Term
| 1. What is the purpose of a pressure regulator? |
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Definition
| They reduce high pressure to a lower working pressure. |
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Term
| 2. What may result if a pressure regulator is not used on the type of gas or pressure range for which it was designed? |
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Definition
| There is a possibility of fire or explosion. |
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Term
| 3. Describe how a single-stage regulator operates. |
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Definition
| An adjustment screw puts pressure on a spring that bends the diaphragm inward. This releases some high pressure gas which forces the diaphragm closed unless some of the gas is being released through the hose. In this case the pressure against the diaphragm remains equal to the spring pressure. |
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Term
| 4. Is the torch pressure always the same as the working gauge pressure? Why or why not? |
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Definition
| No. The difference between the torch pressure and the working gauge pressure is the pressure drop (line drop) in the hose due to flow resistance. |
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Term
| 5. Why does the high-pressure gauge on a regulator not always indicate the amount of gas in the cylinder? |
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Definition
| Some cylinders contain liquefied gases such as CO2, propane, and MPS gases. |
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Term
| 6. How does the operation of a safety relief valve differ from the operation of a safety disc valve? |
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Definition
| Safety relief valve uses a spring and ball that open with excessive pressures but will close once the pressure drops to a safe level. Safety disc valve uses a thin rupture disc that, once its pressure has been exceeded, bursts releasing the entire cylinder contents. |
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Term
| 7. Describe the difference between an argon cylinder valve fitting and a carbon dioxide cylinder valve fitting. |
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Definition
| The argon cylinder fitting is internal (female) and the carbon dioxide cylinder valve fitting is external (male), additionally it requires a flat washer. |
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Term
| 8. What is meant by regulator creep? |
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Definition
| The slow increase in working pressure resulting from a leaking seat inside the pressure regulator. |
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Term
| 9. Who can repair regulators? |
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Definition
| All work on regulators must be done by properly trained repair technicians. |
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Term
| 10. Why must the pressure be released from a regulator when work is finished? |
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Definition
| This procedure is done so that the diaphragm, gauges, and adjusting spring are not under load. A regulator that is left pressurized causes the diaphragm to stretch, the Bordon tube to straighten, and the adjusting spring to compress. These changes result in a less accurate regulator with a shorter life expectancy. |
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Term
| 11. Why are combination welding and cutting torches considered to be more versatile? |
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Definition
| Because the torch body can be easily connected to a cutting head, welding tip, or heating tip. |
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Term
| 12. What is the advantage of using an injector-type mixing chamber? |
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Definition
| Injector-type mixing chambers can be used with low pressure fuel gas sources. |
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Term
| 13. What should be done to the valve packing if the valve knob does not turn freely after it has been tightened to stop a leak? |
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Definition
| Valve packing must be replaced with a repair kit. |
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Term
| 14. What may happen to a tip seat if it is incorrectly tightened? |
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Definition
| Using the wrong method to tighten the tip fitting may result in damage to the torch body or tip. |
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Term
| 15. What can happen to a tip if it is excessively cleaned with a tip cleaner? |
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Definition
| Tip cleaners are small round files, and excessive use tends to ream out the orifice making it too large. |
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Term
| 16. What is the difference between a reverse flow valve and a flashback arrestor? |
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Definition
| Reverse flow valves are designed only to prevent backflow of gases. Flashback arrestors will do the job of the reverse flow valve and stop the flame of a flashback. |
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Term
| 17. What are Siamese hoses? |
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Definition
| Two individual hoses that are molded together in one piece. |
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Term
| 18. Why must the pressure be bled off hoses when work is complete? |
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Definition
| This action eliminates a dangerous situation that would occur if the hoses were accidentally cut and prevents fire or explosion from undetected leaks. |
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Term
| 19. What is the difference between a backfire and a flashback? |
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Definition
| A backfire is a loud pop or snap that occurs when the flame goes out. A flashback is when the flame burns back inside the tip, torch, hose, or regulator. |
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Term
| 20. Why is a neutral flame the most commonly used oxyacetylene flame used? |
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Definition
| It adds nothing to the metal being welded. |
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Term
| 21. What properties should a good leak-detecting solution have? |
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Definition
| It must flow freely into small joints, cracks, and other areas that may leak, and produce good quality of bubbles without leaving a film. |
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Term
| 22. Why must the oxygen cylinder valve be opened all the way to the top? |
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Definition
| Back seating the valve prevents leakage around the valve stem when it is opened. |
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Term
| 23. How long should hoses be purged? |
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Definition
| Long enough to allow any air or unwanted gases to be replaced by the gas being used. |
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Term
| 24. What should be done with cylinders that have leaking valve stems? |
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Definition
| Turn the valve off, mark the cylinder, and notify the supplier to pick it up. |
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Term
| 25. How should he sparklighter be held to light a torch? |
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Definition
| It should be held slightly to one side so that it does not cover the end of the tip. |
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Term
| 26. Once the torch is lit, why must the acetylene flow be increased until the flame stops smoking before the oxygen is turned on for adjustment? |
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Definition
| When the acetylene stops smoking, the gas flow to the tip is at the minimum flow rate which will keep the tip cool. |
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Term
| 27. What type of piping can be used for a manifold system? |
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Definition
| All gases except acetylene can use steel, wrought iron, stainless steel, copper, or alloyed copper. Acetylene may not be used in unalloyed copper. |
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