Pumps are a low-cost product when it comes to energy use. Yet they account for 25% of all energy consumed by industrial motors, and for pump-intensive applications such as municipal water, wastewater, and process plants, this figure is much higher.
While pumps are highly efficient-up to 90% for individual units-many facilities don't approach the efficiency they could typically achieve. In fact, a Finnish study of 1,690 pumps in 20 process plants found that the average pump operated at less than 40% efficiency, with one in ten pumps operating at less than 10%.
So when it's time to replace a pump or to make significant cost cuts, optimizing your pumping system may be the way to go.
There are four steps you can take to optimize your pumping system.
First, reduce system head. Reducing system head and the energy required to achieve it is the first step. System head is the sum of (1) the pressure difference and height required for the pump to lift the fluid (static head), (2) the resistance created by the fluid as it moves through the pipe (friction head), and (3) the resistance created by any partially closed valves (control head).
Of the three, control head offers the best energy savings target. Most systems use valves because their pumps are oversized and require throttling to maintain proper flow. For most systems where control heads are oversized and there are ongoing maintenance issues, purchasing a smaller pump that better matches the flow requirements or switching to a variable speed pump allows the user to reduce the system control head and save electricity and maintenance costs.
Second, lower flow rates or operating hours. Some pumps are always running, regardless of whether the process requires all the flow. When the system is diverted, operators are paying for electricity they are not using effectively. There are two ways to solve this problem. One is to switch to a variable speed pump that can increase or decrease flow as needed. The second is to use a mixed group of pumps, some larger and some smaller, and turn them on and off in stages to meet demand. Both methods can reduce bypass flow, thereby saving energy.
Third, modify or replace equipment and controls. If the energy savings of lower heads and lower flow rates/operating hours seem attractive, owners should consider replacing equipment and control systems. If the system uses a large number of valves for throttling, replace them with smaller pumps that do not require throttling and have lower operating costs. For systems with multiple pumps and fluctuating demands, overhauls may include smaller or variable pumps and control logic that automatically turns the pumps on and off as needed.
Fourth, improve installation, maintenance and operating practices. Surprisingly, many maintenance problems start with installation. A cracked foundation or an improperly aligned pump can cause vibration and wear. Improperly configured suction piping can cause premature wear due to cavitation or hydraulic loads. Be sure to discuss installation support when purchasing a pump. For critical applications, it makes sense to pay a third-party expert for pump commissioning to ensure that the new pump operates as designed throughout its service life.
There are many ways to handle routine maintenance. For small, inexpensive pumps that don't meet critical needs, it may cost you to fail to operate. For most pumps, routine preventive maintenance makes sense. Tongda Pump Industry predictive maintenance - collecting data and using it to determine when operators need to intervene - is a powerful tool to keep pumps within specifications. This does not need to be complicated or expensive. By simply measuring factors such as pump pressure, energy consumption and vibration every month or quarter, operators can catch efficiency changes and plan remedial measures before problems that may cause failures occur.