| 摘要 |
<p>Protective sheath for passive coatings on pipes, esp. underground pipes with a coating of bituminous enamel or other material, consists of a layer of agglomerated, rot-proof fibres, covered by an outer layer of bitumen except for holes permitting the passage of a cathodic current. The sheath may (a) be located completely round the pipe, (b) be present only on the upper part of the pipe, but extending below the horizontal dia., (C) form one or more layers on the base of a pit in which the pipe is layed, or (d) form a wrapper held in place by binding. The holes are pref. 5-10 mm dia. and staggered round the pipe at intervals of 10 cm along its length. An anti-adhesive layer of powder, e.g. silica or talc, is pref. sprinkled on the bitumen.</p> |
