how to translate spool
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Alternatively, a pipe spool with bleed may be provided.
spool n. reel, tube for holding thread; something in the shape of a reel; the amount of thread wound on it; a frame for winding thread; vt. to wind something around a reel; to coil; to consider sections of piping as individual units, for example, the pipes shown on a single-line diagram can be divided into several such units for preliminary planning
Alternatively, provide a pipe section with a drain port.
By \"tube segment,\" it refers to something like a removable spool, that is, a detachable tube segment.
The answers are absolutely right!