Standards Committee Report I – Recommendations for pressure measurement
Committee Chairperson, Lawrence Ulfik
The standards committee has convened, voted and has the approval by the Board of Directors for its decision that:
1. The capacitance manometer shall be the device of choice for measuring and controlling pressure in a freeze dryer.
2. That the pascal (Pa) shall be the unit of pressure measurement for freeze drying systems, and for reporting results we agree that for 1-2 years the society will request that paper submissions include in parenthesis the equivalent measure, e.g., microns of mercury, mTorr, mbar, microbar – etc.
As you may know the capacitance manometer is an absolute pressure measuring instrument, in that it senses the combined forces exerted by all of the gas partial pressures present in a freeze drying system and can present a linear signal as a force per unit area. The committee and the board of directors of our society request that practitioners use or refer to the capacitance manometer measuring system where possible, to allow standardization of the chamber and condenser pressures in freeze drying systems so that others may repeat work with complete understanding of this process variable.
We have chosen the pascal for the standard measurement scale because of the direct correlation to force per unit area. The pascal (Pa) is the unit of measure in the MKS metric system (Meter Kilogram Second system) equal to one newton per square meter. The Newton (N) is defined as the force necessary to accelerate 1 kilogram at the rate of 1 meter per second per second.
Submitted: February 1, 2003
Standards Committee Report II – Standards Committee: Update for Board Meeting 2nd Feb 2006
Committee Chairperson: Dr. Paul Matejtschuk
In the Autumn of 2005 we ran a survey of which other physicochemical units should be used for ISLFD conferences/publications etc. We also requested a list of topics for further discussions. I sent this to 56 addresses of which 8 were undeliverable, a further 6 acknowledged receipt but did not reply and 8 responded.
I received 8 responses (thank you very much to those who replied and gave me something to report) and the outcomes are summarised on the attachment.
1) On the topic of other numerical units commonly used in reporting freeze drying – the majority agreed that MKS system (metre kilogram second and hence the SI system) would be appropriate. Practically, most people requested that Centigrade be used for temperature, there was a pretty equal split on Kcal or Joules (Joules would be SI unit) , mostly people felt the metre was appropriate unit for length (i.e. when discussing shelf dimensions) although as Jon Bill pointed out when specifying new freeze dryers it is most likely that millimetres would be used for the dimensions on plans drawn up by companies and so some flexibility is required. With regards to time this would depend on context, for most freeze drying activities hours/minutes is probably the most applicable. There was no real agreement on units of power, so I propose we accept a range of units, although the Watt would be the MKS or SI unit so perhaps should be preferred
2) Priorities for future discussion. The most voted for issue was thermal analysis and related methods, closely followed by leak rate testing, scale up between freeze dryers and clean in place procedures. I suggest that we will undertake a discussion on these four areas during the coming 12 months and then review progress
3) Membership of the committee. I said in my previous report that the large number of names subscribed to the committee was not viable and I think the response to the survey has indicated that we are in fact likely to only have responses from a small proportion of those “signed up”. For the next mailing I will keep the full list, but reduce it sharply thereafter, if I do not receive responses.
Paul Matejtschuk PhD
Chair -Standards Committee
2nd February 2006