A down-the-hole drill, usually called DTH by most professionals, is basically a screwed on the bottom of a . The fast hammer action breaks hard rock into small cuttings and dust that are evacuated by a fluid (air, water or ). The DTH hammer is one of the fastest ways to drill hard rock. The system is thought to have been invented independently by Stenuic. [pdf]
DTH is short for “down-the-hole”. Since the DTH method was originally developed to drill large-diameter holes downwards in surface-drilling applications, its name originated from the fact that the percussion mechanism followed the bit down into the hole. Applications were later found for the DTH method underground, where the direction of drilling is generally upwards instead of downwards. [pdf]
Suqian was put under the jurisdiction of Huaiyin in 1934. The county was converted as a county-level city in 1987, later was elevated to prefecture status in 1996.CountryProvinceArea code527Municipal seatWatch full videoOverviewSuqian is a in northern Province, China. It borders to the northwest, to the northeast, to the south, and the province of to the west. .
Suqian was said to be the site of a military grain store built when the Emperor Yuan of Jin reigned. Thus, the former Xiaxiang county where the store located was renamed Suyu (; means "prepared" or "usually pre. .
As of the , Suqian had a recorded population of about 4,986,192 whom 1,622,912 lived in the built-up (or metro) area made of Sucheng and Suyu urban districts. .
Local Yanghe along with and , are the three biggest manufacturers of . Besides, several domestic companies followed to site their in Suqian. [pdf]
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