Commercial kegs are designed to be cleaned upside down.
Pump in through the Dip Tube (Outlet) and return through the Gas side of the coupler.
They are made so the cleaner coming up the dip tube spreads out and runs down the sides evenly and cleans all of the keg. One thing you do need to do is open and close the flow a couple of times so cleaner runs down the dip tube cleaning the outside of it, means a valve between the pump and the coupler is a must.
We use Caustic but at home I would recommend PBW at 45-55oC and as above at 1-2% depending on how many kegs you are going to clean in a batch. I normally clean 20-30 in a run so have to be sure the caustic is going to be active in the last keg.
Remember that Caustic reacts with CO2 very quickly, especially hot, so if you are using Caustic it needs to be blown out with clean oil free compressed air (not a Bunnings or Supercheap compressor) not CO2. Using something like PBW means you can just use your existing CO2 system.
Not that: -
On the inlet side you need to be able to send in Air/CO2, Water, Cleaner and Sanitiser.
On the outlet side you need to be able to send to Waste, Cleaner Return, Sanitiser Return
A manifold made up of Tees and ball valves on both sides of the keg will make life a lot easier.
You need a pretty decent pump, effective cleaning involves both the chemical action and the physical washing action so more flow than you will get from a little home brew mag drive pump is a must.
At work all our beers are cask conditioned so they tend to have a fair bit more crap in then than would most commercial kegs, probably more like what most home brewers are going to get.
It takes 15 minutes to cycle a keg on out Premier Systems keg cleaner, cycle goes:-
Make sure all valves are closed, cleaner is hot, water, air and CO2 are available.
Mount keg upside down, action coupler
Open waste outlet, let any internal pressure will blow out any dregs and CO2 in the keg.
Rinse to waste with Tap water until waste looks clean.
Blow out any water with Air.
Close all valves.
Turn on pump, open Cleaner Return valve, open Cleaner Supply valve, allow to run for (well I do a timed 8 minutes) long enough to clean, make sure you open and close (Flutter) the Cleaner flow valve to clean the spear.
Close Cleaner flow valve, open Air Supply valve blow all cleaner to cleaner storage tank.
Close all valves.
Open waste outlet, Open tap water supply, rinse to waste Flutter water supply to rinse dip tube, close water supply, open Air Supply blow to waste.
About here at home I would just flush the keg with CO2 and sanatise by hand (a funnel in the top of a coupler) before use, pour a liter or so of an acid bases sanitiser in, roll the keg around, turn upside down, shake the **** out of it, fit the coupler turn upside down and allow to drain....
If you want to use a pumped sanatiser its pretty much a repeat of the cleaning cycle (shorter contact time), you need another tank and pump, more valves, many more chances to stuff up. Sending Caustic to the acid tank or vise versa is a favorite.
Strongly recommend you avoid a foaming acid sanitiser in pumped systems.
Might sound complicated but loosing beer to infections sux, if you want good beer cleaning has to be part of your religion, it isn't easy and takes work, cut no corners take no risks. Especially with Caustic its really dangerous I have a 30+ year old scar from a caustic splash, it can blind you for life - be extra careful if you use caustic.
Mark
