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Overview
When a sensor unit on a Daihatsu oil mist detection system fails, the entire crankcase monitoring installation is compromised — and replacing the complete system to restore a single detection point is neither practical nor cost-effective. The Daihatsu MD-9M Detector Head is the genuine OEM sensor unit for the MD-9M oil mist detection system, available as a standalone replacement component for vessels and installations where the controller remains serviceable but one or more sensor units require replacement.
This detector head is the active sensing element of the MD-9M system — the unit that physically draws crankcase atmosphere, measures oil mist concentration using an optical dispersion method, and communicates mist level data and alarm status back to the MD-9M controller. Each sensor unit monitors one crankcase detection point continuously, with a response time of under one second and a detection range extending to 2.0 mg/l. A single MD-9M controller supports up to 16 sensor units, meaning individual detector head replacements can restore multi-point installations to full operational status without any controller-level intervention.
What makes the genuine Daihatsu detector head the correct choice for MD-9M maintenance — rather than aftermarket alternatives — is the combination of factory-verified optical calibration and confirmed compatibility with the MD-9M controller’s communication and power architecture. A sensor unit that is physically compatible but not factory-calibrated to the MD-9M system’s optical detection thresholds will not deliver reliable mist concentration readings, which directly undermines the protection the system is installed to provide.
Key Features
Natural Diffusion Sampling with Optical Dispersion Detection
The MD-9M detector head uses a natural diffusion sampling method — crankcase atmosphere enters the detector head by diffusion rather than forced suction — combined with an optical dispersion detection system that measures how oil mist particles scatter a light beam passing through the sampled atmosphere. The optical method provides a quantified concentration reading across a range of 0 to 2.0 mg/l, rather than a simple threshold trigger, giving the MD-9M controller the data it needs to generate accurate pre-alarm and high-alarm outputs at the correct concentration levels. Natural diffusion sampling means the detector head has no moving parts in the sampling path — reducing maintenance requirements and eliminating a common failure mode found in suction-type sensor units.
Sub-Second Response Time
The detector head achieves a response time of one second or less from the point at which oil mist concentration reaches the detection threshold to the point at which the output signal is generated. In crankcase oil mist monitoring, response time directly affects the margin between pre-alarm activation and the concentration level at which crankcase explosion risk becomes critical. A sensor unit that responds in under one second gives the MD-9M system the best possible chance of generating a pre-alarm output while there is still time for the crew to reduce engine load and investigate the source of mist generation — before the high-alarm threshold is reached.
Wider Detection Range — Up to 2.0 mg/l
The detector head monitors oil mist concentration across a range of 0 to 2.0 mg/l — a broader upper range than some comparable sensor units. The extended range ensures that the detector head continues to provide quantified concentration data even as mist levels rise above the high-alarm threshold, rather than saturating at a lower concentration value. For engine room officers monitoring a developing crankcase event, accurate concentration data above the high-alarm threshold provides better situational awareness of the rate at which conditions are escalating.
IP55 Ingress Protection
The detector head carries an IP55 ingress protection rating, confirming resistance to dust ingress and protection against low-pressure water jets from any direction. In a marine engine room environment where sensor units are mounted directly on or adjacent to diesel engine crankcases — environments that combine oil vapour, heat, mechanical vibration, and periodic cleaning water exposure — IP55 protection is the practical minimum for reliable long-term operation. A sensor unit that degrades in the conditions it is installed to monitor is not a reliable safety component.
Direct Controller Compatibility — DC 24V Supply from Controller
The detector head draws its operating power directly from the MD-9M controller via the existing system wiring, operating on a DC 24V supply with a tolerance range of +30% to -25%. Power consumption is a maximum of 60 mA per unit — a low demand that allows the MD-9M controller to power multiple replacement sensor units simultaneously without requiring any modification to the existing power distribution arrangement. Replacement sensor units install into the existing MD-9M system wiring without additional power supply work, minimising installation time and the scope of the maintenance intervention required.
Compact Form Factor with Status LED Indicators
The detector head weighs approximately 500g including accessory hardware (nuts and mounting fittings), and is finished in Munsell N1.0 black to match the MD-9M system’s existing components. The unit carries three status LED indicators — Power, Alarm, and Failure — providing local visual status indication directly at the sensor unit, independent of the controller display. For engine room staff carrying out rounds, local LED status indication allows a quick visual check of each sensor unit’s operating status without having to return to the controller panel to interpret system status.
