Servicing submersibles

Electrical Apparatus, Jul 1998 by Nailen, Richard L

The care and maintenance of fluid-filled motors is this Texas company's only business

LUBBOCK, TEXAS-"Water and electricity don't mix; everybody knows that. But if you do it carefully, you can have them in close proximity to each other."

So says Dexter Duhan, founder and now chairman and chief financial officer of Sun-Star Electric, Inc., here in the South Plains. Nowhere is his statement more true (and sometimes more challenging) than in a liquid-filled submersible motor-the only product his firm handles.

Duhan was careful to point out that "We don't work on pumps. Fluidfilled motors are our only business. Generally we sell new motors to OEMs such as pump builders, and repair jobs come back to us through them. But we deal with people at every level-specifiers, contractors, installers, or users. Our concern, though, is with the proper application, installation, and use of the motor itself."

These units are all of the "wet winding" type, in which the stator winding is directly immersed in the liquid-not sealed off by encapsulation or liners. Shop time for a full repair and rewind of such a submersible runs from 60 to 90 man-hours; more if the stator needs re-stacking.

Added Marketing Vice President Jim Rice, "After the equipment has been out there operating for several years, needing service often perhaps because of a misapplication, the pump OEM may not want to be directly involved any more, and we repair the unit for whoever needs it done, including other service shops."

Driving along a rural road through miles of cotton fields, until recently outside Lubbock city limits, one comes unexpectedly upon the SunStar shop, with its 60 employeesthree separate structures of 50,000 square feet (now being expanded to 65,000) on a 30-acre site. The business here involves motor ratings from 5 to 3000 horsepower; voltages from 460 to 6600-all three-phase, except for an occasional single-phase 230 volt unit.

Sun-Star Electric is affiliated with several water-related industry organizations, including the National Ground Water Association, Texas Ground Water Association, American Water Works Association, and the Marine Technology Society.

Both Duhan and Rice credit their place in the industry to the pioneering work of Bert Magney (now retired), whose Arizona firm led the way many years ago in application and servicing of large submersible motors. Four Magney "alumni" (including SunStar's President, Randy Gage) now form part of the Lubbock firm's management.

Sun-Star was founded in 1977. Originally, Rice explained, the goal was to introduce the Hitachi line of submersibles (units in the 5-300 hp range, 2 and 4 poles) to the U.S. market. "Based on our experience in the water pumping industry," he continued, "there were some modifications we felt were needed. In Japan, wells tend to be shallower, and thrust loads lower. The motors tended to be shorter and fatter." (The main reason for a submersible's high length-to-diameter ratio is that most such motors must fit into a well casing. The deeper the well, the greater the economic incentive to reduce that casing diameter.)

"Tandem and triple seals were cumbersome and had high failure rates," added Rice. "We wanted to see an open, repairable winding-not a canned type unit, as most U.S.-built submersibles then were. Few motor shops would try to repair them because it wasn't economical. But an open, wet winding can be repaired."

"Once we started selling these, after a few years, we had to start servicing what we sold," said Duhan. "So we got into repairs. A few other shops have tried it, but few have had much luck." Today, about 60% of Sun-Star Electric's business volume is in repair work.

The firm started with one employee in a 4,000-square-foot facility elsewhere in this area, which constitutes one of the two leading market areas in the U.S. for submersible water well motors (the other being California's San Joaquin Valley). At one time, 21 different pump manufacturers were located in Lubbock.

A fourth employee was added after four years. The firm then moved a few miles to an industrial building where successive expansions increased the floor space to 10,000 square feet. But electric power and crane capacity limits eventually brought the business to its present site, then providing 22,000 square feet.

Through its own inventory here in Lubbock, plus stored and consigned stock at numerous other locations, Sun-Star still functions as the outlet for new Hitachi units. That's another 20% of the business. Speeds are typically 3600 rpm for irrigation uses; 1800 for municipal or industrial applications. Besides complete "motor-ina-box" units, however, Sun-Star also carries a selection of "kits"-stator and rotor only. Windings can be designed and installed to meet specific needs, such as a special voltage.

Other variations may be mechanical. Explained Rice, "As complete motors, the smaller sizes come with epoxy-coated cast-iron end brackets and a stainless-steel casing. We will often replace those brackets with 316 stainless-steel fabrications made here. Larger ratings will have carbon steel casings, and we'll coat those with a coal-tar epoxy. We'll cut off shaft extensions and weld on stainless steel stubs. Conventional double-lip seals will be converted to mechanical type."