Astell has been helping organisations achieve effective steam sterilisation for more than 140 years. Over that time, we have learned that regulated users need more than a machine that reaches temperature; they need a process they can prove. This article draws on lessons from an anonymised pharmaceutical project where the defining task was to specify and validate real loads before the autoclave entered routine use.
The challenge: proof, not just heat
The importance ensuring sterilization has been effectively performed varies depending on the use case. A home cook failing to sterilize jars may ruin a batch of jam, a microbiologist might invalidate an experiment, but for a pharmaceutical manufacture the repercussions could affect thousands of at risk members of the public. In these Good Manufacturing Practice (GMP) environments, certainty is essential. In these situations, autoclave validation is an important step to test, document, and ensure all parts of the autoclave load are heating to the correct temperatures at the correct rate, and are sterilizing correctly.
That means documentation is not an afterthought. For regulated production, the cycle record, validation evidence and defined load schedule are part of the deliverable.
Define the real loads first
In this anonymized contract development and manufacturing organization (CDMO) project, the user did what good validation practice demands: it defined its loads before relying on a generic cycle. The schedule covered eight distinct loads across four programs. Those loads ranged from a minimum load of a single six-piece manifold with a rinse-water and mixing vessel, through racks of media universals, to bottles of water in 100 ml, 250 ml and 1,000 ml Durans, a plastic-discard load of consumable waste, and an empty-chamber cycle.
Both minimum and maximum loads were specified, because the most awkward case is often the one that decides whether a cycle can be signed off. A light load and a densely packed liquid load may both be valid, but they do not behave in the same way.
Prove the coldest case
The common target across the schedule was deliberately tight: 121-124 °C, held for 15 minutes, with the discard load taken to 121 °C or above. Bands like that give the validation engineer something concrete to test. They allow the chamber to be mapped, the slowest point of the load to be identified, and the cycle to be signed off with evidence rather than confidence alone.
For a maximum liquid load, a suitable approach is to time the hold from a probe in the reference vessel, so the hold begins only once the liquid core has reached temperature. Waste, meanwhile, normally belongs on its own discard program rather than being forced into the same cycle as clean media.
What this means for regulated users
The sequence matters: define the real loads first, specify minimum and maximum cases, then choose a machine with the specifications and options to meet those demands, then perform and record the validation process needed to prove each cycle.
And the proof is not a one-off. In the case behind this article, the relationship did not end at delivery: the same manufacturer’s autoclaves have since been independently validated many times over, across several machines — ensuring the sterilization process remains within the required tolerances.
How Astell can help
In this project, Astell helped the customer connect the autoclave specification to defined GMP loads, operating cycles and validation requirements. If you have a similar regulated-production challenge, or another autoclave-related question, contact Astell to discuss it. With hundreds of autoclaves available, highly customisable builds, versatile installation options and an expert team of in-house service engineers, Astell has the skills and experience to help solve your steam sterilisation challenges. Contact Astell today at Info@Astell.com.
