The greatest weakness in many spare parts processes is treating all items equally. A gasket ring for the bilge pump and an injector valve for the main engine go through the same ordering process with the same approval levels and the same lead times. This is inefficient and risk-blind.
The solution is a criticality classification of spare parts, derived from the equipment criticality in the PMS. Class A: parts for safety- and operation-critical assets with long lead times (cylinder liners, pistons, turbocharger rotor sets, main bearings). These must be stocked on board or in an accessible warehouse. Class B: parts for important assets with short to medium lead times (pump shaft seals, filter sets, control valves). These can be ordered on demand if the supply chain is reliable. Class C: consumables and non-critical parts. Standard ordering rhythm.
This classification reduces inventory holding costs (fewer Class C items in stock) whilst simultaneously increasing supply security (more Class A items available). The classification should be reviewed annually – particularly after changes in operating profile or following incidents.
Spare parts management works better when maintenance planning and material requirements follow the same logic. When the PMS shows a cylinder inspection due in 2,000 running hours, the system should simultaneously check: are the required spare parts on board? If not, when must they be ordered to deliver in time?
This linkage requires three data sources: the PMS calendar (when is which job due), the bill of materials per job (which parts are needed) and onboard inventory (what is available). Most PMS systems offer this function in theory, but in practice the bills of materials are often incomplete or the inventory data is not current.
The consumption history over 12–24 months provides valuable input for quantity planning. If a specific filter type consumes an average of 24 pieces over a year, stocking 6–8 pieces on board (quarterly consumption) is sensible. Without this data, ordering is based on estimates – and from experience, these are either too high (cost) or too low (shortage).
In mixed fleets, there are usually enough common parts among filters, gaskets and sensors to enable standardisation. If three vessels have identical separators but each carries them under a different order number, three separate procurement processes are triggered rather than one bundled order.
The first step is a cross-reference catalogue: which parts are identical or compatible across vessels? For filters, O-rings, gaskets, sensors and standard valves, the overlap rate is typically 30–50% – even in apparently heterogeneous fleets. For sister vessels, it exceeds 90%.
Bundling offers a double advantage: lower unit prices through larger order quantities and reduced administrative effort. It also facilitates the transfer of surplus parts between vessels – an aspect rarely utilised systematically in practice, although considerable inventory is tied up in onboard stores.
Bundle foreseeable demand early and actively manage critical suppliers – those are levers four and five. Forward planning means evaluating the PMS calendar 6–12 months ahead, determining the resulting material requirements and consolidating them in quarterly batch orders. This saves not only costs but also reduces delivery risks.
For critical suppliers – typically engine manufacturers (MAN, WinGD), turbocharger OEMs (ABB, MHI) and specialist manufacturers for pumps and separators – active management is necessary. This means regular communication about upcoming requirements, framework agreements for frequently needed parts and monitoring of delivery times. Since the COVID pandemic and subsequent supply chain disruptions, lead times for many maritime spare parts have permanently lengthened – 12–16 weeks for standard parts and 6–12 months for special manufacturing are no longer exceptions.
The fifth lever is securing alternative supply sources. For many standard wear parts, approved aftermarket suppliers exist offering shorter lead times and lower prices. Technical suitability must be verified, however – particularly for class-relevant components. IACS UR Z10.5 provides recommendations for evaluating non-OEM parts.
The total cost of spare parts supply comprises three components: procurement costs (unit price, freight, customs), inventory holding costs (tied-up capital, space, obsolescence) and shortage costs (off-hire, express delivery, workarounds). The challenge is to minimise the sum of all three – not just the unit price.
For Class A parts, the shortage costs are so high (off-hire: EUR 15,000–50,000/day) that inventory holding costs become irrelevant. Stockholding here always pays off. For Class C parts, inventory holding costs frequently exceed the potential shortage costs – demand-driven procurement is more economical here.
A simple indicator for inventory health: if more than 20% of onboard stock has been untouched for longer than 24 months, a review is due. Either the parts are intended for rarely performed jobs (then check criticality) or they are surplus (then transfer to another vessel or return to supplier).
Freight cost optimisation is another underestimated lever. Individual part deliveries by courier to a vessel are extremely expensive – EUR 500–2,000 per shipment depending on port. Bundling orders to planned port calls and delivering to a local agent warehouse can reduce freight costs by 60–70%.
An operator of eight bulk carriers with MAN B&W engines switched spare parts procurement from reactive individual ordering to quarterly batch ordering. The steps: create a cross-reference catalogue for all eight vessels, evaluate the PMS calendar 12 months ahead, consolidate material requirements and place them as quarterly framework orders with the manufacturer and two aftermarket suppliers.
Result after one year: 18% lower unit prices through volume advantages, 40% fewer individual orders (administrative saving), 70% fewer express deliveries and zero off-hire days due to missing spare parts. The total saving was estimated at approximately EUR 120,000 per year – with an implementation effort of 3 weeks for the procurement manager and one superintendent.
Optimising spare parts procurement starts with criticality classification – that is lever 1 and the foundation for everything else. Then the PMS linkage (lever 2) and in parallel the cross-reference for the fleet (lever 3). Forward planning (lever 4) and supply chain management (lever 5) follow once the data basis is established.
For fleets under five vessels, a single superintendent can implement all five levers within 4–6 weeks. For larger fleets, a dedicated project with procurement support is recommended.
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