Causes 1. cast iron casting quality is not high, the valve body and the valve body with trachoma, loose tissue, slag and other defects 2. Day cold cracking; 3. Poor welding, there is slag, welding, stress cracking, etc. Defects 4. Cast iron valve is hit by heavy objects damage prevention and solutions 1. To improve the casting quality, strictly in accordance with the provisions of the pre-installation strength test; 2. For the temperature of 0 ° and 0 ° below the valve, insulation or heat should be mixed , Stop the use of the valve should be ruled out stagnant water 3. The weld consisting of the valve body and the valve cover should be carried out according to the relevant welding procedures, testing and strength testing should be carried out after welding; 4. Do not push the valve on the weight Material, does not allow the hand hammer hit the cast iron and non-metallic valves, large-diameter valve installation should be supported