Allowances may be made for the expansion and contraction in piping by the use of expansion joints or ______.
A.unions
B.retractable flanges
C.union bulkhead fittings
D.bends or loops in the line
正确答案是B
Allowances may be made for the expansion and contraction in piping by the use of expansion joints or ______.
A.unions
B.retractable flanges
C.union bulkhead fittings
D.bends or loops in the line
正确答案是B