GB2085727A - Fire fighting buoy for offshore structures - Google Patents

Abstract

Water mains for fighting fires on offshore structures are usually energised by Diesel-driven pumps which are located on the structure with the fuel supply. The fuel and the pumps are vulnerable to the fire, and, because of congestion, the fuel supply is limited. If the fire-fighting pumps are housed on a special-purpose buoy moored near the platform, the pumps and the fuel supply are remote from the fire. The buoy would be spar-type with a single mooring line to a cellular concrete anchor base. The compartments in the anchor would be ballasted to allow tow-out; when on location they would house ample supplies of fuel. A water pipe would connect the buoy to a riser at the structure, which would energise the water main. Alternatively the buoy would house only Diesel generators with an electric cable to the sea-bed at the base of structure, where electrically-driven pumps could be located. <IMAGE>

Description

SPECIFICATION Fire fighting buoy for offshore structure The present invention relates to the provision of seawater for fi re-fi g hti ng and cooling on offshore oil and gas production facilities or other offshore structures.

Ip conventional installations seawaterforfire control purposes is generally provided by designated seawater lift pumps. These pumps are usually locatedon the offshore structure. The pumps are often diesel driven with the fuel supplied from a day tank by gravity feed. In the event of a major hazard occurring such as the ignition of escaping hydrocarbon gas these pumps are required to maintain pressure in the fire ring main on the structure and to deliver sufficient seawater to serve the various outlets (fire monitors and sprinkler systems) around the platform.

Where these pumps are electrically driven the power is often supplied by diesel driven electrical generators. These generators are again often supplied by gravity from an elevated tank. In both the above examples the delivery of seawater will be terminated when the fuel supply runs out. Generally during a platform shutdown which occurs during this type of hazard no means of replenishment of the day tank is provided. Where an alternative means of supplying fuel is available it may be damaged by the hazard or may fail to operate after a long period of unattended use. In either case the ability to spray waterforfire control or protect the structural integ rity of the platform is compromised.

In accordance with the present invention there is provided a means of delivering seawater into the offshore structure by using a nearby float or buoy.

The invention comprises a buoy (1) anchored by a tension member (2) or members to one or more anchor points on the sea-bed, a rigid or flexible hose of steel or other suitable material.

With such an arrangement pumps powered by diesel engines can be housed in the buoy to deliver seawater into the oil platform's ring main system. In this way the source of delivery of the seawater necessary to control a fire or cool a structure is sited remotely from the structure so that the fire, explosion or other hazard cannot affect its operation. In a preferred arrangement two such buoy systems are provided on either side of the offshore structure so that one or other can be used in any prevailing wind direction.

As an alternative the buoy can be designed to accommodate only diesel-electric generator sets which will connect through electrical cables on the sea-bed to submersible pumps attached to the underwater structure of the oil platform.

It will be noted that a hollow concrete gravity base (3) is used to anchore the surface buoy using a single tension member (2). The base could equally well be of ballasted steel construction or a piled anchor could be used.

In this preferred example the tension member is a hollow steel tube riser. It has a mechanical universal joint (4) at the connection with the base and at the connection with the buoy. The universal joint (4) at the connection with the buoy is also capable of transferring sea water th rough it into the buoy. At the connection with the base a short length of armoured flexible hose joint the riser to a steel seabed pipeline which in turn connects with another riser pipe on the offshore structure.

The buoy is of all steel construction and is divided into separate watertight compartments for damage security. The upper end of the buoy is fitted with steel fendering.

The base is of concrete construction and comprises four cylindrical concrete pressure vessels arranged around a central steel core. The purpose of the steel core is both an attachment for the tension member and to form a ballast/air distribution system. The base is intended to be towed to site in a deballasted condition. Once on site the base is lowered in a partially ballasted condition to the sea-bed where it is fully ballasted.

Compartments in the base can also be used for fuel storage for the pumps and generators.

1. A fire fighting buoy for use adjacentto off- shore structures that houses:- (a) Diesel-electric generator sets and water pumps and connected the oil platform by water pipes.

