thanks a lot for the valuable contribution. today only i overcame this thread.
you have covered the complete welding process. i will look into that leisurely, as your inputs are huge.
dipil / hansa, thanks for your contribution too.
please find some details from my side.
actually the file named acetylene cylinders was prepared for dipil. since i saw this post, i thought of sharing here too.
From India, Delhi
Good inputs again... Let's gather all what need related to Welding Here...
Thanks a lot for your concern and sharing information...
The Acetyline cylinder write up also not just clearing my doubt..
How the acetone will escape from the acetylene cylinder if it's idely kept in horizontal condition?
Is there chance to escape through fusible plug? Please explain?
Dear All: Anyone know the answer please come forward...
Please find the attached "ELECTRIC AND MAGNETIC FIELDS may be dangerous”. Hope this information helps. . .
Dear KVS& Dipil,
Thanks for your input it’s add spirit on this thread. . .
I have some documents in Hindi but I do know it’s related to hot work or not (I am only speaking Hindi I can’t read it) sometimes my friends explain Hindi articles . . . SORRYYY!!!. . .
From United States, Fpo
From United States, Fpo
Good work again... Thanks a lot and Keep up the pace...
Let me give more clarrification to my last query...
Acetylene stored in a free state under pressure greater than 15 PSI can
be made to break down by heat or shock and possibly explode. Under pressure of 29.4 PSI acetylene becomes self-explosive and a slight shock will cause it to explode spontaneously. However, when dissolved in acetone it can be compressed into cylinders at pressures up to 250 PSI.
Acetylene, when not dissolved in a solvent (free acetylene), can begin to dissociate (decompose) at pressures above 15 pounds per square inch gauge (psig). The products of dissociation are carbon, in the form of lampblack, and hydrogen. Considerable amounts of heat are generated by dissociation, which may produce explosions of great violence.
To prevent loss of acetone which reduces the cylinder’s ability to hold dissolved acetylene. Hence always store and use acetylene cylinders in an upright position.
Now my question is how the acetone will escape from the cylinder if we store it in horizontal position? It's happen always or probability to occur the same is there?
From United States, Fpo
From Malaysia, Kuala Lumpur
Welding is the most common method of joining metals in industry today. When welded, two pieces of similar metals are fused (melted) together. Once completed, the welded joint is as strong or stronger than the pieces from which the joint is formed. General hazards of welding include impact, penetration, harmful dust, smoke, fumes, heat and light radiation. The proper personal protective equipment can protect you from these hazards.
Types of Welding -- Gas Welding, Arc Welding, Oxygen and Arc Cutting
Gas Welding -- In gas welding, two metals are joined by melting or fusing their adjoining surfaces. This is done by directing a gas flame over the metals until a molten puddle is formed. The energy for gas welding comes from the combustion of a fuel with oxygen or air. A few of the most popular fuels are acetylene, Mapp gas and hydrogen. Since gas welding is slower and easier to control than electric arc welding, it is often used in applications such as general maintenance work, brazing and soldering.
Arc Welding -- Arc welding involves a different process - two metals are joined by generating an electric arc between a covered metal electrode and the base metals. Heat is produced by the arc which in turn melts the metal and mixes the molten deposits of the coated electrode. The arc energy is provided by a power supply unit that furnishes direct or alternating current. The electrodes carry the current to form the arc, producing a gas that shields the arc from the atmosphere, and add metal to control the weld shape.
When an arc is struck using a coated electrode, the intense heat melts the top of the electrode. The drops of metal from the electrode enter the arc stream and are deposited on the base metal.
The equipment needed for electric arc welding is a power supply, electrode holder, ground clamp, protective shield, and welder's protective clothing.
Oxygen and Arc Cutting -- Metal cutting in welding is the severing or removal of metal by a flame or arc. The most common cutting processes are:
Oxygen Cutting: Metal is heated by gas flame and an oxygen jet does the cutting.
Arc Cutting: Intense heat of electric arc melts away the metal.
