THE ROOTS OF INCONSISTENCY
In the past, it has been impossible to predict the life of a diaphragm until tested in the user's full-size commercial system. Although expensive and risky, this has also meant that suppliers are often distanced from the end user's real-world application and reliability experiences. Meanwhile, replacement parts are often supplied through distributors, further distancing suppliers from end-user's performance issues.Case Study, Bayer HealthCare, San Francisco
Divakar Amin, engineering manager, final product manufacturing at Bayer HealthCare, described the implications of inconsistent diaphragm valve performace to the BioPhorum Operations Group:
"I have experienced two recent incidents involving valve failure during the fill-finish process, causing leakage into a final processing operation. The cost of the lost batch each time was measured in millions of dollars. When we opened each valve up, we found that the diaphragm material had deformed because the material was not suitable for the thermal cycling of the valve.
"We need to ensure that valve manufacturers match the process application to the capabilities of their products. Bulk tanks are exposed to high temperatures during sterilization, peaking at 130 °C. Valve manufacturers tell us that their diaphragm material can withstand 150 °C, but what they don't tell us is how many thermal cycles their material can withstand, especially if the cycle includes low temperature processing. If the polymer is not tested against the full thermal cycle, we have no level of confidence that it's not going to fail and leak.
"It's very important that suppliers perform the reliability testing in the lab and tell us how many thermal cycles the diaphragms will sustain. Without this information I'm left having to change-out my diaphragms every three months because I simply cannot risk losing another batch."
INCONSISTENT CHANGE CONTROL
Barak Barnoon, director of process engineering and analytics at Pfizer, raised another example of inconsistent diaphragm valve performance in real-world applications to the BioPhorum Operations Group:
"What is missing currently, is control on their part of their suppliers and their diaphragm raw materials. We have seen impaired performance due both to changes in their sourcing and also in the manufacturing processes of their diaphragm suppliers. There's a big opportunity to increase the level of control and good manufacturing practices."
Divakar cites a further example of inadequate change control:
"If very small changes are made to the diaphragm material, then they can have a big impact on performance. We have experienced a situation where an autoclave valve was replaced with an 'identical' product. Subsequently, the heat-up time of the autoclave went out of its validated range. After extensive investigations we discovered a very minor, undisclosed change to the valve that impacted the process."