The breweries, as well as we at Micro Matic base pressures on the Zahm Nagel pressure chart. You must gain equilibrium between the gas in the product with the head space in the keg. If you enter 38 degrees F with 2.6 vols into the Kegman's calculator it gives you 12.3 PSI equilibrium. No gas coming out of beer or being absorbed. This is in a keg with no pressure drop such as opening the faucet.
When the faucet is opened a pressure drop occurs. This drop must be compensated by what the industry for years has called push pressure. This equates to two PSI more than equilibrium of 12.3 or 14.2. Call it 14 PSIG and control the flow with the beer line. Will this pressure allow the beer to absorb excess CO2 gas. Absolutely! Enough to cause dispensing problems or taste issue with in three to four days? No. Especially with as much beer that Topgun and USMC Retired drink!
We have made a career (job security) out of too many techs out there thinking they are successful simply by trying to get the beer to come out of the faucet clear. We have tasted flat beer, over carbonated beer, beer that we could not drink because it smells so bad all come out of the faucet clear. The day you can accomplish clarity and a quality presentation the life of a keg will be the day you can declare success.
This is why we are so adamant about temperature, pressure, restriction, leak testing and cleanliness.
If you truly would like to accomplish success easily, push your ale/lager @ 22 PSIG with a 60% CO2 / 40% Nitrogen blend.
Scott Zuhse, Instructor
Micro Matic Dispense Institute