambient Temperature: Environmental Influences

Outside of the adiabatic temperature issues, considerations should also be given to ambient factors. While many clean rooms and testing locations for parts are controlled, it is possible to still see temperature effects related to the environment. While it may not be possible to fully control the physical location where part testing takes place, there are ways to help lessen the effects. Be sure that parts are not being tested near any type of heater or process where heat is applied. These types of temperature swings will cause inconsistencies from test to test. It is also important to make sure that the testing location doesn’t have any fans or vents that blow across the area. Even temperature changes of +/- 1℃ can affect the leak rate seen on a part.

Ensuring Reliable and Repeatable Test Results

While temperature is not the only factor leading to inconsistent results, it can be controlled to prevent false positives and negatives when testing medical devices. For more information on the theory behind temperature affects, check out our application note on Temperature Effects.

Need Expert Guidance? 

If you need immediate assistance with an application or project don’t hesitate to reach out to our team.  Click here to email us or call us at +1-281-671-2000.

Let us know how we can help!