一、概述大钳是起下钻和修井操作的主要工具之一。二十年代末期开始使用手动大钳,在这个时期,除材料、强度外,对大钳本身没有作什么重大改进,直到四十年代才制造出目前广泛采用的、可换钳头以适应不同管径的手动大钳,而开始采用动力大钳是在五十年代初期。随着石油工业的发展,钻井平均井深和深井数逐年增加。如美国从1946年到1968年平均井深增加了45%,从1959年到1968年每年完成大于4575米的井数增加了78%。又如苏联从1957年 I. Overview Tongs are one of the main tools for drilling and workover operations. At the end of the 1920s, manual tongs began to be used. During this period, no major improvements were made to the tongs except material and strength. Until the 1940s, the widely used interchangeable tongs were used to accommodate different tubes Diameter manual tongs, and began to use dynamic tongs in the early fifties. With the development of petroleum industry, the average drilling depth and the number of deep wells have been increasing year by year. For example, the average well depth in the United States increased by 45% from 1946 to 1968, and the number of wells that completed more than 4,575 meters per year increased by 78% from 1959 to 1968. Another example is the Soviet Union from 1957