UNDER WATER WELDING:
The Welding is an unavoidable process of modern engineering – civil, electrical,
mechanical, automobiles, marine aeronautical – in all branches. It is used in
fabrications and erections in infrastructures and installations. It joins metals
or thermoplastics.
The Hyperbaric welding OR UNDER WATER WELDING is the process of welding at elevated pressures, normally in underwater. It is of 2 types DRY & WET Welding. The Hyperbaric welding can either take place wet in the water itself OR dry inside. Here a specially constructed positive pressure enclosure is used and hence it is called dry welding. Similarly Hyperbaric welding term used in dry environment & underwater welding term used as in wet environment. The hyperbaric welding is used to repair damaged ships, under water pipe line & etc.
INTRODUCTION:-
The fact that electric arc could operate was known for over a 100 years. The first ever underwater welding was carried out by British Admiralty – Dockyard for sealing leaking ship rivets below the water line.
Underwater welding is an important tool for underwater fabrication works. In 1946, special waterproof electrodes were developed in Holland by ‘Van der Willingen’. In recent years the number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. Some of these structures will experience failures of its elements during normal usage and during unpredicted occurrences like storms, collisions. Any repair method will require the use of underwater welding.
UNDERWATER WELDING PRINCIPLES:-
Underwater welding can be performed under wet or dry conditions. Dry underwater welding refers to underwater welding which is performed under hyperbaric conditions (an underwater habitat is displacing the water with a gas at the prevailing pressure), and wet underwater welding refers to welding which is performed in fresh- or salt-water without a protecting habitat.
Wet underwater welding will here after be referred to as ―wet welding‖, and wet/dry underwater welding will simply be referred to as ―underwater welding‖. The most commonly used wet welding technique is shielded metal arc welding (SMAW), also known as manual metal arc (MMA) welding or informally as stick welding. The main differences for the welding equipment (wet welding equipment versus ―workshop‖ welding equipment) are shown in Figure 1. Note that wet underwater welding is performed by using a (usually motor generated) power source generating DC current only (for wet welding AC is not used on account of electrical safety and difficulty in maintaining a welding arc underwater), the inclusion of a single or dual pole knife switch (circuit breaker), which protects a welding diver from electrocution, and the use of double insulated cables. Both the power source and knife switch (capable of breaking the full wet welding current) are secured above water (grounded) and controlled (on the diver welders command) by an operator. The cross section of the welding cable is adjusted to the length of the cable and should be highly wear resistant (marine growth) and sufficiently flexible; special welding electrode holders are used with extra insulation against the ingress of water.
CLASSIFICATION OF UNDERWATER WELDING:-
The Underwater welding can be classified as:-
1) Wet Welding:- In wet welding the welding is performed underwater, directly exposed to the wet environment.
2) Dry Welding :- In dry welding, a dry chamber is created near the area to be welded and the welder does the job by staying inside the chamber
COMPONENTS OF WATER WELDING:-
Electrode Holder:-
This new generation compression type welding stinger is engineered with features that let you know it’s from Broco. Lightweight, durable and designed to hold the electrode at the optimum angle to reduce diver fatigue. The new BR-21... Setting the wet welding standard.
Water Resistant Electrodes:-
The fundamental process of welding underwater does not differ from welding on land. An electrode carrying a direct current creates an arc of electricity. That arc is then applied to melt the target metal. The difference is that the electrodes used underwater are waterproof. Extra insulation around the connections ensure that the current will be able to generate the arc and not degrade the copper wiring. Doing this underwater presents a new set of risks. Both the risk of electrocution and the technical difficulty of maintaining the electrical arc underwater, is the reason why direct currents are used instead of alternating currents.
Line Diagram :
The power source should be a direct current machine rated at 300 or 400 amperes. Motor generator welding machines are most often used for underwater welding in the wet. The welding machine frame must be grounded to the ship. The welding circuit must include a positive type of switch, usually a knife switch operated on the surface and commanded by the welder-diver. The knife switch in the electrode circuit must be capable of breaking the full welding current and is used for safety reasons. The welding power should be connected to the electrode holder only during welding. Direct current with electrode negative (straight polarity) is used. Special welding electrode holders with extra insulation against the water are used. The underwater welding electrode holder utilizes a twist type head for gripping the electrode. It accommodates two sizes of electrodes. The electrode types used conform to AWS E6013 classification. The electrodes must be waterproofed. All connections must be thoroughly insulated so that the water cannot come in contact with the metal parts. If the insulation does leak, seawater will come in contact with the metal conductor and part of the current will leak away and will not be available at the arc. In addition, there will be rapid deterioration of the copper cable at the point of the leak.
