Babcock Oil In Water Alarm - OPM 2

The OPM 2 Oil Content Alarm has been specifically designed for the monitoring of effluent in hazardous areas.  At present there is no formal international specification for 'industrial' effluent monitors.  For offshore application the OPM 2 is fully compliant with IMO specification A393X and MEPC60(33).

The design of the OPM2 Oil in Water Monitor is the result of more than 25 years experience in the development of oil content monitors, making use of advanced techniques and very high specification components.  The very low level of concentration in parts per million of oil in water is displayed on a back lit LCD digital indicator.  Facilities are provided for remote indication, recording, and alarm status.

Principle of Measurement
Continuous Operation
Simple Installation
Low Maintenance Cost
No Warm Up Period
Factory Calibration

The OPM2 (Option 1) is housed in a die-cast aluminum case providing protection to IP65 requirements, and is certified for use in Zone 1 and Zone 2 areas.  The measuring cell is housed in a die-cast aluminum case providing Explosion Proof Protection.

A further option is the OPM2 (Option 2) which allows the control unit to be mounted in a safe area.  The OPM2 (Option 2) which allows the control unit to be mounted in a safe area.  The OPM2 (Option 2) control unit is housed in a deep drawn steel case providing protection to IP55.

The monitor and cell can be mounted independently of each other.  Interconnection is by intrinsically certified cable.

Operating Technique

The side stream sample flows through the cylindrical glass cell, through which a low intensity beam of infrared radiation is projected.  Two silicon photodetectors are provided to detect the direct path of radiation, and radiation scattered by oil particles.  The angles and fields of view of the detectors have been carefully selected to provide high sensitivity to oil and very low sensitivity to solids which may be present in the sample stream.  This, coupled with the wavelength of light chosen, ensures minimal sensitivity to water color, and other soluble components, and is inherently self compensating for window fouling, mains voltage variation, and changes in ambient or sample temperatures.


The unit construction allows factory calibration, and interchange of detector assemblies and electronic units can then be carried out on site without further calibration being required.  The design utilises all solid state components.


Installation of the unit must in accordance with codes of practice for the country of installation.  In the United Kingdom the flameproof code of practice is BS5345 parts 1 and 3.  Bristol Babcock Ltd recommended that in absence of a local code the United Kingdom code of practice be used.

The OPM2 should be installed as close as practical to the sampling point.  Access is only required to the front and top of the instrument, and the connection requirements should closely follow the installation diagram.

Little maintenance is required and is confined to a periodic check of zero against clean water, and occasional cleaning of the glass sample cell.  Access to the cell is provided via a screw cap, permitting insertion of a tube cleaning brush.
Quality Assurance
Bristol Babcock Ltd is approved to BS En9001 (BS5750 Pt 1) In addition, the factory in which this unit is manufactured holds BASEEFA licence MO102.
Area Classification  
Cell Assembly EEx ia IIC T.4
Control Unit OPM2(1) EExd ia IIB T.6
Control Unit (Option) OPM2(2) Safe Area
Range 0 - 20 ppm
Accuracy ±2 ppm
Alarm Relay 1  Instant Alarm: Factory Set To 15ppm
Alarm Relay 2 Delayed Alarm at instant alarm level: Delay time variable 5 to 55 s (factory set at 20 s)
Alarm Contacts Single Pole c/o Rating 2.5A @ 240V 5.0A @ 110V
Alarm Indication Instant: Red LED Delayed: Red LED
Fault Alarm Monitor fault sets alarm condition
Fault Indication Red LED
Concentration Readout Back Lit LCD display     
Output Signal 4 - 20 mA
Electrical Supply: Standard

240V ac ± 10% single 

  50-60 Hz ± 10%
Electrical Supply: Optional 110V ac ± 10% single phase
  50-60Hz ± 10%
Power Consumption 11 VA
Sample Pressure 2 bar to 8 bar
Sample Flow 1.0 litres/min
Sample Temp +2C to +50C
Sample Connections Compression fitting for 10mm outside diameter pipe
Ambient Temp -15C to +50C
Clean Water Requirement Pressure 2 bar to 8 bar for cleaning and zero check
Cell: 260mm H x 120mm W x 80mm D
Control Unit: OPM2(1) 445mm H x 345mm W x 210mm D
Control Unit; OPM2(2) 400mm H x 380mm W x 150mm D
Cell: 1Kg
Control Unit: OPM2(1) 30Kg
Control Unit: OPM2(2) 11Kg