Building Better Pumping Systems: Optimizing New Designs
By Hydraulic Institute Members and Pump Systems Matter
Fluid Power design hydraulics maintenanceAn opportune time to carefully analyze system requirements and reduce unnecessary margins is during the design stage.
Margin in System Design
All pump systems contain various levels of overdesign known as design margin. This can cover design imperfections or errors, pump and system degradation, and evolving system requirements.
When optimizing a new system design, a common concern is that the optimization process will eliminate the design margin. Without margin, various events could render the pump system incapable of achieving contract requirements. Design margin is introduced through intentional and unintentional sources. Intentional margin is built into design requirements, while unintentional margin is introduced due to imperfections and unwarranted assumptions. Unintentional margin is unquantifiable and normally conservative, the role of optimization should be to eliminate all unintentional margins to produce systems that meet initial and anticipated requirements.
How Pumping Systems Change Over Time
Initial start-up conditions may change due to passive or active influences. Table 1 lists some of the passive and active influences that may produce serious consequences. A change in the pumping system can affect the pump’s flow, efficiency, power consumption, maintenance needs and its service life. It may be advantageous to design flexible and resilient systems that may adapt to conditions varying over time.
Table 1
| Passive Influences | Active Influences |
|---|---|
| • Change in pipe diameter due to corrosion, abrasion or sclerosis • Change in pipe wall roughness due to corrosion, abrasion or sclerosis, which will affect resistance to flow • Change in capacity requirements due to groundwater infiltration into the force main • Change in static head due to varying liquid levels in the intake source or recipient tank • Wearing of piping components, such as valves • Wearing of pump components, such as impellers and wear rings |
• Change in control scheme • Change in piping configuration |
As the system ages or operational requirements change, the head generated by the pump may need to increase. If the pump impeller was selected with some trim, the pump head may be increased by substituting an impeller with larger trim. This will increase the power requirements of the pump, so consider the cost effectiveness of specifying an oversized driver for initial duty.
