管道环焊缝距支、吊架净距不得小于（）mm。15.高温或低温管道法兰的螺栓，在试运行时，热态紧固或冷态紧固应在达到工作温度（）h后进行。
参考答案：50；2
用20的4个因数组成一个比例式是（ ）。
How should you signal the crane operator to dog everthing?（）.
A.Place both fists in front of the body with the thumbs pointing outward each other
B.Clasp hands in front of your body
C.Extend arm with the palm down and and hold this position rigidly
D.Extend arm with the thumb pointing up, and flex the finger s in and out
