Pump Shaft Alignment Standard and Rectification
Pump shaft alignment is a critical component of the pumping system, and whether the alignment is correct or not can affect the operation of the machine and the service life of the equipment. There are certain standards to meet when aligning pump shafts, and appropriate rectification methods must be used in order to ensure the equipment operates as expected. This article will discuss the pump shaft alignment standards, pump shaft misalignment measurements, and some of the rectification methods available.
Pump Shaft Alignment Standards
In general, pump shafts should be aligned to within 0.002 inches of its nominal shaft position, with the exception of vertical turbine pumps which should be aligned to within 0.005 inches. In some cases, the manufacturer may require tighter tolerances, so it is important to refer to the specification manual for all shaft alignment requirements. Additionally, the tolerance of the alignment must be within 0.004 inches of the number given by the manufacturer.
Pump Shaft Misalignment Measurements
The most common method for measuring misalignment is the “reverse dial” method, wherein two pointer dials are used to measure the position of one shaft relative to the other. If one pointer is placed at the top of the furthest shaft and the other at the bottom, then the misalignment can be read off of the dial, with the angle and clearance being calculated accordingly.
The “offset roll” method is also useful as it can be used to accurately measure the horizontal and vertical misalignments between two pump shafts. In this method, aside from the reverse dials, a rotatable spacer block is used to align one of the shafts with the other.
Rectification Methods
There are two main methods for rectifying the alignment of pump shafts, the “cold” and the “hot” method. The cold method involves gradually moving the shafts until the desired alignment is achieved. The hot method, on the other hand, involves heating the shafts to allow for easier sliding and adjustment of the two components.
The most common method used to heat the shafts is the electric-resistance heating method, which utilizes a current passed through the pipes to heat the shafts along their length. Heat is also applied using oxy-acetylene torches, however this method should be used with caution and only under a controlled environment.
Conclusion
Regardless of which method is used, all pump shaft alignments must meet the manufacturer’s specifications. However, it is important to note that proper alignment will not only ensure that the maximum efficiency is achieved, but also extend the life of the equipment. Additionally, careful and routine maintenance of the pumping system should be performed to ensure that the alignment of the pump shafts remains correct.
