Tham khảo tài liệu 'welding materials handbook part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Section 4. MAPP Gas INTRODUCTION Methylacetylene propadiene MAPP gas is a versatile multi-purpose industrial fuel gas that offers excellent performance safety and economy. It is used to flame cut flame weld braze solder pre-heat and for stress relief. The only equipment usually required to convert from acetylene to MAPP gas are new torch tips. One cylinder of MAPP gas will do the work of five acetylene cylinders. MAPP GAS IS SAFE At 70 F MAPP gas can be used safely at full cylinder pressures of 94 psig pounds-per square inch gauge . Acetylene is limited to 15 psig. MAPP gas toxicity is rated very slight but high concentrations 500 ppm can have an anesthetic effect. Local eye or skin contact with MAPP gas vapor has caused no adverse response but the liquified fuel may cause frost-like burns. MAPP gas is chemically inert to most common materials including steel brass most plastic and rubber. There is a slight possibility MAPP gas may react with copper or alloys of more than 67 percent copper to produce explosive acetylides when the gas is under high pressure. To be on the safe side use steel or aluminum fixtures. DISADVANTAGES Stabilized MAPP gas requires special tips for oxygen cutting. Sometimes high capacity mixers are required to convert equipment from acetylene to stabilized MAPP gas. BREAKTHROUGH IN PERFORMANCE The performance of acetylene had never been equaled until the advent of MAPP gas. It has little or no backfire or flashback even when the torch tip is placed right up against the work. On aluminum braze welds MAPP gas will leave no spatter carbon smutting or large areas of metal flux on the surrounding metal. 4-1 MAPP gas is excellent for selective flame-hardening. It bums efficiently at various oxygen-to-fuel ratios and port velocities and permits a wide range of hardness depths. The stable clean burning MAPP gas flame virtually eliminates dangerous flashback. It is ideal for cambering large beams and other heating applications because it heats wider .
