Welders, pay attention when distinguishing oxygen and acetylene hoses by color

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This post was last edited by hcwang12345 on 2011-12-23 at 16:06. I searched on Taobao today; it’s the same standard GB2550～92, but the colors of the oxygen hoses vary – there are red, blue, and green ones. On the morning of December 2, 2010, at 9 o’clock, a branch factory of a company in Henan Province assigned welder Li × to carry out gas cutting operations on quenching machines. Once the work began, welder Li × first adjusted the acetylene pressure to 0.03 MPa and the oxygen pressure to 0.5 MPa. He then opened the acetylene valve on the welding torch and ignited the acetylene gas. Just as he was about to open the oxygen valve on the torch, the oxygen hose suddenly exploded; the 30-meter-long oxygen hose burst completely. Fortunately, no injuries were reported. Immediately after the accident, the company sent an investigation team to inspect the scene. The on-site investigation revealed that the oxygen cylinder and the acetylene cylinder were located 6 meters away from the work site, with a distance of 3 meters between the two cylinders. The excess oxygen and acetylene hoses were coiled up and placed next to the cylinders. All of the oxygen hoses had burst, but there were no signs of combustion on their inner walls, which ruled out the possibility of a backfire explosion. The red hoses were marked with the word “oxygen”, while the green hoses were marked with “acetylene”. The hoses also carried the standard designation “GB2550-92”. In fact, the color of oxygen and acetylene hoses in China has been changing since standards were established in 1965. In 1965, oxygen hoses were green; acetylene hoses were red. According to the Ministry of Chemical Industry, oxygen hoses are red while acetylene hoses are green. Under ISO standards, oxygen hoses are black and acetylene hoses are red. GB2550–81 specifies that oxygen hoses are red, while acetylene hoses are black, with a working pressure of 0.3 MPa. GB9448–88 states that oxygen hoses are black and acetylene hoses are red. GB2550–92 specifies that oxygen hoses are blue, while acetylene hoses are red, with a working pressure of 0.3 MPa. GB2550–2007 specifies that oxygen hoses are blue and acetylene hoses are red, with a working pressure of 2.0 MPa. The new standard GB2550–2007, “Rubber Hoses for Welding, Cutting, and Similar Operations in Gas Welding Equipment,” stipulates that oxygen hoses should be blue with a working pressure of 2.0 MPa, while acetylene hoses should be red with the same working pressure. Analysis of the accident cause: Firstly, there was inadequate promotion and implementation of the updated standards. The standards issued in 1992 had been replaced by newer ones, yet the manufacturing companies were only aware of the existence of these standards without knowing their actual content. Despite the fact that the standards GB2550-92 \"Rubber hoses for welding and cutting, oxygen rubber hoses\" were indicated on the hoses, production continued according to the old standards. In fact, the new standard GB2550-2007 \"Rubber hoses for welding, cutting and similar operations in gas welding equipment\" specifies that oxygen rubber hoses should be blue in color and operate at a pressure of 2.0 MPa; acetylene rubber hoses should be red in color and also operate at a pressure of 2.0 MPa. The new standard specifies the colors for oxygen and acetylene hoses in line with GB2550-92 \"Rubber Hoses for Welding and Cutting, Oxygen Rubber Hoses\", but for safety reasons, it mandates that the operating pressure for oxygen and acetylene hoses be uniformly set at 2.0 MPa. **The relevant regulatory authorities should step up efforts to promote and implement safety technical standards, and at the same time strengthen supervision and inspection of special-purpose products related to safety.