Hi bidyut100:
It is not recommended as per my previous posts in this topic. Certainly not for anyone with less than a decade or more with a stable routine in daily deep meditation, spinal breathing pranayama and other practices in the AYP baseline system. If you proceed in your pursuit of mechanical vajroli it will be at your own risk. Natural vajroli is far beyond all that, and it is not attained with a catheter. See these lessons.
All the best!
The guru is in you.