By Gene Vogel
EASA Pump & Vibration Specialist

Vertical turbine pumps (VTPs) are workhorses in the petrochemical, power generation and manufacturing industries, and prolific in municipal water applications that handle the primary intake load. The ability to develop high head with multiple impeller bowls—coupled with the ubiquity of standard vertical motors that can support heavy pump shaft loads—makes VTPs a good choice. Although these machines are ruggedly built, abrasive sediments in the pumpage take a toll, particularly on line shaft and pump bowl bearings, so periodic overhauls are often necessary. Rather than simply replacing the bearings, however, it is important that repairs address all of the issues needed to restore maximum operating life.

This article covers:

• Common repairs
• Fit and alignment
• Bearing-to-shaft clearances
• Primary repair concerns

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Until now, governmental and market forces have tried to reduce electrical energy usage in industry primarily by targeting electric motors. While these “green” initiatives have often raised concerns for manufacturers, repair facilities and end users, they have also spurred innovation.

But the commercial and regulatory landscape continues to evolve, and the horizon coming into view includes a new focus on pumps and pump systems. Starting in January 2020, the U.S. Department of Energy (DOE) will begin implementing the first ever energy efficiency standards for freshwater rotodynamic (centrifugal and axial flow) pumps. These standards will directly affect pump manufacturers and, to a lesser extent, the pump repair market, while ultimately benefiting end users if the new focus can reduce their energy costs.

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Gene Vogel
EASA Pump & Vibration Specialist

Vertical turbine pumps (VTP) commonly have rotors with multiple mixed-flow impellers (sometimes 12 or more) that are supported by a vertical pump motor. Such designs offer a lift adjustment for raising or lowering the pump rotor to properly position the impellers within the bowl. Depending on the type of pump, this may be critical for maximizing pump efficiency and could have a significant impact on motor load (current) and reliability. Given the importance of VTP lift adjustments, it is necessary to recognize that procedures vary with the characteristics of the pump and motor.

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Gene Vogel
EASA Pump & Vibration Specialist

Shaft alignment is a critical step in the installation of rotating machinery, in a new installation or a repaired machine. Skipping or botching this step can decrease operating efficiency and shorten machine life. The procedure for aligning two rotating machines requires measuring their relative shaft positions and adjusting one or both machine cases, usually by shimming at the feet. Until recently, though, how closely the shafts need to be aligned was an open question. That changed with the publication of American National Standards Institute/Acoustical Society of America (ANSI/ASA) standard 2.75-17. Here is a summary of what it covers and how it will benefit users involved with shaft machinery alignment.

• The need for a standard
• Purpose and scope
• Tolerances
• Alignment principles
• Alignment quality grades
• Making machine moves

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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.

The effectiveness of an O-ring static seal depends on the dimensions of the mating parts, the surface finish of the mating parts and the characteristics of the elastomeric O-ring. The focus of this article is the dimensions and condition of the mating parts.

Topics covered in the article include:

• Dimensions
• Identification of critical surfaces
• A case study

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Gene Vogel
EASA Pump & Vibration Specialist

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.

• Suction side wear rings vs. rear wear rings
• Open vs closed impellers
• Wear ring clearances & specific speeds
• Wear ring clearance guide

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