14.01.2009 | Editor: Gerd Kielburger
How does a user know that degradation is taking place in a pump and that it will eventually lead to a major fault? Manufacturers are working hard to develop intelligent diagnostic systems. The goal is to develop simple solutions which are cost-effective even on small pumps. Suppliers are developing early fault detection strategies which are designed to enhance pump availability. PROCESS takes a look at the latest developments.
Pump manufacturers and users both know that out-of-spec operating conditions rather than natural wear and tear are often the root cause of equipment failure. The process industry is no exception, and according to insiders that is in fact the case more than 60% of the time. If this is true, the strategy of having a redundant B pump to ensure safety and availability becomes questionable, because what happens to the B pump if no one realizes that out-of-spec operation caused pump A to fail?
Monitoring and early fault detection are designed to address this issue. They alert the user if the pump is operating outside of the intended operating range and could sustain damage. Manufacturers and universities are driving development of intelligent diagnostic systems. The introduction of pump diagnostic systems by companies outside the industry shows the extent of the market potential. VCI (the German chemical industry association) estimates that redundant pump systems account for 9% of the total construction cost of a chemical plant. Elimination of redundant pumps would reduce annual investment costs by € 500 million in Germany alone.
A number of commercial solutions are already available. These systems process vibration, pressure, temperature or motor current signals and provide information about current process conditions and the state of the pump. A lack of standardization, for example connectivity to higher-level process control systems, discourages users from deploying these systems. The systems are also often perceived as being too expensive. However, a solution is in sight, namely VDMA’s (Verband Deutscher Maschinen- und Anlagenbau – German Engineering Federation) non-proprietary device profile for pumps. The pump profile gives users the information they need in a standardized function. The following article discusses developments which the editorial team has not addressed in the past.
Siemens has developed the PumpMon module for Simatic PCS 7 systems. PumpMon is a cost-effective monitoring solution for centrifugal pumps, which also identifies opportunities to save energy. The module provides early warning of pump degradation which is likely to lead to pump failure, and it also supports statistical analysis of long-term operational data (load spectrum) which can be used to optimize pump design. According to the supplier, the module is suitable for constant speed and variable speed electrically driven pumps.
The PumpMon module alerts the user about operation outside the nominal range and deviations from the expected operating curves, and data is provided at the module outputs for further processing. Siemens emphasizes that all of the data can be processed using standard Simatic PCS 7 tools (algorithms, curve generation, alarm history, etc.). Module functionality is restricted to diagnostics, and the module does not actively intervene in pump operation. As a result, it can be deployed (as a retrofit) without having any influence on the process. On request, the module outputs can be processed to support active intervention (e.g. speed reduction when the risk of cavitation exists).
At the upcoming Achema show, the pump producer KSB will be showcasing the E-Monitor which was developed by the company’s joint venture partner Nikkiso. The system, which was developed specifically for canned motors, monitors the condition of the axial and radial bearings and provides a continuous indication of the changing state of the sliding bearings. When used under proper operating conditions, the pumps can operate continuously for eight to ten years. The diagnostic unit gives users plenty of time to plan the next required maintenance activity. The supplier claims that users can avoid expensive downtime and costly damage to the cans and windings. The service team can perform maintenance on a predictive basis. Eight sensors in the motor’s stator chamber supply information to the monitoring unit. The sensors use the rotor’s magnetic field to sense the position of the rotor. The probes detect deviation from the rotor’s allowable position. After the data is digitally processed, the state of the pump bearing is indicated on a red-yellow-green display.
Pumps are often hidden from view. Grundfos has developed a pump-specific remote management system which is designed to provide monitoring functionality as well as secure Internet access to individual pumps and pump systems. The pumps, sensors and control systems are connected to a GPRS data logger. A PC, which is connected to the Internet, and a central server provide access to the data, giving the user a complete picture of the state of the installed pumps. The goal is to enable the user to communicate with the installed equipment and, for example, to save energy by optimizing speed control.
Remote management offers:
Modules which support remote management have to be installed on the pumps.
Pump manufacturers are exploiting current technology to develop service strategies which support mobile pump condition analysis. Operational availability is the goal, and timely service combined with sophisticated spare parts management is needed to ensure maximum operational availability. Lewa has come up with a practical solution. If remote diagnosis of a machine indicates that a part is very likely to fail in the near future, the service team contacts the customer and sends the spare part before the failure occurs. Special services, e.g. for machines which are installed on oil platforms, are included in the portfolio. As an alternative, the company offers to take responsibility for operating the system on the oil platform. For an annual flat fee, the supplier provides a pump solution and guarantees a defined availability level. There are also other options. KSB will set up and operate a service center at the customer site. If you need a water pump for a limited period of time, you can order a rental pump. Grundfos offers condition monitoring service as defined in VDI 3839. The results of vibration measurements are recorded, and the user receives a failure risk assessment for the pump system. Users have time to put together a corrective action plan and repair the equipment before a failure occurs. A similar approach is suitable for detecting out-of-spec operating conditions. Shock pulse measurement can provide timely, detailed information about rolling bearing damage and lubrication problems, which are the most common cause of machine failure and downtime.
Uhthoff & Zarniko is a service provider which specializes in pumps. The company is currently expanding its service, maintenance and diagnostics business. To improve the performance of existing systems and reduce CO2 emissions, the company is ramping up its DIN 31031 based weakness/fault diagnostic capabilities including vibration and shock pulse analysis and industrial thermography. The company also offers regeneration and retrofit services to improve pump performance (increased pump efficiency).
Conclusion: In order to detect mechanical wear, the primary objective of early fault detection is to detect and properly interpret indications of trouble at an early stage. Users benefit from increased availability of their production assets, longer equipment overhaul intervals, lower costs per repair call and (possibly) a reduction in reserve equipment (see box). What is missing now is a reliable prediction of the remaining life of critical parts. Users and manufacturers have joined forces in the Fraunhofer IML ReMain project to look for a solution.
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