Flow Switch BilgMon 488

Flow Switch BilgMon 488 - Optional Sample Flow Monitoring

The Brannstrom Flow Switch provides optional sample flow monitoring for the BilgMon 488 15 ppm bilge alarm system. It detects insufficient or interrupted sample flow, helping protect against accidental pollution caused by blocked or disconnected sample lines.

When connected to a BilgMon 488 Series 5 Master Unit, the Flow Switch enables a dedicated "No flow" alarm displayed and recorded in the system log. Alternative connection arrangements may be possible for older Master Units, subject to technical verification.

Key benefits:

Detects low or interrupted sample flow
Helps protect against blocked or disconnected sample lines
Supports dedicated alarm handling and event logging with Series 5
Available in different switch ranges to suit the installation

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Low sample flow detection for the BilgMon 488

A flow sensing switch installed in the sample flow loop reacts to a too low sample flow. Connected to the 15 ppm bilge alarm or the ASD, it triggers the alarm or stops the discharge, which protects against accidental pollution.

Sample flow can fail if the sample line becomes blocked, if the sample pipe is incorrectly installed, or if someone opens a sample pipe drain plug or disconnects the pipe from the sample inlet. A flow switch is not mandatory, but it is a possible extra protection against these situations.

The flow switch should be of good quality, suitable for the flow rate of the installation, and not easily clogged by oil and solid particles that may pass through the oily water separator.

Related BilgMon 488 components

Brannstrom BilgMon 488 Master Unit

The BilgMon 488 Master Unit is the central control module of Brannstrom’s bilge alarm system, featuring a durable housing with LCD display, buttons, and LEDs. It stores all alarm data in its integrated memory and receives wireless signals from the sealed sensor unit. The Master Unit processes oil content and separator signals, triggers alarms, and logs events to ensure compliant bilge water monitoring.

Brannstrom BilgMon 488 Calibration Kit

The Calibration Check Kit allows crews to perform quick and reliable calibration checks on the BilgMon 488 directly on board. Since these checks may be required more frequently than the calibration certificate’s validity period, the kit provides an easy way to verify accuracy and ensure ongoing compliance at sea.

Brannstrom Bilgmon 488 15 Ppm Bilge Alarm

Brannstrom BilgMon 488 Bilge Monitoring & 15 ppm Bilge Alarm

Brannstrom BilgMon 488 is a bilge water oil content monitor designed for marine applications. It is used to ensure compliance with IMO MEPC.107(49) regulations by continuously measuring the oil content in bilge water before discharge overboard.

Brannstrom BilgMon 488 Measuring Cell (Black)

Replace your BilgMon 488 sensor unit easily when the 5-year calibration certificate expires or if a calibration check fails. The measuring cell installs in minutes without changes to the master unit and comes with a new, valid calibration certificate for continued compliant operation.

Where to install the Flow Switch

The flow switch can be installed anywhere in the sample flow loop of the 15 ppm bilge alarm. The most effective position is the drain line.

In the drain line (recommended): here the flow switch reacts to a too low sample flow whatever the cause, and it also reacts if someone opens a sample pipe drain plug or disconnects the pipe from the 15 ppm bilge alarm sample inlet. This currently seems to be the most common cause of sample flow failure.

Elsewhere in the sample flow loop: the flow switch still reacts to a too low sample flow, for example if the sample line becomes blocked, but it may not react to an opened drain plug or a disconnected pipe.

Optional extra protection: a flow switch is not mandatory, but it is a possible extra protection against accidental pollution if the sample line is blocked or disconnected. When planning the installation, avoid arrangements that could accidentally disable the equipment, for example a manual valve in the sample line that can be left in the wrong position.

The drawing shows the BilgMon 488 fitted with an optional flow sensing switch. For connection to the Master Unit, see flow switch compatibility and connection.

Flow Switch compatibility and connection by Master Unit version

How the Flow Switch is connected depends on the BilgMon 488 Master Unit:

Master Unit	How the Flow Switch is connected
Newer Master Units (series 5, serial number in the format 5XXX-NNNN)	Dedicated signal input for the flow switch. The flow alarm is treated like any other alarm (high oil content, malfunction etc.), with “No flow” shown on the display and recorded in the log.
Older Master Units (no dedicated input)	Connected in series with the “Separator status” signal input. This activates the ASD in case of low flow, but the separator is logged as running even if the water is dumped back to the bilge.

