The dark-rod wedge-type cast iron valve handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited. 5), the gate valve with the transmission mechanism, installed according to the provisions of the product manual. 6. Execution standard 1), product standard "General valve flange connection iron gate valve" GB/T 12232-2005 "General requirements for steel valves" GB/T 12224-2005 "Steel slab gate valve for pipeline" JB/T 5298 -91 "Inspection and Test of Valves" JB/T 9092-1999 "Safety Evaluation Standards for Drinking Water Distribution Equipment and Protective Materials" GB/T 17219-1998 2), Engineering Standards "Building Water Supply and Drainage and Heating Engineering" Construction Quality Acceptance Specification GB 50242-2002 "Code for Construction Quality Acceptance of Ventilation and Air Conditioning Engineering" GB50243-2002
The history of stone carving can be traced back to the middle of the Paleolithic Age, which is about 120000 years ago. Since then, stone carvings have been handed down to this day. In this long history, the creation of stone carving art has been constantly updated and improved. In different periods, there were great changes in the types and styles of stone carvings; Different needs, different aesthetic pursuits, different social environments and social systems are restricting the development and evolution of stone carving creation. The history of stone carving is not only the history of art, but also the history of rich cultural connotation. It is more vivid and real human history.
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