AWS C4.3/C4.3M pdf free download

AWS C4.3/C4.3M pdf free download.Recommended Practices for Oxyfuel Gas Heating Torch Operation.
The terms listed are used in various sections of this document and require definition for correct interpretation. Most of these terms are not contained in AWS A3.0M/A3.0, Standard Welding Terms and Definitions, or if they are listed in AWS A3.0, their definitions have been enhanced to clarify their use in this document. These terms describe potentially hazardous events that can occur when using oxyfuel gas equipment. Operators and their employers should understand these events and the terms that are associated with them. See 6.2. For the purposes of this document, the following definitions apply: backfire. The momentary recession of the flame into the torch, potentially causing a flashback or sustained backfire. It is usually signaled by a popping sound, after which the flame may either extinguish or reignite at the end of the tip. See also flashback and sustained backfire. flashback. The recession of the flame through the torch and into the hose, regulator, and/or cylinder, potentially causing an explosion. See also backfire and sustained backfire. sustained backfire. The recession of the flame into the torch body with continued burning characterized by an initial popping sound followed by a squealing or hissing sound, potentially burning through inside the torch body. See also backfire and flashback.
4.1.1 Liquid Oxygen. Use of portable liquid oxygen cylinders is often advantageous. It should be noted that these cylinders, without additional external vaporizers, are limited to continuous withdrawal rates of 250 cu ft/h to 300 cu fth [117 L/min to 142 L/min]. If requirements exceed these withdrawal limitations, these cylinders are not recommended. Oxygen vigorously accelerates combustion. Improper use can result in fire or explosion. Oxygen shall not be used in pneumatic tools, to clean equipment, dust off clothing, provide ventilation, or any other application not intended for pure oxygen. Oil, grease, and dust are highly combustible when mixed with pure oxygen. Equipment damage or a serious per- sonal injury can result from improper use of oxygen. 4.2 Fuel Supply. Many different fuel gases are utilized in the oxyfuel gas heating process (see Annex C). They include acetylene, propane, natural gas/methane, propylene, hydrogen, and several propane- based mixtures. The different fuel gases vary in flame characteristics. The oxyfuel operator should become familiar with the proper flame adjustments for the fuel gas being used. The gas supplier should be contacted for the proper fuel gas parameters. Fuel gases are supplied in individual cylinders (see Figure 2) or distributed by pipeline from manifolded cylinders or bulk sources. Every fuel-gas cylinder has a limit as to its maximum safe withdrawal rate capabilities (see Annex B). Contact the gas supplier or equipment manufacturer to determine the number of cylinders to be manifolded for proper operation.
4.3 Maximum Acetylene Pressure. Acetylene shall not be piped (except in approved cylinder manifolds), or utilized at a pressure in excess of 15 psig [103 kPa] (gauge pressure), or 30 psia [207 kPa] (absolute pressure). Use at higher pres- sures is hazardous, resulting in the possibility of acetylene decomposition (explosion) from sudden shock or heat. The 30 psia [207 kPa] limit is intended to prevent unsafe use of acetylene in pressurized chambers such as caissons, underground excavations, or tunnel construction. Absolute pressure is equal to gauge pressure plus atmospheric pres- sure, which at sea level is approximately 15 psia [103 kPa]. Thus, at sea level, a gauge reading of 15 psig [103 kPa] is equal to an absolute pressure of 30 psia [207 kPa].AWS C4.3/C4.3M  pdf download.