1. Seminar of Underwater Welding & Inspection
4/12/2018
Seminar of Underwater Welding & Inspection
Salamu’ alaikum and Good Morning,
The purpose of my presentation today is to introduce you to the underwater world. But what you are going to see here are not fishes, corals or other undersea creatures. What you will learn here is the other side of atmospheric welding, the underwater welding. .
I am presenting this on behalf of the team that worked on the Recognition item following the Team Alignment Process (TAP) Meeting.
CLICK
Ali Malik Saadoon University of Baghdad Engineering Affairs Department

2. Purpose:
The purpose of this Seminar is for general knowledge only on how “underwater welding” is carried out. Safety is also emphasized here as we are dealing with two types of activities, Diving and Welding. One must remember that underwater welding is a different world, and so special precautions are adhered to for maximum safety of the welder/diver.

3. List of Content: 1- Introduction 2- Uses 3- The Welder/Diver
4- Classification
5- Principle of Operation
6- Codes, Standards & Specifications
7- Characteristics of a Good Underwater Welding
8- Application of Underwater Welding
9- Some characteristics of underwater welding
10- Underwater Inspection
11- Risk Involved
12- Safety
13- Developments
14- References:
15-Appendix

4. 4/12/2018
1- Introduction:
Underwater welding began during World War 1 when the British Navy used it to make temporary repairs on ships. These repairs consisted of welding around leaking rivets of ship hulls. Underwater welding was also restricted to salvage operations and emergency repair works only. In addition, it was limited to depths below the surface of not over 30 ft (10meters).
At first, underwater welding was just applied to weld a patch until a more thorough repair could be performed. But as soon as more experience was gained, ambitious individuals and companies joined forces to improve results and to establish achievable specifications.
At present, underwater welding becomes more sophisticated and can be done deeper. GTAW has been used to weld pipes at depths of 200 ft (61 m) and has produced an X-ray quality welds meeting the requirements of API 1104 Standard. Offshore oil explorations have increased the interest in underwater welding.

5. 2-Uses:
While underwater welding have been used for new construction & installation of offshore structures, subsea pipelines, & harbor facilities, it is most often used for maintenance and repair applications. These includes repair of damage caused by corrosion, fatigue, and accidents of offshore structures such us oil platforms, repair & replacement of damaged subsea pipeline sections, repairing holes in ship’s hulls or collision damage to harbor facilities.

6. Uses (cont’d)
Photos below shown, it is obvious that these structures has to be repaired. And one of the tools of repair is underwater welding.
Damaged Offshore Structure
Sinking Offshore Structure

7. 3- The Welder/Diver:
Welder/diver – is a certified welder who is also a commercial diver, capable of performing tasks associated with commercial subsea work, weld setup and preparation, and who has the ability to weld in accordance with the AWS D3.6, Specification for Underwater Welding (wet or dry), and other related activities.
Welder/diver qualifications required for a given assignment vary from project to project. Most diving contractors would like their welder/diver to be “a jack of all trades”. This means that the welder/diver must know how to do underwater cutting, fitting and rigging, inspection and nondestructive testing, and underwater photography.
Welding
Cutting

8. 4- Classification According AWS D3.6M:2010:
There are five basic methods of underwater welding currently in use: (1) Welding in a pressure vessel in which the pressure is reduced to approximately one atmosphere, independent of depth (dry welding at one atmosphere). (2) Welding at ambient pressure in a large chamber from which water has been displaced in an atmosphere such that the welder/diver does not work in diving equipment (dry welding in a habitat). (3) Welding at ambient pressure in a simple open-bottomed dry chamber that accommodates, as a minimum, the head and shoulders of the welder/diver in full diving equipment (dry chamber welding). (4) Welding at ambient pressure in a small, transparent, gas-filled enclosure with the welder/diver outside in the water(dry spot welding). (5) Welding at ambient pressure with the welder/diver in the water without any mechanical barrier between the water and the welding arc (wet welding).

