GB2331612A - Apparatus for detecting sea water in marine vessels - Google Patents

Abstract

The apparatus detects salt water and comprises an electric circuit, 100, comprising three sections. A probe circuit, 110, comprises two electrodes which form an open circuit unless the circuit is closed by sea water. A sensing circuit, 120, can be tuned with a potentiometer to trigger the alarm circuit, 130, only when liquid of a minimum salinity, and hence conductivity, bridges the two electrodes.

Description

1 2331612 APPARATUS FOR DETECTING SEA WATER IN MARINE VESSELS This

invention relates to apparatus for detecting the presence of sea water, or more generally salt water, particularly in marine environments.

It is recognised that it is desirable to provide an early warning or alarm to operating personnel on a marine vessel in the event of an ingress of sea water. In recent years a number of fatal accidents have occurred by reason of the ingress of water onto the vehicle deck area of Ro-Ro ferries when the free movement of a relatively shallow depth of water may destabilise the vessel. Typically, this has resulted from the failure to close or properly seal the large doors that provide access to the cargo or vehicle decks in the vessel's hull.

In consequence to these accidents, procedures have been standardised and implemented which require the ship's captain to ensure that the doors are closed prior to putting the vessel to sea. However, there remains a need for providing a suitable means of alerting the captain and other relevant personnel of a leaking seal or other 2 deficiency which allows the flow of water into the vessel.

In the past, apparatus for detecting water has been provided as a possible solution to this problem. For example, float switches located in pocket holes were employed; the apparatus being associated with an alarm system that provided a visible and/or audible warning when water was detected at the predetermined points on a ship's deck. Also proximity sensors and retro-reflect indicators have been tried.

However, such apparatus has proven unsuitable.as frequently it would be activated under false pretence, such as from the urine of livestock being transported or from fresh water used for cleaning the deck.

As the presence of fresh water is usually not an indication of danger, there has been a need for a suitable means of detecting salt water on a vessel's deck, the means having the ability to discern between salt water and other liquid.

Attempts have been made by some to do this; one company utilising a vibrating reed type switch. This had a further disadvantage, however, in that the switch required a minimum of 5 to 6 mm of water to be present before being activated. Unfortunately, this could effectively mean that 30 tonnes of water would have come on board before the required depth of water spread over an entire deck was acquired. An object of the present invention is to provide apparatus for sensing sea or salt water on a marine vessel; to not so sense fresh water or other liquids typically found on the decks of such a 3 vessel; and to detect the salt or sea water virtually immediately upon it leaking through a door seal or otherwise ingressing into the vessel.

According to a first aspect of the present invention, there is provided apparatus for sensing the presence of water on a marine vessel, the apparatus comprising an open electrical circuit having a power source and two spaced apart electrodes, wherein when salt or sea water is caused to span the two electrodes the circuit closes or switches.

Preferably, the circuit further comprises a potentiometer to increase or decrease the sensitivity of the apparatus, and more particularly enable it to remain as an open circuit when fresh water spans the electrodes, but close when salt water spans the electrodes.

Typically, the circuit might close when the salt density in the water is at least 18 parts per thousand.

Preferably, the apparatus includes a visual and/or audible alarm which is activated when the circuit closes or switches.

The electrodes may be strategically placed on the vessel's deck and/or near the vessel's doors around the hull.

The electrodes may be arranged spaced a predetermined distance from the deck surface so as to detect the presence of water in excess of this depth.

4 Typically, the distance by which the electrodes are spaced from the deck may be from 1.5mm.

An example embodiment of the invention will now be described with reference to the following Figures, which:

Figure 1 is a circuit diagram of an example circuit of a salt water alarm system; Figure 2 is elevation and plan illustrations of the electrodes incorporated into a probe; and Figure 3 is an example embodiment of a panel layout associated with the invention.

Referring first to Figure 1, a basic circuit diagram of one embodiment of a salt water alarm system is illustrated. The overall circuit 100 is provided with a low voltage dc supply 101 and a backup battery 102 which operates in event of main supply failure. The circuit comprises three sections, a probe circuit shown generally as 110, a sensing circuit shown generally as 120 and an indicator circuit shown generally as 130. A key to the individual component types is provided on the diagram.

