Blog · Sourcing guide · 2026-07-24
Marine lubricating oil system spare parts — a sourcing guide for purifiers, duplex filters, coolers and circulation pumps
A vessel's lubricating-oil system commonly includes purification or filtration, cooling and circulation equipment, with the arrangement varying by engine and vessel design. Those are four different worlds to buy from, and the thing that brings someone to this page is usually a symptom of the system rather than of a part. Water in the oil points at the cooler or the purifier; a rising differential across the filter points at the oil or at what is getting into it; a falling oil pressure points at the pump, at the relief valve or at a bearing that is now passing more oil than it did. Naming the symptom alongside the component turns one order into the right order, because the four groups fail in ways that look alike from the control room and nothing alike in the workshop. This guide covers frequently encountered OEM families across four recurring spare-part groups, the data needed to identify each component and the choice between an OEM route and a documented alternative. It does not quote lead times or prices — those depend on the specific unit, vessel schedule and confirmed supply route.
Which OEM families are common on commercial vessels
- LO purifiers (centrifugal separators for lubricating oil) — Alfa Laval (S, MMPX, MOPX, LOPX, WHPX series), GEA Westfalia (OSD, OTA, OSC series), Mitsubishi (SJ series). See our separators sourcing guide for the full separator identity pattern — LO purifiers share the same bowl components, gravity discs and gasket kit logic.
- Duplex and simplex filters — Boll & Kirch (Bollfilter automatic and manual duplex), Fleetguard (Cummins Filtration), Mahle (Filterwerk Mann + Hummel), Hydac, Parker, Donaldson, Cim-Tek. Element codes are typically a 4- or 5-digit alphanumeric on the filter cartridge.
- LO coolers (shell-and-tube heat exchangers) — Bloksma, Blohm+Voss, Alfa Laval (Aalborg), Bowman, Serck Como, Kelvion, and OEM engine-builder coolers (MAN B&W, Wärtsilä, MAK, MAK-Caterpillar). Tube stack, tube-sheet gaskets and end covers are the main RFQ line items.
- LO circulation pumps — Imo (three-screw and twin-screw series), Naniwa, Allweiler, Kral, Bornemann, Leistritz. See our pumps sourcing guide for the general pump identity pattern.
- LO service valves and instrumentation — Klinger, Georg Fischer (GF), Sarco, Yarway. Pressure gauges: WIKA, Nuova Fima, Trerice.
LO purifiers — service kit and gravity disc identity
Service kits, seals and gravity discs recur in lubricating-oil purifier RFQs. One difference from the fuel side is worth stating first: a lubricating-oil unit is usually run as a clarifier rather than as a purifier, because the aim is to take solids and small quantities of water out of an oil that is meant to stay in service, not to split a fuel from its water. That changes which internals the machine has and whether a gravity disc is part of the conversation at all. Send the following:
- Purifier nameplate photo — with maker, model (e.g. Alfa Laval MOPX 205 SGT-24, Westfalia OSD 18-91, Mitsubishi SJ-15G), and serial number.
- Service kit level — Alfa Laval uses labels such as Minor, Major and Intermediate, while kit contents and maintenance intervals depend on model and schedule. Send the current kit reference or planned maintenance scope. The scope is the more useful of the two, because a kit reference carried forward from a previous order describes what was bought last time rather than what the machine is due for now.
- Gravity-disc inner diameter — send the current marking or measured dimension and note the oil specification and operating condition. Do not infer the disc from the separator family alone. On a lubricating-oil machine running as a clarifier there may be no gravity disc fitted at all, and a sealing disc sits in its place; establishing which of the two is in the bowl before the line is written saves the whole exchange.
- Bowl and hood gasket set — separate line items from the main service kit on some models.
- Application — main engine LO, auxiliary engine LO, or cross-purpose (some vessels share a purifier stand across services).
