Pumps are used for transporting and pumping liquids in the widest range of applications. Since many pump motors - irrespective of the industry - are started by contactor/circuit breaker combinations, compact motor starters or soft starters, Siemens, as one of the world’s leading manufacturers of industrial controls, has set itself the task in recent years to use these products to develop solutions to the specific challenges encountered in pump applications. To this end, the company collaborates with experts from research and practice.
Dry running is a typical problem encountered in pump operation in all industries: If insufficient liquid is transported, the pump may be irreparably damaged. Therefore the liquid level is usually monitored by sensors. Alternatively, the condition of the pump can be assessed by measuring the active power and detecting dry running at an early stage. For some time now, Siemens has been offering for this purpose special current and voltage measuring modules of the Simocode pro motor management for measuring and reporting the corresponding values, and switching the pump off automatically when necessary. The advantage: Sensors and their regular, timeconsuming maintenance are eliminated.
More safety in acordance with SIL requirements
Centrifugal pumps running dry is especially critical in hazardous areas if, for example, overheating of the pump could ignite highly flammable materials. However, products have to be certified for use in such areas. Siemens therefore had the principles and practical applicability of this technology investigated in a research project held in collaboration with the Physikalisch-Technische Bundesanstalt (National Metrology Institute of Germany) so that the Simocode pro motor management system could be certified as an ignition source monitoring device corresponding to a type b1 ignition protection system according to ATEX and IEC Ex. Thanks to this certification, it is now possible to detect centrifugal pumps that are running dry and stop them safely in accordance with SIL1 safety requirements (IEC 61508).
Blocked pumps are another widespread problem, encountered most frequently in waste water disposal. Such blockages are caused by wet wipes and other sanitary articles not suitable for disposal in waste water. In most case, clogging is caused by waste materials clumping together so that they collect even more readily in the pump. The resulting stoppages of operation may not only damage the system, but also incur considerable maintenance costs. Here again, Siemens has been able to find an innovative solution with the Simocode pro motor management system as a result of cooperation with the Water Innovation Network, founded by Anglian Water, a British water utility, and the Allia Future Business Center.
Simocode pro monitors current levels and the power factor on the motor to determine the condition of the pump. Apart from the Simocode basic device, this monitoring only requires an additional current/voltage measuring module. If a predefined threshold is exceeded, Simocode pro automatically reverses the direction of rotation of the pump with the aid of a configurable internal logic. The pump alternates between forward and backward operation to dislodge contamination from the impeller. The sharp edges of the impellers cut through pieces of the clogging. The procedure is repeated until the pump is once again running within its rated load range. The advantage: Cleaning takes place completely automatically, so it does not require any software instruction or further training of employees.
Soft start and stop functionality
With the Sirius 3RW55 soft starter, Siemens has been offering this pump cleaning function for several months, as well as in another product group. During the cleaning operation, the pump alternates between forward and reverse operation at rated speed or at reduced speed but with maximum possible torque. The 3RW55 provides not only intelligent motor monitoring, but also the option of starting the motor softly, that is with a slowly increasing speed. Starting the motor softly reduces the peaks in the power supply network and also places considerably less stress on the mechanical mechanisms.
The Sirius 3RW55 soft starter also has another function that prevents the very common phenomenon of water hammer. Stopping pumps that convey large volumes of water or other liquids is a difficult challenge. The pump stops immediately, so the water in the pipes also stops immediately, but the kinetic energy still present in the water is transmitted to the pipes, couplings, valves, and seals. This results in damage, and may even cause a breakage in the pipe system.
Therefore, pumps should always stop as softly as possible. The Soft Torque pump run-down function of the Sirius 3RW5 soft starter not only reduces torque peaks shortly before the rated speed is reached, but also supports the pump run-down and stops the motor gently. This avoids water hammer and the associated mechanical stresses on the system. That means lower maintenance costs and a longer plant life.
All in all, Siemens offers not only specific solutions for pump applications, but also increasingly equips its products for starting motors with functions such as recording measured values, communication links and integrated safety, which render additional hardware superfluous and permit condition monitoring and predictive maintenance. Innovative solutions will continue to be produced in future by collaborating with experts from research and practice.
