Hey Beefcake. What fermentation pressures were you using?
As you know we use two silicone o-rings on the pill hydrometer. Silicone is a great o-ring material as it's got good spring properties and is fairly chemically resistant. One of the issues with silicone is that it has high gas transmission rate meaning both oxygen and co2 and other gasses can pass through the silicone.
When the fermenter is under pressure CO2 gradually seeps into the pill housing through the o-rings. From our testing this is fine and has not significant impact to the accuracy but if the gas in the pill gets too great and then all of a sudden the external atmosphere drops in pressure(ie you open the all rounder lid) the gas cannot be released out of the pill housing fast enough and this can cause the pill housing to pop open. From our experience this is extremly rare and the only time we have heard of this is when customers are fermenting at higher than recommended pressures. Generally speaking we recommend fermenting at about 2-10psi. If the fermenter is at an elevated pressure (above 20psi) for a long time (several weeks) this CO2 can ingress into the housing and cause this issue.
I should not that there are benefits to fermenting at low pressures but pressures above 10psi have a negative effect on the yeast so there is no reason to really be fermenting at higher pressures than 10psi.
One thing we have been considering is changing the o-rings in the pill to EPDM as EPDM has about 30times lower gas transmission rate than silicone.
If you dont mind me asking what pressure was the fermenter at prior to opening up the lid.
If you purchase the Pill from us please contact our customer service team and we will supply you with a free replacement.