Washing of Metal Casks

General Considerations

The cask washing regime depends on:

• Size of containers and degree of soiling
• Production requirements, temperature and pressure of water and steam and cycle time.
• Nozzle spray efficiency, external cleaning brushes, cleanliness reguirements and sterility of casks after washing and rotation/use of casks in trade.

The important parameters in the washing regime are:

• The total spraying time in conjunction with adequate pressure.
• The total time for which the temperature exceeds 82° C (180° F).
• Suitable detergents should be used.
• Efficiency of cleaning must be checked to ensure that cask washing is not a source of infection.
• High levels of cask beer returns may be indicative of inefficient cask washing.

Range of Values

• Microbiological examination of washed casks should ideally give zero cell count.
• Water temperature is typically in the range 82° – 88° C (180° – 190° F) when using steam and 99° – 104° C (210° – 220° F) when not using steam
• Water pressure is typically in the range of 5·5 – 7·6 bar g (80 – 110 psi), the exact value depending on the type of cask washer employed.
• Steam pressure is typically 6·2 – 7·6 bar g (90 – 110 psi).
• Holding time will depend on the number of stations but is typically 16 – 18 seconds.

Operational Protocols

• The casks are drained and washed, shive hole downwards to prevent any washings running back into the casks
• Cask interiors should be visually inspected at the end of the washing cycle, immediately prior to filling

Measurement Protocols

• Temperatures and pressures of water and steam are monitored
• Sterility of washed casks is monitored
• After washing each cask is sited for a final visual check of the cask interior, prior to immediate filling. Unacceptable casks (i.e. those with soiling, debris remaining or off-taints) are returned for washing and then re-examined
• Casks with damaged interior surfaces or with off odours are set aside for repair or special treatments.
• Washer cycle time should be checked
• Nozzle spray efficiency is checked daily using a glass-ended cask and feeler gauges.