Combined Cycle Industry Pump Repair

  • Case Study Summaries
  • KSB Ring Section Pump
  • IDP Ring Section Pump
  • Sulzer Ring Section Pump

Being Independent Makes All the Difference

Combined cycle power plants are the “new kids on the block” of the power generation industry. Designed with engineering technology that combines both gas and steam turbines, combined cycle power plants can produce up to 50 percent more electricity with the same fuel usage as simple-cycle power plants.

As electricity demand changed and combined cycle plants began replacing conventional thermal power plants, the type of pumps utilized has changed as well. Thermal power plants use robust, long lasting, reliable barrel pumps. For example, boiler feed pumps in conventional thermal power plants are designed and built with the “spare no expense” mindset. These pumps operate for long uninterrupted periods of time and plants are generally fitted with two 100% or three 50% installed pumps per unit. Additionally, the pumps are designed with a double jacketed pressure containing device commonly referred to as a barrel (BB5).

Combined cycle plants have been designed and built with the “low bid process” mindset which drive new equipment to be built as inexpensively as possible. The demand for robust, yet expensive, barrel pumps dropped, and demand rose for less expensive and inherently less reliable segmental rings pumps (BB4) with only one 100% pump per unit installation.

Additionally, combined cycle plants are not designed for “base loading” where a plant is called to run for long uninterrupted periods of time. Instead, these plants are required to quickly react to the power grid demand which results in frequent starts and stops. Combined cycle plants often operate with less robust pumps in a more severe service resulting in lower MTBR, extremely high internal wear issues, high vibration issues, and a myriad of unexpected critical failures.

"Hydro faced a steep learning curve in dealing with different failure modes, attempting to understand the logic behind the OEM’s design, and eventually finding solutions to every single problem that cycling power plants and segmental ring pumps posed to us. Many hidden, inherited “built it” OEM problems were uncovered, redesigned and improved on, making Hydro a top tier rebuilder of BB4 pumps. Some of our repairs have survived more than 486 starts and stops in four years without any signs of performance deterioration."

–Alex Manchenkov, Operations Manager, Engineering, Evans Hydro

Click on any of the links to the left to learn more about our experience in improving the performance and reliability of your critical pumps.

Quality Repair & Testing Optimize Multistage Ring Section Pump

A power utility was experiencing problems with many of its multistage ring section (BB4) pumps in several of their plants.

In this case, Hydro was able to develop a long-term engineering solution for the unit in focus, and with the help of Hydro's independent test lab in Chicago, Illinois, they were able to provide performance testing and verification of the upgrades prior to installation.

Applying Barrel Pump Repair Fundamentals to Ring Section Pumps

A utility’s ring section pump was continually failing in service, resulting in high maintenance and operating costs to the plant.

A thorough inspection revealed contact between rotating and stationary components in a radial direction, contact between rotating and stationary components in an axial direction and axial misalignment between rotating and stationary components.

Hydro tightened the fit between the covers as well as the fit between the shaft and the impellers. This ensured concentric running clearances throughout the entire length of the pump. To eliminate the problem of contact between the rotating and stationary faces in the axial direction, Hydro manufactured a balancing disc with a tapered face. Hydro performed its rotor centralization process and modified the rotor to ensure perfect alignment between rotating and stationary hydraulic passageways.

While ring section pumps are much less costly to manufacture, they are not built to the same exacting standards as highenergy barrel pumps. As a result, their MTBR will be much shorter than for a barrel pump. However, by applying the technology and engineering standards which Hydro has developed through many years of experience with barrel pumps, we believe that we can improve the MTBR for many of the installed ring section pumps.

Engineered Rebuild and Upgrade for Ring Section Pumps

A 1000MW natural gas-fired combined cycle facility in California's central valley worked with Hydro to rebuild their 13-stage ring section pumps. The boiler feed pump exhibited problems after operating only 30 hours from the time it was installed by a previous repair provider.

Hydro's engineers discovered that the balance sleeve had a tapered fit onto the shaft, which was a design long abandoned by most major manufacturers due to inherent design problems and associated safety concerns. The plant accepted Hydro's proposal to upgrade the shaft journal and balance sleeve to a straight interference fit.

This engineered upgrade would benefit the combined cycle plant in the following ways:

  • Less expensive to manufacture and repair (shaft and sleeve)
  • Ease of removal and installation
  • Eliminate need for special tooling
  • Improved safety by reducing employee exposure to high pressures

Once the rebuild was complete, the pump was sent to Hydro's Test Lab in Chicago for an NPSH test and a performance test, both of which confirmed positive results.