Planned maintenance, systems and usage

Commercial Planned Maintenance (PM) systems are a collection of very variable beasts, some good, some bad and some indifferent. One system, oldish when used, probably obsolete now, took 240 separate entries to update the main engine running hours. I have also used a brand new system with many errors, one of which was adding in some hours’ updates more than once and this error, when reported, would only be corrected “at the next upgrade”. Had there not been a very unofficial system used in parallel it is unlikely this would ever have been noticed.

When the entries are being written, particularly from scratch, they should be done by a person with appropriate, and relevant, experience. This applies to both maintenance and spare parts entries. A good system will have a ‘training section’ where procedures can be practised before final entries are made; it is not always possible to make changes in the working system.

All sections and levels should be password protected with each individual rank only allowed to access the sections and levels that they require.

The hierarchy is the basic component of any PM System and, as far as is possible, should be consistent across the fleet. The main groups list can be written to cover all ships in the fleet and either entered in full, but omitting sub-groups if not necessary, or the unrequired groups can be omitted. Sub-groups must also be treated in the same way. For example, potable water can, realistically, be in a sub-group under either ‘fresh water’ or ‘hotel services’. Once the grouping has been decided, this should be applied consistently throughout the fleet.

As far as possible, machinery items should be entered with hours-based service intervals rather than calendar intervals. This, largely, prevents over-maintenance and maintenance of unused machinery.

Deck machinery is, however, a good example of items that can benefit from calendar intervals as they are subject to the effects of weather, even when not operated often. Any form of tank, be it ballast, fresh water, bunkers etc. are also obvious items for calendar based schedules.

Months of varying lengths do not generally suit computerised systems so it may be better to base calendars on days. This works out as: monthly = 30 days, quarterly = 90 days, half-yearly = 180 days and year = 360 days. This gives a 5-day error per year and 25-day error over a 5-year survey period. For weekly-based calendars, monthly = 4 weeks, quarterly = 12 weeks, half yearly = 24 weeks and yearly = 48 weeks, this represents an error of 4 weeks per year and 20 weeks per 5 years, which is too large an error for a normal survey interval.

Quarterly intervals, i.e. 13 week quarterly, 26 week half yearly and 52 week yearly periods, mean that months have to be ‘stretched’ which may or may not be considered acceptable.

Unnecessary items should not be entered into a service schedule, neither should anything serviced at less than monthly intervals e.g. items such as filters unless included with parent items. This allows for variations in use and conditions.

Maintenance records should only be kept in the PM system, in order to avoid inconsistencies, which how up as instant non-conformity at a QSMS audit. The exceptions to this rule are the items required by statutory regulations to be entered in the deck log book but are needed in the PM system for scheduling.

Normally the Chief Engineer should be the only person on board responsible for the PM system. He should print out work orders and hand them to those responsible for particular items. When completed they should be returned to the Chief for entry into the system.

Any changes to maintenance routines or service periods should only be made after consulting with the responsible superintendents and should be applied to all vessels in the class. Alterations to service intervals should be made from head office and not by individual engineers. This applies particularly to for items which are dismantled before the normal interval and are entered as such in the maintenance systems, e.g. some main engine pistons are recommended to be inspected at 5,000h for the first service, after which they revert to full service intervals. These are probably best entered for the full service interval and carried out early at a suitable time rather than being set at 5,000hrs and then changed to the full period. It will also apply to items which experience has shown have either a too short or too long service interval.

All maintenance personnel, and Chief Engineers in particular, should be given adequate training in the use of the system. One thing that must be understood is that a 250-hour service is part of a 1,000-hour service which, in turn, is part of a 4,000-hour service, as shown in the table. These are inherent predecessors. This means that when the 4,000-hour service is carried out the lesser hour’s services must be carried out at the same time.

Obviously, the style of work schedule used in the right hand column of the table is less likely to cause the service to be carried out piecemeal, as when the 4,000-hour service is entered in the system as complete it should also enter the two lesser hour services (inherent predecessors) completely. This is the ideal but not all PM systems will do this and the minor services have to be entered manually.

