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Tuesday, 5 January 2016

Acetylene safety - Safety Begins With Good Equipment

A Little Known Fact About Acetylene Gas and Heating Tips

Acetylene Gas
What is this fact?Only so much acetylene can be drawn off of an acetylene gas cylinder in a set period of time.Unlike oxygen where you can turn it up about as much as the regulator will allow acetylene has different properties. The withdrawal rate of an acetylene cylinder is 1/7 of the cylinder contents per hour.

OK... now what does that mean?Heating tips have a specification as to how much acetylene is required to be properly used. For example the Victor MFA-6 tip requires 14 cubic feet per hour minimum to 40 cubic feet per hour maximum.Taking the withdrawal rate of 1/7 or .143 x the size of acetylene cylinder lets say a B acetylene of 40cf .143 x 40 = 5.72 cfh this would not be enough acetylene to properly operate the rosebud.

The next acetylene cylinder size larger would be a #3 with 74cf. Multiply .143 x 74= 10.58 which still does not supply enough acetylene. The next is the #4 acetylene which have approximately 104 to 140 cf of acetylene. Again multiply the cubic footage of the cylinder (written on the shoulder of the #4 cylinder) for demonstration purposes 130cf 130 x .143 = 18.59 which is enough to properly operate the heating tip. An easy way to figure the size of acetylene cylinder you need is to multiply the amount of acetylene needed to operate the heating tip by 7 or for this example 14 x 7 = 98cf. Minimum

Acetylene is vaporized from the acetone in the cylinder at the rate of 1/7 of the contents per hour. What happens if it is exceeded? Acetone is drawn from the cylinder and drawn into the torch. Not only is acetone hard on the o-rings on the torch but the acetone that helps stabilize the acetylene is reduced.

How can you tell if you don't have enough acetylene to run the rosebud properly? The rosebud can become hot, make popping noises or even make a whistling sound. The popping sound is the result of an explosion taking place inside the heating tip. If there isn't enough acetylene being supplied to keep the flame outside of the tip the flame will actually go inside of the rosebud and into the handle. If flashbacks are not on the torch it can even reach the cylinders and create a fire or even explosion.

Victor Acetylene and Oxygen Gas Torches are the Industry Standard

Victor Acetylene
Victor has been around for decades. It isn't out of the question that the equipment from 40 years ago is still in use. The 315 and 100 series handles are the workhorses in the industry. Though basically the same, Victor has made modifications to these torches. The 315 became the 315C and the 100 became the 100C. The C stands for check valve. These were once a safety add on to the torch, but Victor incorporated them into the handle so the customer would not have to purchase them separately. Check valves prevent the mixing of gases within the hoses. The present day handles are the 315FC and the 100FC meaning they have flashback arresters and check valves in the torch. Buying the check valves and flashback arresters separately can run into about $70.

Check Valves and Flashback arresters are safety devices for protecting workers using oxy fuel cutting and welding equipment. A check valve is a device that is designed to prevent the unintentional back flow of gases. A flashback (flame) arrester is a device that prevents the propagation of a flame from the torch, through the hose and to the cylinder. Flashback arresters are not needed for other gasses such as Argon, Helium, Nitrogen or CO2 that are used in other welding processes.

Note that these devices reduce the volume of gases available at the tip/nozzle.

A proper oxygen acetylene setup should include cutting attachment or tip,handle then check valves and flashback arrestors hose then another flashback at the regulators.This is also an OSHA requirement. So if you are looking for a new oxy acetylene set, look to Victor and get the check valves and flashback arrestors included in the set as well as the quality and safety you deserve.

Please view the following videos.Even though the acetylene fire was caused by a defective fitting at the acetylene plant, you can see the destructive force behind an acetylene cylinder. Flashbacks without arrestors could cause a similar explosion!!! Always use common sense when Acetylene and Oxygen Cutting.

Worst Case Scenario for Acetylene Cylinders

Systematic name EthyneThis is just about as bad as it can get as far as showing the
Systematic name Ethyne
dangers of acetylene.What I do want you to take notice of is the individual explosions. These are single cylinders going off one at a time. Acetylene cylinders are equipped with a fuse plug that are designed to melt at 212 degrees allowing for the acetylene to escape so it will not increase cylinder pressure and explode. In some of the flames you can see this happening. There will be an intense, fast moving flame from the middle of other flames.

What is of the utmost importance is the cylinders that explode and are hurled on fire hundreds of feet into the air. Some of these cylinders weigh in excess of 100 lbs. Imagine just one of these acetylene cylinders exploding in an enclosed shop.

Acetylene Gas Safety DataAcetylene cylinders, unlike high pressure cylinders are not hollow but are filled with a porous fiber. The older cylinders contained asbestos or cellulose fiber while newer cylinders are asbestos free.

Acetone is added to stabilize the acetylene and cylinders should never be used lying down. When an acetylene cylinder is placed on its side, the acetone will seek its own level and may come out of the valve if used right away.This is not the only problem. The lack of acetone can create pockets of pure acetylene thus increasing its instability.

