Conduit tubes are classified into three types of thick rigid steel conduit tubes, thin rigid steel conduit tubes and threadless rigid steel conduit tubes.
This Japanese Industrial Standard specifies rigid steel conduits for protecting electric wires in electrical wiring work. Conduit tubes are classified into three types: thick rigid steel conduit tubes, thin rigid steel conduit tubes and threadless rigid steel conduit tubes.
Materials and Manufacture of Galvanized Steel Conduits:
The materials for conduit tubes shall be the steel strips specified in JIS G 3132, or JIS G 3141, or steel strips at least equivalent thereto, or those galvanized. Conduit tubes are made by electric resistance welding. Both ends of a conduit tube shall be cut at right angles to the tube axis and chamfered.Both ends of a thick rigid steel conduit tube and thin rigid steel conduit tube shall have external threads.The inspection of the thread shall be carried out in the similar way to that specified in JIS B 0204.The inspection of the thread shall be carried out in the similar way to that specified in JIS B 0204. The inside and outside surfaces of conduit tubes shall be treated deterrent using by means of galvanizing (including the ones galvanized by hot dipping, thermal spraying or electrically and then chromated). The rust prevention of inside surfaces and threaded parts may, however, be accomplished by coating.
Bending Performance Galvanized Steel Conduits:
When a conduit tube is subjected to the test of 9.1, the variation in outside
diameter shall be ± 20 % of the original outside diameter, and no separation or split of
the welded seam shall take place and no crack or peeling off shall develop on the galvanized
surface or coated film.
Corrosion-resistance of Galvanized Steel Conduits:
The rust prevention given to conduit tubes shall comply with the relevant items described below.
a) The surface treated by galvanizing or thermal spraying shall not reach the
end point when subjected to the uniformity test of 9.2.1.
b) No white corrosion product shall be produced on the surface electrically
galvanized and chromated, when the salt-spray test of 9.2.2. is carried out
c) Neither blister, peeling off, nor rust shall develop on the coated surface when the salt-spray test of 9.2.2 is carried out.
Properties of Coated Film:
The inside surfaces of conduit tubes which have been treated deterrent to rusting by means of coating shall not cause breakage of coated film or any flaw when subjected to the test.
Dimensions of Galvanized Steel Conduits:
Conduit tubes shall be practically straight and their both ends shall be cut perpendicular to their axes and chamfered.The inside and outside surfaces of conduit tubes shall be smooth and of good finish,and the inside surfaces shall particularly be free from projections detrimental to practical service.