On older units, the added safety of a low flow alarm may not outweigh the incorrect log entry, so the recommended solution is to replace the Master Unit with a newer one that has a separate flow switch input, see the BilgMon 488 Master Unit. Newer Master Units also have slightly different terminal numbering, so a Master Unit should be replaced by a competent electrician who understands the documentation.

On Series 5 Master Units, a low-flow condition triggers a dedicated "No flow" alarm, which is displayed on the Master Unit and recorded in the event log.

Before ordering, please confirm:

The installed Master Unit and its serial number
The sample flow rate of the installation, to select a suitable switch range
The connection arrangement: dedicated input or in series with the separator status signal
The manufacturer’s installation instructions

Contact Insatech Marine with the installed system version and your flow switch requirements, and we will verify compatibility and prepare a quotation. Source: Brannstrom technical information “Optional Sample Flow Monitoring” (1 September 2023).

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Flow Switch Dimensioner Brannstrom 1024 16X9

Flow Switch Models and Flow Ranges

Brannstrom recommends selecting a Flow Switch based on the sample flow rate and operating conditions of the bilge alarm installation.

Model	Connection	Flow Range
BFS-2	1/4"	0.4–2.0 l/min
BFS-5	1/4"	1.0–5.0 l/min

The selected switch should be suitable for the installation and resistant to clogging from oil and solid particles.

Not sure which model to choose? Send us your sample flow rate and BilgMon 488 Master Unit version.

Find the Right Flow Switch

How to install the Flow Switch

Prepare: confirm compatibility with your bilge alarm (see compatibility) and select a flow switch with a suitable switch range.
Choose the location: anywhere in the sample flow loop. For best effect, install it in the drain line.
Follow the manufacturer’s guidelines: refer to the installation instructions for specific steps and recommendations.
Secure the flow switch: use the recommended mounting method, and make sure all connections are secure and free from leaks.
Connect the signal: to the dedicated flow switch input on series 5 Master Units, or in series with the separator status signal on older units.
Test: power on the system, verify that the flow switch functions correctly, and check the signal to the bilge alarm or the ASD.
Seek assistance if needed: for older systems or complex setups, contact us.

Need help? Contact us now

Flow switch and regulations: optional extra protection

Regulation 14 of MARPOL Annex I requires ships of 400 gross tonnage and above to be fitted with oil filtering equipment. IMO Resolution MEPC.107(49) contains the guidelines and specifications for this equipment, including type approval tests and installation requirements. The BilgMon 488 15 ppm bilge alarm is type approved according to MEPC.107(49).

A flow switch is not mandatory. The Guidelines do not require the installation to be tamper proof, but arrangements that could accidentally disable the equipment should be avoided, for example a manual valve in the sample line that can be left in the wrong position. A flow switch is optional extra protection against accidental pollution caused by a blocked or disconnected sample line.

During Port State Control, AMSA (Australian Maritime Safety Authority) officers test that the sample flows to the 15 ppm bilge alarm and that the ASD activates when the oil content exceeds 15 ppm, per Resolution A.1185(33). Read more at AMSA.

Get in Touch with Our Experts

For technical questions

Martin Søvind Jensen

Tel: +45 2761 4502

Email: Marine@insatech.com

Write to Martin

For commercial inquiries

Our team of Sales Specialists

Tel.: +45 5537 2095

Email: quotes@insatech.com

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Brannstrom

Trusted Brannstrom Distributor

At Insatech, we are an authorized distributor of Brannstrom Sweden, supplying advanced oil-in-water monitors, bilge alarms,
turbidity meters, and customized inline measurement systems for demanding marine and industrial applications.

Brannstrom solutions meet IMO and Classification Society requirements.

Originating from bilge alarm and pollution control technologies, Brannstrom now delivers a broad range of precision inline monitoring systems
for vessels, water treatment facilities, paper mills, and other process installations.

Visit our Brannstrom supplier page

Why We Offer Brannstrom Products

Insatech offers Brannstrom solutions for their engineering precision, durability, and proven compliance with strict environmental standards. With full in-house design and manufacturing, Brannstrom delivers monitoring systems tailored to specific operational needs - for example the 15ppm bilge alarm type BILGMON 488

These solutions enable reliable performance and regulatory compliance across marine and industrial applications.

