Periodicity Codes

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Periodicity Codes

D - DailyQ - Quarterly
2D - Every 2nd day4M - Every 4th month
3D - Every 3rd dayS - Semiannually
W - Weekly8M - Every 8th month
2W - Every 2nd weekA - Annually
3W - Every 3rd weekxM - Every x months
M - Monthly"x"= number of months
2M - Every 2nd month


An asterisk (*) following the periodicity code indicates a Safety of Ship item and requires the ship/or user to comply with reference (a).

Maintenance requirements with calendar periodicities greater than every 60 months may be developed for applicable ship classes in extended operability programs up to the length of the maintenance cycle. These periodicities must be evenly divisible by six months (i.e., 66M, 72M, 78M, 84M, etc.).

Non-Calendar Periodicity

R- Situation Requirement
U - Unscheduled Maintenance

Inactive Equipment Maintenance (IEM)

LU - Lay-Up
PM - Periodic Maintenance
SU - Start-Up
OT - Operational Test

The periodicity code also includes a number for specific identification. When more than one MRC of the same periodicity exists in the same MRC set, the MRCs in most cases, will be numbered consecutively, e.g., "D-1," "D-2," "D-3," or "M-1," "M-2," etc. An existing MRC may be reapplied to a revised MIP even though the periodicity code of the reapplied MRC may not fall within the normally sequential numeric periodicity codes. For example, W-1, W-2, W-3, W-6 may appear on a MIP, where W-6 was an existing MRC that was reapplied to this equipment. Technically, valid MRCs will not be reprinted merely to change the periodicity code number. Non-sequential numbers will not affect scheduling or management control.

(1) Monthly--Will be scheduled within the interval between 3 and 6 weeks following the last accomplishment. A monthly PMS maintenance requirement must be scheduled three times in a quarter. Note: If a monthly maintenance check is circled and...
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