Cart (
Overview
A crankcase explosion on a diesel engine is not a gradual failure — it is a sudden, catastrophic event that can destroy an engine room, injure or kill crew members, and put a vessel out of service for months. The conditions that lead to one build up quietly: oil mist accumulating inside the crankcase until concentrations reach the explosive range, often without any visible warning. The Graviner MK-5 oil mist detector exists specifically to detect those conditions before they reach that point — monitoring crankcase oil mist density continuously and alarming automatically when concentrations approach a dangerous threshold, giving crew time to respond before a disaster occurs.
The Graviner MK-5 Control Bulk Unit is the complete, self-contained oil mist detection system — the main detector enclosure housing the sampling system, control electronics, display panel, and alarm relay outputs in a single wall-mounted unit. This is not a spare part or sub-assembly; it is the full MK-5 detector as installed on a vessel’s main engine or auxiliary diesel. Supplied in refurbished condition, it provides a complete system restoration or replacement solution for vessels where the existing MK-5 unit has failed beyond economical component-level repair, or where a replacement unit is required for a new installation or system upgrade.
What makes the Graviner MK-5 the correct choice for marine crankcase protection is its five decades of proven performance in the marine industry. Few safety systems in the marine sector have the installation history and class society recognition that the MK-5 carries. It is not a new entrant competing on specification — it is an established platform with a known maintenance ecosystem, documented spare parts availability, and classification society acceptance across all major flag states and class societies. For vessels where class compliance, operational reliability, and engine room crew familiarity all matter, the MK-5 remains the reference-standard oil mist detection solution.
Key Features
Sequential Multi-Point Sampling System — 4 to 10 Inlets Selectable
The MK-5 samples crankcase oil mist from between 4 and 10 individual sample points — selectable to match the number of engine bays or crankcase sections being monitored. Each sample point is surveyed sequentially, with the system cycling through each inlet at one-second intervals. This means the MK-5 provides comprehensive crankcase coverage across the entire engine length from a single detector unit, rather than requiring individual sensors at each point. For large two-stroke main engines with multiple crankcase bays, this multi-point sampling architecture is what makes full crankcase monitoring practical and cost-effective.
Average Alarm and Deviation Alarm — Two-Level Detection Logic
The MK-5 operates two independent alarm modes: an average alarm triggered when the overall oil mist concentration across all sample points reaches a set percentage of the alarm threshold, and a deviation alarm triggered when any single sample point shows a significantly elevated reading relative to the others. The deviation alarm is particularly important because a localised bearing failure or hot spot in one crankcase bay will initially show as an elevated reading at a single sample point, rather than raising the average across all points. The deviation alarm catches that localised condition early — before it has spread to the point of raising the average alarm.
Display Panel — Percentage of Alarm Level and Sample Number
The MK-5’s front panel displays the current oil mist concentration as a percentage of the alarm level, and shows which sample point is currently being read. This gives the engine room watch a continuous, readable indication of crankcase conditions without requiring interpretation of raw sensor values. The panel also carries dedicated indicator lamps for system on, simulation mode, lamp test mode, average alarm, deviation alarm, flow fault, and optical fault — giving the operator a clear, at-a-glance status picture of the entire detection system at any moment.
Engine Slowdown Signal Output
In addition to the main alarm relay outputs, the MK-5 provides a dedicated engine slowdown relay output — a volt-free changeover contact that connects directly to the engine’s slowdown system. When the MK-5 triggers a main alarm condition, the slowdown output signals the engine control system to reduce engine speed, lowering the rate of oil circulation and reducing the risk of further oil mist generation while the crew investigates. This automated protective response means the MK-5 is not just a detection system — it is part of the engine’s active protection chain.
