Causes, risks and constructive solutions for compensating the pressure deformation residue in Elastomere diaphragms
Sealing systems under aseptic operating conditions
Diaphragm valves are a central functional element in biotechnological production plants and play an essential role in the safety separation and control of aseptic processes. Their sealing function is crucial
for maintaining sterile conditions. Against this background, sealing systems are increasingly coming into focus, especially when they are used under recurring thermal and mechanical loads.
Leakage problems observed during plant operation
Recently, Goetze KG Armaturen, a manufacturer of diaphragm valves, has received an increasing number of reports of leakage problems with diaphragm valves from various manufacturers that are currently in use.
These occur in particular after repeated sterilisation in the SIP process with saturated steam and manifest themselves as leaks in the transition area between the valve body and the diaphragm. The cause of these leaks lies in the setting behaviour of the elastomere diaphragms used.
The so-called compression set describes the permanent deformation of an elastomer seal under long-term mechanical and thermal stress. This material-typical behaviour is a fundamental property of
elastomer seals. In addition to classic elastomere diaphragms, multi-layer sealing systems are also affected by this, for example combinations of PTFE and EPDM.
As a result of this settling behaviour, the originally set sealing pressure between the diaphragm and valve body is reduced with increasing operating time. This can initially result in minor leaks, which
later become increasingly pronounced.
Effects on sterility, product quality and plant operation
Leaking diaphragm valves can lead to contamination of the environment, cause sterility problems and favour cross-contamination within the production facilities. In sensitive biotechnological processes, there is a risk of losing entire production batches. Regardless of the specific extent of the damage, such leaks always pose a considerable risk to microbiological safety and the validation of the system.
Plant operator requirements and regulatory framework
Against this backdrop, plant operators are increasingly looking for practical solutions to sustainably manage this problem. The focus is increasingly shifting from the diaphragm as an individual component to the interaction between the diaphragm, valve body and actuator. What is required is a coordinated sealing system that takes into account the material-related changes in the elastomer seals over the entire service life.
It is clear that users are prepared to abandon their previous reticence towards new, optimised technologies if they make a significant contribution to avoiding batch losses that threaten the existence
of the company.
At the same time, plant operators are pursuing the goal of not jeopardising existing qualifications and certifications, for example in accordance with FDA requirements, due to technically avoidable leakage
problems.
Constructive compensation of the settling behaviour
A sealing system that minimises the effects of the settling behaviour of elastomer seals must therefore compensate for this with suitable design compensation elements. It is crucial that the pressing force
required for the sealing function is maintained permanently regardless of thermal cycles, pressure loads and material fatigue. This is the only way to ensure a stable and reliable seal between the diaphragm and valve body.
Patented solution with mechanical equalisation
The patented design of Goetze KG Armaturen offers a possible solution in which the residual pressure deformation of the elastomere diaphragms is specifically compensated. A stainless steel pressure sleeve integrated into the actuator takes on the function of a mechanical equalising element and ensures constant compression of the diaphragms.
This design from GOETZE eliminates the need to retighten the diaphragm after the first steam sterilisation, which is otherwise often necessary.
Sustainable problem solving through system customisation
In practical applications, the leakage problem can be permanently solved by replacing the diaphragm in combination with a suitable actuator. Various diaphragm materials and actuator designs are available for this purpose, which can be adapted to the process conditions in each case. In many cases, it is not necessary to replace the entire valve, but it may make sense to do so depending on the system concept and life cycle strategy.
The basis for a sustainable solution is a qualified root cause analysis in which both the material used and the specific operating conditions and sterilisation cycles are taken into account. In addition,
application-related technical advice from the manufacturer in each case is required to ensure long-term stability and process reliability when sizing the sealing system.
Conclusion:
Leakage problems due to the settling behaviour of elastomere diaphragms pose a relevant risk to sterility, product quality and system availability in biotechnological applications. A purely component-based approach falls short of the mark. Only a systemic approach that takes into account the diaphragm, actuator and design compensation elements makes it possible to permanently ensure the required sealing pressure. Suitable technical solutions can reduce leakage risks, minimise maintenance costs and stabilise the operational safety of aseptic systems in the long term.
