Oil Mist Detection and Alarm system

QMI Multiplex Monitor and Alarm Unit can monitor up to 12 individual input points. Can be mounted in the control room or on the bridge. Facility for output to data/event logging system More Information below
Atmospheric Detector - for Engine Room, Purifier Room, Steering Gear,  Hydraulic Pump & Bowthruster Space monitoring More Information below
Engine Detector - for Engine Crank Case, chain case and Gear Box monitoring More Information below

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Description of QMI Multiplex^TM  System

The equipment consists of a small number of components such as The Monitor, Detectors, Fan and Multi-way Junction Box. 

The Multiplex Monitor

The QMI Multiplex Monitor is normally placed in the control room or on the bridge well away from the danger zone i.e. the engine. Therefore should conditions become dangerous no personnel will be injured. Nowadays most engine rooms are unmanned, therefore all information about the engine should be immediately transmitted to control room staff.

Other types of oil mist detectors allow the user to raise the alarm setting indefinitely. QMI has a maximum pre-set program and can only be changed for higher readings by changing the EPROM and this is not freely available.

The Monitor processes all the information transferred from the Detectors that are mounted on the engine. It gives continuous information to operatives in three ways:-

1. Traffic Lights - Red, Amber and Green                     
   These indicate the state of oil mist and areas of alarm within the engine or the monitoring system. There is a set of lights for each detector.
        Green - indicates up to 80% of Alarm Setting
        Amber - indicates from 81% to 99% of Alarm Setting
        RED   - indicates 100% of Alarm Setting
        Three Lights Flashing - indicates an instrument fault

2. Digits
   The digits are used to set the alarm levels in mg/l (mg of oil per liter of air) during the setting up procedure, as a percentage of the alarm setting in the run mode. It also indicates system faults should they occur by means of a self diagnostic program.

3. Alarm Relays and Engine Slow/Shutdown
   There are four relays built into the unit. The first is used as an early warning alarm when 80% percent of the alarm setting is reached. The second and third are activated when the oil mist gets to its full alarm setting i.e. 100%. The second relay operates the main alarm and the third the engine slow or shutdown system. A fourth relay comes into use when there is a fault in the operating system, which is independent of the engine operation.

As the Monitor is completely micro processor driven a number of other useful functions can be incorporated such as using the Monitor on more than one engine each with its own slow/shutdown function. Oil mist readings from each detector can be data-logged. The program also allows it to ignore transient blow-by and indicates the area of the engine where the trouble has occurred. In the event of a failure it locks onto the channel that first went into alarm.

The  Detectors

The Crankcase Detectors are mounted at each crank compartment, gear or chain case housing and thrust bearing housing if it has its own space. The detector incorporates LED optos and a PCB. A microprocessor that is built into the unit, sends five sets of information to the monitor every .5 seconds via a cable connection where it proceeds to give all the relevant readings to the operatives. There is no interaction between detectors as they are independent of each other.

The Atmospheric Detector uses the same technology as the crankcase detector but has its own internal fan  for drawing sample air from the space being monitored into the photoelectric chamber of the monitor. It is connected to the Monitor in the same manner as the Crankcase Detector.

Both types of detectors can be used with the Multiplex Monitor.

The Multi-way Junction Box

This a junction between the detectors and the monitor. Each detector is wired together with the Fan Failure Sensor to the junction box that is located near to or on the engine. A multi-core cable is run from this unit to the monitor.

The Fan and Magnetic Sensor

This is a small 110/240V unit that is used to draw the oil mist through all the detectors via a single manifold. Mounted on this fan is an electromagnetic sensor to prove that the impeller is rotating.

Pipework Layout of the QMI Multiplex^TM Monitoring System

Mist is continuously being extracted from by means of a fan attached to the end of a manifold, to pull oil mist into the detector where it is measured. From the fan the oil mist is usually ducted to the engine breather or returned to the crank case.

To get the best overall advantage of the system it is necessary to either manually or electronically log the detector readings. The readings will then indicate at an early stage when a bearing or piston failure starts.

Remedial work can be carried out long before a major incident occurs. QMI have overcome most false alarm problems and have a system that responds very quickly to oil mist level changes.

The Advantages of the QMI Multiplex^TM Monitoring System

1. True measurement of oil mist concentration is achieved
2. Oil mist drop-out is minimized
3. Direct measurement at the crankcase by multiple measuring cells gives high redundancy to the system
4. Faster response (0.5 seconds) means saving the engine from damage caused by bearing failures
5. Continuously parallel sampling directly eliminates the use of valves, which are high maintenance
6. Continuous true readings give trends for analysis and accurate fault prediction