Safe monitoring of industrial valves.
Wherever they are used, things are usually pretty rough: Industrial valves from Stahl-Armaturen PERSTA GmbH, Warstein, have been working for 70 years in the chemical and petrochemical industry, in waste incineration plants, in conventional and nuclear power stations. Failures often lead to expensive downtimes of entire production plants or endanger people and the environment.
In contrast, PERSTA has developed the "Smart Valve Monitoring System" for condition monitoring. This is intended to permanently record the condition of the plant components and derive trends for predictive maintenance. However, such monitoring represents a challenge. Valves are usually relatively simple electromechanical elements that are not easily accessible to electronic monitoring by sensors. The importance of these elements is illustrated by Alex Martens, who is responsible for innovation at PERSTA and played a decisive role in the development of the system: "We manufacture industrial valves with nominal diameters of up to 800 mm with unit prices of up to one million Euros. The production times for such custom-made products are up to one year. "These valves must never fail suddenly."
Four monitoring areas crystallized out
Martens continues: "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 loss due to triggering of the body rupture safety device.
From this, the team derived four monitoring areas, which are monitored with different sensors and methods: actuator, stem seal, valve seat and body rupture protection. In the case of the actuator, it is primarily the position and the torque that allow conclusions to be drawn about its condition. Preload force and leakage characterize the condition of the stem seal. The valve seat must also not show any leakage. Triggering of the body rupture safety device must be signalled immediately. The most important factor in monitoring the valve, however, is the valve seat, "since this is decisive for the functional efficiency," says Martens.
Smart measurement technology realizes condition monitoring
The measurement technology for the implementation of condition monitoring is supplied by optiMEAS GmbH from Friedrichsdorf. "We use our smartPRO devices to record and process the data supplied by the sensors with every valve movement," explains Dr. Jens-Achim Kessel, responsible for automation, control engineering and standard software products at optiMEAS. PERSTA provides the algorithms for monitoring.
Dr. Kessel: "If the measured values leave a specified bandwidth, we trigger an alarm in time to allow sufficient time for a planned and calculable reaction. And Alex Martens adds: "We can derive concrete statements from the trend analysis 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 is carried out on site at the valve, a normally 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 both for new plants and for the expansion of existing plants and is therefore suitable for many fittings on the market," says Alex Martens. PERSTA expert Alex Martens is convinced that the functionality of the Smart Valve Monitoring System can basically be used for numerous components in the field. For example, it is conceivable to use a mobile radio solution at pipeline stations.