Ship Salvage, Harbor Clearance and Wreck Removal oftentimes require extensive underwater cutting and welding. The lack of recent fleet experience in these areas dictates the need for a manual that incorporates state of the art equipment and tried and proven underwater cutting and welding techniques. The knowledge contained in this manual is a collection of fleet and commercial experience. It has been reviewed by technical experts with extensive salvage and underwater cutting and welding experience.

This revision of the Underwater Cutting and Welding Manual has been prepared to provide the most current information on equipment and procedures available. All of the equipment covered may not be found on the Diving Equipment Authorized for Navy Use (ANU) list (NAVSEAINST 10560.2), but is included in this manual as an aid to the salvor who finds himself in a “must get the job done” situation. Further guidance can be found in Appendix E. Due to limited time allocation, there is a lack of realistic underwater cutting and welding training in the Navy’s diving schools. Students are given only the basics in school and thereafter must practice to become proficient and gain the experience necessary to become “qualified underwater cutters and welders.” I therefore charge all diving officers, master divers and diving supervisors to establish or maintain existing training programs for underwater cutting and welding.

INTRODUCTION

1-1    SCOPE

This manual is intended to provide information on the use of conventional techniques for cutting and welding metals underwater. It is written for the U.S. Navy diver who specializes in ship salvage and harbor clearance operations. It is not a procedural guide for certifiable welding used in pre-planned underwater ship husbandry applications.

Divers who perform underwater cutting and welding must have greater skill and stamina than those doing the same work topside. The success and speed of operations depend upon the conditions under which the diver must work because the underwater environment imposes numerous limitations and restrictions on the operator and equipment. The diver is often restricted to working for only a short time on the bottom, particularly at deeper depths. The use of correct techniques and equipment becomes extremely important in terms of work accomplished per hour. Diving apparel, great depth, adverse currents, low temperature, lack of visibility and unstable footing are all factors which make underwater cutting and welding difficult. Whenever practical, cutting techniques are preferred over welding during ship salvage operations. For example, when wrecking in place is the salvage technique, a chain reved through two holes cut in the hull and around a transverse frame is the preferred attachment method over a welded padeye. Only personnel trained and qualified in underwater cutting and welding may be assigned to use the procedures and techniques described herein. Additionally, the procedures in this manual must be carried out in conformance with the U.S. Navy Diving Manual (NAVSEA 0994-LP-001-9010) and standard Navy safety practices. Appendix D covers safety in greater detail.


1-2    UNDERWATER CUTTING OVERVIEW

There are two underwater cutting processes currently approved for Navy use. They are:

• Oxygen-Arc cutting with exothermic electrodes, Steel-tubular electrodes and Kerie Cable; and,
• Shielded metal-arc cutting.

Of these, oxygen-arc (oxy-arc) is preferred because of its ease of use. Two types of electrodes (also called rods) are used for oxy-arc cutting: the exothermic and the steel-tubular electrode. Of these, the exothermic is preferred because it will burn independently after an arc is struck and oxygen is flowing. The second method of underwater cutting is the shielded metal-arc process in which the metal is cut by the intense heat of the arc without the use of oxygen. This method is preferred over oxy-arc when cutting metal of 1/4-inch or less in thickness or when cutting non-ferrous or corrosion-resistant metal of any thickness. Each underwater cutting method is covered in detail in Chapter 2.


1-3    UNDERWATER WELDING OVERVIEW

The installation of large patches, as well as the attachment of suitable pad-eyes presents a more complicated problem to the diver than does underwater cutting. Considerable practice is necessary to achieve a consistently good standard of underwater welding for salvage work. As a result, the diver’s underwater welding techniques must conform to acceptable standards. Also, the ocean acts as a large heat sink and draws off the heat of the electrode. This may cause blow holes and possible loss of strength between the patch and hull. This is true because the gas cannot escape from the molten pool of metal due to sudden cooling by the surrounding water. Despite the above shortfalls, underwater welds of good strength that are acceptable for salvage work are possible. Unless otherwise specified, the term “underwater welding” as used in this manual refers to the wet welding technique where no mechanical barrier separates the welding arc from the surrounding water.

The two types of welding to be covered in this manual are:
• wet welding and
• dry welding at the “splash zone.”

Shielded metal-arc welding is the most widely used process for wet welding. Specific welding procedures for underwater maintenance work on ships is addressed in the Underwater Ship-Husbandry Manual (NAVSEA S0600-AA-PRO-010) and the Naval Ship’s Technical Manual, Chapter 074 (NAVSHIPS 59086-AA-STM-010).

Wet welding is accomplished with both the diver and the work completely submerged. The advantages and disadvantages will be discussed in detail in Chapter 3. Dry welding at the “splash zone” is generally conducted in a dry box or cofferdam at atmospheric pressure. It is essentially conventional welding and is discussed in Chapter 3 to provide the salvor with methods to exclude water from the weld area. Before proceeding with any cutting or welding procedure described in this manual, all personnel involved must thoroughly review and comprehend the applicable safety precautions, warnings and cautions. This information, which is based on knowledge and experience gained through many years of Naval and commercial operations, is presented in Appendix D and the Safety Summary. Strict adherence to the safety regulations is required. Before starting any new job, a thorough inspection of the situation must be made to determine hazards to personnel, equipment or ship that may exist. Appropriate action must be taken to eliminate or minimize noted hazards.


2-2 OXYGEN-ARC CUTTING

There are two types of electrodes used for oxygen-arc (oxy-arc) cutting—steel-tubular (manufactured by Arcair) and the exothermic types (Arcair’s Sea-Jet and BROCO’s Ultrathermic - see Figure 2-1). These electrodes provide excellent cutting results and can be used with a constant current DC welding generator set on straight polarity (electrode negative) supplying current to the electrode. With the work grounded, the electrode will ignite as it touches the work. Oxygen-Arc is preferred because it cuts plain and low-carbon steel easily which metal is severed by means of the chemical reaction of oxygen with the base metal at elevated temperatures. The heat of the arc brings the metal to its kindling temperature, then a high velocity jet of pure oxygen is directed through a tubular cutting electrode at the heated spot. The metal oxidizes and is blown away. The tip of the electrode, which is exposed to both heat and oxidation, is consumed in the process and must be replaced frequently. 2-2.2 Steel-Tubular Electrodes. The steel-tubular electrode consists of a steel tube with a waterproofed flux coating which is applied during the manufacturing process. The electrode is 14 inches long with a 5/16-inch outer diameter and a bore diameter of slightly less than 1/8 inch (see Figures 2-2a and 2-2b). The waterproof flux coating is similar in composition to the coating on welding electrodes. The flux coating serves the following purposes:

a. It promotes easy starting and maintenance of the arc.
b. It liberates gases, thus forming a protective bubble around the arc.
c. It serves as an electrical insulator, even in wet conditions, thereby assisting in safeguarding the diver in the event of accidental body contact while cutting.
d. It prevents arcing from the side of the electrode when working in confined quarters.


DOWNLOAD PDF VERSION  -  2,38Mb