Rebuilding Boiler Feed Pumps for the Wastewater Industry

Author:

Bob Bluse, Hydro East Inc., and Scott Morisi, Passaic Valley Sewerage Commissioners

Publisher:

Pumps & Systems

Date Published:

October, 2009

 

Repairing multistage, segmental diffuser, boiler feed pumps and maintaining the original performance can be difficult and challenging. In this case study, a comprehensive inspection and repair program was applied to rebuilding six boiler feed pumps to improve MTBR and hydraulic performance to meet system demands.

 

Background

The pumps sent for rebuilding played an important role in maintaining plant performance for one of the six largest wastewater treatment plants in the United States, located in northeastern New Jersey. The plant, operated by the Passaic Valley Sewerage Commissioners (PVSC), uses the boiler feed pumps in a wet air oxidation (WAO) process.

The WAO process treats combined thickened waste activated sludge and primary sludge with heat (420 deg F) and high pressure (650 psi) for 30 minutes in a reactor to reduce the volatile solids content, break the chemical bond between the solids and the water, facilitate a high degree of dewaterability, sterilize the sludge and minimize the volume to be removed for beneficial reuse.

 


Facility’s boiler house
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Improving Pump Efficiency to Save Energy and Increase Generating Capacity

Author:

Ross Bertoli, Hydro Australia, and Mark Moerke, International Power Hazelwood

Publisher:

Pumps & Systems

Date Published:

August, 2009

 

As the global demand for energy grows, power companies are working to implement new technologies that would enable them to produce more power from existing stations. The following example demonstrates how International Power’s Hazelwood power station in Australia improved the efficiency of their motor-driven boiler feed pumps to produce a higher megawatt output without burning additional fossil fuels.

 

The Growing Demand for Energy

Built between 1964 and 1971, the Hazelwood Power Station in Victoria’s Latrobe Valley originally planned to have six units producing 200 MW each. However, growing electricity demand in the late 60s prompted the approval of a proposal to add two units to the station to increase generating capacity. The eight-unit power station was producing 1,600 MW output by the early 70s; each unit generated 200 MW of power. In recent years, this power station has moved to improve its output through thermal efficiency gains and increasing each unit’s capacity by 20 MW.

 

Engineered Modifications to Improve Pump Efficiency

Having modified the turbines to use less power, the plant needed to upgrade the 11-stage ring section, boiler feed pumps to meet the newly elevated performance requirements. International Power Hazelwood (IPRH) contacted a pump aftermarket service center in the Latrobe Valley to determine if modifications could be made to seven of these pumps within a two-year time period.

Though the original pump curves implied that the pump would have sufficient head and flow to handle the increased service conditions, several factors were discovered during inspection that would determine the course of action. Due to a vane pass vibration, the diffuser vanes had been machined to correct a vane pass issue that the pump experienced early on in its life. As a result, the hydraulic performance of the diffuser was compromised, and the pump no longer matched the manufacturer’s original design. The motor size also limited the power usage.

 


Rotor Centralization was performed to improve pump efficiency

 

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Service Center Engineering for a Power Plant

Author:

George Harris, Hydro Inc.

Publisher:

Pumps & Systems

Date Published:

December, 2008

 

Many pumps in power plants and other heavy industries are designed and custom engineered for specific applications. The repair and servicing of these pumps should also include careful engineering review. Very often, smaller local repair shops attempt to repair these engineered pumps without the input and oversight of an engineer to ensure that the proposed repairs meet the original design’s intent.

When emergencies occur and practical solutions are needed, a service center engineer is invaluable in developing and guiding the pump repair plan. When a plant is down and the pump needs immediate attention, this crucial part of the process may be overlooked or eliminated.

This case history illustrates what can happen when a low cost repair leads to catastrophic failure and the importance of experienced engineering support from the service center was to returning a plant to service.

 

Circulating Water Pump Fails

Prior to the high demand summer season, a Midwest plant’s circulating water pump (a 54-in mixed flow pump) failed. When the vertical pump was pulled, it was discovered that both the impeller and suction bell required complete replacement. After checking with the OEM, it was determined that replacing the components would take 8 months. With this pump out of service, the plant was in danger of being derated during the high demand summer season. The pump had been repaired one year earlier, but was no longer under warranty.

At this point, the plant asked a pump service center experienced in engineered pump repairs and upgrades to evaluate the pump and offer a plan for bringing the plant online and running at full rating. The service center’s engineering and operations team evaluated the hydraulic, mechanical and logistical data and developed a plan to meet the plant’s critical requirements and need for a quick turnaround.

 

 

Broken Suction Bell

 

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Big Savings for Small Pumps

Author:

Alex Manchenkov, Hugh Sosbee and Jim Byrom Sr., Evans Hydro Inc., and Valero-Wilmington Refinery

Publisher:

Pumps & Systems

Date Published:

October, 2008

 

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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Rerating a Pump for a New Service

Author:

James A. Shaffer, HydroTex Dynamics, Inc.

Publisher:

Pumps & Systems

Date Published:

June, 2008

 

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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