Journal
Separating planned maintenance from hours the line simply did not run
Many UK plants keep two clocks. The maintenance diary shows windows that were booked weeks ahead. The shift log shows when the line actually stood. Factory managers who overlay the two often find that ‘planned’ time is shorter than the diary, or that the diary was never used and every stop sits under a single engineering code.
Start with a week you trust. Mark the windows that had a job card, a named fitter, and a sign-off. Everything else in that calendar slot is not planned maintenance; it is lost running time wearing a convenient label. Draw both as stacked bars by day. The gap between diary and log is usually the first argument worth having in the production meeting.
Night shifts complicate the picture. A window booked for days can overrun into the first hours of nights, and the night log may call it ‘waiting for engineering’ rather than an extension of the job. Ask the night supervisor which stops they inherited. Those inherited minutes belong to the planned job, not to the night crew’s unexplained losses.
Do not average the week into a single percentage. A clean Tuesday and a wrecked Thursday cancel in a mean and hide the Thursday. Keep the days visible. Throughput questions are almost always about particular days, particular SKUs, and particular crews — not about a smoothed month.