One of the major issues in contamination prevention is ensuring that the tubing is completely compressed at the section where the hot blade cuts through before fusing. The importance of this is to assure that the hot sterile blade melts through the compressed section and seals it immediately on both sides.
This also avoids remaining media in the inner hose bore contacting the hot blade and causing burned media or gases (particles) inside the sterile fused hose. During the aligning and fusing process, the compressed sections must be kept sealed to avoid contamination.
It is well known that dry heat is effective for sterilization. It is therefore essential for the hose welding equipment to provide reproducible temperature control as well as a programmable temperature profile.
In this profile the equipment must ensure that the surface temperature of the cutting blade is high enough to provide sufficient inactivation for the time the blade is disconnecting and fusing the hoses together. The D-value of this process can be calculated as follows.
The D-value (time to reach 10log reduction in bioburden) of this process can be calculated according to:
D(T) = Dref x 10(Tref-T)/Z
F(T) = Fref x 10(Tref-T)/Z
In this equation the D-value at a certain temperature can be calculated with the difference between a reference temperature (Tref) and the sterilizing temperature (T). The z-value is the temperature increase in C needed to obtain an extra 10log bioburden reduction.
Depyrogenization procedures typically require an exposure of 30 sec at 250C or 3 sec at 320C. Using an exposure over 350C for 1 sec exceeds this requirement.