Technical Specifications
Component: Detector Head (Sensor Unit)
Compatible System: Daihatsu MD-9M Oil Mist Detection System
Manufacturer: Daihatsu Diesel Mfg. Co. Ltd., Osaka, Japan
Detection System: Optical dispersion system
Sampling Method: Natural diffusion, continuous
Response Time: ≦ 1 second
Detection Range: 0 – 2.0 mg/l oil mist concentration
Detection Points: 1 point / 1 unit (up to 16 units per controller; 8 units × 2 engines)
Status Indicators: 3-colour LEDs — Power, Alarm, Failure
Contact Output: 5 points via controller: 2 × Pre-Alarm, 2 × High Alarm, 1 × Failure (AC 125V / 0.4A or DC 24V / 2A)
Power Supply: DC 24V (+30% / -25%), supplied from controller
Power Consumption: 60 mA max. per unit
IP Rating: IP55
Weight: Approx. 500 g (including accessories: nuts, mounting fittings)
Paint Colour: Munsell N1.0 (Black)
Benefits
Restores full MD-9M system functionality at sensor unit cost, not full system cost. When a detector head fails on an MD-9M installation, the affected crankcase monitoring point goes offline — leaving a gap in the crankcase explosion protection coverage. Replacing only the failed sensor unit restores full monitoring coverage at a fraction of the cost of replacing the complete MD-9M system. For ship managers maintaining cost-effective compliance with crankcase explosion protection requirements, individual sensor unit replacement is the correct and economical maintenance response to a single-point sensor failure.
Genuine OEM calibration maintains detection accuracy. The optical detection threshold calibration of the MD-9M detector head is factory-set to match the pre-alarm and high-alarm concentration levels programmed into the MD-9M controller. An aftermarket or non-OEM sensor unit may be electrically compatible with the MD-9M system while delivering concentration readings that are systematically offset from the controller’s alarm thresholds — generating nuisance alarms at low concentrations or, more critically, failing to alarm at the correct high-alarm concentration. Genuine Daihatsu detector heads maintain the factory calibration that the entire system’s alarm accuracy depends on.
Supports dual-engine installations with a single controller. The MD-9M system supports configurations of up to 8 sensor units per engine across two engines — a total of 16 sensor units per controller. For vessels with twin-engine installations, individual detector head replacement allows maintenance of the full dual-engine monitoring configuration without any controller reconfiguration, provided the replacement unit is the correct genuine OEM component.
Low power draw simplifies fleet spare parts provisioning. At 60 mA maximum per unit, the detector head’s power consumption is low enough that carrying a replacement unit as a vessel spare does not require any special storage or handling provision. For fleet managers building vessel spare parts inventories for Daihatsu MD-9M installations, the compact size and weight (500g including accessories) of the detector head make it a practical stock item for vessels on extended voyages or trades where port procurement support may be limited.
Minimal installation scope reduces maintenance intervention time. The detector head connects to the MD-9M controller via the existing system wiring and draws power directly from the controller — no additional power supply work, no controller reconfiguration, and no system-wide recalibration required. Replacement can be carried out by a marine electrician or electronics officer familiar with the MD-9M system during a planned maintenance period, without requiring a specialist field service visit.
Who It’s For
The Ship’s Electrical Officer or Marine Electronics Engineer
You’re carrying out routine maintenance on the MD-9M oil mist detection system and have identified a sensor unit showing a Failure LED indication or delivering anomalous concentration readings that don’t correspond to actual crankcase conditions. You need a confirmed genuine Daihatsu replacement detector head with the correct part specification for the MD-9M system, available with a lead time that fits your vessel’s maintenance schedule or drydock programme. You want to carry out the replacement yourself using the existing system wiring, without requiring a field service visit or full system recalibration.
The Marine Superintendent Specifying Fleet Spare Parts Inventories
You manage a fleet of vessels with Daihatsu diesel engine installations and MD-9M oil mist detection systems across multiple vessels on different trade routes. You want to ensure that each vessel carries a spare detector head for the MD-9M system so that a sensor unit failure can be rectified on board without waiting for port procurement. You need a supplier who holds genuine Daihatsu detector heads in stock, can confirm compatibility with the MD-9M system, and can support fleet-level procurement across multiple vessels on a standing order basis.
The Ship Repair Yard or Marine Electronics Service Company
You carry out safety system maintenance and survey preparation work on vessels during drydock periods and scheduled class renewals. You need to source replacement MD-9M detector heads for vessels where sensor units have reached their service life limit or failed functional testing during pre-survey inspection. You need a supplier who can support multiple vessel orders within the drydock schedule, provide function-tested components with the appropriate documentation, and turn around orders quickly enough to fit within the yard’s maintenance programme timeline.
