Pump Monitoring How to Rectify Any Pump Inefficiency Before It Becomes a Problem

Author / Editor: Hans-Jürgen Bittermann / Dr. Jörg Kempf

How can operators ascertain whether a pump is deficient and a failure imminent? The traditional approach: Installing sensors, e.g. for structure-borne noise, pressure, temperature, flow, power consumption, bearing position, at critical points and continuously evaluating the collected data. For non-critical applications, there is an easier way: A drop in energy efficiency indicates a possible problem.

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How to reduce unexpected, costly downtime of pumps to an absolute minimum? Early fault detection systems promise a solution.
How to reduce unexpected, costly downtime of pumps to an absolute minimum? Early fault detection systems promise a solution.
(Picture: © robert6666 - Fotolia)

In the classic movie “Das Boot” there is a scene where the engineer listens in to the marine diesel with an ear trumpet — an early stethoscope — to recognize bearing damage at an early stage. KSB has now practically replaced the ear trumpet with a Smartphone app called “Sonolyzer”. It uses an algorithm to determine the efficiency of fixed speed pumps from the noise spectrum of an asynchronous motor. Specifically, the measurement result indicates whether the operating point lies inside or outside the part-load range.

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The technology behind this system is also used in “Pump Meter”, which replaces the “Pump Expert” system, which operators deemed too complex. With considerable success, as Dr. Thomas Paulus, project manager startup Industry 4.0 at KSB, reports: “An early fault detection system should cause no additional effort for operators and should already be integrated in the system — like our Pump Meter. With a few sensors, we determine the pump’s operating point and load profile. This information can be used to determine whether a pump is working well or not. Moreover, it also allows estimating the pump's expected availability. The system was very well received on the market. Approximately 35,000 pump meters have already been installed. With costs of around € 400 we are obviously within operators' accepted budget range.”

The CR monitor concept by Grundfos also uses relatively few sensors: Based on the state at new installation, the system monitors deviations from the pump system’s original efficiency. The CR monitor configures itself automatically, with a controller monitoring the data collected on site during the phase of learning. If measurements deviate from the reference value or exceeds the limits set by operators, the CR monitor emits an early warning message before potential faults occurs. These alerts can be sent via data bus to a control center, via text message or simply via signal light. When issuing a warning message, CR monitor does not transmit the complex raw data, but already provides a specific error analysis.

Ingo Landwehr from Grundfos outlines future developments: “The CR monitor will be continually expanded to be used by more pumps. To this end, we integrate the early fault detection functionality directly into our MGE motor. For example, we capture data concerning the bearing service life and sealing wear and inform operators which spare parts to order. We also expect operators in the process industry would want to feed the early fault detection system's data into their process control system for central analysis. After all, the approach is outlined in the Industry 4.0 concept.”

Low-cost Solution for Control system

Siemens sets an example with the monitoring module “Pump Mon” for the Simatic PCS7 process control system: Pump Mon is used to warn of damages to centrifugal pump under unfavorable operating conditions, for early detection of imminent pump failures and in the long term to optimize pump design by statistical analysis of the collected operating data of the load spectrum. The module can be used for electrically driven centrifugal pumps with constant and with variable speed.

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Dr. Thomas Müller-Heinzerling, Manager Chemical Industry Technology & Concepts, Siemens: “The basic idea behind developing our Pump Mon was to be able to offer a very low-cost diagnostic system for centrifugal pumps. To this end, known data from the process — power consumption, flow rate and pressure across the pump — is used in the process control system. By evaluating this information with a special software, the operator can determine whether their pump is healthy or not. If the relevant sensors are already installed in the process, the operator needs only to install the appropriate software. The licensing costs are well below € 200, a fraction of the costs of a typical hardware solution.”

