26-03-2011, 10:13 AM
Presented by:
CLIND M.B
[attachment=11029]
UNDER WATER WELDING
What is under water welding?
Under water welding is the process of welding at elevated pressures, normally underwater.
Under water welding can either take place wet in the water itself or dry inside a specially constructed positive pressure enclosure.
TYPES OF UNDER WATER WELDING
RISKS INVOLVED
SAFETY MEASURES TO BE TAKEN
It is unsafe to operate the torch without the flash arrestor in place. To do so may cause injury and destroy the torch.
Do not attempt to speed up the welding by creating a fire deep inside the metal. Such a situation can lead to an explosion.
NEVER bring a cutting torch into a cell with the oxygen on or with the welding generator running.
Never put down or carry an electrode holder while the power is on.
Never allow any metallic part of the diving dress to touch the work.
Advantages of wet welding
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.
6) Readily available standard welding machine and equipments are used.
Disadvantages of wet welding.
ADVANTAGES OF DRY WELDING
1. Welding is performed in a chamber, immune to ocean currents. The warm, dry habitat is well illuminated and has its own environmental control system.
2. This method has ability to produce welds of quality comparable to open air welds as no water is present to quench the weld.
3. Joint preparation, pipe alignment etc can be monitored visually.
4. Non-Destructive testing is also facilitated by the dry habitat environment.
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.
3) At greater depths, the arc constricts and corresponding higher voltages are required. The process is costly $ 80000 charge for a single weld job. One cannot use the same chamber for another job, if it is a different one.
Scope For Further Developments
Dry Hyperbaric welds are better in quality than wet welds. Present trend is towards automation. THOR – 1 (TIG Hyperbaric Orbital Robot) is developed where diver performs pipefitting, installs the trac and orbital head on the pipe and the rest process is automated.
Developments of diverless Hyperbaric welding system is an even greater challenge calling for annexe developments like pipe preparation and aligning, automatic electrode and wire reel changing functions, using a robot arm installed.
This is in testing stage in deep waters. Explosive and friction welding are also to be tested in deep waters.
CLIND M.B
[attachment=11029]
UNDER WATER WELDING
What is under water welding?
Under water welding is the process of welding at elevated pressures, normally underwater.
Under water welding can either take place wet in the water itself or dry inside a specially constructed positive pressure enclosure.
TYPES OF UNDER WATER WELDING
RISKS INVOLVED
SAFETY MEASURES TO BE TAKEN
It is unsafe to operate the torch without the flash arrestor in place. To do so may cause injury and destroy the torch.
Do not attempt to speed up the welding by creating a fire deep inside the metal. Such a situation can lead to an explosion.
NEVER bring a cutting torch into a cell with the oxygen on or with the welding generator running.
Never put down or carry an electrode holder while the power is on.
Never allow any metallic part of the diving dress to touch the work.
Advantages of wet welding
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.
6) Readily available standard welding machine and equipments are used.
Disadvantages of wet welding.
ADVANTAGES OF DRY WELDING
1. Welding is performed in a chamber, immune to ocean currents. The warm, dry habitat is well illuminated and has its own environmental control system.
2. This method has ability to produce welds of quality comparable to open air welds as no water is present to quench the weld.
3. Joint preparation, pipe alignment etc can be monitored visually.
4. Non-Destructive testing is also facilitated by the dry habitat environment.
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.
3) At greater depths, the arc constricts and corresponding higher voltages are required. The process is costly $ 80000 charge for a single weld job. One cannot use the same chamber for another job, if it is a different one.
Scope For Further Developments
Dry Hyperbaric welds are better in quality than wet welds. Present trend is towards automation. THOR – 1 (TIG Hyperbaric Orbital Robot) is developed where diver performs pipefitting, installs the trac and orbital head on the pipe and the rest process is automated.
Developments of diverless Hyperbaric welding system is an even greater challenge calling for annexe developments like pipe preparation and aligning, automatic electrode and wire reel changing functions, using a robot arm installed.
This is in testing stage in deep waters. Explosive and friction welding are also to be tested in deep waters.