9. So underwater welding is classified into two categories.
Welding in-the-wet environment = This was used primarily for emergency repairs and salvage operations in shallow waters due to poor quality welds.
Welding in-the-dry environment = This technique produces high-quality welds that meet X-ray and code requirements.

10. Welding in-the-wet environment
4/12/2018
Welding in-the-wet environment
Underwater wet welding is done in an environment where the base metal and the arc are surrounded entirely by water. The electrode types used conform to AWS E6013 classification. These electrodes are waterproofed by wrapping them with waterproof tape or by dipping it into special sodium silicate mixes and allowing them to dry. The power source is a direct current machine rated at 300 or 400 amperes.
The power of the arc generates a bubble of a mixture of gasses which lets metal melting and joining occur more or less normal.
The power of the arc generates a bubble of a mixture of gasses which lets metal melting and joining occur more or less normal as shown on the above photo.

11. Welding in-the wet (cont’d):
4/12/2018
Welding in-the wet (cont’d):
Below is a typical underwater welding equipment set up.
Waterproof Electrode
Holder
Power Supply _ +
electrode
Wet Underwater Welding method uses a waterproof welding electrodes. The power of the arc generates a bubble of a mixture of gasses which lets metal melting and joining occur more or less normal.
work
Knife switch

12. Advantages of Wet Welding
Wet underwater MMA (Manual Metal Arc) welding has now been widely used for many years in the repair of offshore platforms. The benefits of wet welding are: -
1) The versatility and low cost of wet welding makes this method highly desirable.
2) Other benefits include the speed. With which the operation is carried out.
3) It is less costly compared to dry welding.
4) The welder can reach portions of offshore structures that could not be welded using other methods.
5) No enclosures are needed and no time is lost building. Readily available standard welding machine and equipments are used. The equipment needed for mobilization of a wet welded job is minimal.

13. Disadvantages of Wet Welding
Although wet welding is widely used for underwater fabrication works, it suffers from the following drawbacks: -
1) There is rapid quenching of the weld metal by the surrounding water. Although quenching increases the tensile strength of the weld, it decreases the ductility and impact strength of the weldment and increases porosity and hardness.
2) Hydrogen Embrittlement – Large amount of hydrogen is present in the weld region, resulting from the dissociation of the water vapour in the arc region. The H2 dissolves in the Heat Affected Zone (HAZ) and the weld metal, which causes Embrittlement, cracks and microscopic fissures. Cracks can grow and may result in catastrophic failure of the structure.
3) Another disadvantage is poor visibility. The welder some times is not able to weld properly.

14. Welding in-the-dry environment
Welding in-the-dry environment can be divided into main two categories:
Hyperbaric welding, in which a chamber is sealed around the structure to be welded and is filled with breathable gas at the prevailing pressure.
Cofferdam welding, which is carried out in the dry, in air, where a rigid steel structure to house the welders is sealed against the side of the structure to be welded, and is open to the atmosphere.

15. Welding in-the-dry Environment:
4/12/2018
Welding in-the-dry Environment:
Hyperbaric welding is done with the use of a welding chamber or habitat. This method provides high quality weld joints that meet radiography and code requirements. The chamber is sealed into a structure or pipeline and filled with breathable mixture of helium and oxygen (90-95% helium and 5-10% oxygen).
Welding Chamber
The bottom portion of the chamber is exposed to open water and is covered by a grating. This is done to equalize the chamber pressure to the outside water pressure at certain depth. The chamber provides the welder/diver with all necessary welding equipment for welding in a dry environment.
Welding Chamber Internal

16. Welding in-the-dry (cont’d)
Cofferdam welding is also a type of dry welding where a rigid steel structure to house the welders is sealed against the side of the structure to be welded and is open to the atmosphere. It is normally used for harbor works or ship repair.

17. Welding in-the-dry (cont’d)
Photographs below are examples of Cofferdam
Welding.
Dummy structure
Actual structure

19. Advantages of Dry Welding
1) Welder/Diver Safety – Welding is performed in a chamber, immune to ocean currents and marine animals. The warm, dry habitat is well illuminated and has its own environmental control system (ECS).
2) Good Quality Welds – This method has ability to produce welds of quality comparable to open air welds because water is no longer present to quench the weld and H2 level is much lower than wet welds.
3) Surface Monitoring – Joint preparation, pipe alignment, NDT inspection, etc. are monitored visually.
4) Non-Destructive Testing (NDT) – NDT is also facilitated by the dry habitat environment.

