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Figures nobody else publishes
Limits, dimensions and intervals from association documents and manufacturers’ data – with source and caveat where one is needed.
Load limits during cleaning
These values come from the warranty conditions of a leading spear manufacturer. Exceed them and you age the valve rubber artificially.
| Medium | Limit | Effect if exceeded |
|---|---|---|
| Steam | 135 °C · max. 2 min | accelerated ageing of the CO₂ valve |
| Caustic | 80 °C · max. 10 min · ≤ 3 % | seals swell and deform |
| Acid | 80 °C · max. 10 min · ≤ 3 % | ditto |
Dimensions and intervals
| Item | Value | Applies to |
|---|---|---|
| Body diameter, flat spear type A | 74.5 mm ± 0.1 | all designs with right-hand thread |
| Body diameter, flat spear (A-type), left-hand thread | 68 mm | this version only |
| Flange dimension, triangular spear type G | 70 mm ± 0.1 | technically identical inside to type A |
| EU Sankey spear type S | 50.8 mm | no housing above the neck: sits inside the neck, outside diameter of the standard 2″ × 14 TPI thread |
| Valve lift, beer valve | 8 mm | D system, documented |
| Valve lift, CO₂ valve | max. approx. 6 mm | D system, documented |
| Opening travel, coupler | 14 mm ± 1 | A and G systems – our own workshop figure |
| Opening travel, filling and cleaning head | 13.5 mm | A and G systems – our own workshop figure |
| Tightening torque, threaded spear | approx. 75 Nm | first installation |
| Re-tightening torque | approx. 47 Nm | after first installation |
| Distance from top of neck to chime | 8.5 mm ± 1.5 | the neck must never stand higher |
| Overhaul interval, spear and down tube | 7 to 8 years | recommendation of the industry association |
| Onset of valve delamination | from approx. 10 years | CO₂ valve |
| Retaining ring threadless systems only | Single-use part | new at every removal |
| Bottom clearance, spear – A and G systems | 9 mm | manufacturer’s figure |
| Bottom clearance, spear – S system | 14 mm | manufacturer’s figure |
| Bottom clearance, spear – M system | 15 mm | manufacturer’s figure |
| Bottom clearance, spear – D and U systems | 14 mm | manufacturer’s figure |
The half millimetre that is no accident
On the flat (A-type) and triangular spear (G-type) the filling and cleaning head opens the valve 0.5 mm less far than the coupler – 13.5 against 14 mm. That is intended in the design, and the reason lies in the loading: during dispense the coupler sits on a keg for hours and is rarely operated. The wash probe couples on and off again on every single cycle.
Whatever travel is too much there adds up. Over a hundred cycles, half a millimetre of excess turns into a tired valve spring – and the keg into a “seeper” that gives off small quantities of beer unpredictably. In the fault list of the American brewers association this very cause stands in first place: overstretched springs from wrongly set wash probes.
Hence the practical advice: measure the opening travel of your wash probes. It costs an hour and is the single most effective step an operation can take for the service life of its keg fleet. Changing keg supplier instead treats the symptom.
Why cleaning runs through the spear
For cleaning, the keg is turned upside down and coupled up. The medium runs in through the down tube and out again via the annular channel. That is why a bent neck is a genuine reason for withdrawal: it misdirects the flow, and on coupling it damages the plant.