Double Suction High Capacity Pump

The Double Suction High Capacity Pump represents the ultimate in high flow pumping technology. Double suction impeller pumps are the preferred choice for applications requiring flow rates above 2,000 cubic meters per hour, including municipal water supply, power plant cooling water, large-scale irrigation, and industrial process water. Unlike single suction pumps, which experience significant axial thrust that must be absorbed by thrust bearings, the double suction impeller is hydraulically balanced. Liquid enters the impeller from both sides simultaneously, creating equal and opposite axial forces that cancel each other. This fundamental design advantage results in longer bearing life, reduced vibration, higher efficiency, and smoother operation at high flow rates.

The double suction impeller is the heart of this pump. The impeller has two suction faces, with vanes arranged symmetrically around the centerline. Liquid enters from both sides through two separate suction passages in the casing. The hydraulic forces on each side are equal and opposite, resulting in zero net axial thrust on the shaft and bearings. This eliminates the need for heavy-duty thrust bearings and balance devices. The impeller is of the enclosed type, with shrouds on both sides to contain the vanes. The shrouds are precision machined to close tolerance with the casing wear rings to minimize internal recirculation and maximize efficiency.

The pump casing is of the axially split (horizontal split) design. The casing is split along the horizontal centerline into an upper half and a lower half. The lower half contains the suction and discharge flanges and supports the bearing housings. The upper half is removable, allowing access to the impeller, wear rings, and shaft for inspection and maintenance without disturbing the suction or discharge piping. This feature is critical for large high capacity pumps, where disconnecting large diameter piping would be time consuming and expensive. Maintenance that would take days with other pump types can be completed in hours with the split-case design.

The suction and discharge flanges are located on the lower half of the casing. The suction flanges are on both sides of the pump (dual suction), with the two suction passages merging into the double suction impeller. The discharge flange is located at the top of the casing or on the side depending on configuration. The flange orientation can be customized to suit the installation requirements. Flanges are available in ANSI, DIN, JIS, or GB standards.

The bearing system is designed for long life with minimal maintenance. Two independent bearing housings are located on each side of the pump. Each bearing housing contains a radial bearing (cylindrical roller or deep groove ball) that supports the shaft and impeller weight. Because the double suction impeller produces no axial thrust, no thrust bearings are required. This simplifies the bearing arrangement and extends bearing life. Bearings are oil-lubricated with a constant level oiler that maintains the correct oil level automatically. Bearing housings are equipped with labyrinth seals to prevent oil leakage and contamination ingress. Bearing temperature monitoring (RTD sensors) is standard.

The shaft is supported between two bearings (between-bearing configuration), providing maximum rigidity and minimizing deflection. The shaft is manufactured from high-strength stainless steel (SS420 or SS630) to resist corrosion and fatigue. The shaft diameter is selected to maintain critical speed margins well above the operating speed. The impeller is mounted on the shaft using a key and locknut system, with the locknut secured against loosening by a locking device or thread locking compound.

Materials are selected for long service life in water and cooling applications. The standard casing material is cast iron (GG25) for clean water and cooling water service. For higher pressure applications, ductile iron (GGG40) provides higher strength. For corrosive water or seawater, stainless steel (SS304, SS316, or duplex) is specified. The impeller is cast iron, bronze, or stainless steel. Bronze impellers provide excellent corrosion resistance for cooling tower and seawater applications. Wear rings are replaceable and available in cast iron, bronze, or stainless steel.

The shaft sealing system uses mechanical seals or gland packing. For most water applications, single mechanical seals with silicon carbide faces and EPDM elastomers provide long service life. The seal chamber is generously sized to accommodate large mechanical seals with adequate cooling. For high temperature applications (above 80°C), we offer Plan 23 seal flush systems with a cooler. For applications where zero leakage is required, double mechanical seals with barrier fluid (API Plan 52 or 53) are available. Gland packing is offered as a low cost alternative for non-critical applications.

The driver is typically a high efficiency electric motor, mounted on a common baseplate with the pump. A flexible coupling connects the motor shaft to the pump shaft. The coupling is selected to accommodate misalignment and to protect the pump from excessive torque. For high power applications (above 300 kW), we offer high-voltage motors (3.3kV, 6.6kV, 10kV, or 11kV) with direct on-line or VFD starting. For variable flow applications, we offer VFD packages with inverter-duty motors.

Quality assurance includes 100 percent hydrostatic testing of all pressure-containing castings. Performance testing is performed to ISO 9906 Grade 2 standards. Each pump is dynamically balanced (impeller and shaft assembly) to ISO 1940 Grade G2.5. For critical applications, we provide witnessed factory acceptance testing.

In summary, the Double Suction High Capacity Pump delivers the highest flow rates, highest efficiency, and longest bearing life in a robust, maintainable package.