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Centrifugal Pump Minute
All things relating to centrifugal pumps
Griswold's platform to provide educational resources for centrifugal pump technology and industry news.
Once out of service and disassembled, it’s crucial to conduct a thorough inspection of an ANSI centrifugal pump before returning it to service. By examining and/or testing each part prior to reassembly, operators can ensure that all features of
the pump are functioning properly, require no maintenance and are able to resume service. This evaluation can also help operators determine the lifespan of a part, or whether a particular area requires cleaning or remachining.
When conducting a pump inspection, Griswold® recommends beginning with an assessment of the pump’s hydraulic components. In this assessment, operators should check the casing for excessive wear, gouging or pitting on the hydraulic
surfaces, especially internal to the flow path. Should you notice a defect greater than ⅛” of wear, it’s time to replace the casing.
Next, you should examine the gasket surface where the case gasket sits during operation. Checking here for defects helps eliminate the possibility of leakage.
Moving onto the impeller, operators should inspect it to ensure that
no defects, gouges or pits are present in the top surface of the impeller. While evaluating the impeller, we recommend that operators check the pump out veins on the back side for any corrosion or pitting in the casting. If either are evident, the
impeller requires replacement.
You should next go over the seal chamber, otherwise known as the stuffing box. This feature is essential to fluid containment, so it’s important to look for any wear or defects greater than ⅛”. The seal gland gasket and casing gasket within
the seal chamber must also be free of any defects, as this can affect the seal efficacy.
Additionally, while the pump is out of service operators should examine the rotating assembly, including the shaft and bearing housing. If the dimensions do not meet specifications, the shaft should be replaced. While inspecting the rotating assembly,
operators should look for any wear on the seal area of the shaft, as well as the sleeve, if present. Following this assessment, move on to inspecting the bearing housing. Checking the diameter of the thrust bearing and ensuring there are not any defects
in the snap ring groove and the O-ring groove can help protect the longevity of your pump.
After this initial inspection has been completed, it’s important to continue evaluating the pump as you reassemble to confirm that all components are within tolerance. You should begin by observing the end play of the shaft, using a dial indicator
to see how much play there is and whether the performance meets manufacturers’ recommendations. Using the dial indicator again, we suggest testing the run out of the shaft next. This allows you to measure shaft deflection near the seal. Once
this meets manufacturer standards, move on to check the run out of the impeller, re-installing the stuffing box onto the shaft and once again utilizing the dial indicator to ensure a standard run out.
Once these visual and dimensional inspections have been fulfilled and each part is cleared for service, you can finish assembly with the casing. After concluding reassembly, the pump is ready to go back into service. By following this critical inspection
process, operators can secure safe, reliable pump performance.
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