Duplex filters — element identity and change-over valve wear
Duplex filter elements come in two main patterns: pleated paper / synthetic (Fleetguard, Mahle, Bollfilter type S6) and cleanable stainless steel wire mesh (Bollfilter type 6.60, type 6.72). The two are a maintenance philosophy rather than a specification: a disposable element is consumed and reordered on a schedule, while a mesh candle is cleaned and returns to service until it is damaged, so a request for elements against a mesh housing usually means something has gone wrong with a candle rather than that a routine change is due. Whichever is fitted, the instrument that decides the job is the differential pressure across the filter, and quoting the differential the crew are seeing tells more about the order than the element code does. Send the following:
- Filter maker and housing model (e.g. Boll & Kirch 6.60-1300, Fleetguard LF3000).
- Element code and micron rating (10, 25, 50, 100 µm are common for LO service).
- Whether the RFQ is for the element only, the O-ring / gasket set, or the change-over valve internals. The change-over valve is the part of a duplex filter that nobody orders until it leaks. It is worked every time the filter is switched, often under pressure and often against oil carrying whatever caused the switch, and its seats and seals are a separate order from anything in the element chamber.
- Housing pressure and temperature rating — PN6, PN10, PN16 for the housing; oil operating temperature 60–95°C typical. Where the housing has been in service through more than one oil specification, state the current one: element media are selected against the oil as well as against the rating.
LO coolers — tube stack and gasket identity
LO coolers on medium-speed and low-speed engines are typically shell-and-tube with copper or copper-nickel tubes. Before the parts, one diagnostic point decides the scope. A tube leak moves whichever way the pressure difference pushes it, so oil appearing in the cooling water and water appearing in the oil are not the same fault: the first is usually a running leak with the oil side higher, the second often shows only when the engine is stopped and the oil pressure falls away. Saying which one was observed, and at what condition, changes whether the order is a tube stack, a set of gaskets or a pressure test first. Send:
- Cooler maker and model (e.g. Bloksma 1200-DN200-3P).
- Duty side (oil vs sea water vs fresh water) and design pressure.
- Tube material — copper, brass (CuZn), CuNi 90/10, CuNi 70/30 or titanium where specified by the original cooler design and duty.
- Tube count (from vessel documentation or a tube-sheet photo).
- Whether the RFQ is for the full tube stack, individual tubes, tube-sheet gaskets, or end-cover gasket set. Add the sacrificial anodes on any cooler with sea water on one side. They are a routine consumable, they are what protects the tube material once the cooler is back together, and they are almost never on the enquiry that renews the tubes.
LO circulation pumps — screw pump identity
LO circulation pumps are typically three-screw or twin-screw positive-displacement pumps (Imo, Kral, Bornemann, Leistritz). These pumps almost always run with a standby alongside them, and after some years of separate repairs the two are frequently no longer identical. Say which of the pair the line belongs to and whether the other has already been renewed, because a spare bought to match the wrong one of a pair is a common way to end up with two different pumps and one set of spares. The identity evidence is:
- Pump maker and model (e.g. Imo ACG 052 N7 IRBP, Kral K-32ARP).
- Rated flow (L/min), rated pressure (bar), rated speed (rpm).
- Rotor set material — steel, hardened, or hardened + coated for high-pressure duty.
- Mechanical seal specification and shaft-seal type (mechanical seal, lip seal, or packing).
OEM route vs verified alternative
For purifier service kits, duplex-filter elements, gasket sets and standard O-rings, a documented alternative may be considered when material, dimensions, duty, warranty and class requirements allow it. Gravity discs, bowl parts and cooler tube stacks require closer review of geometry, balancing, materials and traceability for the exact unit. On the cooler in particular the tube material is chosen against the water on the other side rather than against the oil, so a tube stack cannot be assessed from the cooler designation alone. Vessel Core records the proposed route for each RFQ line.
What we cannot promise before the RFQ is reviewed
Vessel Core does not quote lubricating-oil spare-part prices, lead times or supply route before the specific unit, application and identification data are confirmed. Every quotation is prepared for the specific request. A gravity-disc quotation remains preliminary until the current inner diameter and operating context are known. The same applies to a filter element quoted without the housing model, and to a tube stack quoted without the water side, because in both cases the component that fits is decided by something the part number does not carry.
How to send the RFQ
Use the RFQ form. Attach a clear nameplate photo and include the component reference, application and current dimensions or material specification where relevant. Use the RFQ evidence checklist to review the fields item by item.
