This project is applied for melting of chromites and ferroalloy electric arc furnace，the gas-off is used for collect gas and burned outcome. Gas with high temperature and massive dust, the work environment is bad, and the gas-off suffers from the wash of dust and high temperature corrosion of gas. Original gas-off adopted water cooling clamp type, with poor performance, and leakage etc. problem occurred, therefore, after adopted as the forged copper slab drilling structure gas-off, which was delivered and put into application in 2012, the product is operation normally till now.