## 3 Results and Discussion
### Critical Roughness Parameters for Leakage Detection
If the difference in the value of the surface topography parameters is smaller than the base surface with the following values of parameters: \(Sq=1.54\)\(\upmu\)m, \(Sp=3.96\)\(\upmu\)m, \(Sz=6.72\)\(\upmu\)m, \(Sa=1.25\)\(\upmu\)m, and \(Spc=8454\)\(1/\)mm, then the tightness remains at the same level. However, in the case of applying surfaces with sharper peaks than the base surface, leakage remains at the same level until the limit value is established. When the limit difference is exceeded, there was a rapid increase in leakage values. This is due to the loss of the required contact between the parts. Analyzing the results of testing pairs of samples in which the base part was characterized by parameters belonging to code group E, and the second sample by the surface parameters belonging to code groups A, B, C, D, and F, a relationship was observed between the results of leak tests and the parameters of the surface topography, similarly to the previous analyses. For a compressive force equal to 2280 N, a relationship was observed between the leakage values and the values of the parameters \(Sq\), \(Sp\), \(Sa\), \(Sz\), and \(Spc\). Figure 15 shows the dependence of value of leakage to difference between \(Sa\) parameter of samples, where one of the samples has got the value of \(Sa=0.33\)\(\upmu\)m. It was observed that for kits that contain samples with a parameter of more than 3 \(\upmu\)m for the Sa parameter, the  
Figure 14: The value of leakage \(Q\) as a function of the difference in the value of the surface topography parameter Sa for a constant compressive force of 2280 N for the base surface with a value of \(Sa=1.25\)\(\upmu\)m.  
leakage value increased. Below the indicated thresholds, and when the second pair of parts had a parameter with a lower value, the leakage remained at the same level. The surface parameters \(Sz\), \(Sq\), \(Sp\), and \(Spc\) show a similar relationship. If the difference in the value of the surface topography parameters is smaller than the base surface with the following values of parameters: \(Sq=0.414\)\(\mu\)m, \(Sp=1.12\)\(\mu\)m, \(Sz=1.84\)\(\mu\)m, \(Sa=0.33\)\(\mu\)m, and \(Spc=2602\)\(1/\)mm, then the tightness remains at the same level. However, in the case of applying surfaces with sharper peaks than the base surface, leakage remains at the same level until a limit value is established. When the limit difference is exceeded, there was a rapid increase in leakage values. This is due to the loss of the required contact between the parts. When analyzing the test results of sample sets, in which one part belonged to code group F and the other part belonged to one of the other code groups A, B, C, D or E, the influence of the surface topography parameters on the values in the leak test was observed, as previously mentioned. For the compressive force equal to 2280 N, a relationship was observed between the leakage values and the values of the parameters \(Sq\), \(Sp\), \(Sa\), \(Sz\), and \(Spc\). Figure 16 dependence of value of leakage to difference between \(Sa\) parameter of samples, where one of the samples has got the value of \(Sa=0.187\)\(\mu\)m. It was observed that for assemblies that contain samples with a parameter of more than 3.1\(\mu\)m for the Sa parameter, the leakage value increased. Below the indicated thresholds, the leakage remained at the same level. The surface parameters \(Sz\), \(Sq\), \(Sp\), and \(Spc\) show a similar relationship. If the difference in the value of the surface topography parameters is larger than the base surface with gentle peaks, then the tightness remains at the same level until a limited value is established. When the limit difference is exceeded, there was a rapid increase in leakage values, which is due to the loss of the required contact between the parts.