Modifications can be made to many older pumps to improve on their original design. Pump rebuilders with experienced engineering staffs can provide these modifications and upgrades to substantially extend mean time between repair (MTBR) and increase pump longevity. In the following case history, an ash handling water pump that had been experiencing a short operational history was removed from service on an emergency basis because of catastrophic bearing failure caused by poor lubrication.

This pump was shipped to the service center where it was disassembled and inspected. It was observed that the bearings had failed and the rotor had moved axially toward the non-drive end, allowing the second stage impeller to contact the pump casing (see Figure 1).

Figure 1

Excessive wear was noted at all running clearances. Discussions with the plant subsequently revealed that these pumps have an average MTBR of 18 months. Excess running clearances accompanied by rotor axial movement have resulted in similar failures on sister pumps. Continue reading →

Valero-Wilmington, a midsize refinery (135-kb/d) located in Los Angeles, Calif., was experiencing problems with oil lubricated vertical in-line pumps (API type OH3). Though Valero-Wilmington uses the vertical in-line pumps for multiple applications, several are used as internal transfer pipeline pumps that operate within the refinery.

Problem

The Byron Jackson pumps, model MVILD, were not equipped with any type of instrumentation, and since most of the pumps are located in remote areas, daily observation and monitoring were not possible. After running for two to four months, the pumps were losing flow and lubrication pressure, causing a rise in bearing temperature and resulting in abrupt catastrophic failure of the thrust bearing. This failure also caused damage to the mechanical seal, pumping ring and impeller.

In January 2007, Valero-Wilmington sent one of these pumps to Evans Hydro with a request to investigate the failures. To determine the root cause of the problem, the engineers started by reviewing the original sump design. The original oil sump design had a magnetic seal at the bottom (see Figure 1, Item 117). The second-generation design had eliminated the magnetic seal and added the riser pipe-the significance of which will be illustrated in the discovery of the problem.

The obvious problem was that oil was leaking from the bottom of the sump. After disassembly and inspection, the cause of the problem was not immediately apparent. The oil level was set correctly, there was no problem with the pumping ring and no scoring or wear was found on the stationary parts. The big question was how the oil was leaking from the sump, causing lack of lubrication and the overheating and failure of the bearings.

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With large-scale consolidations of OEMs in the pump industry and the closure of foundries in North America, advanced non-OEM pump rebuild shops have emerged that offer creative solutions, competitive pricing and quick turnaround time to pump users. A qualified independent rebuild shop employing highly experienced personnel and a range of advanced technologies can offer cost effective and creative solutions to long lead times on new pumps, which often range from 6 to 12 months.

The following example demonstrates how a petrochemical pump user utilized the capabilities of a competent pump repair shop to achieve a cost-effective solution for their plant expansion.

Creative Solutions for Chemical Plant Expansion

A petrochemical plant in the Gulf Coast region was expanding production. Because of the time frame involved in completing the project, they elected to source a surplus pump from the used pump market and modify it to suit their needs rather than purchasing a new pump. Delivery of a new pump would have taken 6 to 8 months and they wanted to be online in just 44 days! This plant needed a solution to this challenging engineering problem and intensely demanding production schedule.

The plant chose to work with a pump repair shop that employs CAD/CAM, CMM and Romer Arms in addition to Computational Fluid Dynamics software and material analyzers. With the added resources of skilled engineers and experienced technicians, many with engineering or operations backgrounds from major pump manufacturers, this plant chose a repair shop with exceptional hydraulic design and reverse engineering capabilities to address their emergency situation.

With guidance from the repair shop, the plant purchased an 8-stage pump that could be modified to meet their specific needs. After a thorough engineering review and inspection of the existing pump, the pump repair shop not only proposed a solution to the emergency situation, but also offered upgrades to improve both pump performance and reliability of the pump for this chemical application.

Engineering Review and Proposed Upgrades and Modifications

An assessment of hydraulic performance is high on the list whenever upgrades are contemplated. For this particular pump, the performance curves (see Figure 1) had to be examined first. Then, a dimensional drawing of the barrel (casing) had to be prepared by the repair shop. These two steps enabled the parties to determine desired and feasible modifications and upgrade options.

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