One of the most common repairs on centrifugal pumps is replacing worn or damaged wear rings. To restore efficient, reliable operation and prevent catastrophic pump failure, it is critical to restore proper clearances between the stationary casing wear ring and the rotating impeller wear ring. Although many pump manufacturers provide clearances and dimensions, some do not. There are plenty of aging pumps around from now-defunct manufacturers for which dimension data is simply not available.

In such cases, the rule of thumb that follows provides some guidance for acceptable running clearances, or the minimum running clearance chart in American Petroleum Institute (API) Standard 610 can be used as a guide.

The repair of the various types of pumps represents an important segment of the service center repair market. Electric motors and pumps are the two most widely used industrial machine components.                                                                                                                                                                                                                       

Although there are two principle pump types (dynamic and positive displacement), this manual focuses on dynamic pumps and the fundamentals of dynamic pump repair. The information it contains will be helpful to both novice and experienced pump repair technicians, to supervisors and managers of pump repair operations, and to customer service and sales personnel who communicate with customers about pump repair issues.

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It is commonly known that pump mechanical seals are temperamental devices that fail frequently. The fact is, mechanical seals are simple devices that are often misapplied, sometimes installed incorrectly, or perhaps installed on pumps that are not well suited for the application.

Centrifugal pump failures are most commonly attributed to seal failure, impeller damage and bearing failures. A good understanding of failure modes for seals, impellers and bearings is essential to providing customers with reliable pump repairs.

A leak rate of one drip per minute equals about a liter (quart) of water in three days. For an O-ring on a submersible pump, that is a major problem. O-rings are often used for static seals on submersible pumps. Understanding what makes a good static seal and what causes one to leak is important for pump maintenance and repair technicians.

Para aquellos que son nuevos en el negocio de la reparación de bombas, los sellos pueden resultar intimidantes, sin embargo, es bien conocido que los sellos mecánicos de las bombas son dispositivos temperamentales que fallan con frecuencia. El hecho es que los sellos mecánicos son dispositivos simples que a menudo son utilizados de forma inadecuada, algunas veces instalados incorrectamente o tal vez montados en bombas que no son aptas para la aplicación. En la mayoría de las aplicaciones, los sellos mecánicos son lo suficientemente macizos para tolerar condiciones de operación y de manejo menos óptimas. Para aplicaciones exigentes todo debe estar bien.

For most centrifugal pumps, the shaft has packing or a mechanical seal where the shaft enters the wet end. Fundamentally, a sealless pump substitutes a magnetic drive for the shaft seal. The impeller shaft is fitted with a magnetic rotor which is contained in a thin metal cover. The shaft, impeller, the rotor and the bearings are all "wet" components; that is, they are completely submersed in whatever liquid is being pumped. Over the outside of the magnetic rotor and cover is a magnetic drum which is driven by the power source, usually an electricmotor. The magnetic coupling between the rotor and drum delivers torque to the shaft and impeller. There are a number of variations in design, but all use sleeve type bearings lubricated by the pumpage.

The pump repairs are completed! Now the pump needs to be tested. This presentation discusses the procedures for the basic tests that can be performed on pumps that have been repaired in the service center.

For many larger centrifugal pumps, there are options for installing “component” or “cartridge” mechanical seals. Understanding the advantages and limitations of each will allow you to recommend the best solution for customer applications.