(b) Alternatively diesel-electric generator sets and connected by electrical cable to submersible pumps attached the underwater structure of the oil platform.

2. A fire fighting buoy which is connected to a base by single tension member.

3. A fire fighting buoy which is connected to an anchor which can be ballasted by water.

4. A fire fighting buoy which is connected to an anchor which has compartments which can be used for fuel storage.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Fire fighting buoy for offshore structure The present invention relates to the provision of seawater for fi re-fi g hti ng and cooling on offshore oil and gas production facilities or other offshore structures. Ip conventional installations seawaterforfire control purposes is generally provided by designated seawater lift pumps. These pumps are usually locatedon the offshore structure. The pumps are often diesel driven with the fuel supplied from a day tank by gravity feed. In the event of a major hazard occurring such as the ignition of escaping hydrocarbon gas these pumps are required to maintain pressure in the fire ring main on the structure and to deliver sufficient seawater to serve the various outlets (fire monitors and sprinkler systems) around the platform. Where these pumps are electrically driven the power is often supplied by diesel driven electrical generators. These generators are again often supplied by gravity from an elevated tank. In both the above examples the delivery of seawater will be terminated when the fuel supply runs out. Generally during a platform shutdown which occurs during this type of hazard no means of replenishment of the day tank is provided. Where an alternative means of supplying fuel is available it may be damaged by the hazard or may fail to operate after a long period of unattended use. In either case the ability to spray waterforfire control or protect the structural integ rity of the platform is compromised. In accordance with the present invention there is provided a means of delivering seawater into the offshore structure by using a nearby float or buoy. The invention comprises a buoy (1) anchored by a tension member (2) or members to one or more anchor points on the sea-bed, a rigid or flexible hose of steel or other suitable material. With such an arrangement pumps powered by diesel engines can be housed in the buoy to deliver seawater into the oil platform's ring main system. In this way the source of delivery of the seawater necessary to control a fire or cool a structure is sited remotely from the structure so that the fire, explosion or other hazard cannot affect its operation. In a preferred arrangement two such buoy systems are provided on either side of the offshore structure so that one or other can be used in any prevailing wind direction. As an alternative the buoy can be designed to accommodate only diesel-electric generator sets which will connect through electrical cables on the sea-bed to submersible pumps attached to the underwater structure of the oil platform. It will be noted that a hollow concrete gravity base (3) is used to anchore the surface buoy using a single tension member (2). The base could equally well be of ballasted steel construction or a piled anchor could be used. In this preferred example the tension member is a hollow steel tube riser. It has a mechanical universal joint (4) at the connection with the base and at the connection with the buoy. The universal joint (4) at the connection with the buoy is also capable of transferring sea water th rough it into the buoy. At the connection with the base a short length of armoured flexible hose joint the riser to a steel seabed pipeline which in turn connects with another riser pipe on the offshore structure. The buoy is of all steel construction and is divided into separate watertight compartments for damage security. The upper end of the buoy is fitted with steel fendering. The base is of concrete construction and comprises four cylindrical concrete pressure vessels arranged around a central steel core. The purpose of the steel core is both an attachment for the tension member and to form a ballast/air distribution system. The base is intended to be towed to site in a deballasted condition. Once on site the base is lowered in a partially ballasted condition to the sea-bed where it is fully ballasted. Compartments in the base can also be used for fuel storage for the pumps and generators. CLAIMS

1. A fire fighting buoy for use adjacentto off- shore structures that houses:- (a) Diesel-electric generator sets and water pumps and connected the oil platform by water pipes.

(b) Alternatively diesel-electric generator sets and connected by electrical cable to submersible pumps attached the underwater structure of the oil platform.

2. A fire fighting buoy which is connected to a base by single tension member.

3. A fire fighting buoy which is connected to an anchor which can be ballasted by water.

4. A fire fighting buoy which is connected to an anchor which has compartments which can be used for fuel storage.