This insight article hopes to show the relationship between these two properties, and the resultant impact on the potential level of leachables in process.13 May 2022
Here we are looking at extraction data, alongside intrusion data, from James Walker EP75B 1" gaskets, and comparing this to three 1" gaskets from different competitors.
The four 1" gaskets were extracted in hot water in accordance with the first extraction process in FDA 21 CFR 177.2600. This is a 7 hour soxhlet extraction in deionised water, with a limit of 20 mg/in2. The results from this
are shown in table 1 below for James Walker EP75B gaskets and competitor products (identified as A, B and C).
Extractable value (mg per inch2)
The first thing to notice is that all gaskets comply with the requirements of FDA CFR 177.2600 and on the face of it there seems to be very little difference between them. EP75B is the cleanest material, due to careful material design and clean manufacturing processes. The ratio James Walker : A : B : C is 1 : 1.25 : 1.06 : 1.55, showing gasket C, with the highest extractables, to have 55% greater extractables than the James Walker material.
For each gasket the intrusion was measured at room temperature after torqueing to 5 Nm and leaving for 4 hours before measurement. The results are shown below in table 2
|Surface area exposed
|James Walker||0.05||88.7 (20% increase)|
|Company A||0.45||196.9 (176% increase)|
|Company B||1.04||362.7 (401% increase)|
|Company C||1.00||349.6 (396% increase)|
Naturally, with increased intrusion, there is a greater surface area of the gasket exposed to the process fluid, also shown in table 2 above. These figures are surprising in that all three competitor gaskets show a large
increase in surface exposed to the process fluids, and hence a greater likelihood of leachables entering the process media.
Additionally, though not a subject for this discussion, increased intrusion results in product build up, difficulties in cleaning (CIP) and the possibility of cross contamination. The next section, combining extraction and intrusion data, explores how the increased exposed surface area affects the potential leachable levels.
Combined extraction and intrusion data
Naturally, with increased surface exposure, it can be expected extractables will increase correspondingly.
(mg per inch2)
|Surface area exposed
|James Walker||0.05||1.42||88.7 (20% increase)|
|Company A||0.45||1.77||196.9 (176% increase)|
|Company B||1.04||1.50||362.7 (401% increase)|
|Company C||1.00||2.02||349.6 (396% increase)|
Note, as EP75B shows minimum intrusion into the bore when installed correctly, the potential level of extractables remains essentially unchanged. It is also interesting to note that gasket B, although having a lower extractable value on material testing than gasket A, has a greater potential extractables per gasket than gasket A when intrusion is accounted for.
The new ratio, accounting for intrusion, is James Walker : A : B : C is 1 : 2.8 : 4.4 : 6.8, showing gasket C, with the highest extractables, to have 680% greater extractables than the James Walker gasket, whereas based simply on material testing was calculated to be only 55% higher.
This data clearly shows that material testing alone, in isolation from product performance, does not give
a true picture of the extractables/leachables potential from different gasket suppliers.
Extraction testing on material alone, without considering gasket performance, although giving useful data on the cleanliness of the material and the processes of manufacture, may not always give a true picture of the risk of extractables / leachables from the gaskets, in process.
The greater the seal intrusion into the pipe bore, then the greater the area of the gasket exposed to the process fluids, and hence the higher level of potential leachables entering the process stream. As the analysis above shows, to get a more realistic value of extractables / leachables, it is essential to take intrusion into account.
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