| 摘要 |
A high-temperature parallel-resistance pipe heater is described which is capable of being maintained at a high temperature level of approximately 600 DEG F on a sustained basis and is capable of withstanding temporary occasional heating up to 1,000 DEG F. A twisted pair of flexible electrical conductors with micaceous and fiberglass braid insulation layers have short segments stripped bare on alternate conductors at uniformly spaced intervals along their length, the conductors each including multiple fine nickel-clad copper strands, and a nickel-alloy resistance wire is helically wound around the twisted pair with two bights of the resistance wire engaging many of the strands in each bared segment for establishing numerous points of high unit area pressure contact at the junction between conductor and resistance wire. An anti-fraying agent on the fiberglass braid prevents the fibers from interfering with these points of contact. This assembly is enclosed with layers of micaceous and fiberglass braid insulation and sheathed in a metal tube to form a long length of heater cable which can be cut to length for making individual heaters as desired in the field.
|
