The three-petal clamp quick opening closure has function of safe self-locking. This function prevents the closure loosing while tightening, also avoids opening the closure under pressure. This kind of equipment is widely used in the fields of natural gas, chemical industry, metallurgy and medicine. Structure features: 1 There is no relative motion between sealing surface of closure and sealing ring. It is not easy to damage the sealing ring, which can make the whole system achieve better sealing effect; 2 Three-petal clamp takes motion while tightening and reduces the length of open screw; 3 The bearing capacity area of teeth is simultaneously enlarged (interlocking area is more than 90%). It is more suitable for the gas pipeline with high pressure and large caliber. The main pressure-bearing part has no welding connector; 4 There is safe self-locking function. Application field: Natural gas, chemical industry, metallurgy and medicine Operating instructions: 1 Inspect whether each instrument on the machine indicates normally; 2 There should not be leakage among the container and quick opening closure, as well as each connection part; 3 Necessary explosion tools, fire extinguisher, firefighting felt and other equipments should be enough; 4 The quick opening closure should be operated by one person under the guard of other person; 5 No person is allowed to stand in the front of the quick opening closure while opening or closing.