Personal Protective Equipment
Eye and Face Protection -- Proper eye and face protection varies depending on the particular task being performed. Helmet, hand shield, goggles and safety glasses or combination of these are acceptable protection in various applications. All filter lenses and plates must meet the test for transmission of radiant energy prescribed in the ANSI standard Z87.1968, Practice for Occupational and Educational Eye and Face Protection.
According to OSHA 29 CFR 1910.252, "Helmets and hand shields shall protect the face, forehead, neck and ears to a vertical line in back of the ears, from the arc direct radiant energy, and weld splatter."
Welding helmets with filter plates are intended to protect users from arc rays and from weld sparks and spatters which strike directly against the helmet. They are not intended to protect against slag chips, grinding fragments, wire wheel bristles, and similar hazards which can ricochet under the helmet. Spectacles, goggles or other appropriate eye protection must also be worn to protect against these impact hazards.
OSHA requires that when arc cutting and arc welding with open arcs, helmets or hand shields with filter lenses and cover plates shall be used by operators and nearby personnel viewing the arc also subject to wear proper protection. Spectacles with a shade 2 lens are recommended for general purpose protection for viewers. When resistance welding or brazing: operators of resistance welding must use face shields, spectacles, or goggles depending on the particular job to protect their faces and eyes from welding hazards.
Protective Clothing -- According to ANSI Z49.1.88-Welding and Cutting (4.3), appropriate protective clothing for any welding and cutting operation will vary with the size nature and location of the work to be performed. Clothing shall provide sufficient coverage and be made of suitable materials to minimize skin burns caused by sparks, spatter or radiation. covering all parts of the body is recommended to protect against ultraviolet and infrared ray flash burn.
Dark clothing works best to reduce reflection under the face shield. Heavier materials such as wool clothing, heavy cotton or leather are preferred as they resist deterioration. Materials that can melt or can cause severe burn due to sparks that may lodge in rolled-up sleeves, pockets of clothing or pant cuffs are not recommended.
The ANSI standard requires all welders and cutters to wear protective flame-resistant gloves, such as leather welder's gloves, which provide the heat resistance needed for welding. A gauntlet cuff offers additional arm protection, and insulated linings should be used to protect areas exposed to high radiant energy.
Other protective clothing would include durable, flame-resistant aprons made of leather or other suitable materials to provide protection to the front of the body when additional protection against sparks and radiant energy is needed.
Ventilation refers to changes of room air as often as necessary to prevent welders and other workers from breathing high levels of airborne contaminants. Ventilation is a means of providing adequate breathing air, and must be provided for all welding, cutting, brazing and related operations. Adequate ventilation depends on the following factors:
Volume and configuration of the space where the welding operations occur
Number and type of operations that are generating contaminants
Natural air flow rate where operations are taking place
Locations of the welders' and other workers' breathing zones in relation to the contaminants or sources
Proper ventilation can be obtained either naturally or mechanically.
Natural Ventilation -- Natural ventilation is considered sufficient for welding and brazing operations if the present work area meets these requirements:
Space of more than 10,000 square feet is provided per welder;
A ceiling height of more than 16 feet
Welding is not done in a confined space
Welding space does not contain partitions, balconies or structured barriers that obstruct cross ventilation
If your specific operation does not fall within these guidelines, mechanical ventilation will be required.
Mechanical Ventilation -- Mechanical ventilation options generally fall into two basic categories. The first is the low vacuum system which takes large volumes of air at low velocities. These systems consist of hoods positioned at a distance from the work area. The hood and housing may have to be repositioned by the worker to get maximum benefit from this means of ventilation. Hoods generally remove the fumes and contaminated air through ducting and exhaust the contaminants to the outdoors. Hoods should be placed as near as practical to the work, and should provide effective air flow with a velocity of 100 linear feet (30m) per minute at its most remote distance from the point of welding. Processes where low vacuum systems work best are arc air gouging, taking afterburner, and arc cutting.
Another category of mechanical ventilation is the high vacuum system. These are close-range extractors that are aimed at capturing and extracting fumes as near to the work as possible. Fume extractors often have an immediate area of welding. By removing a small volume of air at a high velocity, the potentially hazardous materials are effectively removed before reaching the welder's breathing zone. These systems often are equipped with a fan that pulls the contaminants into a filtration system, with a HEPA (High Efficiency Particulate Absolute) filter or combination of HEPA filter and prefilter and then recirculated the clean air back into the work area. Advantages of high vacuum systems are greater flexibility for job adaptation, more efficient means of fume removal, and greater visibility to the welder due to reduced clouds of fumes and vapors being created.
