hard coal

In coal gas drilling, coal collapse led to drilling hard trip and other accidents.

在煤层气钻井中, 煤岩坍塌造成接单根困难、起下钻遇阻遇卡、蹩泵等事故和井下复杂.

Study on Wear Resistance of Composite Alloy Reinforced with Hard Alloy Grains for Coal Crusher

磨煤机用硬质颗粒增强复合合金材料的耐磨性

Throwing a pick around in a coal mine& that's hard work.

就像用鹤嘴锄在煤矿里挖煤，这是项非常辛勤的工作。

Under Datong two hard conditions coal plow system research and application

大同两硬条件下刨煤机系统的应用实践

Xinli mining area of Sanshandao gold deposit is the first hard rock mine which belongs to the under-sea deposit in our country, and only Longkou is mining coal under sea in domestic.

三山岛金矿新立矿区是我国第一个进行海底采矿的硬岩矿山，国内仅龙口在海下采煤。

Small traders find it hard a foothold in the export of coal to Japan.

小的贸易商在对日的焦煤出口中不好插足.

Caving mining under the condition of hard coal and rock

坚硬煤岩条件下放顶煤开采

Study of Pre-cracking Hard Coal by Water Infusion in Sub-level Caving Mining

坚硬煤层放顶煤注水弱化研究

Hoist, ventilator, air pressure machine and water pump are main fixed equipment which play important roles in coal mine production and consume most of the power. Traditional testing by manual is hard to satisfy the demands of determining operating status and technical parameters.

提升机、通风机、空压机、水泵是煤矿生产建设中起重要作用并且耗电量占很大比重的主要固定设备，对这些设备的运行状况和技术参数的确定，传统的人工测试已经很难满足。