Development Testing of Hydraulic Valves

How can we determine if a valve meets application requirements?

Whether a valve's performance meets application requirements can ultimately only be confirmed through actual application. However, prior to that, through testing, understanding application requirements, and then conducting tests on the valve as close to those requirements as possible, we can gain insight into the valve's suitability. A valve's functionality is achieved through its structure, while its performance must be determined through testing!

Testing of valves can be divided into development testing and production testing. The excellent performance of a hydraulic cartridge valve is achieved through comprehensive development testing, while stable manufacturing quality of the hydraulic cartridge valve is confirmed through rigorous production testing.

Development testing is a comprehensive testing of prototype characteristics. The development process of a hydraulic cartridge valve should generally follow the outline shown in Figure 5-8. After receiving a development task, designers analyze requirements (in the task document), perform necessary calculations and conceptualize solutions, and design drawings. However, even the wisest have their moments of oversight. Therefore, after a prototype is trial-manufactured according to the design drawings, comprehensive performance testing must be conducted.

Test results are compared with requirements, and design improvements are made to address any gaps, followed by further trial production and testing to compare the effects of improvements. This process is repeated. During this period, requirements may also be revised and supplemented as appropriate until the prototype's performance meets the requirements. Throughout this process, testing is an indispensable and important link.

The Role of Development Testing

Development testing is not only conducted during the development process but also upon completion of development to provide a final evaluation of component design and manufacturing processes. This involves considerations of production equipment and process stability. For example, the stability of manual welding differs from that of automatic welding. With automatic welding, the weld strength may vary each time process parameters are modified, potentially requiring additional targeted testing.

If manufacturing processes are unstable, test results have limited value. Therefore, test specimens must possess the characteristics of mass-produced products, utilizing mass-production materials and processes. This ensures that test results accurately represent the quality level of mass-produced hydraulic cartridge valve products.

1. Performance Testing

In actual hydraulic system operation, short-term overpressure is common. Therefore, testing only at the allowable pressure is insufficient. Generally, a pressure resistance test at a static pressure value of 125% of the allowable pressure should be conducted. It is important to note that another performance test should be performed after this pressure resistance test. Only if the performance remains essentially unchanged can it be concluded that the hydraulic cartridge valve can withstand this overpressure without sequelae.

For the hydraulic cartridge valve, steady-state performance testing is particularly critical due to its compact design and integration into complex hydraulic systems. Even minor deviations in pressure-flow characteristics can have significant impacts on overall system performance. Testing protocols must therefore be rigorous and precise, utilizing advanced measurement equipment to capture even subtle performance variations.

Transient performance testing of the hydraulic cartridge valve involves analyzing how the valve responds to sudden changes in operating conditions. This includes measuring response times, pressure overshoot, and flow stabilization periods. These characteristics are especially important in applications where rapid system adjustments are required for safety or operational efficiency.

2. Durability Testing

Durability testing, also known as life testing or fatigue testing, is essential for ensuring the long-term reliability of the hydraulic cartridge valve. Despite extensive research on the durability of material components and the availability of numerous theoretical calculation methods—including well-established finite element calculation methods for complex shapes—ultimate verification through actual testing remains necessary.

The hydraulic cartridge valve's durability test protocols typically include cycling the valve through its full operating range while monitoring key performance indicators such as leakage rates, response times, and pressure drop. These parameters are recorded at regular intervals throughout the test duration to establish performance degradation trends.

Accelerated durability testing may also be performed, where the hydraulic cartridge valve is subjected to more severe conditions than encountered in normal operation. This approach can provide valuable reliability data in a shorter timeframe, although correlation with real-world performance must be carefully established.

3. Application-Relevant Testing

Hydraulic valves, in general, are universal components that can often be used in different applications. However, when a specific application is identified, in-depth research should be conducted to understand any special requirements—such as sudden load changes, special hydraulic fluids, or unique operating cycles—and testing should be performed that closely approximates these application requirements.

For the hydraulic cartridge valve, which is often used in specialized machinery and equipment, application-relevant testing is particularly important. Each application may place unique demands on the valve, from high-frequency cycling in industrial machinery to extreme temperature variations in mobile equipment.

Application-relevant testing ensures that the hydraulic cartridge valve not only meets general performance specifications but also performs reliably in its intended operating environment. This type of testing often reveals subtle interactions between the valve and system components that might not be apparent during standard performance testing.

4. Environmental Simulation Testing

Environmental simulation testing involves creating conditions similar to those encountered in the application environment to evaluate the hydraulic cartridge valve's performance under these conditions. This type of testing is crucial for ensuring reliability in harsh or specialized operating environments.

Environmental test chambers used for temperature, humidity, and vibration testing of hydraulic cartridge valve components

Environmental testing is particularly important for the hydraulic cartridge valve, as it is often used in mobile equipment and industrial machinery that operate in challenging conditions. These tests help ensure that the hydraulic cartridge valve maintains its performance characteristics and reliability throughout its service life, regardless of environmental stresses.

5. Testing Standards

To summarize experience and facilitate communication and comparison, various standards have been developed for hydraulic component testing. International standards typically recommend testing methods but do not specify performance指标 that should be achieved. Most Chinese national standards related to hydraulics are equivalent to or modified from international standards.

For example, GB/T15623 regarding electro-hydraulic control valves is modified from "ISO10770", and GB/T8107 regarding the determination of pressure difference-flow characteristics of hydraulic valves is modified from ISO4411. These standards provide guidelines for conducting consistent and comparable tests on the hydraulic cartridge valve.

In China's machinery industry standards (JB), type testing roughly corresponds to development testing, while factory testing roughly corresponds to production testing. Adhering to these standards ensures that the hydraulic cartridge valve testing process is systematic, repeatable, and comparable across different manufacturers and testing facilities.

It is clear from the above that a high-performance valve cannot be achieved through theoretical calculations alone but through repeated testing and improvement. Simply acquiring drawings from a reputable valve manufacturer is insufficient, as numerous other factors are involved, including materials, components (such as springs), processing equipment, and process conditions—all of which significantly impact the final performance of the hydraulic cartridge valve.

The development testing process for the hydraulic cartridge valve represents a critical investment in product quality and reliability. By systematically evaluating performance, durability, application-specific characteristics, and environmental resistance through standardized testing protocols, manufacturers can ensure that their hydraulic cartridge valve products meet or exceed customer expectations and perform reliably in real-world applications.