How to Manage the Performance of Valves?

Valve products are widely used in chemical industry, medical food, urban water supply and drainage and other major industries. It can be said that it is closely related to the country's main economy and life. However, there are various performance characteristics, advantages and disadvantages of various types of valves. In practical applications, the combination of these characteristics can not only save costs, reduce failures, but also achieve twice the result with half the effort.

Several categories of valves

The valves are mainly divided into the following categories: cut-off valve, regulating valve, check valve, diverter valve and safety valves. To sum up, each type of valve has its corresponding performance characteristics. Understanding these corresponding performance characteristics can properly and effectively manage the valve and extend its service life.

Problems in valve performance management

According to relevant data and some media reports, in addition to various technical performance indicators, when analyzing foreign advanced products, you will notice that the shape is beautiful, the structure is exquisite, the inner cavity is clean, and the details are elegant.

For example, in order to prevent the operator's hand from being scratched, the ends of the connecting bolts of the flange are processed into curved surfaces, etc. The differences in these specific details should cause me to think deeper: why does it do this? How could you have thought of doing this? The conclusion must be attributed to the humanized design concept.

Understanding from this level will make our product design no longer stay in the simple and advanced stage, but from the perspective of ergonomics, from more safe, reliable, energy saving, environmentally friendly, clean production, convenient operation, easy to disassemble maintenance and other aspects to study and think. Then give the valve this traditional product with a new concept and image to form its own characteristics.

According to experience, about 30% of control valves have mechanical problems during use. The valve may be too large and has been operating at 2% to 3% capacity, so it cannot be controlled too much. The valve may also be too small, so it needs to be 100% open at all times, and no flow control can be performed at all.

Another problem may be that the valve is stuck-having "stickiness", a combination of jamming and friction. It cycles back and forth under control, unnecessarily wearing out valve components (seals, packings, and the valve itself). This shortens the service life of the valve and affects reliability. Static friction can also have deleterious effects on the process. When the valve moves back and forth, it changes the flow of the process. Static friction can usually be easily eliminated by, for example, adjusting the tightness of the packing and performing some simple maintenance on the valve (such as checking the air supply and ports for blockages). These issues can affect valve life, reliability or process quality and production.

Four goals of valve performance management

The idea of valve performance management is to use the available data to aggregate these four goals:

1. Improve the performance of the valve

Observe whether the valve has been opened to the extent indicated and should be opened as soon as possible. It should maintain its position accurately. It should not move irregularly. It shouldn't be too small or too large for its assigned function.

2. Extend the service life of the valve

It is very expensive to remove the valve from the pipeline and repair or replace it. Any measures to extend valve life can save money and increase reliability.

3. Minimize unplanned downtime

Reliability is key. By analyzing the available data, it is often possible to identify and predict when a serious problem with a valve may occur and it may fail in an unplanned manner.

4. Centralized maintenance resources

In most plants, maintenance staff has too much to do and not enough time. Ideally, you should decide which valve to repair during the next shutdown based on data that indicates which valve is likely to fail first or which valve is performing the worst.

Performance management pay attention to the following three factors

To achieve the above four goals, we need to pay attention to the following three factors:

1. Tools: Use tools (mainly software) to collect and inspect data about valves and their performance and process variables. These tools are important, but not all,

2. Organization and skills: The next requirement is people. They need to organize and provide structures in a way that enables them to use tools and make the right decisions.

3. Best practices and workflow: Who should look at the tools and how often? How should they handle this information? The way things happen in a factory may be accidental-the operator may record the problem, but the information may or may not be communicated to someone who is capable of doing something.

Valve performance management example

1.Valve analysis

In a pulp mill, the monitoring software will automatically detect that the valve is continuously oscillating, so that the flow through the valve suddenly changes, above and below the required level. This behavior is a characteristic of valve stickiness. However, in this particular case, in addition to the valve being sticky, a leak was found in the actuator diaphragm. The valves and actuators were replaced at the next plant shutdown. After that, valve control and the resulting flow become smoother.

2. Valve wear

Inspection of the valve showed that some valve seats had corroded. This results in less force required to open the valve. The diagnosis for this valve comes from a smart positioner that not only provides data on the position of the valve, but also data on the air supply and the load required to open and close the valve. It can be repaired or replaced before a fault occurs.

3. Control loop analysis

In a refinery, a valve known to have previous problems demonstrated many movements around its commanded position, plus or minus 10%. This creates fluctuating process flow rates. The solution was to readjust the control loop and make small adjustments to the positioner. The result is less valve movement, more stable flow, and longer valve life. The valve itself does not need to be repaired or replaced.

4. Avoid downtime

The monitoring software detected a sudden increase in valve movement. The inspection revealed that the actuator was barely tightened. Of the four bolts holding the actuator to the valve, two are fully loosened and the other two are partially loosened. The actuator itself is closing the valve. If no problems are detected, the actuator may fall completely, keeping the valve in whatever position it happens to be. The solution is to simply fix the bolts, including applying a thread-locking adhesive.

In summary, we learn the performance characteristics, advantages and disadvantages of the valve. In practical applications, the combination of these features can save costs and reduce failures.