Flooding in the aftermath of tropical storms, including hurricanes, monsoons and cyclones, and with their associated heavy rainfall can shut down hundreds of plants along the Gulf Coast, from Florida to Texas, as well as in other places around the world. And they are doing so more often. To get them up and running again, maintenance departments and motor repairers face the daunting task of cleaning muck and moisture from many thousands of electric motors and generators. The process involved in such situations can take weeks, if not months, and requires special clean-up procedures for motors contaminated by saltwater.

Flooding in the aftermath of tropical storms (hurricanes, monsoons and cyclones) with heavy rainfall will often shut down hundreds of plants along the Gulf Coast from Florida to Texas and other places around the world. To get them up and running again, maintenance departments and motor repairers face the daunting task of cleaning muck and moisture from many thousands of electric motors and generators. The process in such situations can take weeks, if not months, and requires special clean-up procedures for motors contaminated by saltwater.

A menudo, las inundaciones producidas por las intensas lluvias de las tormentas tropicales (huracanes, monzones y ciclones) colapsan cientos de plantas industriales a todo lo largo de la costa del golfo de México, desde la Florida hasta Texas y en otros lugares del mundo. Para retomar las actividades productivas, los departamentos de mantenimiento y los reparadores enfrentan la difícil tarea de limpiar la suciedad y desalojar la humedad en miles de motores y generadores eléctricos. El proceso en tales situaciones puede tomar semanas o meses y requiere procedimientos especiales para limpiar los motores contaminados con agua salada.

I suspect that just about everyone in our industry at one time or another has had the joy of repairing a “purpose-built” motor. This kind of motor is built for a specific purpose and has characteristics that may allow it to operate under non-standard conditions. Due to the limited information that some of them display on the nameplate, the repair of these motors can be somewhat of a challenge. Sometimes these motors possess differences such as the color of paint, the shaft size, the bearing size, or type. It can be the operating temperature and at times it can be the motor in its entirety. Following are a few useful tips we use when repairing a motor with so many question marks.

There are benefits and drawbacks to the use of multiple circuits in a 3-phase winding. Whether discussing a random winding or form coil winding, some of the considerations are shared. Topics covered include:

• Increasing circuits, turns
• Rotor pullover during starting
• Increased risks
• Factors beyond our control

Existen beneficios e inconvenientes al usar circuitos en paralelo en un bobinado trifásico. Sea que estemos hablando de un bobinado de alambre redondo o de pletina (solera), algunas de las consideraciones se comparten. Los temas cubiertos incluyen: Aumentando los circuitos en paralelo y las espiras Descentrado (pull-over) durante el arranque Aumento del riesgo Factores fuera de nuestro control.

Sospecho que casi todos en nuestra industria alguna vez han tenido el placer de reparar un motor “fabricado con requisitos especiales”. Este tipo de motor está construido para un propósito específico y tiene características que le pueden permitir funcionar bajo condiciones no habituales. Debido a la información limitada que algunos de ellos muestran en su placa de datos, la reparación de estos motores puede resultar un reto.

Accuracy and precision of measuring & test equipment (M&TE) have been topics of previous Currents articles (November and December 2014). A related topic that was not covered in the previous articles is resolution. The Joint Committee for Guides in Metrology document JCGM 200:2012 defines resolution as “the smallest change in a quantity being measured that causes a perceptible change in the corresponding indication.” Simplified, it’s the smallest difference that can be measured by the subject equipment. The accuracy of the M&TE must be greater than (less accurate) or equal to the resolution. That is, the M&TE must be able to indicate the value that is compared to the standard during calibration.

Let's briefly revisit the importance of accuracy and precision.

La precisión y exactitud de los equipos de prueba & medida (M&TE) han sido tratadas en artículos previos de Currents (noviembre y diciembre de 2014). Un tema relacionado que no fue cubierto en dichos artículos es la resolución. Este artículo cubrirá ese tema.

One of the most common repairs on centrifugal pumps is replacing worn or damaged wear rings. For pumps with closed style impellers (impellers with a front shroud as described below), there will be a casing wear ring and possibly an impeller wear ring which is fitted to the outside diameter (OD) of the impeller suction eye. Impellers may also have rear wear rings which are important for controlling axial thrust. Pumps with open style impellers generally do not have suction eye wear ring clearance concerns, but they often have rear wear rings. The clearances between the stationary casing wear ring and the rotating impeller wear ring are critical to proper pump operation. Although many pump manufacturers will provide proper clearances and dimensions, some do not; there are plenty of old pumps around from now defunct manufacturers where dimension data is simply not available.