Complex Monitoring of Positive Displacement Pumps

Even with a technically advanced positive displacement pump, like the Feluwa Multisafe, operators would regularly use additional, high-quality monitoring equipment, Daniel Hagnbuchner, Regional Sales Manager Africa, North and South America reports: “We offer various systems for early fault detection in our pump systems, for example an acoustic system indicating the wear and tear on conveying valves. Important is also a system signaling possible damage to the membrane before a conveyed medium can penetrate the pump’s hydraulic area. Because our pumps are usually operated in sensitive production areas, many customers use these fault detection systems — with an estimated more than 4000 installations by now.”

Generally, customers are operating processes that can’t be stopped without causing major problems, like carburetor feeding in coal gasification, or when a mining operator must convey solid slurry over several kilometers — if a pump stops unexpectedly, the entire pipeline is at risk. According to Hagnbuchner, an early fault detection would enable operators to do without the additional security of a redundant pump installation.

The most probable sources of interference in case of process diaphragm pumps are, depending on their application, fluid valves, vibrant seals (like piston seals) in the hydraulic part of the pump head and of course the membrane itself. Especially in cases of great capacity, high-pressure of more than 150 bar and high costs of plant downtimes, monitoring and early fault detection are particularly important for plant operators.

To achieve cost benefits in continuous operation, the relevant parameters must be collected and analyzed via the monitoring system, says Joachim Bund, Sales Manager Process Industry & Downstream at Lewa. The expert explains: “With our early fault detection system, we analyze essentially the parameters of structure-borne noise, pressure and temperature. There are two versions of the system available: A cost-effective traffic light system, Lewa CMS, for the operator to see at a glance the state of their pump. The real-time indication of the cause makes it easier for the operator to perform an analysis and take appropriate further measures. In a further expansion stage, the data is fed into an application-specific analysis system. Another option is that Lewa experts access the pump via data line and consultation with the customer.”

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While the relevant parameters are currently captured through mechanically installed sensors, Bund expects that in the future these sensors will already be integrated in the pump in the course of the implementation of Industry 4.0.

Leak-free, But Not Maintenance-free

If used properly, hermetic centrifugal pumps with split tube motor are hydro dynamically (radial) and hydraulically (axial) balanced and thus wear-free. However, axial thrust balancing is affected by the pump’s operation mode, conditions in the plant and various physical properties of the conveyed medium. A rotor-position monitoring is advised to ensure timely recognition of possible sources of faults.

Dr. Andreas Wolf describes the solution by Hermetic: “Our early fault detection system, MAP, inductively measures the axial displacement of the motor shaft.” If the system is calibrated for the relevant application, this gives the operator decisive parameters that allow avoiding serious damage to the pump in a timely manner. To put it another way: If our pump runs optimally at the operating point, there is zero wear and tear.” Operators in the chemical industry use this early fault detection system for about ten percent of installed Hermetic pumps. Usually, these are operators of critical production processes.

Of course, faults can’t be wholly ruled out even with magnetic drive pumps, as Carsten Holldack, Sales Director Pumps Europe at Richter Chemie-Technik explains: “Our early fault detection system is based on the contactless measurement of temperature, rotation speed and torque, integrated in the can — based on these data, we compute the performance and know the pump's position in its characteristic map. Today, we equip about five percent of our heavy duty pumps of the MNK series with such a system, and that percentage is rapidly increasing. While operators initially used the early fault detection system mainly with continuous processes, we now observe also its application in batch processes, because of the improved operating comfort. Acceptance in the market is continuously growing.”

Cost-effective Solution for Non-critical Processes

Sensors to monitor temperatures, pressures, structure-borne sound and the position of the shaft bearings: These offer the best possible protection against unplanned extraction downtimes for particularly expensive pumps, or in cases where the production process must not under any circumstances be interrupted.

For less critical operations, particularly centrifugal pump manufacturers have found a much cheaper way to monitor their pumps with the energy efficiency parameter. It is little surprising that industry 4.0 is already included in early fault detection concepts.

* The author works as freelance journalist for PROCESS.