20. Disadvantages of Dry Welding
1) The habitat welding requires large quantities of complex equipment and much support equipment on the surface. The chamber is extremely complex.
2) Cost of habitat welding is extremely high and increases with depth. Work depth has an effect on habitat welding. At greater depths, the arc constricts and corresponding higher voltages are required. The process is costly – a $ charge for a single weld job. One cannot use the same chamber for another job, if it is a different one.

21. 5- Principle of Operation:
4/12/2018
The sketch at right shows the general arrangement for underwater welding. Underwater welding should always be a direct current machine grounded to the ship. The welding circuit includes a knife switch that is operated on the surface by an assistant upon the signal of the welder/diver. The knife switch cuts off the welding current and is design this way for safety reasons. The electrode holder utilizes a twist type head for gripping the electrode. The work lead is attach within 3 ft. from the point of welding and is perfectly insulated to avoid leaks. The welding circuit should be direct current electrode negative.

22. 6- Codes, Standards & Specifications:
4/12/2018
6- Codes, Standards & Specifications:
Underwater welding is covered under:
AWS D3.6 Specification for Underwater Welding.
ASME N-516 Underwater Welding Section XI Div. 1
BS EN ISO :2002 Qualification Testing of welders for underwater welding.
ASTM
ANSI/AWS D3.6 provides essential information to:
The Welding Engineer - for selecting the recommended welding-underwater process (wet or dry)
The Stress Engineer - for verifying the requirements of fitness for purpose.
The Design Engineer - for specifying details in structural fabrication.
The Purchaser - for establishing acceptance requirements.
The Contractor – for estimating means and cost of the project.

23. 7-Characteristics of a Good Underwater Welding
The characteristics of a good underwater welding process are:
(a) Requirement of inexpensive welding equipment, low welding cost, easy to operate and flexibility of operation in all positions.
(b) Minimum electrical hazards, a minimum of 20 cm/min welding speed at least.
(d) Permit good visibility.
(e) Produce good quality and reliable welds.
(v) Operator should be capable in supporting himself.
(vi) Easily automated.

24. 8- Application of Underwater Welding
The important applications of underwater welding are:
(a) Offshore construction for tapping sea resources,
(b) Temporary repair work caused by ship’s collisions or unexpected accidents.
(c) Salvaging vessels sunk in the sea
(d) Repair and maintenance of ships
(e) Construction of large ships beyond the capacity of existing docks.

25. 9- Some characteristics of underwater welding
1. Rapid Cooling Rate
The weld microstructure is affected by the rapid cooling rates incurred in underwater welding. The use of a continuous cooling transformation (CCT) diagram can explain this microstructure. Figure (1) is a CCT of simulated single pass welds on A516 Gr 70 steel which was generated using a Gleeble machine. The microstructures and corresponding temperatures at which each will start and finish can be identified on the diagram. Because the weld samples of interest were multipass welds, an important variable known as bead tempering is introduced. The subsequent weld passes and its affect on the previous weld pass microstructure. Figure (2) shows how multiple weld passes can affect the HAZ of the weld pass made previous to it. Multiple weld passes provide bead tempering to the previous weld pass which refines the coarse grains in the HAZ which is where hydrogen under bead cracking commonly exists.

