Pump trend report

Tuesday, 07 April, 2009

Practical experience has shown that there is still considerable potential for reducing the operating costs of existing systems in primary industry. Particularly on continuous-flow machines such as pumps that operate at partial load, changing to high-efficiency motors and variable-speed drives can reduce energy consumption by as much as 50%. The payback period for a frequency converter can be as short as a few months.

In response to rapidly increasing energy costs, more and more electronic components and sensors are being installed on rotating equipment (pumps, compressors, fans, etc). Pumps, in particular, have evolved into mechatronic systems. Control software which is stored on the chips can be modified as needed to meet the specific needs of the customer or application.

For example, frequency converters are normally used to reduce pump speed so that flow or pressure matches actual demand, but the Danish pump manufacturer Grundfos uses them to increase pump speed as necessary. In supersynchronous mode under software control, the motor speeds up to an amazing 5800 min-1. At these speeds, pumps do not have to be very large to generate a lot of power (remember the affinity law: doubling the speed increases the pressure by a factor of four) and equipment manufacturers can save space.

The German pump manufacturer Wilo SE is taking a new approach, and the company has announced a paradigm change in heating systems. The central pump will be eliminated, and a mini pump will be installed on each radiator instead. Distributed mini pumps could be a viable alternative in other applications as well. The German KSB AG has added mini pumps to its portfolio in response to demand in the microprocessor industry for centrifugal process pumps with a flow volume of only a few millilitres per hour.

At the other end of the scale, customers are continually pushing the capacity envelope in power generation applications and in production of basic chemicals at world-scale plants. The Sulzer AG (Switzerland) makes feedwater pumps with drives rated at an incredible 50 MW.

Functionality and availability are the critical factors

Regardless of whether the pumps are in the mini or maxi range, users are mainly interested in three things: rotating equipment has to offer the right functionality for the application, it has to deliver high availability and the costs must be as low as possible.

It is up to the individual manufacturer to figure out how to provide all three of these deliverables at the same time. Exotic solutions are probably not the best choice. Users in the chemical industry and particularly in the pharmaceutical industry tend to make conservative choices when they select equipment that plays a central role in the process such as pumps and compressors. A proven track record is more assuring than abstract claims.

How can manufacturers improve equipment availability?

Besides optimising materials and introducing new material combinations, producers continue to improve production quality and develop increasingly sophisticated early failure detection systems because in the process industry it is absolutely essential that the pumps and compressors keep running. Before looking at anything else, process engineers want to be sure that the equipment delivers high availability. However, because users and maintenance teams are aware that moving mechanical parts are subject to wear (even if high-grade, durable parts are designed into the equipment), they rely on early failure detection features to flag problems before availability starts to degrade.

The solution is to detect degradation before major problems occur, and the correct interpretation of sensor signals plays a major role in the detection process.

Which signals provide an early indication of trouble?

Researchers in the industrial and academic communities are investing a lot of effort in the development of intelligent pump diagnostic systems. The fact that companies from outside the industry offer special diagnostic systems for pumps is an indication of the perceived market potential. The systems use data from vibration, pressure, temperature or motor current sensors to assess process conditions and the current state of the pump.

However, none of the diagnostics systems which are currently available on the market is capable of predicting the remaining life of critical components. Existing predictive maintenance systems are simply unable to provide this information.

The ReMain project (Reliability Centred Maintenance) was launched to investigate techniques for predicting the remaining life of a pump. A special sensor set will be installed by eight partners from industry and research and 14 further participating companies on 100 pumps which are used in production at Evonik Stockhausen to collect data which will then be summarised and analysed.

The success of the project depends on having a good set of data for the models. The predictive failure model will be derived from a physical knowledge base, and empirical information from field trials will then be used to optimise the model in an iterative process. Accelerated time tests will be conducted on test beds to simulate individual failure mechanisms and identify characteristic wear patterns. Mutual interactions will be reflected in the final model when the two models are combined. The next step will be to make the technique available for online use and validate the model in practical application. At the same time, the new predictive tool is integrated into the maintenance process and cost effectiveness can be assessed.

The approach has enormous potential:

  • Elimination of redundant pumps in the chemical industry.
  • 25% reduction in failures. 
  • Avoidance of environmental damage caused by cleaning, disposal and contaminants that escape when faults occur.
  • Up to 50% annualised ROI.

An industrial energy-efficiency campaign by the German Energy Agency (dena) and the Pumps + Systems Association of VDMA (German Engineering Federation) offers on-site analysis services to companies that are willing to accept external advice. More than 50 companies, including producers in the chemical and pharmaceutical industry, have improved the energy efficiency of their pump systems based on in-depth advice provided by expert consultants, and in some cases the results have been truly surprising.

Annualised ROI (return on investment) on energy-efficiency pump systems can be as high as 50%. Spectacular results like this have been achieved during the course of the EnergyEfficiency initiative which is borne by the European Companies E.ON Energie AG, EnBW AG, RWE Energy AG and Vattenfall Europe AG.

To cite one example from consultancy projects which have already been completed, an analysis was carried out at Unilever’s plant in Mannheim, Germany, which produces soap products. Most of the approximately 200 pumps in the plant are used as process and circulation pumps. The energy consultants focused on optimisation of the process water and circulation pumps and the recooling systems.

The results showed that flow control on all of the pumps in the recooling system was provided by butterfly valves on the delivery side. Due to the characteristic curve of the pumps, the pumps were operating at low efficiency, and they were consuming a lot of energy. The pumps were also operating at or above their rated capacity, which had a negative impact on service life.

The consultants identified an opportunity to reduce energy consumption by 925,000 kWh (a 37% reduction compared to actual consumption prior to the study), which equates to annual savings of 74,000 euros. To achieve the savings, Unilever has to invest 295,000 euros. The payback period is 4 years (annualised ROI: 21.4 %).

Unilever is another example which shows that conventional flow control technology such as butterfly values or bypass lines is still used on many existing systems, and energy losses can be very high. It should come as no surprise that a pump system with throttle control runs at 90% of its electrical power rating to produce 60% of the rated flow. At the same flow rate, electricity consumption on a pump with speed control is reduced to less than 30% of the power rating to maintain the same flow rate (60% of rated capacity).

Energy-efficient control also increases pump life. Lower speeds at partial load reduce wear on mechanical parts such as shafts, bearings and seals. In addition, starting and stopping is less abrupt on systems with frequency converters. This places less stress on the entire drive train and reduces the mechanical load on the pump system. High-wear parts have to be replaced less frequently on pump systems that have been optimised to reduce energy consumption, and maintenance intervals are longer. The bottom line is that energy costs are lower, and users also save money on maintenance.

The findings of the consultants show that companies of any size in any industry have opportunities to increase energy efficiency. Because energy prices continue to increase, installation of state-of-the-art motors and electronic drive controls for the entire range of rotating equipment (pumps, compressors, fans, etc) is an investment that produces an attractive return. Users are keenly interested in early fault detection systems and predictive systems which provide information on remaining life.


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