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September 03, 2013

Serious Product Contamination.

Again a serious contamination problem has resulted in serious product damage occurring.  Although  the actual problem is and has been documented in our website since 1997 at

We have known about this type of problem for some time.  In all inspections we do look out for such clashes of functionalities.  Our original case had cost the clients “an undisclosed sum”.

So here it is again.

The normal requirement in designing process equipment installation is that all powered valves must fail into a safe condition.

So with a loss of power (pneumatic or electric) : -

  • A steam supply valve will fail shut.
  • A supply valve to a vessel (water – product – whatever) will fail shut.
  • A steam exhaust valve will fail open.
  • A drain valve will fail open.

Now take out your P & ID for your mixer / sterilizer / homogenizer / blender process stage and follow through from the main vessel body.  For now; forget about all other pipes and vales, and just concentrate on the vessel drain system.  Now consider the holiday or clean-down / shut-down times when the HVAC is off and the machines are at rest, usually with access doors open.  On examination you will find that open pipe rout route from each vessel interior through the drain valve into the foul drain.

Some machines will have air-breaks; some will not (autoclaves), so depending on the pressure regime in use and or the prevailing ambient conditions, there will be an almost constant flow of air.

In the current case the flow was very high.  The differential between the autoclave interior and the drain was -45Pa.  The vessel interior and all the associated pipes were very significantly contaminated.

HEPA Filer Compliance Issues.

High Integrity air filters have recently figured in a several very targeted warning letters. It is very important to remember they are not Fit and Forget items; you must establish the filter dirty pressure-drop (change filter) indication. (i.e filter clean pressure-drop + filter range = filter change pressure).
To reiterate; the filter manufacturers clean pressure drop value is always given at a specific flow rate. When the actual flow in your system is lower than this flow; your filter clean pressure drop will also be low and when it is high your filter clean pressure drop will also be high. You must therefore measure the flow and calculate what your pressures are to enable you to declare what the filter dirty change pressures is. Regulators expect to be able to review your documented methodology for this important task.
We have a very simply easy to use test script used for this purpose. Why not purchase it and paste it into all you SOP's and protocols that deal with HEPA filter testing.

HEPA Filter Clean PD Correction - $26.00.

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