Horizontal split-case pumps transfer gas from storage wells to the pipeline.
By Bryan Orchard
The BB3 horizontally split-case API pump is used extensively by pipeline companies operating in the shale gas, liquefied-petroleum gas (LPG) and liquefied-natural gas (LNG) markets.
“BB3 pumps are used within terminals to transfer the gas into the pipelines from storage wells,” explained Richard Martinez, managing director at Standard Alloys Inc., Port Arthur, TX. “These pipelines employ pump stations at various intervals along their length, and many of these pumps are coming to the end of their service lives. There is no desire to replace redundant pumps with new units. The last thing that they want to do is change drivers, put in new foundations, and change piping connections to accommodate new designs.”
The most cost-efficient solution is to use a bare-shaft pump that can be easily dropped into the existing infrastructure where operators know that the nozzles, casing feet, and shaft couplings will fit.
A SUCCESSFUL APPLICATION
Targa Resources Corp., Houston, is a provider of midstream services in North America. In 2015, Targa installed a BB3 pump for the specific duty of injecting ethane propane mix (EP) into storage wells at the plant’s salt dome. The double volute, eight-stage split-case centrifugal pump is fitted with 10.187-in. closed impellers and provides a flow of 1,200 gpm running at 4,000 rpm, with a suction pressure of 260 psig, and a total developed head of 3,800 ft. The pump can graduate from moving a product of specific gravity 0.38 all the way up to 0.50, which gives them the ability to move heavier end products. Installed on an existing product train, the pump has been built specifically for this application.
“We were given the flow parameters and head capacities. We went into our database to see what we had that was closest to the specification,” Martinez said. “We found a closely-matched pump and used this as a platform to custom build the flow and head required. We produced a special package that went beyond the generic specification typically found in API-610. It had to fit the same foundation as the original pump, so a custom base was designed to facilitate a perfect fit.”
Martinez said his company had already supplied similar pumps for transfer duties, but this one was specifically engineered for well injection.
Steve Ferguson, Targa’s rotating-maintenance supervisor emphasized the importance of extreme reliability for this application. Regular maintenance inspections are implemented by Ferguson’s reliability team. The new injection pump has replaced a standby pump that had reached the end of its service life. For reasons associated with the casing, it had to be condemned. “A problem with older pumps is that in the event of failure, weld repair from erosion will be required,” Ferguson said. “This is not possible because, over time, electrolysis leaches the carbon out of the material so the base metal will not accept the weld metal. Also, there is the problem of carbons leaching, which weakens the case. Pressure testing repairs cannot be performed. Therefore, replacement pumps are required.”
For years Standard Alloys’ core business was in manufacturing replacement pump parts. In 1992 this changed when the company made its first complete bare-shaft pump. Now they produce API qualified bare-shaft replacement pumps for brownfield and greenfield applications, exploiting opportunities where an existing pump may be obsolete or where material or engineering upgrades are needed.
“Our target is pump operators that may have seventh or eighth edition API pumps that need replacing with a direct ‘drop-in’ ,” Martinez said. “They don’t want to change the foundation due to the casing foot location or modify the suction and discharge nozzles. They also don’t want to relocate the drive unit. RP
Bryan Orchard is an independent journalist reporting for KSB Group.