Figure 2 illustrates a probe comprising two electrodes 111 and 112 which are a pre-set distance apart. These are encased in an epoxy box 113 at either end but are exposed where they cross a hemispherical indentation 114. The epoxy box may be mounted in position through two holes for screws 115. A vent hole 116 allows liquid to enter or drain from the hemispherical indentation. Wires to the two electrodes enter through conduit 117. The electrodes are connected through a 10k-ohm resistor 118 which provides a trickle current.

The operation of the circuit is determined by the conductivity of any liquid which in practice bridges the gap between the two electrodes 111 and 112. The circuit can be tuned using a potentiometer to ignore fresh water but to be activated into alarm mode when salt/sea water of a predetermined salinity is present. Typically, this will be eighteen parts per thousand and above. The presence of liquid of the designated minimum salinity, and hence conductivity, between the electrodes is detected by the sensing circuit 120 which operates to switch the indicator circuit 130 from the non-alarm condition shown in Figure 1, when a green LED 131 is illuminated to the alarm condition when a red LED 132 is illuminated and an audible alarm 133 sounds. Once the probe is activated the system will remain in alarm mode due to capillary action. To reset the device the probe must be rinsed clean with fresh water.

Turning now to Figure 3, an example control panel layout is illustrated. In this example the alarm system is installed in a vessel shown schematically as 300. In this example, there are three port sensors 301 and three starboard sensors 302. On the schematic 300 the sensors are each provided with an associated green non-alarm light 303 and red alarm light 304. Detection of salt/sea water by any of the probes causes an alarm condition to show at the associated alarm light 304. The control panel illustrated also includes indicators for power supply 305 and probe fault indicators 306. A probe fault is detected if the trickle current through resistor 118 fails. A mute switch 307 allows the audible alarm 308 to be silenced if desired and a system test button 309 is 6 also provided. Finally, an alarm test facility 310 for testing each of the probes is provided.

Obviously, alternative configurations of electronic circuit can be utilised for the probes and the front panel configuration will vary depending on the details of any specific installation.

The circuit described provides a simple and effective means of indicating the presence of unwanted salt/sea water on the decks of Ro-Ro ferries in particular but is not, of course, restricted in usage to such vessels. The system is designed to provide a prompt alarm regarding the presence of salt/sea water, which might indicate a failure to close the cargo doors or a leaking seal on such doors but to ignore fresh water, eg water draining from loaded vehicles in poor weather conditions.

The system can be configured in a number of different ways and to include various features. The probes can be set to detect the presence of water from a depth of 1.2mm upwards. Various safeguards can also be built in to provide indicators of faults such as broken cables, damaged probes, power failure etc. In the event of power failure, the backup battery system would typically provide power for up to three days. The system can be interfaced with computer control systems already present on the vessel and in general any number of zones can be provided, with the control panel configuration providing easy identification of the zone raising the alarm.

In the example, the probe itself is constructed of high strength epoxy resin with the actual electrodes being 7 stainless steel or otherwise having a high silver content to minimise corrosion.

A simple re-configuration of the system would allow it to be set up to detect fresh water rather than salt or even no water.

various further modifications and improvements can be made within the scope of the present invention-

Claims (1)

1. 8 1 Apparatus for sensing the presence of water on a marine vessel, the apparatus comprising an open electrical circuit having a power source and two spaced apart electrodes, wherein when salt or sea water is caused to span the two electrodes, the circuit closes or switches.

   2 Apparatus according to Claim 1 wherein the circuit further comprises a potentiometer for altering the sensitivity of the apparatus.

   3 Apparatus as claimed in Claim 1 or Claim 2 adapted to remain as an open circuit when fresh water spans the electrodes, but close when salt water spans the electrodes.

   4 Apparatus according to any one of the preceding Claims wherein the circuit will close when the salt density in the water is at least 18 parts per thousand.

   Apparatus according to any preceding Claim which includes a visual and/or audible alarm which is activated when the circuit closes or switches.

   6 A vessel according to any preceding Claim where the electrodes are strategically placed on the vessel's deck- 7 A vessel according to any of Claims 1-5 where the electrodes are placed near the vessel's doors around the hull.

   9 8 A vessel according to Claim 6 where the electrodes are spaced a predetermined distance from the deck surface so as to detect the presence of water in excess of this depth.

   9 A vessel according to claim 8 in which the distance by which the electrodes are spaced from the deck is from 1.5mm.

   Apparatus substantially as described herein with reference to the accompanying description and drawings.