Determining the use of open or enclosed lineshaft

 

2009-09:1

 

Q. When selecting a vertical turbine pump design, what factors should be considered when determining the use of open or enclosed lineshaft?

A. An open lineshaft and an enclosed lineshaft-type deepwell pump are shown in ANSI/HI 2.1– 2.2, Rotodynamic (Vertical) Pumps for Nomenclature and Definitions.   

The open lineshaft pump is often referred to as a product-lubricated or water-lubricated pump. The lubrication for an enclosed lineshaft pump may be oil, grease, filtered pump discharge water or clean water from an external source. Representative cutaway sections of open and enclosed lineshaft construction for vertical turbine pumps are shown in Figures 2.3.3.4c and 2.3.3.4d.

 

 

 

The open lineshaft bearing bushings are subject to abrasive wear when the pumped liquid contains sand or other suspended solids. The open lineshaft type does not have a possible contamination problem, which can exist with the enclosed lineshaft type when drip oil or packed grease is used. Other examples of product-lubricated pump constructions can be found in ANSI/HI 2.1–2.2.

 

The enclosed lineshaft bearing bushings are protected from pumped abrasives and are lubricated by drip feed oil, packed grease or pressurized water in the standard pump configurations. The shaft-enclosing tube is provided to protect the shaft and bearing bushings from the liquid being pumped and to provide a means for abrasive-free water, grease or oil to lubricate the bearing bushings. A bypass port in the top of the bowl assembly, not necessarily used on lower head or single-stage applications, prevents the buildup of pressure in the shaft-enclosing tubes.

Mineral oil contamination of wells is a possible problem with enclosed lineshaft; therefore, biodegradable oils are frequently used. Selecting proper biodegradable oil is important because many of these oils promote molds and bacteria growth.

Numerous variations of the open and enclosed lineshaft constructions exist, especially in the short-setting pumps and custom engineered-to-order verticals. A variety of bearing constructions and lubrication systems are applied to suit different applications.