Plastic kegs

I'm going to be putting a couple of batches in to plastic kegs in a week or so for priming. Do I need to purge them with Co2 at this time or do I let the co2 produced purge the oxygen I think they have 10psi blow off valves. I know they need to be pressurised with aditional CO2 at the time of serving.

Another question I have is regarding O2 ingrestion, if the barrels are presurised with this stop the O2 getting in. I know that a fair few Microbreweries around here use this type of kegs for transporting and serving small batches of cider.


The barrels are like these.

Doesn't anybody use these or have any views?
I've just used 2 and pressurised with 70% Nitrogen an 30% CO2.

Hi Orfy,
presume you're talking king keg or similar.
don't purge them until you need to get the beer out.the co2 from secondary will build up in them, and yeah they have valves all right.

Thanks,

Too late this time.I already purged and pressurised them.Should I loosen the cap or just leave it?