‘Maintenance due orders’ or ‘work orders’ are normally issued based on estimated running hours which are entered when the system is set up. The problem with this occurs when machinery is not run and the maintenance periods are fairly short. If, for example, a generator service interval is based on 16h/day and the order is printed on Sunday showing the maintenance is due on Thursday this assumes that it runs for 16h/day for four days to the service due time. If it is not used in that time the maintenance will be done early. However, if it runs for 24h/day the service will be carried out late. This can be avoided if the work order also shows the running hours at which the service is due. If the system in use does not allow this to be done the actual hours when the service is due can be written in by the Chief Engineer.

Care should be taken when linking items that are serviced together as circumstances may arise where they are done separately e.g. cylinder heads/liners/pistons.

The running hours record is best updated on the day before the next set of work orders are issued and, for any items that are serviced, when they are serviced.

Nothing on this earth can stop work being entered as done which has not actually been done, but this is more likely to be on small services as major services/overhauls are more easily monitored, e.g. by the spares used.

Shore based maintenance can be entered in exactly the same way as if ship’s staff had carried out the maintenance. If CSH (continuous survey of hull) and CSM (continuous survey of machinery) data are entered in the PM System then the system used must not only allow for completed work orders to be stored, and accessible, but for associated photographs, measurements and calibrations to be entered and saved. If this facility is not available, it could possibly be achieved by using a hyperlink to the photographs and information stored elsewhere.

A problem can arise if CSM is included and the engine maker and the Classification Society number the engine differently i.e. one from the drive end and one from the free end. A decision must be made as to which end is No1 cylinder or bearing for maintenance purposes which will then be applied to all of the vessels fitted with that type of engine.

Spare parts must be entered into the system very carefully or chaos can ensue. An example of this comes from experience on two sister ships. Both were built with four generators with the same model number but with different suffices. Three were cooled from a central seawater system but one was used as an emergency generator and was radiator cooled. If these are cross-referenced, spares will be listed that are not required. The three seawater cooled gensets could be cross referenced completely but only the truly common items cross referenced with the emergency genset. One generator on one of the vessels had been replaced with an updated version which had many parts common with the older machines but some that were different. The common parts, unfortunately, had different part numbers from the older machines so no cross referencing was possible.

Cross referencing can be used within the machines themselves as some parts, such as bolts, nuts or weashers, are used in more than one place. This will save excessive stock levels.

The spares list must be carefully checked for correct part numbers as these may vary according to the serial number of the machine.

Another problem occurs with machinery built under licence and the licensee alters part of the design. This can mean that some parts can only be obtained from the builder and others from either the builder or the designers. In the second case both builder and designer part numbers should be listed. Unfortunately this may only show up when spares are ordered and received from the designer and then do not fit.

Great care must be taken to correctly enter spares used and spares delivered. This may be automatic for some PM systems. Spares delivered may be automatically entered as stock when taking delivery; this becomes critical if automatic re-ordering is used. Ideally, re-order levels should reflect usage and lead time for deliveries but this is normally an unknown until an order has been placed. Allowance must be made for exceptional orders for upcoming work.

Automatic re-ordering should be treated with extreme care to avoid unnecessary expense. Systems often involve Max/Min/Re-order levels. The minimum quantity is meaningless because spares are used as required and not according to a fixed quantity, so in practice minimum and re-order levels are the same. For older ships a thorough and accurate stock check must be taken, and a decision made as to appropriate levels without using the next few years’ budgets. Automatic re-ordering is probably best used on new or fairly new vessels when the original system is set up and the inventory is known to be correct.

Updated or equivalent parts may be delivered with different part numbers from those ordered; in this case the new number can be added to the inventory, either as a replacement number or as a secondary number.

It must be possible to order manually as well as automatically to allow for dry-docking and other upcoming repair periods. This can be done from the office by the superintendent but not all systems can automatically enter office based orders to the vessel stock levels.

For a common system to work properly and efficiently there must be consistency between all vessels in the fleet with similar machinery.