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Valcom OMD (Oil Mist Detection) Series

The OMD is a monitoring unit designed to identify oil mist in the air for both marine and industrial environments. It’s intended for use in spaces such as engine rooms and pump rooms on commercial ships, naval vessels, and ro-ro ships, meeting the requirements of current IMO guidelines (circ. 1086).

This detector functions as a self-contained system that both measures and transmits data. It delivers a 4–20 mA signal with HART® capability, along with photorelay outputs, each reflecting the concentration of oil mist present in the sampled airflow.

Its detection method is based on optical scattering: an infrared LED projects light into the chamber, and two photodiodes, one dedicated to measurement and one used as a reference, capture the reflected signal. By evaluating the difference between these two readings, the device can determine when oil mist is present.

Oil mist typically becomes flammable at a concentration of about 50 mg/l. For safety, the OMD sets its alarm limit at 2.5% of that threshold, which corresponds to a calibrated value of 1.2 mg/l.

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What is it?
The OMD is an atmospheric oil mist detection system designed to continuously monitor the concentration of oil droplets suspended in the air. It is a standalone measuring and transmitting device that provides 4–20 mA and HART® outputs, along with photorelay signals, all proportional to the detected oil-mist density.

Where is it used?
It is mainly installed in machinery rooms, engine rooms, and pump rooms on commercial, naval, and ro-ro vessels, in accordance with IMO regulations. It is also suitable for industrial environments where the early detection of oil mist is critical for safety.

How does it work?
The detector uses the principle of optical scattering. An infrared LED emits light into the sampling chamber, and two photodiodes, one for measurement and one for reference, capture the reflected signal. By comparing the outputs of the two photodiodes, the system determines the presence and concentration of oil mist in the air.

What problems does it solve?
The OMD prevents hazardous conditions created by the accumulation of oil mist, which becomes flammable at around 50 mg/l. By triggering alarms at a calibrated level of 1.2 mg/l, it provides early warning, reduces the risk of explosions or fires, and enhances safety in marine and industrial installations.

Electrical / Output

  • Supply voltage: 24 V DC ±20 % 

  • Output signal: 4–20 mA + HART® protocol

  • Photorelay outputs for alarm, pre-alarm, and fault (max 50 V DC, 100 mA)

  • Fault output: 21 mA 

Measurement Performance

  • Measuring range (oil mist density): 0 ÷ 2 mg/l

  • Pre-alarm threshold: 0.2 mg/l 

  • Alarm threshold: 1.2 mg/l 

  • Full scale: 2 mg/l (corresponding to 20 mA) 

  • Detectable particle diameter: 0.4 ÷ 10 µm

  • Resolution: 0.01% Full Scale (i.e. 0.0002 mg/l)

  • Total accuracy: < ± 13% (for the full measurement range)

Physical / Environmental

  • Operating ambient temperature: –20 °C to +70 °C

  • Storage temperature: –40 °C to +75 °C

  • Housing: Aluminum alloy (Anticorodal 6082) plus stainless steel AISI 316; O-ring cover in EPDM 

  • Electrical connection: standard cable entry M20 × 1.5 with cable gland PG 13.5 (for 7–12 mm diameter cable) 

  • Terminal board: 6 terminals for signal wiring (up to 2.1 mm² / 14 AWG), plus ground and cable shield connection

  • Dimensions: approximately 175 × 165 mm

  • Weight: approx. 2.7 kg

Functional / Safety / Compliance

  • Self-test functionality, with fault detection and monitoring of photodiode degradation

  • Meets marine-type approval (e.g. RINA), and complies with EMC directive 2014/30/EU

  • Designed and calibrated according to manufacturer specifications using a certified oil mist generator (as per IMO recommendations)

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