Monitoring systems enhance availability
Pump monitoring: there are a number of aspects which need to be considered

Every plant engineering organization keeps a close watch on mission-critical pumps, but the cost and amount of effort needed to monitor what is going on can vary significantly. Regular checks supplemented by ongoing pressure
and temperature monitoring are usually sufficient. If personnel resources are limited, then more instrumentation has to be put in place. PROCESS takes a look at a few systems which react proactively and help prevent faults before they occur. These solutions largely eliminate the risk of unplanned stoppages.

Pump manufacturers realized the potential of monitoring and early fault detection systems years ago and have developed more or less elaborate monitoring solutions, but industrial users have been slow to take the new technology on board. In the view of many customers, the systems are too expensive, require too much effort and do not deliver sufficient payback on investment. The fact is that pump manufacturers have a hard time selling the systems, but time is actually on their side. A constant reduction in operating and repair staff is pushing customers in the direction of early fault detection solutions.

Efforts to eliminate redundant pumps (B pumps) wherever possible increase the attractiveness of high-performance monitoring equipment. Plant operators are also becoming increasingly aware of the fact that pumps can function as an indicator of unplanned system events. A damaged mechanical seal may, for example, be caused by the presence of gas in the process medium.
Documented cost savings
Basically, all suppliers of monitoring and early fault detection systems are faced with the same problem. They talk in qualitative terms about higher availability and shorter return on investment time, but they are unable to support these claims with hard quantitative data. KSB is now able to provide data on its PumpExpert system which was collected during a practical application. The list below contains a few facts about the system:
-Monitoring: PumpExpert detects, merges and consolidates signals (e.g. level measurement, motor temperature and bearing temperature). This data is then used to provide information about the pump, system and process status as well as any initial indication of a possible fault.
-Diagnostics: Preventive diagnostics provide early warning that a fault is likely to occur. Incoming data is constantly monitored for unexpected deviations and consolidated into a small set of relevant information.
-Recommended action: The system clearly indicates what action needs to be taken.
In the actual field application, two 30 kW CPK pumps with a volumetric rate of 40 l/s at full load operate for 22 hours a day in an acid treatment process at a medium-size chemical plant. The pumps supply media to various tanks with different lift, and this changes the load on the pumps. The pumps have operated at partial or excessive load in the past, and this has caused damage to the pumps. MTBF without a diagnostic system was 7,500 hours. PumpExpert quickly detects out of spec operating conditions and brings the pumps back within the specified operating range. MTBF increased by a factor of three, and repair costs were reduced by 72 percent. A comparison of the results is shown in Tables 1 and 2. The PumpExpert payback period is 2.5 years, and this is certainly a very satisfactory result from the customer’s point of view.
Other systems are available for monitoring centrifugal pumps. PumpSmart from ITT Industries essentially consists of a standard centrifugal pump and intelligent microprocessor-based monitoring and control system. The system runs dedicated software which continually monitors the operation of industrial pumps and adjusts the speed of the pump to match current demand in the system. It reacts to all deviations from the expected values and prevents the occurrence of “critical” situations. PumpSmart prevents:
-Cavitation and dry running. If
cavitation is detected, the controller reduces the speed until the pump operates without cavitation.
-Startup with a closed suction line (prevents dry running) and operation with a closed delivery line (prevents overheating and vaporization of the media).
-The system detects changes in the process or system; it operates automatically without manual intervention after startup and continually monitors energy consumption.
Hermetic also offers a monitoring system for its leak-proof pumps. The ARM 2000 axial monitor keeps an eye on the axial play of the shaft (the position of the rotor is monitored). Preventive maintenance can be scheduled if play starts to increase. LEDs can also be used to detect the direction of rotation of the rotor. The device also acts as an effective automatic early warning system for faults on canned motor pumps.
For positive displacement pumps
All of the systems discussed above are examples of solutions for centrifugal pumps. Lewa has developed an on-line monitoring system for process diaphragm pumps, which detects impending faults and provides a basis for condition-based maintenance. In contrast to off-line technology which has been used successfully for many years, on-line monitoring offers the advantage that data can be acquired and analysed on a continuous basis rather than sporadically. Information on the current status of the equipment is available at any time. The data is also available world-wide on the Internet/Intranet. Support teams based in the US for example can keep a watchful eye on pumps which are operating in Spain. If changes are detected, the data can be forwarded on the Internet for analysis by the pump manufacturer, and corrective action can then be initiated. The Lewa CMS Condition Monitoring System uses structure-borne noise to detect one percent leakage at the fluid valves to provide early warning of an impending failure. By analyzing structure-borne noise and pressure data, the manufacturer claims that 90 percent of potential faults can be detected.
Feluwa has developed the FVPMS valve performance monitoring system to detect wear at the delivery valves of hose diaphragm piston pumps. Detection is based on an analysis of structure-borne noise at the delivery valves, and leakage is detected when the reduction in delivery rate is less than ten percent. The manufacturer claims that this is a major advantage, because it is possible to identify the specific valve that is causing the problem. It is no longer necessary to prophylacticly replace all of the valves during a maintenance call. For example on a quad pump, the engineer would not have to disassemble all eight valves to find out which one is defective. FVPMS provides reliable information that indicates which of the eight valves is leaking and may have to be replaced.
The Bran + Luebbe CSM (Continuous Status Monitoring) system for oscillating positive-displacement pumps is based on the pV diagram, which is generated from data on the pressure in the hydraulic chamber and the position of the piston during a revolution of the pump crankshaft. The diagram can then be used to detect fault conditions in the pump, activation of the overflow valve or cavitation. The systems consists of one pressure transducer per pump head, a sensor on the drive unit to measure the angle of rotation, the CSM computer and a remote monitoring PC (where the analysis software is installed). The pump status (good, satisfactory or bad) can be sent directly to a higher-level controller.
Sensors: the eyes and ears of industrial pumps
Grundfos claims to have made a breakthrough in the development of very small industrial sensors. The silicon-based
3-in-1 sensors acquire flow rate, pressure or differential pressure data, and they also measure temperature. In addition to offering a very compact design, the new sensors are also extremely rugged and are suitable for use in harsh environments with hot fluids, vapor, acids and high pressures. The Direct Sensor is a MEMS component (micro electro-mechanical system). A special coating is applied to the wafer on the semiconductor chip to make it more rugged.
On conventional sensors, the sensing component is either encapsulated in metal or brought into contact with the medium without protection. The Direct Sensor is coated with a metallic glass-
like material which provides a minimum of ten years protection against aggressive media. The new material combination is only half as expensive as a metal-only coating. This solution has the following advantages:
-intensive contact with the medium increases measurement accuracy (and repeatability): pressure 62%, differential pressure 62%, flow rate 61.5% and temperature 61.5 °C
-direct contact with the medium reduces response time, and this speeds up the measurement process (<1s;
< 2.5 s for temperature sensing);
-the compact design of the sensor minimizes pressure loss.
In summary, there is a big difference between “nice to have” and “cannot do without”, as all pump manufacturers can probably confirm. There has to be a reasonable balance between the expense and effort involved in monitoring and the value of the pump or the quantifiable reduction in maintenance and repair costs.
The rule of thumb which says that a monitoring system should not cost more that ten percent of the pump price needs to be carefully reexamined. The crucial factor is how important pump availability is to the customer rather than what the monitoring system costs in relation to the value of the pump. Lower maintenance and repair cost is a tangible additional benefit to the customer. The desirability of keeping pumps running which have been adapted to a specific process and which cannot be replaced quickly is another important consideration. Monitoring will undoubtedly remain a hot topic in the industry.