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Wednesday, 8 April 2015

List of and gas welding equipment guide

List of and the gas welding equipment guide for newbie


Here are many components that make up the Oxy-Acetylene outfit such as cylinders, regulators, hoses etc.If you are new to welding and the metal arts in general, you have probably tried to find instructional information on basic welding techniques for artists with a simple Google or Yahoo keyword search. If you have, you know that getting this basic information in a simple, easily-digestable format, is a really tough nut to crack. 

Sure enough, a web search on basic welding techniques will bring up thousands of pages of information for you to sink your teeth into, but the topic is usually delivered in such a complex and technical manner that it is virtually useless to the aspiring welder-artist.The following is a typical outfit listing each component with a brief description of each.

CYLINDERS

Oxygen and Acetylene are stored under pressure in steel cylinders . They are sized by the cuft. of either Oxygen or Acetylene that they hold.Cylinders should be tested regularly with the date of the last test stamped on the top of the cylinder.Cylinders should always be secured and used in the upright position. When a cylinder is not being used, the valve cap should always be in place.

OXYGEN CYLINDERS

These cylinders are made of steel and are usually painted green. They range in size from less than 20 cuft. To over 300 cuft and contain compressed Oxygen at pressures that can be as high as 2200 psig. All cylinders have valves and ( except the small "R" tank ) are fitted with a screw on steel cap that protects the cylinder valve when the cylinder is not in use. If Oxygen comes into contact with oil or grease, it will burst into flame. Never use oil or grease on Oxygen cylinder valves or regulators.


Make sure hands and gloves are free of oil and grease before handling cylinders. Crack open the cylinder valve then close it before installing the regulator to clear the valve of any dirt. With the regulator installed, always crack the cylinder valve open first, then open it fully. This will lessen the chance of recompression which is caused by high cylinder pressure entering the regulator, heating up and damaging the regulator.

ACETYLENE CYLINDERS

These cylinders contain Acetylene under pressure, are painted black, ( small "B" and "MC" tanks can be gray, silver or red ) made of steel and have cylinder valves. They range in size from 10 to almost 400 cuft capacity. The cylinders contain a porous filler material which is wetted with acetone that allows the Acetylene to safely be contained in the cylinder at 250 psig. 

Always use an Acetylene cylinder in the up right position so you don't draw any of the acetone out of the tank. Only open the cylinder valve 1 to 1 1/2 turns, leaving the valve wrench on the valve in the event it has to be shut off quickly. Acetylene should never be used at a pressure that exceeds 15 psig as it becomes highly unstable which, depending on the condition, could cause it to decompose and explode. As with the Oxygen cylinder, make sure the cylinder valve is clean before installing the regulator.

REGULATORS

With the pressure in a full Acetylene cylinder at 250 psig and a full Oxygen cylinder at 2200 psig, a way is needed to lower these cylinder pressures to desired working pressures for use in the torch. This is accomplished by using an adjustable pressure reducing regulator. The regulator will also maintain a steady working pressure as the cylinder pressure drops from use.


Basically, regulators work by admitting the high cylinder pressure through a valve which is operated by a flexible diaphragm. By turning the regulator adjusting knob or screw in or out causes a spring in the regulator to operate the diaphragm which opens or closes a valve in the regulator. This in turn regulates the outlet pressure and flow. By turning the adjusting knob in you increase the flow and pressure, out decreases the flow and pressure. Most regulators have two gauges. 

One shows the inlet pressure from the cylinder ( the high pressure gauge ) and the other ( low pressure gauge ) shows the working pressure being supplied from the regulator. There are regulators that are made for heavy duty or rough service that are not equipped with gauges, (referred to as gaugeless) and have a scale in the regulator body that is used to make pressure adjustments.


There are two general types of regulators, single stage and two stage. Both perform the same function but the two stage regulator will supply a more constant pressure as the cylinder pressure falls by compensating for any drop in cylinder pressure better than will the single stage unit. Also, two stage regulators are usually more heavy duty in construction and will last longer in heavy duty use and require less maintenance than the single stage units. 

Two stage regulators can be identified by their second pressure chamber where single stage units have only one. Oxygen and Acetylene regulators connect differently to their cylinders so they can not be mixed up.Oxygen regulators have right hand threads and regulators for Acetylene and other fuel gases have left hand threads.

You will notice a groove around fuel connections which indicate a left handed thread. Finally all outlet (low pressure ) gauges on Acetylene regulators have their gauge scales marked in red starting at 15 psig. This is to act as a reminder not to use Acetylene at pressures over 15 psig as explained in the section on Acetylene cylinders.

WELDING HOSES

 WELDING HOSES
The cylinder regulators and torch are usually connected together by double line rubber hoses. Double line hose is know as type VD. The Oxygen line is green, the fuel line red. Hoses are available in four sizes, 3/16, 1/4, 3/8 and 1/2 inch I.D. There are different grades of double line hose used for Acetylene. They are:
  • Non-oil resisting rubber cover
  • RM- carries both a non-oil and flame and oil resisting cover
  • (for use with all fuel gases & Acetylene) flame and oil resisting cover.

Grades R & RM should be marked for Acetylene only. Grade T should be marked fuel gas. All hoses should be marked as to their service level (light, standard or heavy ). Date of manufacture, maximum working pressure, ( 200 psig ) nominal I.D size and if it meets RMA/CGA IP-90 (Rubber Manufactures Association, Compressed Gas Association ) specifications for rubber welding hose. The fittings on the hoses are marked as to right and left handed threads.


Single line hose come in three grades, L, light duty, S, standard duty and H, heavy duty. And are also limited to a working pressure of 200 psig.

CHECK VALVES

For combustion to occur, fuel and Oxygen have to mix. This should only happen in the torch mixer or the torch tip. Sometimes, due to improper operation, fuel and Oxygen could feed back into the hoses and cause combustion in the hoses or regulators. ( not good! ) Check valves when installed between the hoses and torch prevent this back flow as they close if a reverse flow starts. Check valves should be used with all torches.

FLASH BACK ARRESTORS

A flashback, which is a rapid high pressure flame in the hose can occur if there aren't any check valves or the check valves fail to operate due to improper installation. Once a flashback starts, check valves can not stop it, but a flashback arrestor will! The arrestor connects the same as the check valves, in the hose at the torch or regulator and contains a trap that is spring loaded that cuts off the gas flow in the event of a flashback. Both check valves and flashback arrestors are like they say, cheap insurance and should be included on every Oxy-Acetylene outfit!

TORCHES

TORCHES
The torch assembly consists of the handle, oxygen and fuel gas valves and mixing chamber. Welding tips or a cutting attachment can be used with the handle allowing it to be used for welding, heating and cutting operations. Oxygen and fuel gas flow through tubes inside the handle which blend in the mixing chamber or tip. It is at the tip that the mixed gases are ignited. There are two basic mixer types, the equal or medium pressure type (also known as balance or positive pressure type) and the injector type. 

The equal pressure type is the most common and is used with fuel gas pressures that are above 1 psi. Oxygen and fuel gas enter the torch at almost equal pressures. The injector type is used when fuel gas pressures are less than 1 psi. In this type, Oxygen at high pressure pulls the fuel gas into the mixing chamber.

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