Sometimes called “barrel pumps” because of the cylindrical shape of their outer casing, BB5 pumps are high-pressure pumps with three or more impeller stages. As injection pumps they pump pressurized fluid into the reservoir rock to pressurize the oil and extract it. As charge pumps in oil refineries they put fluids under high pressure to transfer them to various reaction columns. To create this high pressure, BB5 pumps have impellers in multiple stages, and specifications may call for high-speed rotation in the range of 4,000 – 7,000 rpm. They are literally the pumping “hearts” —and the most important pumps—in oil extraction and refining operations. Advanced technology allows them to operate continuously at extreme temperatures (approximate maximum of 400℃) and pressures (approximate maximum of 30 MPa) without leaking. The safety- and reliability-enhancing structural characteristics of BB5 pumps are as follows:

• Casing (high-strength, double-casing structure)
  The inner casing efficiently leads the fluid propelled by one impeller stage onto the next, while the outer casing has the design and the strength required to withstand extremely high pressures. The radially split structure offers excellent seal performance to hold in high-temperature, high-pressure fluids. Non-asbestos-controlled compression gaskets lie between the partitions of the pump, which are metal-to-metal fitted, a structure that makes the pump easier to maintain while providing a complete seal. Centerline support, in which the support elements are attached to the baseplate at the same height as that of the rotor shaft centerline, prevents driver misalignment caused by thermal expansion in high-temperature applications. In addition, the casings are made with a high-quality forging process that gives them greater reliability than cast casings.
• Rotor (high-efficiency, low-vibration "heart")
  The heart of any rotating machine, the rotor of a process pump in particular features advanced technology to support overall efficiency and reliability. The impellers are designed using the latest fluid dynamics analysis software to optimize efficiency and performance curve characteristics. Positioned beyond the final impeller stage, a balance drum reduces the impeller-produced thrust force on the shaft to an optimum level and reduces bearing load. The inner casing with diffusers balances out the radial forces generated during partial load operation. The clearance between the inner casing and the rotating parts (impellers and balance drum) is optimized to lessen internal leakage and raise efficiency, at the same time minimizing shaft misalignment and vibration for stable, continuous operation. Also, to minimize shaft vibration as well as rotary imbalance, the impellers are fixed to the shaft with interference fit, split rings, and double keys. The precision-assembled rotors conform to ISO G2.5/G1.0 and are subjected to thorough dynamic balance testing. This combination of advanced design, technologies, and structural characteristics allows for both high efficiency and fulfillment of the stringent API standard for permissible vibration (30 µm ® 6,000 rpm).
• Shaft seals and seal chamber (high-environmental performance liquid seal system)
  A mechanical seal serves as a liquid seal system to prevent fluid from leaking from the end face. Double seals, which offer enhanced environmental and safety performance, are increasingly popular. An optimally designed auxiliary line system maintains a low seal chamber pressure to prevent fluid vaporization and maximize shaft seal performance.
• Bearings and bearing housings (low vibration and long life)
  The configuration and lubrication system of the bearings, which support the rotor at both ends of the pump, have a great influence on bearing life. Three configurations are offered to meet various service conditions while complying with API standards:
  ･Ball radial and angular contact ball thrust with flooded lubrication
  ･Sleeve radial and angular contact ball thrust with oil ring lubrication
  ･Sleeve radial and tilting pad thrust with pressurized lubrication
  Connecting the bearing housing and the casing, full circular brackets enhance bearing system rigidity while minimizing vibration.

VS6 pumps are vertically suspended with the rotor perpendicular to the installation surface. The pump head (comprising the inlet and outlet nozzles, the shaft seal, and the bearings) is above ground while the impellers and the surrounding casing are below ground in a pit. The main use of the VS6 is the transport of low-temperature fluids (e.g., -104 ℃ ethylene) and highly volatile and flammable fluids in oil refining, petrochemical, and gas processing applications. To create high fluid pressures, VS6 pumps may have up to twenty impeller stages. VS6 pumps also feature advanced technologies to prevent leaks of hazardous materials while maintaining safe, continuous operation. VS6 pumps conform to API standards and, in Japan, depending on the fluid being handled, may also need to conform with the laws pertaining to the handling of high-pressure gasses. The safety- and reliability-enhancing structural characteristics of VS6 pumps are as follows:

