First, the extinguisher valve is removed and the threads and interior of the cylinder are checked for corrosion, pitting, and any other abnormalities. [29 CFR 1910.157(f)(3)] If the cylinder passes the visual inspection, it is placed into a steel chamber, which is then filled with water at normal pressure.
Updated April 17, 2017. The earliest dated printed book known is the Diamond Sutra, printed in China in 868 CE. However, it is suspected that book printing may have occurred long before this date. In 1041, movable clay type was first invented in China.
[coinsky.com]. The Chinese invention of Woodblock printing first appeared over 2,000 years ago, and produced the world's first printings. In the Tang Dynasty (618ï¼907), Chinese began to print with carved blocks. Then in the 1040s, Bi Sheng of the Northern Song Dynasty (960ï¼1127) invented movable clay type printing, which marked a beginning of a major revolution in the history of printing.