New viewpoint and detailed explanation of maintaining pneumatic valve

The viewpoints of pneumatic valve positioner and process sensor are as follows;

It takes only a few seconds to open or close a pneumatic valve and provides a complete set of operation data.

These new valve sensor kits not only provide specific data, but also alarm factory operators in case of system error.

Usually, the electromagnetic pneumatic valve is quite simple equipment. They are usually in one of two states: on or off, and no intermediate state is possible. Because of its simple characteristics, there are some shortcomings in running measurement. Of course, they can detect the action of electromechanical switches. If the valve is in the open or closed state, but it is for the purpose of operation, rather than analysis and measurement. It provides the control room operator with some simple methods to confirm whether there is material flowing through the pipeline.

What else can maintenance engineers do? He can write a calculation program to track the number of open and closed times, which can measure the frequency of valve use. Or, if the engineer has the right to time the equipment, he can measure the time interval between the opening and closing of the valve. Valve travel time is usually very short, for small valves it is usually hundreds of milliseconds, for large valves it is usually 1 or 2 seconds, or even minutes. However, since this is a diagnostic method of, it is worth measuring its accuracy.

Why is that so? If a period of time (several months, a year, or even longer) is passed and the valve travel time is compared, it will be found that the amount of time is longer and longer, and even there will be errors. For example, sometimes there is stagnation. In particular, some deposits can clog mechanical components.

In short, the travel time depends on the compressed air, and it changes a lot in a day. Some trip data are useful for analysis, but after a long time, it is no longer a clear and reliable data.

Current situation

Process automation has changed a lot from what it was 20 years ago. The main difference lies in the emergence of intelligent equipment, which is equipped with a high-speed communication bus, which can easily provide engineers and managers with a large number of factory information, which can not be achieved in the past. From common mobile phones to complex enterprise resource management systems, all these systems rely on communication and intelligence, and their speed is unimaginable 20 years ago.

However, there is also a pity that most of the basic automatic pneumatic valve kits currently installed do not keep up with the pace of rapid intelligence and high-speed communication. Most of the valves are still in discrete monitoring mode, with low or no intelligence. How to make a valve intelligent when it is opened or closed?

There has been some progress. The proximity switch replaces the old mechanical and electrical switch; the reliability is increased and the service life is greatly extended. The application of high-speed data bus, such as as as interface, is becoming more and more extensive. Even industrial bus has become the mainstream communication mode, providing the signal of opening or closing, and verifying the opening position of the valve. However, maintenance still requires a lot of work: running according to the plan, but the plan can not reflect the actual needs of some individual devices.

This situation was acceptable 20 years ago. Now, as time goes by, process managers need more information to help make better maintenance decisions, which need to be based on facts rather than estimates.

Many years ago, the work of improving the maintenance of pneumatic valve began. For R & D personnel, where does the valve information data come from? Generally, it's a sensor problem. Where the sensor is placed correctly, the right data can be obtained at the right time for maintenance analysis.

Since the only action of the valve is the opening and closing of the valve, it is necessary to obtain data at the right time. So what is the right time? The valve opening can be accurately controlled from time, and the pressure of compressed air can be obtained from time to monitor these variables.