INFO: Acetone (systematically named propanone) is the organic compound with the formula (CH3)2CO.[12] It is a colorless,volatile,flammable liquid,and is the simplest ketone.   source - wikipedia

Acetylene cylinders are pressurized to 250 psi and should never be used above 15psi due to the fact that it becomes extremely unstable.If you do find an acetylene cylinder on its side immediately place it in an upright position and do not use for 24 hours allowing for the acetone to redistribute in the acetylene.

When opening an acetylene cylinder it is always counterclockwise and clockwise to close. The acetylene cylinder should only be opened one quarter turn so that you can quickly turn the gas flow off if the need arises to do so.In the event that you can not open the cylinder do not apply too much force.Return the cylinder to the supplier in exchange for another cylinder. If the acetylene cylinder becomes stuck in the open position remove cylinder to a ventilated outdoor area that is free from all flammable sources and once again call the acetylene gas supplier for help.

Compressed Cylinder Gas Safety

There are two major safety concerns with oxygen.The high pressure of the oxygen which is over 2200 psi and the fact that it is an oxidizer.That means that fuels need it to burn. Oxygen is not flammable but it does increase tremendously the heat and flame of an existing fire source.

The cylinder is protected by a burst disc on the back of the valve. If the cylinder reaches too high of a temperature the cylinders gas will expand and rupture the disc and expel the contained oxygen. The oxygen is released at a rapid rate yet not enough to propel the cylinder.

As you will see in the video a cylinder turns into a rocket if the valve is knocked off.This is not limited to oxygen cylinders. Argon, nitrogen, helium and mixed gases will respond in the same manner if the valve is severed from the cylinder. Hydrogen is very dangerous. It is pumped to excess of 2000 psi and is flammable.

High pressure cylinders are manufactured to maximize safety. The cylinder walls are a minimum of 1/4" thick steel. There is no need to fear these cylinders, but you do need a healthy respect for them, properly handle them and understand the potential destructive force that compressed gas possess.

Oxygen Cylinder Regulator

oxygen gas regulator manufactured by Victor
Pictured is an oxygen gas regulator manufactured by Victor. It is a very common regulator configuration with the high pressure gauge for reading tank pressure on the right and a gauge on the right for measuring outlet pressure.

The outlet bushing of the oxygen regulator is right hand thread so it can not be hooked up in error to the notched left hand thread, red fuel hose. The same holds true with the acetylene regulator. It is not possible to attach an oxygen hose to an acetylene regulator.

The CGA 540 oxygen fitting is made so it can only be attached to an oxygen cylinder. These features of the oxygen regulator make the operation quite safe but use common sense still must be adhered to.

Never use any oil or oil based products on oxygen regulators. This can result in a very fast and intense fire. The only time teflon tape should be used is when you are replacing a gauge, outlet bushing, safety or inlet nipple. Never us teflon tape on any cylinder to regulator fittings. The valve of the cylinder and fittings of the regulators are made to close tolerances and will make a tight seal. If for some reason they don't check to see for thread damage on either of the the connecting parts. If the threads on the cylinder are damaged contact your gas supplier for a replacement.

Acetylene Gas Pressure Regulators

Acetylene Gas Pressure Regulators
Acetylene regulators look very similar to other regulators with a few exceptions.Most noticeable is the outlet pressure gauge. It has a definite outlet pressure limit of 15 psi. After 15 psi it shows a solid red line. You do not want to exceed this level because acetylene becomes unstable at this level and becomes susceptible to shock.

As with most regulators they will all have different inlet nuts with a few exceptions with inert gases and special mixes. Take note of the inlet nut and the notches on it. These notches mean that it is a fuel gas. Hydrogen and propane will have these notches as well.

The cylinder pressure gauge is also different than most regulators in that the cylinder pressure is very low. Unlike the oxygen cylinder that can reach 2500psi you will find that a full acetylene is around 250 psi.The outlet bushing you will find that it too has a notched nut showing that it is a fuel gas regulator. The notched inlet and outlets also mean that the nut has left hand threads.

The regulator T handle controls the flow of acetylene from the cylinder to the outlet. Unlike most valves you will increase the gas flow by turning the handle clockwise to open and counter clockwise to close.

Should Teflon Tape Be Used on Fittings?

This is one of the more common questions asked. Gas fittings, outside of those going into the regulator housing, should not have Teflon tape used on them. Gas leakage from equipment usually comes from the over tightening of fittings causing the threads to roll thus disturbing the design of the fitting and allowing gas to leak. It is best to just get the fittings replaced then tighten about 1/4 turn after finger tight. Some Teflon Tape can actually aid in the starting of a fire, especially with oxygen.

Safety Glasses

The intensity of cutting or brazing with an oxy acetylene torch is such that eye protection is required.The most common shade of lens is the shade 5.0. There is also a shade 3 which is lighter. Regular sun glasses are not an acceptable replacement

There are 3 main choices when it comes to eye protection while brazing or cutting. There are welding glasses which are great if you do not wear prescription lenses, goggles that will fit over glasses or the face shield which not only protects the eyes from the intense light but also for pieces of molten metal.

