Real-time monitoring of pump status Talking about the pump maintenance improvements

In the past few years, there has been a growing demand for reducing the cost of chemical engineering facilities, and at the same time , the higher requirements for pump safety standards , efficiency, reliability, availability and diagnostic tools have been raised . These standards are directly related to production loss after parking, parts replacement, maintenance and repair costs.

On-line condition monitoring methods allow for repair of damaged conditions, increased uptime, reduced downtime and consequential cost reductions.

For the piston pump (Figure 1), only the acoustic on-line monitoring system developed for the pump valve can be maintained for the condition of the equipment. Leakage from solid contaminants or seat wear in the seal area can affect the pump output and can even result in the shutdown of the entire unit. This article describes the acoustic online monitoring system can be found as soon as possible the valve leakage.

Diagnosis of acoustic emission analysis

Leakage usually occurs in turbulent flow areas, especially when cavitation occurs under high pressure conditions, where acoustic or ultrasonic waves are generated and sensors can be installed outside the valve for detection. Sound level is the unit of measure for leakage. The requirements of the diagnostic system are:

Observe all the pump discharge valves.
Find leak early.
Not subject to noise from normal operation of the pump.
Can be used over a wide range of pump stroke frequencies.
Can be used over a wide range of pressures.
Allow temporary leaks due to solids attached to the seal area for a short period of time.
easy installation.
Parameterization is simple.
Generate diagnostic information for the monitored acoustic emission sources.
In addition to monitoring the valve, the diaphragm and oil temperature can be monitored.

Sitrans DA, an on-line diagnostics system (jointly developed by Siemens and Feluwa, developed jointly by Siemens) fulfills these requirements. Acoustic emission sensors are mounted outside the valve and are highly sensitive to leak signals and insensitive to pump operating signals. Proper handling of the signal automatically adapts the measurement to changes in load conditions such as pressure or stroke. The operator only needs to set the alarm value.

Maintenance optimization

To date, leaks or malfunctions in the discharge valve can only be detected by a decrease in pump performance such as flow rate, and then the cause of the problem must be carefully examined. Sometimes all the valves need to be disassembled and reworked, and people have to suffer a reduction in pump efficiency.
Figure 2 is the hose diaphragm piston pump discharge valve life characteristics. In the third stage, wear and tear deteriorated the condition of the valve and required repair. Valve wear caused by leakage, and the leakage is growing. In the initial stage, only the seat was damaged, then the ball was damaged. The first valve wear to failure time depends on the actual valve load, working pressure and delivery fluid, perhaps within 5 to 60 days. The transition time from Phase II to Phase III is determined by the load on the valve and may accelerate leakage due to the temporary adhering of solids to the seal zone. It is therefore difficult to predict exactly when the valve will fail and if all valves in the piston pump are subject to the same wear.

Pump maintenance is based on the following three options:

Time-based program
Remedial maintenance program
Situation-based programs.

Depending on the device, which one is suitable for use and determines if a condition monitoring system is required.

Time-based maintenance does not require condition monitoring systems. The worn parts are replaced before they fail. Short maintenance intervals result in frequent maintenance and high maintenance costs, but avoid unplanned parking and allow for planned downtime of the unit.

Remedial maintenance allows the pump to run until it fails; its biggest drawback is unplanned parking maintenance.

Condition-based maintenance requires monitoring the operating conditions of the plant or operating unit, with the following advantages:

The device is found damaged before it fails,
Parking maintenance plan can be developed,
Costly damage has been repaired before it occurs,
Extend the service life of parts,
Automatic inspection of devices or units.

A field test of the Sitrans DA, an on-line diagnostics system started a year ago, proved that the system provides a reliable test of the condition of the discharge valve. Figure 3 illustrates the leak detection of a Feluwa hose diaphragm piston pump. The transport medium is a suspension with a pressure of 150 bar. The measurement showed a sudden increase in the sound level at the suction valve of the pump head 2, well above the alarm value. After about two hours, the pump stopped, the valve changed, and the measured value dropped back. The on-line diagnostic system provided plenty of time to plan a stop because the pump was also able to run for up to two weeks after it was first detected.

Figure 4 shows the investment and maintenance life cycle costs for three different types of pumps of the same performance. Using the online monitoring system can reduce the 30-year cumulative cost by 50%. In addition, the efficiency loss in Figure 5 should also be considered.

Summary: The on-line diagnostic system Sitrans DA's application test showed an early diagnosis of the piston pump bleed valve leak and was instrumental in maintaining the pump because the inspection was done automatically so that a scheduled maintenance program could be developed. Sometimes you do not even have to have a spare pump installed. On-line diagnostic system predicts and economizes pump maintenance.

The monitoring system can be used not only for the discharge valve of the pump but also for monitoring the leakage of the regulating valve, the on-off valve and the discharge valve of the compressor .