Bilge Alarm Tailored to Your Application

Brannstrom has a long tradition of developing application-specific systems, engineered in close collaboration with clients and tailored to their exact requirements - drawing on decades of design and development experience.

See all Brannstrom products here

Technical Specifications BFS-10-N (without indication)
Measuring principle	Variable aera flow meter
Materials	Brass Version: Var. aera flow meter: brass Spring: 1.4571 Spring size G1": ---- Fitting: brass, nickel-plated Housing: brass, nickel-plated Magnets: ferrite Stainless Steel Version: Var. aera flow meter: 1.4571 Spring: 1.4571 Spring size G1": 1.4571 Fitting: 1.4571 Housing: 1.4571 Magnets: ferrite
Operating pressure	Brass: BFS-10-N G1/4: 300 bar BFS-10-N G1/2: 300 bar BFS-10-N G1: 250 bar MS GL: BFS-10-N G1/4: 100 bar BFS-10-N G1/2:100 bar BFS-10-N G1: 100 bar SS: BFS-10-N G1/4: 350 bar BFS-10-N G1/2: 350 bar BFS-10-N G1: 300 bar Pressure drop: BFS-10-N G1/4: 0,02...0,2 bar BFS-10-N G1/2: 0,02...0,3 bar BFS-10-N G1: 0,02...0,4 bar
Operating temp.	100 °C (standard), 160 °C (option HT)
Accuracy	±10% f. s.
Electrical connection	plug acc. to DIN EN 175301-803 (DIN 43650C)
Contact rating	BFS10-N G1/4: 200 V / 1 A / 20 VA (NO) 200 V / 1 A / 20 VA (WE), SPDT BFS-10-N G1/2: 230 V / 3 A / 60 VA (NO) 250 V / 1,5 A / 50 VA (WE), SPDT BFS-10-N G1: 250 V / 3 A / 100 VA (NO) 250 V / 1,5 A / 50 VA (WE), SPDT
Protection class	IP65 (plug acc. to DIN EN 175301-803 former DIN 43650C), IP67 (with moulded cable)
Approvals	e.g. ATEX, GL, BV

Technical Specifications BFS-10-O (with optical indication)
Measuring principle	Variable aera flow meter
Materials	Brass Version: Var. aera flow meter: brass Spring: 1.4571 Fitting: brass, nickel-plated Display Housing: alumin., anodized Glass: Duran 50 Magnets: ferrite Stainless Steel Version: Var. aera flow meter: 1.4571 Spring: 1.4571 Fitting: 1.4571 Display Housing: alumin., anodized Glass: Duran 50 Magnets: ferrite
Operating pressure	Brass: BFS-10-N G1/4: 16 bar BFS-10-N G1/2: 16 bar BFS-10-N G1: 10 bar SS: BFS-10-N G1/4: 16 bar BFS-10-N G1/2: 16 bar BFS-10-N G1: 10 bar Pressure drop: BFS-10-N G1/4: 0,02...0,2 bar BFS-10-N G1/2: 0,02...0,3 bar BFS-10-N G1: 0,02...0,4 bar
Operating temp.	100 °C (standard), 160 °C (option HT)
Accuracy	±10% f. s.
Electrical connection	plug acc. to DIN EN 175301-803 (former DIN 43650C)
Contact rating	BFS10-N G1/4: 200 V / 1 A / 20 VA (NO) 200 V / 1 A / 20 VA (WE), SPDT BFS-10-N G1/2: 230 V / 3 A / 60 VA (NO) 250 V / 1,5 A / 50 VA (WE), SPDT BFS-10-N G1: 250 V / 3 A / 100 VA (NO) 250 V / 1,5 A / 50 VA (WE), SPDT
Protection class	IP65 (plug acc. to DIN EN 175301-803 former DIN 43650C), IP67 (with moulded cable)
Approvals	ATEX not available for version with optical indication

Specifications & Manuals

Data sheet - Flow Switch - BilgMon 488 - Brannstrom
English | pdf

Download
Brochure - Flow Switch - BilgMon 488 - Brannstrom
English | pdf

Download

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Brannstrom BilgMon 488 Flow Switch

Low sample flow detection for the BilgMon 488