Coffee Data Science
Symptoms of O-Ring Failure in an Espresso Machine
Oh the joys of lever machines
I recently discovered the O-rings in my beloved Kim Express were going bad. The last symptom of failure is when water comes up through the spring and the top of the machine resulting in a pressure drop and a hot mess of coffee when I pull the lever down, but I would prefer not to get to that point.
This time, I realized I saw some other symptoms that had been going on for a few weeks at least. I take videos of all of my espresso shots for failure analysis, so I was able to go back in time to see these reoccurring symptoms.
- Dripping water from the shower screen which slowly increases over time.
- Some video evidence with difficult to see symptoms.
- Without the portafilter locked in, some steam or water was coming out of the shower screen.
- After cleaning shower screen, water dripped more and went up into the spring.
I present multiple examples showing an issue in the same spot, which helped me to identify the problem. Had I found it sooner, I could have replaced the O-rings sooner and not suffered from degrading shot quality.
For this shot, on the left size, there is early blonding. I thought this was due to shot preparation or the shower screen, but I suspect now that the O-ring was deficient on that side.
A similar problem of early blonding occurred in this shot as well.
This shows more blonding on the left side.
This shot was high extraction, but there were a few spot of blonding on both sides.
This shot flowed slower, and as a result, the left side blonded much more noticeably.
Each of these images played into a better diagnose of a systematic problem.
Data has been very important for improving my espresso shots and to avoid a failure like this one below. I was able to salvage some of this shot with longer pre-infusion and light pressure pulsing, but that is not sustainable.
Hopefully, video evidence could help others diagnose not just bad shot preparation, but also machine maintenance issues.
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