The Hidden Dangers of Shaft Stiffness

The pump shaft is the central component of the rotating element and is responsible for transmitting energy to the rotating components. The shaft carries the impellers, sleeves and couplings for the rotating element assembly. The stiffness of the combined assembly is responsible for ensuring that the pump stationary components do not come into contact with the rotating components.

Unfortunately, this is not always achieved and many pump rotors cannot be described as classically stiff. This can have dire consequences for machine reliability, particularly if, during the rotor build process, the technicians are not aware of the subtleties of the machine design.

Read the full article by Dr. Gary Dyson at pumpsandsystems.com

How to Diagnose Thrust Pad Failure

thrust pad failure

Many high-energy multistage machines use thrust compensation devices to limit the amount of axial thrust a bearing must accommodate.

The BB3-style machine (axially split pump) uses its opposed impeller construction to limit thrust, while a BB5 machine (radially split pump) uses a balance drum or disc arrangement to fix the issue.

At the higher end of the pump energy spectrum, despite the use of thrust-limiting devices, there is a need to employ a sleeve tilting pad thrust bearing and lubrication system to handle the axial thrust.

Read the full article by Dr. Gary Dyson at pumpsandsystems.com

Engineering Analysis Resolves Startup Issues at Middle Eastern Plant

During the commissioning and startup of an alumina processing plant in the Middle East, a significant recurring pump issue was causing delays to the commissioning of the facility. When de-energizing the equipment, the live steam condensate vertical can pumps experienced repeated failures of all installed units. These seizures occurred at both the design fluid temperature and when pumping cold water.

Because this was a new plant in the commissioning phase, the equipment was under warranty. However, negotiations with the OEM were lengthening the challenged startup schedule. There was little insight into the root cause of the equipment failure.

As the repeated failures were affecting the plant commissioning date, the large architect, engineering and construction (AEC) firm in charge of plant commissioning decided to contact an independent, aftermarket service provider located in Dubai, United Arab Emirates, to conduct an assessment to determine the root cause of the pump failures and provide solutions.

Read the full article at pumpsandsystems.com

Full Refurbishment for Island Refinery

After a refinery closed down its 50-year-old plant, most of the rotating equipment suffered damage from exposure to the tropical climate. To restart the plant, the new owners called upon Hydro, Inc. to reverse engineer, rebuild and perform testing on their critical jet pump.

The process of reopening the plant had uncovered more than 500 pumps that needed considerable refurbishment and repair. The most important of these was a critical jet pump used for hydraulic decoking.

It was badly damaged and sent to the original equipment manufacturer (OEM) for inspection. The OEM recommended that the refinery replace most of the pump parts, as well as a costly repair that would require 35 weeks to rebuild.

Instead, the refinery sent the pump to global aftermarket pump service provider, Hydro, Inc. in Chicago, where it was refurbished for just over half the cost of the OEM proposal.

Read the full article at worldpumps.com

The Dangers of Operating Pumps at Low Capacity

Operating at low flow places the machine under a great amount of duress. It is always wise to have a mental picture of what is happening within the passages of the machine to understand why this is the case.

The days have long passed where pump vibrations were viewed as a matter of mechanical balance. Now, we recognize that even if the pump had perfect mechanical balance, it would still exhibit vibrations.

The intensity of this remnant vibration turns out to be flow related with its minimum level being at or around best efficiency point (BEP).

Read the full column at pumpsandsystems.com