The economic advantages of jet-assisted plowing

Jet-assisted plowing is rapidly becoming recognized as the intelligent and cost effective technique for deeper, low-tension cable burial with standard cable ships and conventional handling equipment. The development of this approach was motivated by the economic advantages associated with its potential to achieve enhanced cable protection at increased speed and reduced tow force. While the standard passive plowing technique has been generally effective and reliable, the resulting depth of burial has been limited by the amount of tow force the towing ship can impart to the plow in a given soil condition. In some soils (fine sand and stiff clay), achieving even the standard one-meter burial depth requirement of most cable burial projects within the bollard-pull capabilities of typical commercial cable ships is difficult with conventional passive plowing. Jet-assisted plows, on the other hand, provide deeper burial at reduced tow tension in a greater range of sea floor soils. Recognizing the need for deeper cable burial to counter the increased threat of larger fishing vessels and heavier trawling gear, the trend with cable owners is to bury much deeper than the one-meter standard, particularly in soft clay and sand-dominated soils (such as those commonly found in the Far East). TyCom have successfully buried more than 2000 kilometers of fiber optic cable at an average depth ranging from 1.2 to 1.6 meters with corresponding tow tensions of about 20 metric tons using their new jet-assisted plows developed by Perry Slingsby Systems, Inc. Indications are that deeper burial to 3 meters in this same range of soils is also possible while keeping within the 50 metric-ton tow limit of most commercial cable ships. This paper addresses the results from field testing and actual burial projects to discuss in detail the benefits and potential economic advantages of jet-assisted plowing