Possible Applications
- Single sensor unit replacement on Daihatsu MD-9M installations — Restoring a specific crankcase monitoring point on an MD-9M system where one detector head has failed, without replacing the complete system
- Planned maintenance sensor unit renewal — Scheduled replacement of MD-9M detector heads that have reached their manufacturer-recommended service life limit as part of a planned maintenance programme
- Drydock and class survey preparation — Detector head replacement during scheduled drydocking to ensure all MD-9M sensor units pass functional testing as part of the vessel’s class renewal survey preparation
- Fleet spare parts stock provisioning — Carrying a replacement detector head as a vessel-carried spare for Daihatsu MD-9M installations on vessels operating on long ocean voyages or trades with limited port procurement options
- Twin-engine vessel installations — Sensor unit replacement on MD-9M systems covering dual-engine configurations, maintaining full 8-unit-per-engine monitoring coverage on vessels with twin Daihatsu diesel main engines or generator sets
- Offshore vessel and platform supply vessel maintenance — Detector head replacement on MD-9M installations in vessels operating in offshore environments where IP55-rated components are required for reliable service in high-humidity, high-vibration engine room conditions
- Marine electronics workshop repair and overhaul — Sensor unit supply for marine electronics service companies carrying out MD-9M system overhaul and functional testing during contracted vessel maintenance programmes
Trust and Certifications
Genuine Daihatsu OEM Component
The MD-9M Detector Head is a genuine OEM component manufactured by Daihatsu Diesel Mfg. Co. Ltd. of Osaka, Japan. Daihatsu is an established manufacturer of marine and industrial diesel engines and associated safety systems, with installations across commercial shipping fleets worldwide. Genuine OEM detector heads are factory-calibrated to the MD-9M system’s optical detection thresholds — the calibration standard that the system’s alarm accuracy is built on. For safety-critical crankcase protection systems, OEM component provenance is not a preference; it is the correct maintenance standard.
IP55 Ingress Protection
The detector head carries an IP55 ingress protection rating, independently verifying dust resistance and protection against low-pressure water jets from any direction. IP55 is the appropriate protection standard for electronic components installed in the marine engine room environment, and its independent verification provides procurement teams and class surveyors with documented confirmation of the component’s environmental suitability for its installation location.
Classification Society Acceptance as Part of MD-9M System
The MD-9M oil mist detection system has an established acceptance record with major classification societies for compliance with SOLAS and class requirements for crankcase explosion protection on diesel engines. The detector head, as a genuine OEM component of the MD-9M system, is the appropriate replacement part for maintaining the system’s class-accepted configuration. Using non-OEM sensor units in a class-accepted safety system may affect the system’s compliance status and could be raised as a deficiency during class surveys or port state control inspections.
Factory After-Sales Support
Daihatsu provides complete after-sales support for the MD-9M system, including function testing of detector heads, repair and overhaul services, and genuine spare parts supply. For ship managers requiring function test documentation for class survey purposes, Daihatsu’s factory testing capability provides the appropriate technical authority for sensor unit functional verification.
Accessories and Variants
Daihatsu MD-9M Complete System (Controller + Sensor Units)
For vessels requiring a complete MD-9M system replacement — either as a newbuild installation or a full system renewal on an existing vessel — the MD-9M is available as a complete system package comprising the controller unit and the required number of detector heads for the specific engine installation. Contact our team with your engine configuration and the number of crankcase monitoring points required for a correct system recommendation and quotation.
MD-9M Controller Unit
The MD-9M controller unit — the central processing and display unit that powers, receives data from, and generates alarm outputs for up to 16 connected detector heads — is available separately for installations where the controller has failed or requires replacement while the existing sensor units remain serviceable. The controller carries a 3-colour LED and bar-graph mist level display, LCD, and 5-point contact alarm output for integration with engine room alarm and safety systems.
Mounting Accessories and Replacement Hardware
Each detector head is supplied with accessory hardware (nuts and mounting fittings) as standard. Additional mounting hardware, cable connectors, and installation accessories for MD-9M detector head installations are available through our team. Contact us with your specific installation requirements for availability and quotation.
Related Daihatsu Oil Mist Detector Spare Parts
MD-9M Controller Unit — Central controller for the MD-9M system; supports up to 16 sensor units
MD-9M Complete System — Full system package for new installation or complete system renewal
MD-14M Oil Mist Detector — Related Daihatsu oil mist detector model for applicable engine installations
Internal PCB and optical components — Controller and sensor unit board-level spare parts available through Daihatsu factory service
Get in Touch
If you need to source a replacement Daihatsu MD-9M Detector Head — whether for an immediate sensor unit replacement, a planned maintenance programme, drydock preparation, or fleet spare parts provisioning — contact our team to confirm stock availability and request a formal quotation.
Our team maintains a large inventory of genuine Daihatsu MD-9M components and can support both individual vessel orders and fleet-level procurement programmes. Reach out with your vessel details and MD-9M system configuration for a prompt response.
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