Service firm specializes in rebuilding and repair of explosionproof motors
GOODWIN Pray Co. Inc., Linden, N.J., affiliated with J. R. Longo & Sons, Inc., was the first service firm in the state to receive recognition under the new Underwriters Laboratories’ program for listing rebuilt motors andgenerators for hazardous locations.
Until recently, an explosionproof motor requiring repair or rebuilding had to be sent back to the original manufacturer to be covered by the Follow-Up Service of Underwriters Laboratories, Inc. In other words, repair by anyone other than the original manufacturer would void the UL listing. Such seemingly inconse quential things as disturbing a motor’s lead wire seal, covering metal joint surfaces with varnish, increasing clear ances at shaft openings, placing shims between surfaces of assembled joints, or marring machined metal surfaces can adversely affect the explosionproof features of the motor, even though operation appears perfectly normal.
Because of many questions arising about the listing status of rebuilt explosionproof motors and to decrease the time and expense involved in ship ping motors, particularly large ones, to the original manufacturer for repair, UL developed a program for listing motor and apparatus shops capable of rebuilding explosionproof equipment, together with a procedure for listing such rebuilt equipment. The firms recognized by UL for such work are listed in the UL Hazardous Location Equipment Directory (Red Book), issued annually, under the heading “Motors and Generators, Rebuilt.”
Goodwin Pray engineers point out that a motor submitted to them for repair must bear an original UL label listing it as a classified-location motor before they can begin work, since the original strength and ability of the listed motor to contain explosions (bar ring undue corrosion or stress cracks) is assumed to still exist.
After a hazardous-area motor has been repaired and tested, it receives a special label stating that the machine has been rebuilt and is listed for use in a particular classified location.
The repair techniques, skill, and facilities of Goodwin Pray, as illustrated by the accompanying photos, provide an indication of the capabilities expected of service firms doing such work.
MICROMETERS used (right) range in size from 18 to 40 in. Machinist shown is measuring outside diameter of motor end bell. Vernier calipers and inside measuring rods are in foreground.
INTERNAL THERMAL overload sensing devices (right) are installed In ail explosionproof motors. Goodwin Pray plant manager shows how devices are Installed-one In each phase, in series with control circuit leads.