Flow Fault and Optical Fault Monitoring — System Self-Diagnostics
The MK-5 continuously monitors its own sampling airflow and optical detection cell for faults, with dedicated fault lamps on the panel for flow fault and optical fault conditions. A flow fault indicates that the sampling airflow has been lost — a blocked sample pipe, pump failure, or air supply problem — meaning the system is no longer actively sampling the crankcase. An optical fault indicates contamination or degradation of the detection cell. Both conditions generate a fault alarm output to the engine control system, ensuring that a system fault is treated as seriously as an oil mist alarm rather than going unnoticed.
Selectable Power Supply — 115V to 240V, 50Hz or 60Hz
The MK-5 control bulk unit accepts a selectable power supply across a range covering 115V, 220V, 230V, and 240V at both 50Hz and 60Hz — covering the full range of vessel electrical supply configurations encountered in international shipping. This flexibility means the same MK-5 unit can be installed on vessels with different electrical system specifications without requiring additional transformers or supply conditioning, simplifying procurement for ship management companies maintaining mixed fleets.
Robust Enclosure with Anti-Vibration Mountings
The MK-5 is housed in a substantial steel enclosure — 608mm wide, 318mm tall, 191mm deep — with integrated anti-vibration mountings that bring the installed depth to 233mm. The anti-vibration mountings are a standard fitting for engine room equipment subjected to the continuous mechanical vibration of a diesel engine installation. At 28kg, the MK-5 is a heavy-duty industrial instrument designed for permanent engine room installation, not a lightweight portable device — a reflection of the robust construction appropriate for continuous operation in the demanding temperature, humidity, and vibration environment of a marine engine room.
Technical Specifications
Model: Graviner MK-5 Control Bulk Unit
Height: 318mm (12.5 in.)
Width: 608mm (24 in.)
Depth: 191mm (7.5 in.) / 233mm (9.2 in.) with anti-vibration mountings
Weight: 28 kg (61.5 lb.)
Power Supply: Selectable — 115V / 220V / 230V / 240V at 50Hz or 60Hz
Power Consumption: 70W (approx.)
Air Supply Pressure: 1 Bar ± 20% (12–18 PSI), internally threaded inlet
Air Consumption: 6 litres/hour (dry air)
Suction Pressure: 12mm water gauge (0.5 in.)
Number of Sampling Inlets: 4 to 10 (selectable)
Time Per Sample: 1 second per inlet
Sample Pipe (recommended): 17mm ID / 19mm OD
Max Sample Pipe Length: 15m (18mm ID) / 7.5m (14mm ID)
Detector Outlet Connection: 45mm ID / 48mm OD — max 10m length
System Signal Outputs: Fault alarm: 1 set volt-free changeover contacts; Main alarm: 2 sets volt-free changeover contacts; Engine slowdown: 1 set volt-free changeover contacts
Displays: System on lamp, % of alarm level, sample number, simulation mode, lamp test, average alarm, deviation alarm, flow fault, optical fault
Condition: Refurbished
Benefits
Complete crankcase oil mist protection restored in a single unit replacement. When an MK-5 main unit fails beyond economical component-level repair, the alternative to replacing the control bulk unit is operating without crankcase oil mist detection — an unacceptable safety and compliance position. A refurbished MK-5 control bulk unit restores full system functionality: sequential multi-point sampling, average and deviation alarm logic, engine slowdown relay output, and system self-diagnostics, all in a single installation.
Proven deviation alarm logic catches localised crankcase faults before they escalate. The MK-5’s deviation alarm — which triggers on an elevated reading at a single sample point relative to the others — provides the earliest possible warning of a localised bearing failure or hot spot developing in one section of the crankcase. This is the alarm that gives the crew time to take protective action before a localised condition becomes a general crankcase oil mist alarm, and it is a capability that simpler single-point or average-only detection systems do not provide.
Automated engine slowdown output reduces damage severity when an alarm triggers. The MK-5’s engine slowdown relay output connects the detector directly to the engine’s protection system — when the main alarm fires, the engine slows down automatically, reducing the rate of oil mist generation and lowering the risk of ignition while the crew responds. This automated response happens faster than manual intervention and reduces the window during which a developing oil mist condition can progress toward an explosive concentration.
