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油气勘探开发正在向环境更加恶劣和地质条件更加复杂的沙漠、高原山区、深海、沼泽、淤泥、丛林和极地等地区推进，因此要求钻井泥浆泵减轻重量、减小体积、改进结构、提高效率以适应各种恶劣环境和条件。文章介绍一种钻井用新型泥浆泵－7NB泥浆泵的结构、工作机理等。该泵与传统的钻井泥浆泵相比具有冲程短、冲数高、排量大且均匀、压力高、压力波动小、结构简单、体积小、重量轻等特点，有良好的应用前景。与此同时，也提出了目前7NB泥浆泵存在的问题和进一步改进的方向。

7NB PLUNGER DISPLACEMENTPUMP WITH STRAIGHT AXIS AND ITS WORKING MECHANISM

Oil and gas exploration and development is being conducted in theregions in which the circumstances is more adverse and the geological condition is more complex such as desert，highland，deep sea， swamp，sludge，jungle and polar region，etc． For this reason，the mud pump is asked to reduce the weight and volume，to improve the structure and to raise the efficiency to adapt to various adverse circumstances and conditions．In this paper，the structure and working mechanism of 7NB mud pump—a new mud pump for drilling are presented． As compared with traditional mud pump，this pump has such features as short stroke，high stroke rate，high and uniform flow rate，high pressure，small pressure fluctuation， simple structure，small volume and weight，etc． and its application prospects are good． The existent problems for 7NB mud pump at present and the direction of further improvement are put forward also．