26. Fig. (1) Continuous Cooling Transformation diagram for a single pass weld on A516 Grade 70 Steel
Fig. (2) Schematic diagram of the multi pass weld HAZ microstructure

27. 9- Some characteristics of underwater welding (cont’d)
2. Hydrogen Cracking
The susceptibility to hydrogen cracking in underwater weldments made on high
strength steels is a major concern. The four conditions which must be present for hydrogen cracking to occur:
1) Susceptible microstructure
2) Critical concentration of diffusible hydrogen
3) Stress intensity
4) Relatively low temperature less than 200°C
As can be expected, all four conditions exist in underwater Shielded Metal Arc Welding SMAW. Obviously the martensitic microstructure ofthe HAZ near the fusion line is susceptible because it is hard and brittle. The dissociation of hydrogen near the weld arc unavoidably supplies hydrogen to the weld metal. Because of the high restraints placed on the weld piece and the superimposing of large thermal gradients, high stresses are likely in the weld. Finally, the temperature ofany underwater body that is available for work to be accomplished in is definitely below 200°C. The comments made in all the subsections of section C clearly indicate that hydrogen assisted underbead cracking of underwater wet weldments on ferritic steel is highly likely unless the steel's carbon equivalent and carbon contents are maintained at suitably low levels.

28. 10- Underwater Inspection:
Underwater inspection also includes visual and photographic examination of underwater structures and repairs, and NDE such as MT, UT, and RT.
Typical underwater Inspector equipped with lights and camera.
An underwater structure showing signs of corrosion.

29. Underwater Inspection (cont’d)
Non-destructive Testing like UT, RT and MT can also be done underwater.
An underwater NDT technician using Magnetic Particle Testing on underwater structural supports.
Note: There are Non-destructive
Examination of Underwater Welded
Steel Structures.

30. Underwater Inspection (cont’d)
Visual, video and photographic examination can also be carried out during maintenance inspection on any underwater structures as shown below.
In order to carry out a
proper visual and NDT
check, blast cleaning has
to be carried out to remove
all seawater organisms
that grows on the
underwater structure
as shown on this
photograph.

31. Underwater Inspection (cont’d)
Latest development in underwater inspection is the use of ROV’s.
These are machines operated by an ROV pilot.
ROV Pilot
Submarine Rescue Machine
ROV machine

32. Underwater Inspection (cont’d)
TWI World Center for Materials Joining Technology
Courses Offered:
Underwater Inspection – Underwater Training and Examinations
CSWIP 3.1U – NDT Inspection Diver
CSWIP 3.2U – NDT Inspection Diver
CSWIP 3.3U – ROV Inspector
CSWIP 3.4U – Underwater Inspection Controller
CSWIP General Visual Inspectors for Offshore Facilities and Structures

33. 11- Risk Involved: Below are some risks involve in underwater welding:
Electric shock – there is a possibility of electric shock when the equipment is not properly insulated, or when the power supply is not shut off immediately when the welder terminates the arc during welding.
Explosion – arc welding produces hydrogen and oxygen. Pockets of gasses can build up and are potentially explosive.
Nitrogen Narcosis – a health hazard normally experienced by divers during the diving activities when safety stops at certain level is not adhered to. Curiously, the risk of drowning is not listed with the hazards of underwater welding.
For welded structures, inspection of welds after welding maybe more difficult than welds made above water. There is a risk of defects that may remain undetected and may cause failure in the long run.

34. 12- Safety: OSHA Standard 1915.6 – Commercial Diving
OSHA Standard – SCUBA Diving
Volume IV, Issue 3, 3rd Quarter 2002
Occupational Health Newsletter – Commercial
Diving Medical Emergencies in Saudi Aramco

35. Safety: (cont’d)
Annex D of AWS D3.6 - Recommended Guidelines for Safety in Underwater Welding
Scope is limited to recommended safe practices specifically related to underwater welding and associated work activities performed in either a dry (hyperbaric) or a wet environment.
Annex D comprises safe practices, underwater communication, electrical equipment, hand-held power tools, preparation for work, performance of work, and inspections and examinations.

36. Safety (cont’d) Welding:
Necessary precautions should be carried out such as:
Follow employers safety practices.
Fumes and gasses can be hazardous to your health.
Arc rays can injure eyes and skin.
Use adequate ventilation while welding.
Wear suitable eye protection and protective clothing.
Do not touch live electrical parts.
Wear rubber gloves.
Only change the electrode when cold.