Class-recognised system eliminates certification uncertainty for survey-compliant installations. The Graviner MK-5 has been accepted by all major classification societies for decades. Vessels replacing a failed MK-5 with a refurbished MK-5 control bulk unit are replacing a class-recognised system with the same class-recognised system — there is no re-approval process, no type approval uncertainty, and no flag state query to resolve. For procurement teams and technical superintendents managing survey timelines, this eliminates a category of procurement risk that arises when considering alternative or newer-model systems.
Refurbished availability supports maintenance planning where new units carry extended lead times or premium pricing. New Graviner MK-5 control bulk units are not available through standard distribution at a practical price and lead time for many vessel operators. A tested refurbished unit sourced through a specialist marine safety equipment supplier provides a functionally equivalent restoration path at a cost and availability profile suited to active vessel maintenance schedules.
Who It’s For
The Chief Engineer or Marine Superintendent Managing an MK-5 Failure
The MK-5 on your main engine has failed — not a component-level fault, but a system-level failure where the control unit itself is no longer operational. You’re looking at a vessel that is either already at anchor or approaching a port call, with class survey requirements and flag state compliance obligations that require the crankcase oil mist detection system to be operational. You need a complete, tested refurbished MK-5 control bulk unit confirmed to your system’s sampling inlet configuration, available on a lead time that fits your operational window, with enough documentation to satisfy your class surveyor that the replacement unit meets the same standard as the original installation.
The Technical Superintendent Planning a Fleet-Wide MK-5 Restoration Programme
You manage a fleet of older vessels where the MK-5 installations are reaching the end of their reliable service life — not failing catastrophically, but generating increasing fault frequencies and maintenance demands that are consuming disproportionate engineer time and spare parts spend. Rather than continuing to chase individual component failures, you’re evaluating a phased replacement of the MK-5 control bulk units across the fleet with tested refurbished units that provide a known-good starting point for the next maintenance cycle. A specialist supplier who can confirm refurbished MK-5 unit availability across a multi-vessel programme is the right procurement partner for that approach.
Possible Applications
- Main engine crankcase protection on deep-sea merchant vessels — Complete MK-5 unit replacement on two-stroke slow-speed and four-stroke medium-speed main propulsion engines aboard tankers, bulk carriers, container ships, RoRo vessels, and general cargo ships
- Auxiliary diesel generator engine rooms — MK-5 system installation or replacement on generator engines where crankcase oil mist detection is required by class rules on engines above the applicable bore diameter threshold
- Offshore platform and FPSO power generation systems — Full unit replacement for MK-5 installations on offshore diesel generator and emergency generator engines where continuous crankcase monitoring is an operational safety requirement
- Drydock and class renewal system replacement — Complete MK-5 control bulk unit renewal during scheduled drydocking for vessels where the existing unit has exceeded reliable service life or failed survey inspection
- Naval and coast guard vessel propulsion engine protection — MK-5 system installation and replacement on naval vessel main and auxiliary diesel engines requiring continuous crankcase oil mist monitoring
- Ferry and passenger vessel engine room safety — MK-5 replacement on high-utilisation passenger vessel diesel engines where continuous crankcase protection is both a regulatory requirement and a passenger safety imperative
- Marine engineering service companies carrying out MK-5 system overhauls — Complete unit supply for service contractors delivering MK-5 system replacement and recommissioning under vessel owner or ship manager service agreements
Trust and Certifications
Graviner MK-5 — Over 50 Years of Crankcase Safety in the Marine Industry
Graviner (now Kidde / UTC Fire & Security) introduced the MK-5 oil mist detector following the identification of crankcase explosion risk as a major marine safety hazard. The system has been continuously deployed in the marine industry for over five decades — installed on tens of thousands of engines worldwide across every major vessel type and flag state. That service history is not incidental; it is the foundation of the MK-5’s classification society acceptance and its status as the reference platform against which crankcase oil mist detection requirements are written in many class society rules.
