Decay curve
The decay curve is used to validate extraction processes in accordance with normative requirements. This action is necessary to develop and specify suitable reproducible, as well as component-specific extraction parameters for routine inspection. It is determined in accordance with VDA 19.1 / ISO 16232.
Table of contents
What is a decay curve?
There are various inspection methods for checking the technical cleanliness of a component, specifically the agitation, ultrasonics, pressure-rinsing and rinsing method. However, these inspection methods are not all suitable to the same extent for all components and each component has specific characteristics due to its geometry. It is necessary to prepare a decay curve to determine whether a method is suitable for checking the technical cleanliness of a specific item.
Quality Analysis determines the decay curve for you
In our laboratory for technical cleanliness verification, we can inspect both small and large components up to a weight of 2.5 metric tons and up to a size of 2 metres. In accordance with VDA 19.1 / ISO 16232, we use the decay measurement to determine the most reliable method for testing the technical cleanliness of your component. We would be pleased to advise you in advance about the possible cleaning methods and component-specific characteristics to keep the effort and costs for you as low as possible. Thanks to our careful residual dirt analyses undertaken using the latest equipment, you receive detailed information about the granulometry of the particles and the gravimetry. You then have everything you need to identify and control contamination in your ongoing production in future.
You will find more information on our webpage covering particulate contamination.
How is a decay curve prepared?
To determine a decay curve, a blank value is first generated to qualify the extraction cabinet without a component. Then the object inspected is sampled six times in succession using the selected extraction method and the specified parameters. Important here: the conditions for the sampling action (initial parameters) such as pressure, quantity of solvent, exposure time, etc. must not be changed during the process. A second blank value is generated at the end of the extraction.
After each of the six individual sampling actions, the detached particles are collected and conditioned in a filter membrane with a specified filter rating. There then follows a fully automatic microscopic analysis for the particle size class and quantity of metallic and non-metallic particles.
Evaluation of the decay curve
The quantity of particles must drop after each sampling action. If these results are depicted graphically, the eponymous decay curve is produced. However, when is the method applied to be considered validated?
After the sixth cleaning operation, the quantity of particles must be 10 percent or less of the total quantity of particles eluted (decay criterion). If so, the method applied and the underlying parameters can be considered validated for cleaning the component sampled. Conversely, if the residual contamination is higher, a different method or modified initial parameters must be selected and then the complete decay measurement repeated on a new test piece.