Oxygen and Acetylene Cutting Torch

Proper Setup and Usage of Oxy Acetylene Smith Cutting Torch - This is an excellent video on how to set up for cutting with a Smith Cutting torch.Smith Equipment like Victor is an excellent choice for Oxy Acetylene equipment.

In the portion of the video where he is checking for leaks he says to use a water base dish washing soap. Make absolutely sure that there are not petroleum based products in it. I prefer that a leak detection fluid such as snoop that is specifically made for leak detection. 

Cutting and Brazing Tip Maintenance

Welding and brazing tips are getting progressively more expensive. Why shell out the money when a small investment in a tip cleaner will extend its useable life.Just by inserting the little round files into the holes at the end of the tip and gently moving in and out will remove the soot built up inside. This will prevent the soot from building up and plugging the holes. Be careful and do not get too big of a file since they can break and get lodged inside the tip.

Transporting Cylinders

I can't emphasize enough how important it is that cylinders are transported in a safe manner. They should not be in an enclosed area.The best way is to have them properly secured in an upright position in an open air vehicle like a pickup. If they are transported in an inclosed area it should be large enough so that the concentration of gas will be insufficient enough so they will not ignite.Large cylinders in an enclosed area is a recipe for disaster.

This is probably the best cylinder cart I have come across.Check out the link

MC Acetylene Tank

When it comes to acetylene cylinder sizes the MC is as small as it gets. It contains only 10 cubic feet of acetylene. These cylinders are pretty impractical for most jobs. If you are going to braze small jobs here and there they are OK, but if you need to do much more you will need a larger capacity cylinder.

In the field these are usually used by heating and air conditioning techs using turbo torch sets. If you purchase one of these cylinders remember that it is essential to find a regulator that it fits. The fitting required on the regulator is a CGA 200. They do make adapters for the standard CGA 510 fitting that is used on the larger cylinders but the tank will not remain in an upright position with it attached.

If you are wondering what the MC stands for it is taken from when motorcycles used acetylene gas for headlamps. MC=Motorcycle

Type Of Acetylene Tanks

B Acetylene Tank

The B comes from back in the early days of transportation when the headlights were powered by acetylene and this was the size used on buses.Thus the designation of the B. They contain 40cf of acetylene.Unlike oxygen where the regulators will fit any size of oxygen cylinder,the B acetylene has a unique fitting all to itself.

If you have an acetylene regulator that does not fit this cylinder there are adapters available or you can take your regulator to a welding distributor and they can install the proper fitting on the regulator to match the B acetylene.The B size like the MC acetylene are mainly used for small brazing jobs for the hobbyist or professionals in heating and air conditioning where portability is crucial.Like the MC acetylene cylinder the B does not need a cylinder cap due to its low volume of gas.

#3 Acetylene Tank

The #3 acetylene tank is a great size for a small shop, farm or light industrial. It contains 75 cubic feet of acetylene. It is small enough for good portability yet large enough to do some serious work.If you intend to do any kind of consistant cutting this is about as small of acetylene cylinder you will want to use.

Explosion Rocks Calcium Carbide Plant

What is all this talk about a shortage of acetylene and sharp price increases? This shortage was created by a carbide explosion back in March at Carbide Industries in the Rubbertown area of Louisvile, Kentucky. Carbide Industries is the nations top supplier of calcium carbide which is the main ingredient in the manufacturing process of acetylene gas.

Along with the shortage of Acetylene comes huge price increases. The company I work for has an acetylene plant and used to get the calcium carbide about 60 miles away now has to import it from China. It is shipped in drums instead of bins and the cost of shipping has almost doubled the price of acetylene. There are no shortages, but there is a premium of a price to be paid.

As of June 20, 2011 there is talk about a $6.5 million dollar state subsidy to help offset the $30 million cost of rebuilding the plant and saving 122 jobs.In the short term you can expect to pay higher prices for acetylene if you can get it. The acetylene alternatives are propane, propylene or mapp gas. This also requires some retooling of equipment for even more expense. Acetylene is the best since it gets the hottest for cutting and brazing but you can't braze with propane.Once the supply lines are back up and the flow is moving I don't see too many shortage problems in the future but I wouldn't hold my breath for any drop in price anytime soon.

Why is there liquid coming out of my acetylene regulator?

More than likely that liquid is acetone that helps stabilize the acetylene. If the acetylene cylinder has been laying on it's side and used before the cylinder has had a chance for the contents to redistribute the acetone at the top of the cylinder will be drawn into then out of the regulator. Secure the cylinder in an upright position and leave overnight. This should allow the acetone enough time to settle into the porous fiber in the tank. Try once again.

Why is my oxygen regulator freezing?

Oxygen regulators will freeze if there is a high flow of oxygen going through the regulator. If a large amount of oxygen is flowing through too small of a regulator it will ice up. A large bodied regulator helps prevent this due to its ability to absorb the ambient air and warm the regulator. The cold temperature of the oxygen can also freeze any moisture on or in the regulator.

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