Just as a matter of interest, how would a person burp a 50 litre keg and later lower the pressure after carbing beer in the keg for a couple of days, other than the "screwdriver method"?
What fittings are you using off the keg adaptor?
If you have the standard pub snaplock fittings, attach the beer out line on to the gas in line. Then purge the gas out through your tap.
It's a standard A type coupler with ball lock adaptors fitted so it can be used on the same system as the corny kegs. There's no relief valve on the side of the coupler body. Thanks for the replies guys.