This question drives clients and critical valve makers crazy. There are loads of folks out there asking YOU to answer this question (it seems so logical, after all). Then, when we tell you we don’t know for sure, it kinda makes you the ham in the sandwich, caught between a demand for information and the lack of same.
So, why can’t we give you any better answer than “It depends…”?
To begin with, we are never told the exact details of the process. This makes it hard for us valve makers to know what we are dealing with.
Exposure to steam is a major factor in diaphragm aging, and the chemicals in the process are also factors—as well as the CIP and SIP cycles, and the temperatures and lengths of these cycles. Some cycles and chemicals even act synergistically to age the diaphragm.
An aseptic biopharmaceutical application that we know quite well makes a good example. Here, cycle parameters were developed specifically to produce an aseptic CIP/SIP process. Validation is the name of the game for most clients, so no cycle is in any way generic. Each is specially developed, tested and proven to do its part in creating a reproducible aseptic CIP/SIP system.
Because each CIP/SIP cycle is custom developed (and we never know what the product really is to begin with), there is no way we can guess what conditions would be appropriate to test for in the lab. This is why valve makers don’t attempt to simulate your processes. Where does this leave you?
Here’s our advice:
- Gather data. Find out what is already known about how certain elastomers perform in your process. Become familiar with how well they perform in the different locations and cycles. The gasket material currently used is a good clue to what works.
- Check the generic chemical resistance charts produced by elastomer makers. This data should tell you what not to select as a diaphragm, which can be very useful.
- Use your best judgment in diaphragm selection based on actual experience at your facility combined with the resistance tables. Nothing we can suggest can match the value of your experience. Here are some other tips we can share with you based on what our diaphragm users tell us:
- Observe the diaphragm as it goes into your process and starts to develop a life. We suggest you look at it weekly or twice a month at a minimum. It only takes a couple minutes to do this!
- Keep your staff on the lookout for any signs of diaphragm wear. Learn what the diaphragm looks and feels like as it ages.
- Our pickiest clients (parenterals makers) tell us that they like to start with these generic rules to ensure that they change the diaphragm long before it’s needed.
- For fewer than 5 SIP cycles/week (less than 2 hours each at temperatures under 135°C), consider annual diaphragm changeout.
- For more than 6 SIP cycles/week (less than 2 hours each at temperatures under 135°C), consider changing out the diaphragms every six months.
Now, keep in mind these are very minimal guidelines. But they are a good rule of thumb. It is critical that you evaluate materials based on your system.
Do you have a materials problem or a diaphragm issue? What are your experiences? We’d love to hear from you!
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