Fumes and gases from welding and cutting cannot be easily classified. The quantity of fumes and gases is relative to the metal being worked and the processes and consumable material being used (such as coatings, like paint, galvanizing and platings), along with contaminants in the atmosphere (such as halogenated hydrocarbon vapors from cleaning and degreasing activities).
Air sampling to verify the concentration levels of toxic fumes and gases is necessary, and respiratory protection is required along with mechanical ventilation in the cutting and/or welding of certain metals and compounds. For more information, see OSHA 29 CFR 1910.252 on welding regulations.
Hope information helps. . .
Keep on sharing & gaining. . .
From United States, Fpo
Here i add few questions related to welding. . .
What is a fume plume?
The fume plume is the clearly visible column of fume which rises directly from the spot of welding or cutting. Welders and cutters should take precautions to avoid breathing this area directly. Ventilation can direct the plume away from the face. (Fume removal is most effective when the air flow is directed across the face of the welder, rather than from behind.)
How do I know what hazardous materials I may be using?
Check the Material Safety Data Sheet (MSDS). The suppliers of welding materials must provide an MSDS or equivalent documentation which identifies the hazardous materials, if any, used in their welding and cutting products.
Where should oxygen not be used and why?
Oxygen should not be used as a substitute for compressed air. It should not be used in pneumatic tools, in oil preheating burners, to start internal combustion engines, to blow out pipelines, to dust clothing or work, or to create pressure for ventilation or similar applications. Oxygen should not be used as described due to the possibility of a raging oxygen-fed fire occurring. Oxygen is not flammable, but vigorously supports combustion. Oxygen can be absorbed by clothing. A slight spark can result in severe burns.
What is Mapp gas?
Mapp gas is a product that was developed as a fuel for welding, brazing, cutting, flame hardening, and metallizing operations. It has many of the physical properties of acetylene, but lacks its shock sensitivity and therefore can be stored and shipped in lighter containers. Mapp gas is the result of rearranging the molecular structure of acetylene and propane. It also has a very distinct odor so any leakage can readily be detected.
Hope its helps. . .
Keep on sharing. . .
From United States, Fpo
When someone is using a blowtorch for welding, cutting or brazing, what they're actually doing is burning a combination of a fuel gas (such as acetylene) that's been mixed with oxygen. A welding torch mixes gases from two separate cylinders and then ignites them to create a flame that's hot enough for the job at hand. However, welding with oxygen-fuel gas has a number of dangers that those who are doing the job should be aware of.
One of the dangers of welding and cutting with an oxygen and fuel gas mixture is the brightness of the flame. The burning of an oxygen and fuel gas mixture can burn extremely hot and bright, which can lead to problems with the welder's vision. Just staring at the flame for a short time may not be much of a problem, but welders are often welding and cutting metal with their torches for hours at a time, which can lead to their eyes becoming damaged by the bright light. This is why it's important that they wear safety goggles that are tinted, which will reduce the impact of the bright light on their eyes.
One of the biggest dangers to welders that use oxygen and fuel gas mixtures in their work is a flashback. A flashback is when one or both of the gases that are being mixed begin to burn inside the blowtorch. The flame begins to burn down the hoses to the canisters, where it ignites the gases and causes an explosion that can cause a lot of damage. For this reason it's important to carefully monitor your equipment when using an oxygen and fuel gas mixture, and it's equally important to install a gasket that will prevent a flashback from occurring.
It's important that you focus the blowtorch very carefully and that you have the proper mixture of fuel gas and oxygen when using this method to weld or cut. Fumes from these gases that escape from the torch or from the canister could lead to fires or other damage to the user or their work area. Additionally, the fumes from the fuel gas are hazardous to breathe. So if the torch is left unlit but open, a small work area could be filled with the fumes from the canister. It's important to check all connections and the canister before lighting your torch for this reason.
From United States, Fpo