With integrated Automatic Loading System and/or due to room restrictions, the position of the lyophilizer maintenance door is a delicate matter.
In another article we will detail the different LUS (loading/unloading system) in the market; for now, we should take into consideration that they will be front-sided LUS or front-back-sided: in other words they will “stress” one or two chamber wings.
From a general point of view a one sided-LUS is able to release the mechanical pressure on the chamber since it keeps 3 free sides for setting up condenser and maintenance door. Is in fact essential to leave one side of the chamber empty or else the hinges will be under higher load and the accuracy of the LUS system will be compromised.
In this case, following the design of the lyophilizer manufacturer, it will result into a side or back maintenance door lyophilizer; mechanically, this represents the best outcome and possible layout constrictions could be resolved placing condenser and maintenance door consequently.
Let’s now have a look on more problematic designs:
Currently in the market 2-sided LUS represents the majority of lyophilizer manufacturer installed base: in fact, historically, push-in-push-out mechanism was the most reliable and the first one to be successfully mounted (GEA 1989).
What happens when 2 sides of the chamber are designed to integrate the loading/unloading pusher?
Well, in this case there are 2 scenarios:
Fixing the unloading arm onto the back maintenance door
Squeezing an unloading device on the back side between chamber and condenser
In the first case the weight of the unloading arm is determinant and is often the cause of some failures: to relieve the door from some stress the unloading device could be mounted on wheels; on the other side, the design in the picture is mechanically preferred although operating maintenance activities can be struggling due to lack of space.
Lyophilizer Door Features
Finally, below are displayed a series of GMP guidelines for the lyophilizer maintenance door:
The door should be latched (for vacuum duty) by a single pin activated by push-button that moves out from the door into a latching detent. Then rotates with a cam action to pull the door securely on the gasket. No manual effort required.
The door should be able to lock (for SIP duty) from the vacuum position by pulling vacuum in the chamber (liquid ring pump). A series of pins around the entire periphery of the door frame are advanced into matching locking detents around the door. The insertion is frictionless due to the vacuum in the chamber, which pulls the door inwards against the compressible gasket.
Self-locking mechanism activated by only two pneumatic actuators. Safe locking in the event of pneumatic air failure.
The door is sealed by a single silicone cord gasket mounted in the door frame.