IMO Resolution A.1050(27) — Performance Standards for Crankcase Oil Mist Detectors
IMO Resolution A.1050(27) establishes the performance requirements for crankcase oil mist detectors on seagoing vessels, covering response time, alarm threshold accuracy, self-monitoring capability, and system output requirements. The Graviner MK-5 was developed and refined in accordance with these performance requirements and is accepted by all major classification societies as a compliant crankcase oil mist detection system under the IMO resolution framework.
Classification Society Type Approval and Survey Acceptance
The Graviner MK-5 carries type approval recognition from all major classification societies — including Lloyd’s Register, DNV, Bureau Veritas, ClassNK, ABS, and RINA. This means that a vessel installing or replacing an MK-5 control bulk unit does not need to apply for new type approval or seek class confirmation that the system meets the applicable crankcase oil mist detection requirements. The MK-5’s class acceptance is established and documented across the global classification system — a significant administrative and regulatory advantage over alternative or newer systems that may still be working through approval processes in some jurisdictions.
Refurbished and Tested — Functional Verification Before Supply
The MK-5 control bulk unit is supplied in refurbished condition, inspected and functionally tested before supply. For a complete oil mist detection system — not just a sub-component — functional testing covers the sampling circuit, alarm logic, relay outputs, display panel functions, and self-diagnostic systems. A tested refurbished unit provides documented system-level functional assurance that is the appropriate standard for a safety-critical engine room installation.
Supplied by Alright Engineering Solutions
The Graviner MK-5 Control Bulk Unit is supplied through Alright Engineering Solutions Pte. Ltd., a specialist distributor of marine safety equipment, gas detection systems, and engine room safety components based in Singapore. Alright Engineering Solutions provides system-level and component-level sourcing support for marine oil mist detection systems across the Singapore and regional market.
Accessories and Variants
MK-5 System Spare Components
Alright Engineering Solutions stocks a range of Graviner MK-5 system spare components for vessels maintaining their installed MK-5 units through component-level maintenance rather than full unit replacement — including main PCB assemblies, pressure switch assemblies, sampling heads, and associated system spares. Contact our team for MK-5 component availability and pricing.
MK-5 Sampling Pipe and Fittings
The MK-5 system requires sample pipes from each crankcase sample point to the detector unit — with recommended pipe specifications of 17mm ID / 19mm OD and a maximum run length of 15m for 18mm ID pipe. Replacement sampling pipe and fittings are available to support MK-5 installation, recommissioning, and sample circuit maintenance.
Related Graviner MK-Series Systems
Graviner MK-4 — Earlier generation Graviner oil mist detector for vessels with legacy MK-4 installations; spare components available on enquiry
Graviner MK-6 — Later Graviner oil mist detector variant; availability on enquiry for vessels transitioning from MK-5 to MK-6 platform
Related Marine Engine Room Safety Products
Graviner MK-5 Main PCB Assembly — Refurbished main control PCB for component-level MK-5 system restoration
Graviner MK-5 Pressure Switch Assembly — Refurbished pressure switch for MK-5 sampling circuit airflow monitoring
GTYQ-DX 102 Fixed Combustible Gas Detector — Fixed gas detection for engine room hydrocarbon monitoring
GX-8000 Sample Draw Multi Gas Monitor — Portable marine sample draw monitor for confined space entry and engine room gas surveys
Get in Touch
If you need to source a Graviner MK-5 Control Bulk Unit for a vessel maintenance requirement — whether for an emergency system replacement, a scheduled drydock restoration programme, or fleet-wide MK-5 renewal — contact Alright Engineering Solutions to confirm availability, discuss your sampling inlet configuration requirements, and request a formal quotation.
Our team can also assist with MK-5 system spare components and related marine engine room safety equipment for your vessel or fleet maintenance programme.
📍 3791 Jalan Bukit Merah #06-01, E-Centre @ Redhill, Singapore 159471
