In this sub-class, pipe-line systems are interpreted as systems described in flow sheets as well as arrangements of co-operating elements, the elements per se being covered in the relevant sub-classes.
for controlling, signalling, or supervising the conveyance of two different products separated by "go-devils", e.g. for switching over from one receiving tank to another
F17D 3/04
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for preventing, indicating, or facilitating the location of leaks
F17D 3/06
· ·
by means of a signalling fluid enclosed in a double wall