The Welding is an unavoidable process of modern engineering – civil, electrical,
mechanical, automobiles, marine aeronautical – in all branches. It is used in
fabrications and erections in infrastructures and installations. It joins metals
or thermoplastics.
The Hyperbaric welding OR UNDER WATER WELDING is the process of welding at elevated pressures, normally in underwater. It is of 2 types DRY & WET Welding. The Hyperbaric welding can either take place wet in the water itself OR dry inside. Here a specially constructed positive pressure enclosure is used and hence it is called dry welding. Similarly Hyperbaric welding term used in dry environment & underwater welding term used as in wet environment. The hyperbaric welding is used to repair damaged ships, under water pipe line & etc.
INTRODUCTION:-
The fact that electric arc could operate was known for over a 100 years. The first ever underwater welding was carried out by British Admiralty – Dockyard for sealing leaking ship rivets below the water line.
Underwater welding is an important tool for underwater fabrication works. In 1946, special waterproof electrodes were developed in Holland by ‘Van der Willingen’. In recent years the number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. Some of these structures will experience failures of its elements during normal usage and during unpredicted occurrences like storms, collisions. Any repair method will require the use of underwater welding.
UNDERWATER WELDING PRINCIPLES:-
Underwater welding can be performed under wet or dry conditions. Dry underwater welding refers to underwater welding which is performed under hyperbaric conditions (an underwater habitat is displacing the water with a gas at the prevailing pressure), and wet underwater welding refers to welding which is performed in fresh- or salt-water without a protecting habitat.
Wet underwater welding will here after be referred to as ―wet welding‖, and wet/dry underwater welding will simply be referred to as ―underwater welding‖. The most commonly used wet welding technique is shielded metal arc welding (SMAW), also known as manual metal arc (MMA) welding or informally as stick welding. The main differences for the welding equipment (wet welding equipment versus ―workshop‖ welding equipment) are shown in Figure 1. Note that wet underwater welding is performed by using a (usually motor generated) power source generating DC current only (for wet welding AC is not used on account of electrical safety and difficulty in maintaining a welding arc underwater), the inclusion of a single or dual pole knife switch (circuit breaker), which protects a welding diver from electrocution, and the use of double insulated cables. Both the power source and knife switch (capable of breaking the full wet welding current) are secured above water (grounded) and controlled (on the diver welders command) by an operator. The cross section of the welding cable is adjusted to the length of the cable and should be highly wear resistant (marine growth) and sufficiently flexible; special welding electrode holders are used with extra insulation against the ingress of water.
CLASSIFICATION OF UNDERWATER WELDING:-
The Underwater welding can be classified as:-
1) Wet Welding:- In wet welding the welding is performed underwater, directly exposed to the wet environment.
2) Dry Welding :- In dry welding, a dry chamber is created near the area to be welded and the welder does the job by staying inside the chamber
COMPONENTS OF WATER WELDING:-
Electrode Holder:-
This new generation compression type welding stinger is engineered with features that let you know it’s from Broco. Lightweight, durable and designed to hold the electrode at the optimum angle to reduce diver fatigue. The new BR-21... Setting the wet welding standard.
Water Resistant Electrodes:-
The fundamental process of welding underwater does not differ from welding on land. An electrode carrying a direct current creates an arc of electricity. That arc is then applied to melt the target metal. The difference is that the electrodes used underwater are waterproof. Extra insulation around the connections ensure that the current will be able to generate the arc and not degrade the copper wiring. Doing this underwater presents a new set of risks. Both the risk of electrocution and the technical difficulty of maintaining the electrical arc underwater, is the reason why direct currents are used instead of alternating currents.
Line Diagram :
The power source should be a direct current machine rated at 300 or 400 amperes. Motor generator welding machines are most often used for underwater welding in the wet. The welding machine frame must be grounded to the ship. The welding circuit must include a positive type of switch, usually a knife switch operated on the surface and commanded by the welder-diver. The knife switch in the electrode circuit must be capable of breaking the full welding current and is used for safety reasons. The welding power should be connected to the electrode holder only during welding. Direct current with electrode negative (straight polarity) is used. Special welding electrode holders with extra insulation against the water are used. The underwater welding electrode holder utilizes a twist type head for gripping the electrode. It accommodates two sizes of electrodes. The electrode types used conform to AWS E6013 classification. The electrodes must be waterproofed. All connections must be thoroughly insulated so that the water cannot come in contact with the metal parts. If the insulation does leak, seawater will come in contact with the metal conductor and part of the current will leak away and will not be available at the arc. In addition, there will be rapid deterioration of the copper cable at the point of the leak.
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