In many process engineering applications, pump systems form the backbone of production (Figure 1) and greatly impact the economic efficiency of the entire system. Pumps consume a large amount of the electrical energy used in industry. Depending on the scope of analysis, the potential savings on energy in current industrial systems range between 30% and 40%.
In concrete terms, the German Energy Agency (dena) has calculated that pump system operators in Germany could save as much as 14 billion kWh per year. That would translate into annual savings of 1.12 billion Euros for the operators themselves and a drop of 7.7 million tonnes in CO2 emissions. Plant operators are now much more interested in the power consumption of their systems than they were only a few years ago.
Figure 1. It is particularly in existing plants that much potential for reducing pump operating costs can still be identified.
Wasted energy
There are many reasons why much too much energy is still being wasted in connection with pump operation. In refineries and process engineering plants, maximum priority is attached to productivity and fast restarting following repairs. Frequently, when piping systems have been modified for production-related reasons, the installed pump sizes are not subsequently adjusted to match.
The reasons why far too much energy than necessary is sometimes used has to do with choosing the wrong valves or valves that are not dimensioned correctly, installing inadequate pipe radii or undersized pipe cross-sections. Aggravating the situation is the fact that many pumps are selected with a 10 or 15% ‘safety margin’ – just to be sure. Another widespread problem is that pumps are often left to run far off of their originally envisaged operating point.
It is relatively easy to select a hydraulically optimal pump for new installations. As long as the requirements to be met by the pump are known, a very energyefficient pump set can be chosen with great accuracy by way of pump selection programs like those that most manufacturers have on hand for their customers. It is, of course, essential that a large number of closely spaced pump sizes be available to the user, and that the impeller diameters be trimmed to match the required operating point. Safety margins should be avoided. Even efficient pumps cannot run economically if they are used in the wrong operating mode.
First step
The first step in identifying energy saving potential is to ascertain the pump's present operating point and mode of operation. In the past, this was almost impossible without using additional measuring equipment. Pump manufacturer KSB therefore developed the Sonolyzer app to help plant operators out. This is a free app for smart phones or tablets that can analyse potential savings in a fast and simple measurement process that does not require any additional instrumentation and can even be used in potentially explosive atmos-pheres if the smart phone or tablet PC has appropriate protection.
The advantage of this system is that it can determine within 20 seconds whether or not a pump is working under part load. Use of the app is not restricted to the manufacturer's products – it works just as well on products of other makes. Drawing on the decades-long experience of the pump manufacturer, this app is designed to save valuable time by calculating operating points in a very simple process. Its operation is intuitive. After downloading the app, the user selects the relevant pump type and enters the name plate data of the pump and connected asynchronous motor. It is also possible to enter a designation for the measurement and save it with a photograph of the pump in the data record.
The measurement is then started and the smart phone is held next to the fan hood of the motor for 20 seconds (Figure 2). The motor fan's noise is recorded and the noise spectrum is transferred to the KSB Cloud for analysis via a secure connection. Based on the maximum amplitude of the recorded spectrum, the algorithm now calculates the number of blades of the fan impeller and the blade passing frequency and derives from this information the shaft speed of the machine.
Using the nominal data of the asynchronous motor entered by the user and a slip model, the algorithm then calculates the input power on the basis of the shaft speed. It can estimate the pump flow rate from the input power calculation. By correlating the performance data entered by the user with the hydraulic systems database developed by the manufacturer, the app can conclude whether the pump is operating at part load. The applied algorithm is patented and has already been in use for a number of years in thousands of practical applications as part of the PumpMeter product.
The analysis result is displayed on the mobile phone or tablet (Figure 3). If it is established that the pump is working under part load, then there is potential for energy efficiency optimisation. Using this app, it is possible to identify pumps with optimisation potential simply and efficiently during a site survey or plant walkdown by service staff. Identification of potential on the basis of the pump's age, an inconvenient paper-based process that does not provide meaningful results, is no longer necessary, while checks using the new app can be included in the daily work schedule.
Figure 3. Screenshot of the KSB Sonolyzer measuring a pump operating under part load.
Risk elimination
Furthermore, by repeating the analysis of a pump at different times, it is possible to eliminate the risk that the operating conditions prevailing during one particular measurement have falsified results. Operators or service staff are normally so familiar with their plant that they notice any significant deviations from normal operation and know when further investigation of a pump unit is called for. But it is at moments like these that they can seek support from the pump manufacturer's experts. Users can make contact with KSB using the app. An e-mail containing the analysis results is sent from the app to an appropriately qualified employee of the pump manufacturer closest to the user's location.
Identification of potential, however, is only the first step in analysing pumps for the purpose of optimising energy efficiency and reducing operating costs. It is not only important to assess the individual machine, but to evaluate the system as a whole. In the case of pumps, this means that valves and piping must also be taken into account. Although an assessment of individual components can identify potential savings of up to 10%, an evaluation of the whole system can achieve savings of up to 60%. While identification of potential savings is important, it is also vital to focus on the cost effectiveness of optimisation measures.
Finding ways to reduce the operating costs of pumps and other rotating equipment has been made simple with KSB Sonolyzer. For the actual implementation of energy saving measures, the Frankenthal experts are offering the FluidFuture energy efficiency concept, a structured system of suitable products, equipment and services.
The following options are available, depending on the load profile:
- Operate based on actual demand (variable speed operation)
- Reduce the impeller diameter
- Use smaller pump sizes
- Install high-efficiency motors
- Optimise piping
FluidFuture allows operators and service staff to access the wealth of experience garnered by the pump manufacturer over many decades. Modern centrifugal pumps have already achieved a level of efficiency that could hardly be further improved. When they appear to be consuming more energy than necessary, it is very probably due to the fact that people pay too little attention to pumps that just keep running. No pump can operate more economically than its surrounding system allows.
