Two design principles
The German coupler standards fall into two groups: slide-on systems, where the head is pushed on and locked – flat and combi belong here – and screw systems, where it is screwed on – EU Sankey (S-type) and US Sankey (D-type). Internationally, US Sankey (D-type) and three-lobe are added.
Why this causes trouble in practice
An operation that buys kegs from several markets soon has three systems in the cellar. That is manageable as long as it is documented. It becomes critical when people improvise: a coupler with a burr or a sharp edge cuts into the valve seals – and the damage shows up later on the keg, not on the tool.
Hence the simplest maintenance tip there is: look at the coupler probes at the start of every shift. One minute that saves you leakers.
The alternative to a third system
If a fleet cannot be tapped in the target market, converting the neck is often cheaper than a second keg fleet. That is what the sister company does: neck conversion at Keg Exchange.