Systems and methods for underwater impressed current cathodic protection

Abstract

An ICCPS system includes a waterproof transformer or transformer rectifier adapted for underwater placement, an above-water source of AC power, and one or more cables connecting the power source to either a rectifier on the surface and underwater transformer or to a underwater transformer rectifier to deliver high voltage/low amperage DC power or high voltage/low amperage AC power from the source for underwater conversion to low voltage/high amperage DC power for delivery to on underwater anode.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to underwater impressed current cathodic protection system systems and methods. More particularly, it relates to placing components underwater which are now placed above the water surface.

2. Description of Related Art

Existing underwater impressed current cathodic protection systems (ICCPS) utilize an above water transformer rectifier to power the underwater anode(s). The transformer rectifier is typically powered with facility high-voltage alternating current (AC) which is converted to low voltage, high amperage direct current (DC) at the transformer rectifier. One leg of the transformer rectifier DC output is normally grounded to the structure being protected via the ICCPS and the other leg is connected to a power cable which is connected to the underwater anode(s).

Because low voltage/high amperage is transmitted through the power cable to the anode(s) the power cable diameter is large. Further, the facility structure must be capable of handling the power cable weight and accommodate the transformer rectifier weight and footprint. The facility structure must also bear the weight of an I-tube to protect the cable(s) through the splash zone of the facility.

The topside engineering costs of the existing systems and methods is high. The new methods and systems should eliminate a majority of these costs by placing the transformer or transformer rectifier underwater. They will also reduce the structural load to the platform by moving the transformer or transformer rectifier underwater. Additionally, the heavy low voltage/high amperage cable can be replaced by a lighter high voltage/low amperage cable which will also reduce the weight imposed on the facility. Because the cable is smaller, the associated I-tube is also smaller, and imposes less weight on the facility.

Placing the transformer or transformer rectifier underwater also eliminates the need for specific gravity sleds for the anodes. Instead, the anodes can be mounted directly onto the underwater transformer or transformer rectifier encasement which will function as the gravity sled for the anode.

Additionally, because the transformer or transformer rectifier is located underwater, the effective output of the transformer or transformer rectifier is greater, as current requirements are reduced because of the shorter distance from the transformer or transformer rectifier to the anode, and the structure ground or grounded structure. Cooling constraints are also reduced as the transformer or transformer rectifier uses water as a heat sink rather than air.

SUMMARY OF THE INVENTION

According to the invention, an ICCP system for use with a facility, such as an oil drilling or production platform, and having a portion, e.g., a platform, above water, comprises one or more waterproof transformers or transformer rectifiers adapted for placement on or near the floor of the body of water, one or more AC power cables for connecting these waterproof transformers/transformer rectifiers to a generator or other high voltage AC source above the surface of the water, a waterproof DC ground for underwater connection between the waterproof transformers or transformer rectifiers and the facility, and optionally, an I-tube for the cables.

Alternatively, an ICCP system for use with such facilities comprises one or more waterproof transformers or transformer rectifiers adapted for placement on or near the floor of a body of water, one or more high voltage/low amperage power cables for connecting these waterproof transformers/transformer rectifiers to a high voltage/low amperage DC current source. The high voltage/low amperage DC current source may be the output from a rectifier that converts AC power to high voltage/low amperage DC current.

The ICCP methods comprise connecting a source of high voltage power, above the surface of the sea, e.g., on the platform of a facility such as an oil drilling or production platform, to a waterproof transformer or transformer rectifier placed below the surface of the water, e.g., on or near the floor of the body of water, delivering high voltage power on one or more power cables from the power source to the waterproof transformer or transformer rectifier, converting the high voltage/low amperage power to low voltage/high amperage power in the transformer or transformer rectifier, and delivering the high amperage power to an underwater anode. Grounding of the underwater transformer or transformer rectifier is made underwater to the facility.

Waterproof transformers and transformer/rectifiers may be housed in oil filled containers. These containers are preferably sealed from the environment and substantially watertight because of the housing and oil within the housing.

The housing may be made of a waterproof material, e.g., fiberglass. The oil in the container acts as a coolant, and is equalized to hydrostatic pressure when the container is placed in deep water.

These systems and methods have several benefits:

• • Significantly reduces facility structural weight load and footprint requirements for the ICCPS.
  • Significantly reduces project engineering costs and requirements.
  • Significantly reduces facility construction costs and requirements.
  • Increases effective output relative to water depth of the ICCPS.
  • Increases productivity and reduced operating risk.

BRIEF DESCRIPTION OF THE DRAWING

The methods and systems of this invention are illustrated in the appended, exemplary drawing.

DETAILED DESCRIPTION OF THE DRAWING

In the drawing, generator 1 is placed on the platform 10 of facility 9. Facility 9 is an oil drilling rig with a portion 11 located above the surface 8 of a body of water, e.g., sea 13, and a portion 12 located below water surface 8. Atop platform 10 is generator or other land-based high voltage AC source 1. Source 1 is connected, through high voltage AC lines 2, to underwater waterproof transformers or transformer rectifiers 6, which are connected to underwater anodes 5 through anode power cables 7. I-tube 2 protects AC lines 2 from environmental forces in the splash zone around facility 9. DC ground 4 is connected to facility 9 underwater.

Claims

1. An ICCP system comprises one or more waterproof transformer rectifiers adapted for underwater placement, an above water surface source for AC power, and one or more AC power delivering cables connecting the AC power source to said transformer rectifiers.

2. An ICCP method comprises delivering high voltage/low amperage AC power from the above water portion of a facility mounted underwater with a portion of the facility above the surface of the water, to a waterproof transformer rectifier grounded underwater to the facility, converting AC power to DC power in the waterproof transformer rectifier, and delivering the DC power to an underwater anode.

3. An ICCP system comprises one or more waterproof transformers adapted for underwater placement, an above water source for high voltage/low amperage DC power and one or more high voltage/low amperage DC power carrying cables connecting said high voltage/low amperage DC power to said transformers.

4. An ICCP method comprises delivering high voltage/low amperage DC power from the above water portion of a facility that is mounted underwater with a portion of the facility above the surface of the water, to a waterproof transformer grounded underwater to the facility, converting said high voltage/low amperage DC power to low voltage/high amperage DC power, and delivering the low voltage/high amperage DC power to an underwater anode.