• Casing
  Like BB5 pumps, VS6 pumps have an inner and outer casing. To enhance maintainability and provide a dependable liquid seal for low temperature fluids and highly volatile and flammable fluids, they have a radially split structure with metal-to-metal fitted partitions and controlled-compression gaskets.
• Rotor
  The rotor of a VS6 pump also features advanced technology to support pump efficiency and reliability. As in the BB5 pump, the impellers are designed to optimize efficiency and performance curve characteristics. Balance holes in the impellers balance the pressure in front of and behind the impellers to reduce the thrust force on the shaft to an optimum level. One special element of a vertically suspended pump is its long shaft (up to 10 m). The extra length supports numerous impeller stages for high-pressure applications. It also allows intake impellers to be positioned lower to cover for a deficiency in net positive suction head (NPSH), which may be caused by the characteristics of the fluids being handled, and thereby prevent cavitation. Pumps with long shafts, however, require special technologies to prevent shaft misalignment and vibration: the inner casing with diffusers balances out the radial forces generated during partial load operation; the clearance between the inner casing and the rotating parts (impellers and shaft) is optimized to lessen internal leakage and raise efficiency, at the same time minimizing shaft misalignment and vibration for stable continuous operation; and advanced machining technologies are employed to produce an extremely high-precision shaft.
• Shaft seals and seal chamber (high-environmental performance liquid seal system)
  As is true of BB5 pumps, an increasing number of VS6 pumps have a double mechanical seal as their liquid seal system. In handling low-temperature fluids and high-volatility fluids, it is crucial to design the seal system for optimal seal chamber pressure and thus maximum shaft seal performance. For enhanced maintainability, safety, and environmental performance, a gas seal on the end face side of the double seal is an increasingly popular design element.
• Bearings and bearing housings
  To im handle peller-generated shaft thrust and support shaft deadweight, angular contact thrust ball bearings offer ample rated load-bearing capacity. A constant level oiler maintains consistency in the flooded lubrication system.

In recent years, interest in combating global warming by reducing carbon dioxide emissions and conserving energy has heightened. The following are ways in which pumps are helping to accomplish these goals.

In oil refineries and petrochemical plants, after causing raw materials to react or decompose in high-pressure tanks, it is common to return the products of these processes to lower-pressure tanks. When transferring fluids to a high-pressure tank, pumps add energy, yet that same energy is wasted when a pressure reducing valve or other restriction mechanism is used afterward. In contrast, hydraulic power recovery turbines (HPRTs) can employ that same pressure differential to turn a rotor and effectively recover energy.

• Structure of HPRTs
  The only difference between an HPRT and a pump is the direction of fluid flow; structurally, they are identical. In the case of an HPRT, high-pressure fluid goes in the outlet nozzle, pushing the impellers in the opposite direction to recover power (Chart 5). For this reason, most process pumps may be used without alteration as HPRTs. Since, however, the direction of rotation is opposite, care must be taken so that screws and other parts do not loosen over time.

• Applications for HPRTs
  Chart 6 illustrates the machines and fluid flow of a gas reaction process in which an HPRT provides power assist to the pump drive motor. In this application, there is no need to fit the HPRT with a speed governing device; however, a one-way clutch can prevent the HPRT from serving as a brake during startup or similar operational circumstances. When the cup rings or clutch of an HPRT are compromised, the HPRT becomes load-free, and revolutions greatly increase; to protect the HPRT in this instance, an overspeed trip mechanism is needed to detect excessive rotations and activate an inlet shutoff valve.
  Other applications include connecting the HPRT to the main pump as the primary source of power. In this instance, it is necessary to regulate the revolution of the HPRT with a speed governor that detects rpm and controls an inlet valve.

There are many other environments outside of oil refining and petrochemical plants in which HPRTs can help conserve energy and natural resources. In fact, any time there is fluid in which potential energy is stored, HPRTs should be considered as an energy recovery option.

Material used with permission from article by Kazuhiro Yukinaga (Shin Nippon Machinery Co., Ltd.), Pump Special Edition, Nikkan Kogyo Shimbun, February 5, 2008.