Utility companies have been laying pipes and cables across the ocean floor for more than a century. Prior to the introduction of GPS, marking their position was a difficult and tedious task, fraught with error. It is extremely important to know the exact location of existing lines before undertaking dredging operations or when new pipes and cables are laid down. Regulations require they be buried from several feet to several meters under the bottom to prevent snagging by boat anchors and fishing trawls. The amount of overburden typically makes it impossible to find these lines with conventional metal detectors as they are beyond their detection range. Two pieces of equipment that have proved most effective are the pinpointing magnetometer and the cable tracker. The pinpointing magnetometer is a very sensitive instrument that locates iron and steel pipes buried up to 16 feet in the bottom, and the cable tracker is powerful enough to detect a power or communications cable at more than 30 feet away.
One company using both of these devices is Gray Diving Services in Australia. Founded in 1945 by William Gray, the enterprise has evolved into one of the largest onshore civil diving contractors in the country. They have the expertise and resources needed to design, construct, and manage almost any subsea engineering job. The company has successfully completed projects across Australia, in Southeast Asia and around the Pacific Rim. To aid in their pipeline and cable installation and repair work, Gray acquired JW Fishers PT-1 pinpointing magnetometer and CT-1 cable tracking system. Project manager Adam Gunn reports the PT-1's ability to pinpoint targets, even in areas surrounded by steel structures is extremely helpful as many pipes and cables are near bridges, seawalls, or other structures made of steel or steel-reinforced concrete.
Another company in the Asia Pacific region doing submarine fibre optic and power cable installation and maintenance is NAVA 19 Engineering. To locate and track these cables NAVA 19 is using Fishers CT-1. Owner Vorapoj Tangpojthavipol reports, "We are presently involved in a cable laying project to Samui Island". Ko Samui is Thailand's second largest island after Phuket. "First we had to locate the existing power and fiber optic communication cables so as not to disturb them when we laid down the new 115KV power cable. In the near shore shallow water, we found the CT-1 probe was powerful enough to track the cable from the surface. As the water got deeper, a diver was deployed to follow it. Our divers had excellent results with the CT-1 and found it very precise and easy to operate. Once the old cables had been located, we laid down the new power cable in a 1.5 meter deep trench in the seabed. After the cable was buried, the cable tracker was used to verify its position and also calculate the burial depth. "
The CT-1 is being used on another island half way around the world in Prince Edward Island Canada. Maritime Electric owns and operates a fully integrated power system that includes generation, transmission, and distribution of electricity to customers throughout PEI. Most of the electricity is purchased from off-island sources and is supplied through two submarine transmission cables under the Northumberland Strait. Periodically these cables require maintenance and repair and Maritime Electric employs Fishers cable tracking system to assist in these efforts. The CT-1 can not only locate and track the cables, but also finds faults and breaks in the lines.
In Africa, Subsea 7 a global leader in seabed to surface engineering and construction, is working on the Escravos Gas Project. Chevron Nigeria in partnership with the Nigerian National Petroleum Company is working on what is being called the world's 2nd largest gas project. The partners are constructing the 33,000 barrel per day (bpd) Esrcavos Gas-to-Liquids (EGTL) plant which is expected to expand to 120,000 bpd within 10 years. To allow the movement of cargo to and from the construction site, the Nigerian Ports Authority mounted a major effort to expand the port and its entry channels. More than 53.6 million cubic meters of material has been dredged from the area in order to accommodate ships drafting up to 12.5 meters. In addition, a number of light houses were renovated and 69 channel marking buoys installed. Subsea 7 has been a major provider of services for this huge project. To assist in the location of pipes and cables the company acquired a quantity of the PT-1 magnetometers. The instruments were purchased through TRM, a French distributor of specialty inspection and surveillance equipment.
A few of the many other companies using Fishers pipe and cable trackers are France Telecom Marine, Aquatic Solutions on the Caribbean island of St. Maarten, R S & L Marine in Malaysia, Hong Kong Contractors Ltd., Med Mer Ltd. in Israel, Dorman Long Engineering in Nigeria, Alpha Logistics in Tanzania, Algosaibi Diving and Marine in Saudi Arabia, New Zealand Diving and Salvage, and Underwater Engineering Services in Florida.
Staff of French distributor TRM pose at foot of the Eiffel Tower with Fishers PT-1 pipe tracker
Inset Photo - Crew of Thailand's NAVA 19 Engineering track a cable from the surface using Fishers CT-1.