37. 13- Developments:
With the latest development in construction of offshore oil platforms, there has been an increased demand for underwater welding. The use of hyperbaric chambers to produce code-quality weld is very expensive to operate.
Sea Grant Researcher Dr. Chon Tsai, has developed a new welding electrode for wet welding nickname “Black Beauty” for the black appearance of its waterproof coating. The electrode exhibits excellent visual appearance and profile, micro-cracking of weld has been eliminated, operating characteristics are superior to other commercially available electrodes, and the electrode produces suitable results when used in any position.

38. Developments (cont’d)
Wet-Dry welding – Dry hyperbaric chambers or habitats are extremely expensive. This is because it must be built for special applications such as repairing or making tie-ins on horizontally laid pipes. Recent improvements allowed GMAW (Gas Metal Arc Welding) process to be used in underwater welding with the use of special nozzles, domes or miniature chambers. In using this type of apparatus the welder/diver is in the water but the nozzle of the welding gun and material to be welded is in the dry atmosphere. These localized dry gas environment chambers are inexpensive, small and lightweight. It is made of transparent material or has sufficient number of windows so that the welder can see the inside to properly manipulate and direct the welding gun. This process can be utilized for welding up to 125 ft. (35m) below the water surface.

39. 14- References: TWI Knowledge Summary – Underwater Welding
Underwater Magazine – Commercial Diving
Divers Academy International
Atlantic Welding & Fabrication Centre
Special Applications of Welding – Underwater Welding
Blakemore, G. R. (2000): Underwater Intervention 2000 – Houston, Jan
Chen W, Zhang X, et al. (1998): Proc SPIE, Vol. 3550, pp. 287–297.
Chen HB, Li L, Brookfield DJ, et al. (1993): Multi-frequency fiber optic sensors for in-process laser welding
quality monitoring. Proc NDT E Int., Vol. 26, No. 2, pp. 268–274.
Dawas, C. (ed.) (1992): Laser Welding, Mc. Graw-Hill, N. York.
Duley W. W. (ed.) (1999): Laser Welding, John Wiley & Sons, Inc., N. York, pp. 1
Dutta Majumdar, J. And Manna, I. (2003): Sadhana, Vol. 28, pp. 495.
Farson D, Ali A, Sang Y. (1998): Weld Res Suppl., Vol. 77, No.: 4, pp. 142–148.
Haddad, G. N., Farmer, A. J. (1985): Weld. J., Vol. 64, No. 12, p
Hugel H, Matthias G, Muller G, et al. (1999): Proc SPIE, Vol. 3571, pp. 52–60.
Irie T, Ono Y, Matsushita H, et al. (1997): Proceedings of 16th OMAE, pp. 43–50.
Kern, M, Berger, P., Ugel, H. H., (2000), Weld. J., Vol. 3, pp. 72.
Khanna, O. P. (2004): A Textbook of Welding Technology, Dhanpat Rai Publications (P) Ltd., N. Delhi, India.
Kruusing, A. (2004): Optics and Lasers in Engineering, Vol. 41, pp. 329–352.
Lancester, J. F. (1987): The Physics of Fusion Welding – Part I: The Electric Arc in Welding, IEE Proc., Vol.
134, pp
Oates W. A. (ed.) (1996): Welding Handbook, Vol. 3, American Welding Society, Miami, USA.
Ogawa Y, Irie T, Ono Y, et al., (1998): Proceedings of the 17th OMAE.
Ogawa Y. (1998): Proceedings of Eighth International Offshore and Polar Engineering Conference, vol. 4.

40. 15- Appendix:
Dry Underwater welding

41. Wet Underwater welding

42. Questions

43. "Thanks"

44. List of Symbols:
MMA: Manual metal arc welding (first invented in Russia in 1888.
It involved a bare metal rod with no flux coating to give a protective
gas shield)
NDT : Non-Destructive Testing
ECS : Environmental control system
CCT : Continuous cooling transformation
HAZ : Heat Affected Zone.
MT: Magnetic Particle Testing
UT: Ultrasonic Testing
RT: Radiographic Testing
ROV: Remotely operated underwater vehicle