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Safe monitoring of industrial valves.

Wherever they are used, things are usually pretty rough: industrial valves made by Stahl-Armaturen PERSTA GmbH, Warstein, have been working in the chemical and petrochemical industries, in waste incineration plants and in conventional and nuclear power plants for 70 years now. Failures often lead to expensive downtimes of entire production plants or endanger people and the environment.

Persta flap equipped with optiMEAS smart devices

In contrast, PERSTA has developed the 'Smart Valve Monitoring System' as a condition monitoring system. This is intended to permanently record the condition of the plant components and derive trends for predictive maintenance. However, such monitoring poses a challenge. Valves are usually relatively simple electromechanical elements that are not easily accessible to electronic monitoring by sensors. Alex Martens, responsible for innovation at PERSTA and significantly involved in the development of the system, explains their importance nevertheless: We manufacture industrial valves with nominal diameters of up to 800 mm with unit prices of up to one million euros. The manufacturing times for such customised products are up to one year. These valves must never fail abruptly.

Four areas of monitoring emerged

Martens goes on to explain: 'Our field tests and experience have shown that four problems occur most frequently.' These are: Sluggishness of the valve due to wear of the actuating components and the stem seal, leakage of the stuffing box packing due to wear or damage, leakage in the valve seat due to wear or damage of the sealing surfaces and steam losses due to triggering of the housing rupture safety device.

From this, the team derived four monitoring areas that are monitored with different sensors and methods: Actuator, stem seal, valve seat and housing breakage protection. In the case of the actuator, it is primarily the position and the torque that allow conclusions to be drawn about the condition. Preload force and leakage indicate the condition of the stem seal. The valve seat must also not show any leakage. The triggering of the housing breakage protection must be signalled immediately. The most important factor in monitoring the valve, however, is the valve seat, "as this is decisive for its functional efficiency," says Martens.

Smart measurement technology realises condition monitoring

The measurement technology for implementing the condition monitoring is supplied by optiMEAS GmbH from Friedrichsdorf. We record and process the data supplied by the sensors with every valve movement using our smartPRO devices," explains Dr Jens-Achim Kessel, who is responsible for automation, control technology and standard software products at optiMEAS. PERSTA provides the algorithms for the monitoring.

Dr. Kessel: "If the measured values leave a predefined bandwidth, we trigger an alarm in time so that there is enough time for a planned and calculable reaction. And Alex Martens adds: "We can derive concrete statements from the trend observation as to when maintenance is due, which part of the valve is defective or whether there is an operating error. The system is completely self-sufficient. The evaluation takes place on site at the valve, a usually very complex integration into a central control room is not necessary," says Dr. Kessel.

The advantage: the user can integrate the system, but also operate it independently. It is therefore suitable for new plants as well as for the expansion of existing plants and is therefore suitable for many valves on the market," says Alex Martens. PERSTA expert Alex Martens is convinced that the functionality of the Smart Valve Monitoring System can be used for numerous components in the field. For example, it is conceivable to use a mobile radio solution at pipeline stations.