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MetriGuard
Water Ingress Alarm System
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JOWA Consilium's MetriGuard Water Ingress Alarm System is intended for usage on
bulk carriers. It complies with the proposed SOLAS regulations (Chapter
XII, Regulation 12) requiring water level alarms in cargo holds and
certain other spaces. The major elements of the MetriGuard Water Ingress Alarm System are: 1. Metritape resistance-tape sensor and sensor housing 2. Float switch and junction box 3. Signal Conditioning Unit with intrinsic safety barriers 4. Alarm unit Figure 1 shows a block diagram of a typical system. The primary sensor used in the cargo holds and ballast tanks is the Metritape type LA series water sensor. This continuous sensor allows two alarm setpoints to be derived from one sensor. The sensor mounts in a customer stillpipe which protects the sensor from the cargo. A sensor housing bolts to a pipe flange on top end of the stillpipe allowing the sensor to be easily installed (or removed) from the deck. In addition, all electrical connections are made in the sensor housing.  In other spaces where there is never any cargo or ballast, a simple float switch that does not need a high degree of physical protection may be supplied. The float switch cable must be terminated in a small junction box suitable for the deck cable. All deck cables will be brought to a Signal Conditioning Unit that will contain any required intrinsic safety barriers. This enclosure must be mounted in a non-hazardous protected area but it does not have to be mounted on the bridge or in any area that requires frequent access.  Figure
2 shows the layout of a typical water ingress alarm unit. The alarm
unit has all indicators, switches, relays and power supplies. It will
accommodate a maximum of 16 total spaces (cargo holds, forward ballast
tanks and other spaces) and will provide two high level alarms per
space. The front panel has a common buzzer, an acknowledge (buzzer
silence) switch and a test switch. Associated with each space will
be three light emitting diode (LED) indicators: High Level Alarm (HLA),
High-High Level Alarm (HHLA) and Override. Three switches are provided
to enable or disable (Override) any alarms in each space (that may
be used to carry ballast) when that space is carrying ballast. The resistance-tape sensor may be operated in hazardous classified areas when used with approved intrinsic safety barriers. In addition, the sensor can easily be installed in stillpipes that have slight curves and slopes but some restrictions apply. A sensor or cable open circuit will cause a fault indication - both HLA and HHLA LED's will flash. When acknowledged, only the HHLA LED will illuminate. Any sensor or cable short circuit will actuate both alarms. Key Features
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